Amateur Radio (Ham) Glossary

Compiled by Dick Oakes


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Ø - zero with a stroke - A Ø distinguishes a 0 (zero) from the letter O and resolves ambiguity in call signs. On a Macintosh keyboard, press the caps lock key, then press option-O. On a general personal computer keyboard's numeric keypad, press Alt-O-216. For hyper-text markup language web pages, use Ø or Ø.
1 dB compression (P1db) - Quantity of input power to a linear amplifier that will result in a gain compression of -1 decible (dB) (also called P1dB, point at which the amplifier output power deviates by 1 dB, or about 20%, from perfectly linear). Also known as -1 dB compression.
1.25 meters - An amateur frequency band from 219.000 to 220.000 MHz and 222.0 to 225.0 megahertz (MHz). Also known as 220 MHz band.
3 dB bandwidth - The bandwidth of a filter defined by frequencies at which the output signal strength (power level) is half that of the input signal, so that the output signal is 10log10(1/2) ≈ -3 decibles (dBs) (or 3 dB down). Also known as 3/8-24; half-power point.
10-code - A series of abbreviations (originally 10-1 through 10-29) created by United States Association of Public-Safety Communications Officials-International (APCO) officers for use on 1950s-era police radio. As many localities extended the series with their own non-standard codes, the same codes may have different meanings in different agencies, even between police and fire services in the same town. Ten-codes are never used in amateur, marine, or aviation radio as Q-symbols already are in long-established international use but they may be heard in the unlicensed Citizen's Band (CB) radio service and on local public-service frequencies. Also known as ten code.
10 log - A logarithmic unit of measurement, it is based on the common logarithm of ratios: 10 times the common logarithm of a power ratio or 20 times the common logarithm of a voltage ratio. The bel is the logarithm of a power ratio. It is 10 times the log of the ratio of the output voltage to the input voltage. Since 1 bel represents a large power ratio (10), the decibel was introduced as a matter of convenience. One bel equals 10 decibels and corresponds to a power ration of 10 to 1.
10 meters - The amateur frequency band from 28.000 to 29.700 MHz, and the one perhaps most heavily affected by sunspot activity.
10 over 4 - A 10 code that means I understand and acknowledge, similar to copy and roger.
10 over 9 - A received signal that is 10 decibles (dB) greater than S9 on the S meter, which assumes a readability level of 5.
11 meters - (Archaic) Former amateur frequency band from 26.965 to 27.405 MHz, now assigned to Citizens Band (CB).
12 meters - An amateur frequency band from 24.890 to 24.990 megahertz (MHz).
13 centimeters - An amateur frequency band from 2300.000 to 2450.000 megahertz (MHz). Also known as 2.4-GHz band; S band.
13 meters - An amateur frequency band (also called S band and 2.4-GHz band) from 2300.000 to 2450.000 megahertz (MHz).
15 meters - An amateur frequency band from 21.000 to 21.450 megahertz (MHz).
17 meters - An amateur frequency band from 18.068 to 18.168 megahertz (MHz).
160 meters - An amateur frequency band from 1.800 to 2.000 megahertz (MHz).
18650 battery - An increasingly popular Li-ion battery known for high energy density (high-capacity and high-drain) and wide temperature tolerance, used in numerous applications, such as laptop computers, high-powered flashlights, and even electric vehicles.
1929-type - (Archaic) Stations, transmitters, and receivers that were designed specifically to adhere to the bands and signal characteristics dictated by the 1927 International Radio Convention, whose specifications went into effect on January 1, 1929.
1x1 - The format of an American special event call sign.
2 meters - An amateur frequency band from 144.000 to 148.000 megahertz (MHz).
20 - Morse code (CB) slang and 10 code abbreviation (short for 10-20) for location, similar to current location (QTH).
20 log - (See 10log)
20 meters - An amateur frequency band from 14.000 to 14.350 megahertz (MHz).
23 centimeters - An amateur frequency band from 1240.000 to 1300.000 megaherta (MHz). Also known as L band.
24-hour clock - (See military time)
27 - (Archaic) An outdated radio code for priority or urgent.
2200 meters - An amateur frequency band from 135.7 kilohertz (kHz) to 137.8 kHz, and whose transmissions are limited to 1 watt effective isotropic radiated power (EIRP). Also known as 600 meters.
3 decible bandwidth (3 db bandwidth) - The bandwidth of a filter defined by frequencies at which the output signal strength (power level) is half that of the input signal, so that the output signal is 10log10(1/2) ≈ -3 decibels (dB) (or 3 dB down). Also known as -3 dB bandwidth.
30 - (Archaic) An outdated radio code for priority or urgent.
30 meters - An amateur frequency band from 10.100 to 10.150 megahertz (MHz).
33 - (Archaic) An outdated radio code for fondest regards, typically used only between female hams.
33 centimeters - An amateur frequency band from 902.000 to 928.000 megahertz (MHz).
3/8-24 - A common machine screw thread size (3/8 of an inch in diameter and 24 threads per inch) often used between a base and element pair of an antenna mount.
40 meters - An amateur frequency band from 7.000 to 7.300 megahertz (MHz).
5 by 5 - An audio and radio frequency (RF) signal report used primarily in non-amateur radio communication to indicate loud and clear. Also known as 5 and 5; 5-5; five-five.
5 by 9 - An audio and radio frequency (RF) signal report using the readability, strength, tone (RST) system to indicate loud and clear. Also known as 5 and 9; 59; 5-9; five-nine.
5 over 9 - A received signal that is 5 decibles (dBs) greater than S9 on the S meter, which assumes a readability level of 5.
5/8 wave antenna - A 5/8 λ vertical radiator antenna that is fed at its base. A matching device of some sort must be added between the antenna and the feed line to feed it with coax. Adding a coil in series with the antenna at the base is one such method of matching. The λ is a Greek small lambda.
5x5 - (Archaic) Five-by-five is an older term used to assess radio signals, as in 5 out of 5 units for signal strength and for readability. Other terms similar to 5-by-5 are "Loud and clear" and "Lima and Charlie."
6 meters - An amateur frequency band from 50.000 to 54.000 megahertz (MHz), and the one best suited to communicating via meteor scatter.
60 meters - An amateur frequency band that uses five frequency channels centered at 5330.5, 5346.5, 5357.0, 5371.5, and 5403.5 kilohertz (KHz).
630 meters - An amateur frequency band from 472 kilohertz (kHz) to 479 kHz, and whose transmissions are limited to 5 watts effective isotropic radiated power (EIRP). Also known as 600 meters.
70 centimeters - An amateur frequency band from 420.000 to 450.000 megahertz (MHz).
7O Yemen - For DXers, a most unattainable contact or a non-existent station. The rarest call sign prefix as one of two countries worldwide (the other is P5 North Korea) to have had no licensed radio amateur service at all since 2002.
73 - A radiotelegraph code meaning "Best regards, Best wishes, or Good luck." Used in both Citizen's Band (CB), from where it came, and phone toward the end of a contact.
73 Magazine - (Archaic) A United States-based amateur-radio magazine that was published from 1960 to 200(3) It was known for its strong emphasis on technical articles and for the lengthy editorials in each issue. Also known as 73 Amateur Radio Today.
75 meters - (Archaic) An outdated name for the phone portion, 3.6 MHz to 4.0 megahertz (MHz), of the 80-meter band, and sometimes still used for such.
80 meters - An amateur frequency band from 3.500 to 4.000 megahertz (MHz).
88 - A radiotelegraph code meaning "Love and kisses." Used in both Morse code, from where it came, and phone toward the end of a contact.
800 MHz - A non-amateur frequency band from 790 to 862 MHz, allocated for home security and control equipment and other short-ranged local-communication devices, but in recent years also allocated for migration by official radio services.
92-code - (CW term) A series of telegraphic abbreviations, devised by Western Union in 1859, as numbers 1 to 91. The later Philips Code added abbreviations for news wire service. While many of the codes are long forgotten, 19 and 31 (absolute and permissive) continue as orders for trains in railroad use.

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A battery - (Archaic) In early radio, batteries were the prime source of power. The A battery provided the filament voltage in a vacuum tube, the B battery furnished the B+ or the voltage to the plates of the vacuum tube, and the C-battery provided the grid-bias voltage for the vacuum tube.
A-index - An index of the conditions of the Earth's magnetic field as measured at Boulder, Colorado. Propagation generally improves with lower measurement numbers.
A/B switch - A select key that switches between "A" (upper) and "B" (lower) displays. The frequency or channel on the selected display becomes the active listening and tansmit frequency or channel.
above ground level (AGL) - Intended for antenna installations, AGL has relatively little direct bearing on the broadcast range of a station.
above sea level (ASL) - The vertical height in feet (ft) or meters (m) above sea level.
absorbed glass mat (AGM) - A type of VRLA battery whose acid electrolyte is held in fiberglass mesh mats that surround conductive lead plates, and often used in ham radio stations as standby electric storage.
absorption - The reduction in a radio signal strength due to refraction in the ionosphere.
accessory (ACC) - (Archaic) A socket in the back of a radio.
accessory power outlet (APO) - A cigarette light socket in an automobile that is typically fused at 15 amperes. It should not be used to power any amateur radio device.
access code - (Repeater term) A code to activate a repeater function, for example, auto patch, link, etc. One or more numbers and/or symbols are keyed in with a telephone key pad and transmitted to the repeater.
active antenna - A physically short or small antenna with a high-gain preamplifier that is designed for use indoors or in limited-space areas.
active element - (See driven element)
active filter - (See filter)
active noise control (ANC) - A method for reducing unwanted sound.
active noise reduction (ANR) - A method for reducing unwanted sound. (See active noise control)
active power - (See power factor)
activation - Act of alerting, intiating, mobilizing, and setting in motion a trained emergency service (such as ARES and RACES) to provide their services in a timely manner.
adapter - A device for connecting pieces of equipment that cannot be connected directly.
adaptive filter - Digital filter associated with Digital Signal Processing.
adjacent-channel interference (ACI) - A condition that occurs when a receiver is tuned to a specific frequency and interference is received on a nearby frequency.
admittance - The reciprocal of impedance of a component in a series or parallel tuned circuit. (See parallel tuned circuit)
address - The information in a packet specifying the intended receiving station.
admittance - The quantity of allowance for current flow in a circuit, expressed in siemens (symbol S) and defined as the reciprocal of impedance, such that Y = G + jB, in which Y is the admittance, G is the real conductance, j is the imaginary unit, and B is the susceptance.
Advanced - (Archaic) The Advanced Class operator license for intermediate-level amateur radio operators, whose privileges included 275 kilohertz (kHz) of additional spectrum in the high-frequency (HF) bands over and above that allocated to General Class licensees. It was deprecated by the restructuring in 2000.
advanced digital network (ADN) - A 56-kilocycle-bps dedicated leased line.
advanced intercept point (AIP) - A receiver amplifier feature introduced by Kenwood, in which the third-order intercept point can be manually adjusted, to help extend its dynamic range while reducing both nearby signal interference and intermodulation distortion.
aerial - (Archaic) An antenna; an electrical device that converts electric power into radio waves, and vice versa. The term was used in the early days of radio. The term is still used in the United Kingdom. Also known as outdoor antenna.
aeronautical station - A radio station aboard an airplane or a ground station that communicates with aircraft.
Affiliated Club Coordinator (AC) - An appointee of the American Radio Relay League (ARRL) who specializes in motivating, providing assistance to, and coordinating joint activities of radio clubs.
again - A request to repeat a call sign or other identifying information ("please repeat that").
agw packet engine (AGWPE) - Personal computer software written by George Rossopoulos SV2AGW that allows a computer sound card to emulate a terminal node controller (TNC) for packet operation.
air link - That portion of a data and/or voice transmission that takes place using radio signals with no wires involved. A good example is a microwave link between two towers.
airwaves - Slang for radio frequencies used for broadcasting. Also known as air waves.
alkaline - The most popular type of non-rechargeable battery that offers a higher energy density and longer shelf life than do carbon-zinc batteries, but at a higher cost.
alien - A person residing in the United States, but is not a United States citizen. Also called a resident alien.
alien reciprocal operation - (See reciprocal operation)
alligator - (1) (Repeater term) A repeater that transmits further than it can receive. (2) (Repeater term) Used in reference to a repeater timer timeout. If you talk on the repeater too long, an internal timer will cut you off, and jargon for this is "The alligator got you!" (3) Used in contesting circles to refer to a station whose transmit signal is greater than the receive capability which is usually running high power and under noisy receive conditions. (See elephant)
allocation - A frequency authorized for a particular Federal Communications Commission (FCC) telecommunications service.
AllStar - A software-based system that links ham radio stations around the world through your cell phone or other computing device using VoIP.
alpha - A bipolar junction transistor parameter. Also known as common-base current gain, symbol α) defined as the change in collector current with respect to emitter current.
Alpha - A North Atlantic Treaty Organization (NATO) phonetic alphabet code word representing the letter A. Used in radio communication, particularly when spelling out a call sign.
alphabet - (See phonetic alphabet)
alternating-current hum (AC hum) - Unwanted 60- or 120-Hz modulation of an audio radio frequency (RF) signal due to inadequate filtering in a power supply or improper grounding.
alternating current (AC) - Electrical current that flows first in one direction and then in the other in a wire, reversing polarity at regular intervals. Sometimes written as ac.
amateur - A person who is licensed to operate a radio station for two-way communication within the amateur radio frequency spectrum, often synonymous with "ham," i.e., a ham radio operator.
Amateur Auxiliary An American amateur radio organization consisting, at one time, of official observers and now volunteer monitors, and operated by the ARRL, working in conjunction with the FCC to monitor amateur radio frequencies in the United States to help operators self-police their compliance with rules. Ham police is slang for Amateur Auxiliary.
Amateur's Code - A code of conduct for amateur radio operators written in 1928 by Paul M. Segal W9EEA.

The radio amateur is:
     never knowingly operates in such a way as to lessen the pleasure of others.
LOYAL . . .
     offers loyalty, encouragement, and support to other amateurs, local clubs, and the ARRL through which amateur radio in the Unites States is represented nationally and internationally.
     with knowledge abreast of science, a well-built and efficient station, and operation above reproach.
     slow and patient when requested; friendly advice and counsel to the beginner; kindly assistance, cooperation, and consideration for the interests of others. These are the hallmarks of the amateur spirit.
     radio is an avocation, never interfering with duties owed to family, job, school, or community.
     station and skill always ready for service to country and community.

amateur communications - Non-commercial radio communication by or among amateur stations solely with a personal aim and without personal or business interest.
Amateur Data Interchange Format (ADIF) - A standard specification for format of exported logbook files.
Amateur Extra Class - The top United States license class is Amateur Extra Class. This license requires the same tests as the General Class license plus a 50-question multiple-choice theory exam. Those with Amateur Extra Class licenses are granted all privileges on all United States amateur bands. It does not require familiarity with Morse code. Also known as Extra.
amateur frequency band - A portion of the ultra-high frequency (UHF) (microwave) radio spectrum internationally allocated to amateur radio and amateur satellite use on a secondary basis. Also known as L band; 23-centimeters band.
amateur operator - A person holding a written authorization to be the control operator of an amateur radio station.
amateur radio - A non-commercial radio service as set by a recognized cognizant government agency. A synonum is ham radio. In the United States, amateur radio is defined under part 97 of the Federal Communications Commission (FCC) Rules and Regulations. (See ham radio)
Amateur Radio Association (ARA) - A club of amateur radio enthusiasts. This term is usually prefixed by the name of the community or region served.
Amateur Radio Club (ARC) - A club of amateur radio enthusiasts. This term is usually prefixed by the name of the community or region served. (Also known as ham radio clubs.
amateur radio direction finding (ARDF) - An amateur radio racing sport that combines radio direction finding with the map and compass skills of orienteering. It is a timed race in which individual competitors use a topographic map, a magnetic compass, and radio-direction finding apparatus to navigate through diverse wooded terrain while searching for a radio transmitter (the "fox" or "bunny"). Also known as bunny hunt; contesting; radio orienteering; radio sport; radiosport; fox hunt; foxhunt; T-hunting; transmitter hunting; transmitter-hunting.
Amateur Radio Disaster Services (ARDS) - An organization of licensed amateurs who have voluntarily registered their qualifications and equipment for communication duty in the public service when disaster strikes.
Amateur Radio Emergency Data Network (AREDN) - Wireless high-speed data network (mesh) over amateur radio frequencies using commercial off-the-shelf hardware such as a WiFi router or D-STAR equipment.
Amateur Radio Emergency Service (ARES) - A public service organization of the Amateur Radio Relay League (ARRL) in which licensed amateurs have voluntarily registered their qualifications and equipment for communication duty in the public service when disaster strikes.
Amateur Radio on the International Space Station (ARISS) - A cooperative venture of the National Aeronautics and Space Administration (NASA), the American Radio Relay League (ARRL), and the Radio Amateur Satellite Corporation (AMSAT), and other international space agencies that organizes scheduled contacts by way of amateur radio between spacecraft personnel aboard the International Space Station and classrooms or communities.
amateur radio operator - (See amateur operator)
Amateur Radio Service - (See Part 97)
Amateur Radio Society (ARS) - A club of amateur radio enthusiasts. This term is usually prefixed by the name of the community or region served.
Amateur Satellite Organization (AMSAT) - In particular, the Radio Amateur Satellite Corporation, with headquarters at Silver Spring, Maryland, near Washington DC. (2) Organizations that design, build, arrange launches for, and then operate or command satellites carrying amateur radio payloads, including the Orbiting Satellite Carrying Amateur Radio (OSCAR) series of satellites. Also known as amateur radio satellite.
amateur satellite - An artificial satellite built and used by amateur radio operators.
amateur service - A radio communication service for the purpose of self-training, intercommunication, and technical investigations carried out by amateurs, for example, duly authorized persons interested in radio technique solely with a personal aim and without pecuniary interest. Also known as amateur radio service.
amateur station - A radio station licensed in the amateur service, including necessary equipment, used for amateur communication.
amateur teleprinting over radio (AMTOR) - A version of radioteletype (RTTY). Also used commercially as simplex teletype over radio (SITOR).
amateur television (ATV) - The transmission of broadcast-quality video and audio over the wide range of frequencies of radio waves allocated for amateur radio use. Also known as fast-scan television (FSTV). (See slow-scan television (SSTV).
amateur X.25 (AX.25) - A digital communication protocol designed for amateur radio and used by APRS to transmit and receive packet frames that contain beacon data (location information).
American National Standard Code for Information Interchange (ASCII) - A seven-unit digital code for the transmitter of teleprinter data.
American Radio Relay League (ARRL) - The national association for amateur radio in the United States whose public service mission is based on five core areas or pillars: Public Service, Advocacy, Education, Technology, and Membership.
American Standard Code for Information Interchange (ASCII) - A seven-unit digital code that represents 128 characters, including 32 control characters, for the transmission of teleprinter data made up of 0s & 1s.
American wire gauge (AWG) - A standard for describing the diameter of wire by which the wire size increases as the gauge number decreases.
ammeter - An instrument that measures electric current by connecting it in series with the circuit, and is usually one of the functions found in a multimeter.
ampere (A, Amp) - An abbreviation for the basic unit of electrical current which is a measure of the electron flow through a circuit. (See current)
ampere hour - A term frequently used in measurements of electrochemical systems such as electrical batteries.
amplification - The process of increasing the strength of a radio signal.
amplifier (amp) - A device connected between the transmitter and antenna that amplifies the radio frequency (RF) power output, often to the full legal amateur power limit of 1500 watts (W) peak envelope power (PEP), without changing the signal's characteristics. Also known as linear amplifier; power amplifier.
amplify - To increase the strength or amplitude of a signal.
amplitude - The strength or amplitude of a signal, it is the height of a wave from the average or median position.
amplitude modulated phone - An amplitude modulation (AM) transmission in which voice signals, or phone are used to modulate the carrier.
amplitude modulation (AM) - (1) A modulation technique that varies the power output of a transmitter in accordance with the variations in the modulating audio signal. Part of the modulation index. (2) A method of combining an information signal and a radio frequency (RF) carrier.
amplitude-companded single-sideband (ACSSB) - (Archaic) A narrow-band modulation using a single sideband with a pilot tone, allowing an expander in the receiver to restore the amplitude that was severely compressed by the transmitter.
amplitude-shift keying (ASK) - A low-rate data transmission mode that combines digital communication with amplitude modulation.
analog - Any continuous signal for which the time varying feature (variable) of the signal is a representation of some other time varying quantity, that is, analogous to another time varying signal. Also known as analogue.
analog-to-digital (ADC) - A converter that samples an analog wave and converts it into a digital signal, in which a series of numbers is used to represent the amplitude of the original wave. Also known as A/D; A-to-D.
analog data - Continuous waves that vary or fluctuate infinitely within a range. In comparison, digital data consists of discrete, discontinuous binary digits.
analog signal - A linear signal, usually electrical, that can have any amplitude (voltage or current) value, and whose amplitude can vary smoothly over time. (See digital signal)
analyzer (See antenna analyzer)
Anderson Powerpole - Used by many emergency radio operators to connect 12 volts direct current (DC) to their radios.
Andrew coax - (See Heliax)
angle modulation - The process of varying (modulating) the phase angle of a sinusoidal carrier wave to transmit information, of which frequency modulation and phase modulation are two types.
angle of radiation - The angle (often called takeoff angle), with respect to level ground, of the strongest or average radio frequency (RF) field delivered from an antenna system. (See far-field) Also known as radiation angle; takeoff angle.
anode - An electrode through which electric current flows into a polarized electrical device. (See cathode and electrode)
Anderson connector - (See powerpole)
ante meridian (a.m.) - Before noon.
antenna-matching device - (See antenna tuner)
antenna-matching network - (See antenna tuner)
antenna-tuning unit, impedance-matching device, matchbox, and transmatch.
antenna (ANT) - A rod, wire, or other device used to transmit or receive radio frequency energy or television signals. Also known as skyhook.
antenna analyzer - A portable instrument that combines a low-power signal source, a frequency counter, and a standing-wave ratio (SWR) meter. Also known as analyzer.
antenna array - Multiple antennas installed or configured so that the combination results in a unit that exhibits greater gain and directivity than each might otherwise realize on its own.
antenna coupler - (See antenna tuner)
antenna current - (See common-mode current)
antenna direction - The direction to which an antenna is pointed.
antenna efficiency - The ratio of the total power radiated by an antenna with respect to the net power input to the antenna, equal to the ratio of the antenna's radiation resistance to its total (ohmic plus radiation) resistance, often expressed in decibels or as a percentage.
antenna element - (See element)
antenna farm - A location dedicated to the placement of (usually many) radio and TV antennas. A ham's dream; lots of room for big, high, long, antennas.
antenna feed - (See feed point)
antenna gain - The ratio of the power required at the input of a loss-free reference antenna to the power supplied to the input of the given antenna to produce, in a given direction, the same field strength at the same distance. Also known as gain.
antenna ground system (AGS) - A radio frequency (RF) reference potential for some types of antennas. Most unbalanced or asymmetrical antennas need a good RF ground.
antenna impedance - The impedance of an antenna at its resonance. Although an antenna's impedance fluctuates with the frequency of operation, an antenna should be 50 Ohms for most transceivers.
antenna match - A device or circuit that modifies (matches) the impedance of the antenna to that of the feedline and/or transmitter by presenting a complex conjugate of the antenna impedance, and often achieved by an antenna tuner. Also known as match.
antenna matching - When the antenna's impedance at resonance is at optimum performance for a transmitter output circuit. (See mount)
antenna mount - A device used to connect or install an antenna to a fixture, such as a tower, a building, or a vehicle.
antenna party - A long-standing tradition where several ham operators gather to assist a fellow ham in mounting antennas and/or towers.
antenna pattern (AP) - (1) The relative power density of the wave transmitted by the antenna in a given direction. (2) The response of an antenna to a plane wave incident from a given direction. Also known as radiation pattern.
antenna relay - An electromechanical device that can be used to switch an antenna remotely, typically from transmitter to receiver.
antenna rotator - A device that changes the aim of a directional antenna by rotating the antenna assembly. Also known as antenna rotor; rotor; rotator unit; rotator.
antenna rotator controller - Electrical device that changes the aim of a directional antenna by sending signals to a rotator attached to the antenna assembly.
antenna selector - (See antenna switch)
antenna switch - Device that allows connection between the transceiver feed line and that for any one of several antennas, or between an antenna and one of several transceivers. Also known as coax switch; antenna selector.
antenna system - Collection of components and interconnected devices that support the delivery and conversion of an electrical signal into a radio frequency (RF) field, or reception of an RF field, for conversion into an electrical signal, often including but not limited to a feedline, tuner, antenna (including elements, match, and traps), grounding, mast, tower, guys, and associated connectors (can also include a wattmeter and an SWR meter, but does not typically include an amplifier or analyzer).
antenna tower - A self-supporting structure used to support one or more radio antennas, and/or other equipment. Also known as tower.
antenna trap - (See trap)
antenna tuner - A device that matches the impedance of the antenna system with that of the transceiver to maximize power transfer from the transmitter to the antenna. Also known as antenna tuning unit; antenna coupler; feedline coupler; matchbox; transmatch.
antenna tuning unit (ATU) - (See antenna tuner).
antenna tuner - A device that matches the antenna system input impedence to the transmitter, receiver, or transceiver output impedance. Also called antenna tuning unit, antenna coupler, feedline coupler, matchbox, transmatch.
antennae - (Archaic) Plural for antenna; more than one antenna.
anti-aliasing filter - A filter circuit that prevents or reduces the (usually) undesirable effect known as aliasing, which is the construction of a false (an alias) signal from a sample of the original signal, usually the result of under-sampling. Also known as anti-alias filter.
anti-voice operated (anti-VOX) - A transceiver circuit used in VOX stations to prevent audio from the receiver's speaker from actuating the voice-operated transmitter.
antipode - (Archaic) One of two locations directly opposite one another on the Earth's surface, believed in the early days to favor propagation because of a re-convergence of signals from multiple paths around the globe.
apogee - A point in a satellite's orbit at which it is farthest from the Earth. (See perigee)
apparent power - (See power factor)
appliance operator - An amateur radio operators who neither build nor experiment with radio equipment, but only operate commercial equipment.
acquisition of signal (AQS) - A condition that occurs when a satellite becomes visible to an antenna as the satellite comes up from the horizon.
arcing - Electrical breakdown of one or more gases to produce a plasma discharge, caused by electric current flowing through air, which is normally non-conductive. At one time it was called voltaic arcing. Also known as electric arcing.
armchair copy - Easily copied.
Army-Amateur Radio System (AARS) - (Archaic) The precursor to Military Affiliate Radio System (MARS).
array antenna - An antenna with more than one element. In a driven array, all elements are driven elements. In a parasitic array, some elements are parasitic elements. Also known as array.
arrestor - (See lightning arrestor)
artificial ground - (1) A device or circuit that presents a radio frequency (RF) reference or in the absence of an actual earth ground connection, to allow an antenna to be mounted above ground level (such as on a tower or multi-story apartment building). (2) A device or circuit that maintains a reference voltage at a specific point in the circuit without being directly connected to the actual ground point. Also known as virtual ground.
assistant net control station (ANCS) - The station or person who assists the NCS with net control responsibilities.
Association of North America radio Clubs (ANARC) - An umbrella organization of radio hobby clubs in North America.
Association of Public-Safety Communications Officials-International (APCO) - An independent United States communications consultancy with more than 600 employees in 29 worldwide locations, it is the second largest independently-owned PR firm in the United States. Known as APCO Worldwide.
astable multivibrator - A circuit whose signal continuously alternates between two states without an external clock and can itself function as a clock circuit.
asymmetrical antenna - (See unbalanced antenna)
atmosphere - The layer of air surrounding the Earth.
atmospheric noise - Radio noise that originates from natural atmospheric processes, primarily lightning discharges in thunderstorms.
attended operation - Operation of a radio station with a human operator at the control point.
attenuator (ATT) - A resistive device or network to reduce the amplitude or power of a signal, often expressed in decibels (dB) of reduction. The types of attenuator circuits are the π pads (Greek small pi) and T pads. These may be required to be balanced or unbalanced networks depending on whether the line geometry with which they are to be used is balanced or unbalanced. For instance, attenuators used with coaxial lines would be the unbalanced form while attenuators for use with twisted pair are required to be the balanced form. The pi pad is formed in the shape of the Greek letter π. T pads are formed in the shape of a T. π pads and T pads are easily converted back and forth.
audibility - (Archaic) A measure of signal strength, usually based on audio strength.
audio - (1) An electrical or other representation of sound. (2) Audible (audio frequency) sound, which is modulated and transmitted by one station, then received and demodulated by another, to reproduce the audible sound. (3) Sound quality or level. Also known as volume.
audio check - A test for (report on) sound quality, such as loudness, understandability, distortion, background noise (such as static, steam, and hum), echo, distance from the microphone whether you're cutting out or dropping out, or are using sufficient microphone gain.
audio frequency (AF) - The range of 20 to 20,000 hertz (Hz), the human hearing range.
audio mixer - A circuit or device that adds multiple signals together into a single signal.
audio rectification - Interference to electronic devices caused by a strong radio frequency (RF) field that is rectified and amplified in the device.
audio-frequency signal (AF signal) - An alternating current (AC) electrical signal in the frequency range of 20 to 20,000 hertz (Hz). This is called an audio signal because human hearing responds to sound waves in the same frequency range.
audio-frequency gain (AF-gain) - (1) Receiver output volume. (See gain) (2) The volume control on a radio.
audio-frequency shift keying (AFSK) - As opposed to frequency-shift keying, it is a frequency modulation scheme in which digital information is transmitted through discrete frequency changes of a carrier wave. (See frequency-shift keying)
audion - (Archaic) A three-electrode vacuum tube, the name was coined in 1906 by Lee de Forest of the DeForest Radio Telephone and Telegraph Co. It is widely believed, however, that a Canadian inventor, Reginald Fessenden, actually came up with the idea, but Fessenden didn't seem to make it into the history books for that invention. (See vacuum tube)
aurora - (1) Visible natural phenomenon resulting from the interaction between charged particles in the solar wind and the ionosphere (primarily the E layer), where the earth's magnetic field has deflected the particles toward the regions surrounding its magnetic poles, the display near the north magnetic pole. The one in the north is known as Aurora Borealis or northern lights and the one near the south magnetic pole called Aurora Australis (southern lights). (2) A type of skip propagation made possible by radio waves reflecting off the charged ceiling produced by an aurora (auroral scatter), resulting in a fluttery or raspy sounding signal, making Morse code (CW) possibly the best mode of radio communication applicable to this phenomenon.
aurora E - A type of auroral propagation that occurs as radio waves are reflected off the ionospheric E layer near the earth's magnetic poles, normally during the time of day as auroral activity begins to diminish. Also known as auroral-E.
auroral propagation - Propagation above 30 megahertz (MHz) by means of refraction of highly ionized regions around the Earth's poles. (See propagation)
authorized bandwidth - The allowed frequency band, specified in kilohertz (kHz), and centered on the carrier frequency.
Auto-Range Transponder System (ARTS) - An automatic polling and reporting system in which multiple transceivers communicate with each other through a protocol (handshake) that helps one transceiver determine whether other similarly equipped transceivers are located, within a predefined physical proximity sufficient for reliable communication, found primarily in Yaesu transceivers, but supported in Motorola, TYT, and other radio makes as well.
auto patch - (Repeater term) A device that interconnects a radio system to commercial phone lines and allows repeater users to make telephone calls from a distant station to be completed to anyone within range. Also known as patch; phone patch.
auto repeater - (See automatic repeater shift)
auto tuner - An antenna tuner that automatically senses the mismatch between the transmitter and antenna and does the necessary matching with minimal user intervention. Also known as autotuner; automatic tuner.
automatic control - The use of devices and procedures for control of an amateur radio station when it is transmitting so that compliance with the Federal Communications Commission (FCC) Rules is achieved without the control operator being present at a control point.
automatic frequency control (AFC) - A method or circuit to automatically keep a resonant circuit tuned to the frequency of an incoming radio signal.
automatic gain control (AGC) - A feedback voltage in the receiver circuit to prevent fading, it automatically optimizes receiver gain by adjusting the gain for different input signal levels to maintain a constant output. Automatic gain control slow (AGC-S) is used for Morse code (CW) and automatic gain control fast (ACG-F) is used in most radios to drive the signal-strength meter (S-meter). Formerly known as automatic volume control (AVC).
automatic level control (ALC) - A circuit that limits radio frequency (RF) drive level to the power amplifier during transmit to prevent distortion. A feedback voltage in the transmitter's output amplifier used to prevent amplifier overload. Also used as feedback from a linear amplifier back to the exciter to prevent overdriving.
automatic link establishment (ALE) - Self-controlling transmitter circuit that attempts to maintain a constant level of power output by automatically adjusting the gain of the amplifier to prevent it from overloading, thereby reducing distortion and possible physical damage to the final stage due to excessive drive.
automatic noise limiter (ANL) - A device that eliminates impulse and static noise peaks. Also known as limiter.
automatic notch filter (ANF) - A device that quickly locates and suppresses interfering carriers, such as those caused by other stations tuning up nearby.
Automatic Packet Reporting System (APRS) - An amateur radio-based system for real time tactical digital communication of information of immediate value in the local area.
automatic power control (APC) - Current limiting of a power amplifier to prevent damage to the finals in high standing-wave ratio (SWR) conditions.
automatic repeat query (ARQ) - (Archaic) An error-control method for data transmission that uses acknowledgements, or messages sent by the receiver, indicating that it has correctly received a data frame (packet) and timeouts (specified periods of time allowed to elapse before an acknowledgment is to be received) to achieve reliable data transmission over an unreliable service. Used in amateur teleprinting over radio (AMTOR). Also known as automatic repeat request.
automatic repeat request - (See automatic repeat query)
automatic repeater shift - A technique that allows a transceiver to automatically set the repeater shift (offset) and direction for a manually tuned frequency, with assumptions based on a local (national) band plan.
automatic send-receive (ASR) - A radioteletype (RTTY) terminal mode that allows message composition while receiving text from the another station.
automatic transfer switch (ATS) - A switch that changes equipment to a backup power supply in event of power failure.
automatic volume control (AVC) - (Archaic) A feedback scheme to level out the receiver audio volume. Know known as automatic gain control (AGC).
automatically controlled digital station (ACDS) - An unattended station that communicates primarily in data modes, similar to a digipeater, and typically on high frequency (HF) bands.
autopatch - An interface between a repeater and the local telephone service, allowing you to make regular phone calls from your ham radio by the use of dual-tone multi-frequency (DTMF) tones. Also known as phone patch. Note that one type of autopatch, known as simplex autopatch (or simpatch) is implemented through a non-repeater station connected to the local telephone service.
autopatch, auxiliary remote base; phone patch (See remotely controlled base station)
auxiliary station - A radio system that is part of a radio frequency (RF) control link, often used for control of a remote repeater station.
average power - Power measured on a standard power meter. Also known as mean power, the total amount of energy expended, dissipated, absorbed, transferred, or required in a given amount of time
aviation headset - Combination earphones and attached boom-mounted microphone.
average power - (1) The total amount of energy expended, dissipated, absorbed, transferred, or required in a given amount of time. Also known as mean power. (2) The quantity of real power in an alternating current (AC) circuit.
AX.25 - Amateur version of the X.25 communication protocol. X.25 supports store and forward messaging and insures delivery of American Standard Code for Infomation Interchange (ASCII) text by retransmitting packets in the event an acknowledgment is not received from the destination.
azimuth - A horizontal direction or angle measured clockwise from north. A radial appearance of something as you look down at it from above.
azimuth pattern - Graphical description of the power intensity of radiation from an antenna as a function of the horizontal angle at a specified elevation angle around an antenna.
azimuth plot - Graphical representation of signal strength from an antenna as a function of horizontal angle around the antenna center. It is made of a particular elevation angle, often the angle with the maximum response.
azimuth/elevation (Az/El) - Used to describe an antenna rotator that can change both the azimuth (horizontal) and the elevation (vertical) direction of the antenna.
azmuthal pattern - A graph showing how an antenna radiates and receives in horizontal directions. (See radiation pattern)

To the top!   B

B battery - (Archaic) In early radio, batteries were the prime source of power. The A-battery provided the filament voltage, the B battery furnished the B+ or the voltage to the plates of the vacuum tubes, and the C battery provided the grid-bias voltage to the tubes.
backbone - A high-speed communications line/link or series of lines/links that form a major pathway in which devices can communicate within a network. The term is relative to a single smaller backbone in a group network and that of a larger multi-linked backbone in enterprise networks. A backbone can be wired, fiber optic, or air link.
backlash current - (Archaic) (See reflection)
bacon frying - (See steam)
backscatter - A form of ionospheric propagation by way of the E- and F-layers of the atmosphere allowing stations to hear other stations within the skip zones. Also known as back scatter.
backstay - Rigging to support the mast in maritime mobile installations, usually insulated for HF antenna purposes.
bad solder joint - (See cold solder joint)
balanced line - A feed line with two conductors having equal but opposite voltages, with neither conductor at ground potential.
balanced load - A termination in which each of the two terminals is at the same potential above ground.
balanced modulator - A mixer or modulator in which at least one of the input signals is canceled at the output following generation of the desired modulation or mixing products. The original carrier signal and the audio signal are suppressed.
balanced-to-unbalanced (balun) - A simple transformer used to change an unbalanced input to a balanced output. It is part of an antenna system that provides the transition between a balanced antenna such as as center fed dipole and an unbalanced transmission line such as coaxial cable, or dipole to coax.
ballmount - An antenna mount with a built-in adjustable swivel allowing an antenna to be mounted on a surface that is not exactly horizontal or vertical.
balun - A simple transformer used to change an unbalanced input (such as a coaxial cable) to a balanced output (such as an antenna).
band - A range of frequencies allocated for a particular use. Some of the allocations are:

10 kHz to 30 kHzVery Low Frequency (VLF)
30 kHz to 300 kHzLow Frequency (LF)
300 kHz to 3 MHzMedium Frequency (MF)
3 MHz to 30 MHzHigh Frequency (HF)
30 MHz to 144 MHz
144 MHz to 174 MHz
174 MHz to 328.6 MHz
Very High Frequency (VHF)
328.6 MHz to 450 MHz
450 MHz to 470 MHz
470 MHz to 806 MHz
806 MHz to 960 MHz
960 MHz to 2.3 GHz
2.3 GHz to 2.9 GHz
Ultra High Frequency (UHF)
2.9 GHz to 30 GHzSuper High Frequency (SHF)
30 GHz and aboveExtremely High Frequency (EHF)

band conditions - Atmospheric (weather, etc.), geomagnetic, solar, and other activity that in concert affect radio frequency (RF) propagation for a particular band.
band pass - A range of frequencies permitted to pass through a filter or receiver circuit.
band plan - Agreements between operators about how to use the amateur bands, rather than Federal Communications Commission (FCC) regulations. Portions of each ham band are dedicated to certain modes of operation.
band segment - (See sub band)
band spread - A receiver quality used to describe how far apart stations on different nearby frequencies will seem to be, usually expressed as the number of kilohertz (kHz) that the frequency changes per tuning-knob rotation. Also known as bandspread; band spread.
band-pass filter (BPF) - A circuit that allows signals to go through it only if they are within a certain range of frequencies and attenuates signals above and below that range.
band-reject filter - (See band-stop filter) Also known as band pass filter; bandpass filter; band reject filter.
band-stop filter - A circuit that passes all frequencies with the exception of those within a specified stop band which are greatly attenuated. Also known as a band reject filter.
bandwidth (BW) - The width of a frequency band outside of which the mean power is attenuated at least 26 decibels (dB) below the mean power of the total emission, including allowances for transmitter drift or Doppler shift. Bandwidth describes the range of frequencies that a radio transmission occupies.
bank - (See memory bank)
barefoot - A synonym for transmitting with a transceiver alone with no linear amplifier.
base - (1) A radio station located at a fixed location as opposed to a mobile station. It is used to identify the control location in a network of radio stations. (2) (See transistor)
baseloading - Shortening the physical length of a vertical antenna by substituting a loading coil for inductance at the base for part of the lower section of the antenna. Also known as base loading. (See center-loading coil.
base band - (1) Frequency components present in the modulating signal (in other words, the original unmodulated signal. (2) Bandwidth of an unmodulated signal. Also known as baseband.
base station - (1) A transceiver that is typically too large to be normally carried around by hand or installed in a vehicle. (2) Transceiver that is installed in a home or other fixed location, regardless of transceiver size or facility type. (3) Amateur radio station (also called fixed station) that is established in a permanent structure with equipment not intended for portable operation. Also known as fixed station; fixed-station.
battery - (1) A device that converts chemical energy into electrical energy. (2) (Archaic) In early radio, batteries were the prime source of power. The A-battery provided the filament voltage, the B-battery furnished the B+ or the voltage to the plates of the vacuum tubes, and the C-battery provided the grid-bias voltage to the tubes.
battery pack - Several battery cells connected together to act as a single, larger battery.
batwing antenna - Variation of the normal turnstile antenna, in which the elements are shaped into a characteristic butterfly, bowtie, or bat-wing shape, often used to cover a large bandwidth by broadcast station. Also known as bat-wing antenna; bowtie; bow-tie.
baud (Bd) - The unit of digital-signal speed. It is the unit used to express the speed of transmission of electronic signals, corresponding to one information unit or event per second. The baud unit is named after Émile Baudot. Also known as maximum symbol rate; symbol rate.
Baudot code - (Archaic) A five-digit character set predating extended binary coded decimal interchange code (EBCDIC) and American Standard Code for Information Exchange (ASCII) and was the predecessor to the International Telegraph Alphabet Number 2 (ITA2), the teleprinter code in use until the advent of ASCII. It was invented by Émile Baudot for whom it was named.
bayonet - A fastening mechanism (common with many light bulbs, data cables, continuous wave (CD) packaging spindles, and camera lenses) used by some coaxial cable connectors, such as bayonet Neill-Concelman (BNC) connectors, characterized by a push-and-turn attachment method.
bayonet Neill-Concelman (BNC) - A type of antenna connector commonly used on a hand-held transmitter, receiver, or transceiver for radio frequency (RF) signals. Built like an N-type connector, but smaller, and named after its inventors, Paul Neill and Carl Concelman.
bazooka antenna - A type of wire antenna.
beacon - (1) An amateur radio station transmitting communications for the purposes of observation of propagation and reception or other related experimental activities. (2) A transmitter used or automatically enabled during a time of distress or emergency, to alert others (especially Search and Rescue, military, or other emergency personnel). Also known as beacon station. (See emergency locator transmitter)
beam antenna - A directional antenna, a beam antenna must be rotated to provide coverage in different directions. Also known as parasitic beam antenna.
beam transmission - (Archaic) A term first used in the mid-1920s to refer to a directional signal, especially at very short wavelengths around 1 meter (m) and below.
beam width - The angle between the half-power (-3 decibles (dB)) points on the main lobe of an antenna's radiation pattern.
beat frequency oscillator (BFO) - (CW term) A receiver circuit that provides a signal to the detector. The BFO signal mixes with the incoming signal to produce an audio tone for Morse code (CW) reception. A BFO is needed to copy Morse code (CW) and single sideband (SSB) signals.
bel (B) - A logarithmic unit of measurement named after Alexander Graham Bell. One bel is defined as a power ratio of ten, or ten times the power. (See decibel)
bent-double antenna - A dipole antenna installed with its wires bent so a longer antenna fits into a shorter space.
Benton Harbor Lunchbox - A portable transceiver made by Heathkit Company. Operational band choices were 2, 6, or 10 meters (m).
Beverage antenna - A type of very long and low directional receiving antenna made primarily for high frequency (HF) and medium frequency (MF) frequencies and is characterized by its large size, often extending for miles and has comprised some of the world's largest continuous antennas, but is not typically used for transmitting due to high losses compared with that of other antennas.
bias supply - (Archaic) A power supply designed to provide the usually low-current negative-direct current voltage required by the control grid of a vacuum tube.
big gun - An amateur radio operator with a lot of money who can afford to purchase a boatload of expensive equipment and has a whopping one- or two-thousand watts for DXing and contesting.
binary frequency-shift keying (BFSK) - A low-rate data transmission mode in which the signal is shifted between two frequencies to convey the information, in which a 1 is identified by the mark frequency and a Ø is identified by the space frequency.
binary phase-shift keying (BPSK) - Digital double sideband (DSB) suppressed carrier modulation.
binary-coded decimal (BCD) - Decimal numbers represented in binary code by 0s and 1s.
binocular core - A dual-ferrite core structure often used in radio frequency (RF) transformers.
bipolar complementary metal-oxide-semiconductor (BICMOS) - An integrated circuit logic family that uses both bipolar and CMOS transistors, to offer the high input impedance of complementary-symmetry metal-oxide semiconductor (CMOS) and the low output impedance of bipolar transistors.
bipolar junction transistor (BJT) - A semiconductor device made from a pair of back-to-back positive/negative (P/N) junctions that are controlled by a current. (See transistor) Also known as junction diode.
bilateral agreement - A set of rules agreed upon by two countries to authorize amateur radio operation in one or both countries by a person who is not a citizen of (alien to) one or both countries. Also known as bilateral arrangement; bilateral operating agreement.
bird - (1) Slang for a satellite. (2) Slang for a brand name of a high-end, high quality directional wattmeter.
birdie - Spurious signals produced in a receiver which are usually a product of mixed intermediate frequencies within the radio. Also known as birdy.
bit error rate (BER) - The rate at which bit-level errors occur in a stream of digital data.
bits per second (bps) - The number of bits that are conveyed or processed per unit of time.
black hole - (See dark side of the moon)
blanker - (See noise blanker)
bleed over - Interference caused by a station operating on an adjacent channel.
bleeder resistor - A large-value resistor placed across the filter capacitors in a power supply so that they will have a discharge path when equipment is turned off. This prevents lethal voltages from lurking in an otherwise non-operating power supply.
blind zone - (See skip zone)
block diagram - A drawing using boxes to represent sections of a complicated device or process. The block diagram shows the connections between sections without the detail of a schematic diagram.
blocking dynamic range - The difference in decibles (dB) between the noise floor and the level of an incoming signal that will result in 1 dB of gain compression.
Bluetooth - A wireless communication system intended to replace the cables connecting many different types of devices, from mobile phones and headsets to heart monitors and medical equipment.
boat anchor - Antique ham equipment so named because of weight and size. Also known as boatanchor.
bonding - Interconnecting by way of low-resistance conductors, particularly of separate ground points to avoid potential between them. (Also known as strapping)
bonding - The installation of grounding straps between the frame or unibody and all bolted on hardware. Doors, hood, trunk, and exhaust system are examples. Although bonding may help in reducing egressed noise, its primary function is to improve what little ground plane a vehicle offers.
boom - Structure that forms the support for multiple individual elements on a beam antenna.
booming - (1) Slang for clear and very strong signal. (2) Action of sounding 10 over 9 or better.
boomset - (See headphones)
bootleg - (1) Older slang that describes some sort of illegal (indicating intentional) activity involving radio. (2) Describes illegally modified equipment or illegal radio operation.
bootlegger - Someone, usually not an amateur radio operator but a wannabe, making up a call sign, one usually not in the callbook, and getting on the air. Sometimes it is someone who already bought a radio, took the test and flunked, and then gets on the air anyway. Also called a pirate.
bootlegging - Operation on an amateur radio frequency without an amateur license or operation of a radio station containing illegally modified equipment (once applied primarily to Citizen's Band (CB) operation).
bounce - Reflections of a radio wave off of an object, for example, the ionosphere or the moon.
bottle - (Archaic) Slang for vacuum tube.
bowtie - (See batwing antenna) Also known as bow-tie.
braid - (See ground braid)
brass pounder - (Archaic) (CW term) Someone who sends telegraphy by old fashioned straight key without any paddles.
Brass Pounders League (BPL) - An American Radio Relay League (ARRL) Club for Morse code (CW) traffic net operators.
Bravo - A North Atlantic Treaty Organization (NATO) phonetic alphabet code word representing the letter B. Used in radio communication, particularly when spelling out a call sign.
breadboard - (1) An experimental layout of circuits on whatever media, such as printed circuit boards. Also known as bread board. (See printed circuit board) (2) (Archaic) Early experimenters used a wooden board to lay out circuits.
break - (Repeater term) (1) A term used to interrupt a conversation on a repeater to indicate that there is an emergency or urgent message into a current QSO (with break! break! break!). If non-urgent, an operator simply interjects his call sign. Also known as breaking in. (2) A pause between station key-ups.
break break - (Repeater term) A term used to intercede in an existing conversation with emergency communication.
breaker - (See circuit breaker)
break-in - (CW term) Switching between transmit and receive during Morse code (CW) operation so that one can listen to the operating frequency between Morse elements (full break in) or during short pauses in one's transmissions (semi-break-in). Also known as break in.
breakdown voltage - Minimum reverse voltage applied to a diode or transistor to cause the component to conduct in the reverse direction.
breaking squelch - The action of un-muting the squelched audio while an incoming signal's strength exceeds the receiver squelch threshold. Also known as break squelch.
breaking station - Radio station that is attempting to join (break in) a conversation in progress.
bridge circuit - An electric circuit in which two circuit branches, typically in parallel with each other, are connected (bridged) by a third branch connected between the first two branches at some intermediate point along them, to measure a voltage null (zero volts), which confirms an impedance match between the two branches.
bridge rectifier - (See full-wave bridge)
British Broadcasting Corporation (BBC) - A public corporation for radio and television broadcasting in Britain.
broadband - A system or an antenna that can operate over a wide band of frequencies.
broadband butterfly terminated dipole (BBTD) - An adaptation of the terminated folded dipole antenna, with its elements formed into two equal and opposing triangles, lending itself to improved stealth and slightly greater antenna gain over that of a typical broadband terminated dipole antenna. broadband noise As it applies to radio (as opposed to audio), a type of radio frequency interference that exhibits unusually large bandwidth or that is experienced in many frequency ranges over an unusually large spectrum. Once also called radio frequency (RF) hash.
broadband over power lines - Provides Internet access over power lines.
broadband terminated dipole antenna (BBTD) - An adaptation of the terminated folded dipole antenna, with the added ability to deliver a signal effectively across a wide bandwidth, some reportedly across much of the high frequency (HF) spectrum broadcast.
Broadband-Hamnet (BBHM) - An amateur-radio-based datanetwork using commercial Wi-Fi gear with modified firmware. Also known as High Speed Multimedia (HSMM).
broadcast - (1) A type of one-way radio communication that is meant to be transmitted to the general public. Also known as broadcasting. (2) To transmit to the general public; making a one-way radio communication intended for the general public.
broadcast band (BCB) - An initialism for the amplitude modulation (AM) broadcast band running from 540 to 1700 kilohertz (kHz).
broadcast interference (BCI) - Broadcasts that involve violations of the Communications Act, and/or the Commission's rules, orders, and station authorizations.
broadcast listener (BCL) - (Archaic) A term used to refer to listeners in the early 1920s to distinguish them from amateurs. The term novice was also used at this time to refer to such a listener. Also broadcast listening.
broadcast radio interference (BCI) - The term refers to a time when sunspot activity is low during the nighttime causing heavy interference.
broadcasting - Transmissions intended to be received by the general public, either direct or relayed. Broadcasting is prohibited on the amateur radio bands, other than QSTs (general call preceding a message) that are of interest to all amateur radio stations.
broadside - The side of an object presenting the greatest amount of surface area, such as flat-facing sides of a dipole antenna, rather than its ends. Also known as broad side; broad-side.
buffer amplifier - An amplifier usually attached to an oscillator so as to reduce the drain on the oscillator output.
bug - (1) (CW term) A semi-automatic telegraph or code key that mechanically forms dots while sending Morse code (CW) but is no longer in common use. (2) (Archaic) When used alone, an early term for ham, as in radio bug.
bulb - (Archaic) (See vacuum tube)
bullet connector - (See SAE connector)
bulletin board system (BBS) - A combination of software and personal computer hardware that accepts packet messages for use by multiple users to receive messages at a later time by request.
bunny hunt - (See amateur radio direction finding)
bus - An electrical conductor for distributing power or to provide a common connection. (See ground bus and power bus)
business band - (See commercial)
business communications - Any transmission or communication the purpose of which is to facilitate the regular business or commercial affairs of any party. Business communications are prohibited in the amateur service.
Bustands - (Archaic) A contraction for the Bureau of Standards, the precursor of the the National Institute of Standards and Technology (NIST). Also known as Bustand.
busted call - Slang for an incorrectly logged call sign, usually during contesting.
busy lockout - A circuit that inhibits transmit on a frequency in use. Also known as busy channel lockout.
by name only - (See nominal)
BZ - The direction and strength of the interplanetary magnetic field vector component that is perpendicular to the ecliptic plane, with a southward orientation indicating an increased likelihood that incoming solar particles will cause disturbed radio conditions, such as interference. Also known as B sub Z.

To the top!   C

C battery - (Archaic) In early radio, batteries were the prime source of power. The A battery provided the filament voltage, the B battery furnished the B+ or the voltage to the plates of the vacuum tubes, and the C battery provided the grid-bias voltage to the tubes.
cable television (CATV) - A system of distributing television programs to subscribers by way of radio frequency (RF) signals transmitted through coaxial cables or light pulses through fiber-optic cables. (2) (Archaic) Originally called community television.
cable television interface (CATVI) - A device working directly with cable television (CATV) to provide digital video recorder functions.
Cabrillo - A text file format standard for logging ham radio contacts targeted for contesting submission or simple record-keeping.
cage-dipole antenna - A dipole antenna built for broader standing-wave ratio (SWR) bandwidth than a standard dipole antenna by using multiple wires spaced apart with circular spreaders to create a thick radiator.
California kilowatt - (Archaic) A power setting above the legal limit.
call - (1) Attempt to make contact. (2) Abbreviated form of the words call sign.
call district - One of the ten administrative areas of the United States established by the Federal Communications Commission (FCC).
call letters - (See call sign)
call name - (See call sign)
call sign - A sequence of letters and numbers that identify a person who has earned a specific amateur radio license and the country in which the license was granted. Also may be spelled out by using the North Atlantic Treaty Organization (NATO) phonetic alplhabet. Abbreviated as call. Also known as call letters; call name and historically as call signal.
call-sign area - A geographic area defined by the amateur radio organization overseeing the licensing of its stations, which in the United States is identified by a single numeral, 0 through 9, in the call sign of each of its licensees whose address is registered within that area. Also known as calling area; call sign region.
call-sign assignment - A primary call sign systematically assigned each amateur station by the Federal Communications Commission (FCC). The types of selection are sequential, vanity, and special event.
call-sign system - The method used to select a call sign for amateur station over-the-air identification purposes.
call signal - (See call sign)
callbook - A publication or compact disc (CD) read-only memory (ROM) that lists licensed amateur radio operators. Also known as call book.
callbook address (CBA) - A list of the names and call signs of licensed amateur radio operators.
calling frequency - A frequency on which amateur radio operators establish contact with one another before moving to a different frequency. It is usually used by hams with a common activity or interest.
candy store - Slang for a local amateur radio dealer.
cans - headphones. (1) (Archaic) A pair of earphones typically joined by a band placed over the head, for listening to audio signals such as voice or music. (2) A type of high-Q filter that exhibits high selectivity and stability, used mostly in repeater duplexers to prevent transmitting interference to, or receiving interference from, other nearby repeaters and noise sources, and are typically implemented as band-pass or notch type.
capacitance - The property of a device that defines its ability to store electric energy in an electric field to resist changes in the voltage across it, expressed in farads (F).
capicitance hat - A means of increasing the capacitance of that portion of the antenna above the loading coil, thus raising the current node, and radiation efficiency. Also known as roof capacitor.
capacitive coupling The effect of two or more conductors not connected to each other being close enough to allow an AC voltage present in one conductor to result in an AC voltage at the others, with respect to signal ground. Also known as AC coupling.
capacitive hat - A system of wires, or at very-high frequency (VHF) and above a solid metal disk, added to the top of a vertical antenna to reduce its inductance and increase its bandwidth. Also known as capacity hat.
capacitive reactance - The opposition to current that a capacitor creates in an alternating current (AC) circuit. Reactance is measured in Ohms. (See reactance)
capacitive time constant - (See time constant)
capacitive top-loading - (See top-loading antenna) Also known as capacitance loading.
capacitor. (1) A passive two-terminal electrical component usually formed by separating two conductive plates with an insulating material that stores energy in an electric field. Capacitors are made from a pair of conductive surfaces called electrodes that are separated by an insulator called the dielectric. Also known as cap. (2) (Archaic) (See condenser)
capacity hat - (See capicitive hat)
capture effect - The phenomenon of a receiver demodulating the stronger of multiple received FM signals and completely suppressing the weaker ones.
car-to-car - (See talk-around)
carbon microphone - A microphone element in which a diaphragm is pushed against a cup of carbon granules by acoustic pressure from speech. Also known as carbon mic.
Carolina Windom antenna - A type of Windom antenna that uses a portion of its feedline as a vertical radiating element, typically resulting in a lower angle of radiation than that of a plain Windom antenna.
card checker - A person who is authorized by the ARRL to verify that the contacts made by a United States ham toward an award (such as DXCC, WAS, or WAC) are authentic, according to the QSL cards collected by the candidate.
carrier - An unmodulated transmitted radio frequency (RF) signal. It is a pure continuous radio emission at a fixed frequency, without modulation, and without interruption. Several types of modulation can be applied to the carrier by which information is added.
carrier-operated relay (COR) - (Repeater term) Circuitry that causes a repeater to transmit in response to a received signal.
carrier - An unmodulated transmitted signal.
carrier delay - (1) Amount of time a repeater continues to transmit a carrier signal after the sending station has un-keyed, typically in number of seconds. Also known as hang time; drop-out delay. (2) The time period between the moment when the sending station has un-keyed and the repeater has terminated its transmission, during which the repeater might transmit a courtesy tone or linked system information.
carrier deviation - (See deviation)
carrier frequency - The center frequency of a radio signal.
carrier frequency offset - The distance between a mark frequency condition and a space frequency condition of the radioteletype (RTTY) or similar transmissions. The digital logic levels are +5 volts (a logical 1) or mark frequency and 0 volts (a logical 0) or space frequency. Also known as carrier shift.
carrier power - The average power supplied to an antenna when no modulation is taking place.
carrier shift - (See carrier frequency offset)
carrier squelch (CSQ) - Muting (squelch) of a receiver's audio (less often called noise squelch) when no carrier signal is being received at the selected frequency with at least the signal strength for which the squelch level is set. Also known as noise squelch.
carrier wave - (CW term) A waveform, usually sinusoidal, that is modulated or modified with an input signal for the purpose of conveying information. This carrier wave is usually a much higher frequency than the input signal. The purpose of the carrier is usually either to transmit the information through space as an electromagnetic wave, as in radio communication, or to allow several carriers at different frequencies to share a common physical transmission medium by frequency-division multiplexing, as, for example, a cable television system. The term is also used for an unmodulated emission in the absence of any modulating signal.
Castles on the Air (COTA) - An award program for ham radio enthusiasts who set up transmitting stations (activators) in, on, or nearby historical buildings (medieval castles and fortresses in particular) or contact those who do so (chasers), in conjunction with the World Castles Award (WCA) program, to help draw attention to these sites.
cathode - An electrode through which electric current flows out of a polarized electrical device. (See anode and electrode)
cathode-ray tube (CRT) - A high-vacuum tube in which cathode rays produce a luminous image on a fluorescent screen, used chiefly in televisions and computer terminals. Also known as cathode ray tube.
cat's whisker - (1) An adaptation of the fan dipole antenna, in which the active elements spread out radially from a central point, rather than parallel to each other. (2) A type of loop antenna, in which the looped elements are spread out by non-conductive spacing rods that resemble a cat's whiskers when viewed broadside. (3) A thin conductor of the anode side of a diode, especially that of a crystal detector in a crystal radio. Also known as cat whisker; cats whisker; cat's whiskers.
cavity filter - (Repeater term) A very narrow radio frequency (RF) filter used to pass one single frequency, common in repeater operations where the receiver must be protected from overload by a transmitter on the same band on the same antenna tower.
cell - An electrochemical cell is a combination of chemicals and electrodes that convert chemical energy into electrical energy. (See battery)
center-fed Zepp antenna - A common name for a balanced antenna in a dipole configuration and fed with low-loss open wire or window line to allow operation on multiple bands. Zepp stands for Zeppelin. (See Zepp antenna)
center frequency - The unmodulated carrier frequency of a frequency modulation (FM) transmitter.
center insulator - A non-conductive support component to which the two radiating elements and the feedline of a dipole anttenna are connected, but can be used for other antenna types as well. Also known as dipole center insulator.
center tap - (See tap)
center-fed Zepp antenna - (See double Zepp antenna)
center-loading coil - A loading coil at the center of an antenna to achieve a lower resonant frequency.
centi (c) - A prefix - one hundredth, or the metric prefix for 10-2, or divide by 100.
centimeter (cm) - The unit of length in the metric system equal to one hundredth of a meter (m), which is the International System of Units (SI) base unit of length.
central processing unit (CPU) - The hardware within a computer that carries out the instructions of a computer program by performing the basic arithmetical, logical, and input/output (I/O) operations of the system.
Certificate of Successful Completion of Examination (CSCE) - A document certifying that a person has successfully passed one or more of the amateur radio license examination elements. The term is used in the United States, is good for 365 days, and may be used as evidence of having passed an element at any other amateur license exam session.
certificated - Formerly type-accepted and type-acceptance, as it applies to a radio, that indicates Federal Communications Commission (FCC) Certification or Declaration of Conformity for meeting certain requirements to legally transmit outside the amateur bands (simply put, all radios, and some types of radio support equipment, such as antennas, must be type-accepted or certificated for an operator to use them to legally transmit outside the amateur bands).
certified - Formerly type-accepted and type-acceptance, as it applies to a radio, it indicates Federal Communications Commission (FCC) Certification or Declaration of Conformity for meeting certain requirements to legally transmit outside the amateur bands (simply put, all radios, and some types of radio support equipment, such as antennas, must be type-accepted or certificated for an operator to use them to legally transmit outside the amateur bands). Also known as certification; certified; type acceptance; type-accepted.
channel (ch) - (1) The communications channel connecting the source and drain of a field-effect transistor (FET) and through which current flows. (2) The fixed frequency sequence of memory positions where a frequency and related information is stored. Also known as channelized.
Channel Guard (CG) - General Electric's trademarked name for continuous tone coded squelch system (CTCSS). Radio Corporation of America (RCA) called it QC (Quiet Channel).
channel mode - (See memory mode)
channel spacing - The difference in frequency from one channel to the next.
characteristic impedance - The ratio of radio frequency (RF) voltage and current for a given power level in a transmission line.
characters per minute (cpm) - Morse code (CW) speed is measured in characters per minute (cpm) or words per minute (wpm).
charge - To store energy in a battery by reversing the chemical reaction in its cells.
charge controller - An electric device that controls or limits the rate of electric current through a battery, to prevent overcharging, and can protect against overvoltage, which can reduce battery performance and lifespan.
charge-coupled device (CCD) - An electronic device that uses a combination of analog and digital circuitry to sample, convert, and store a numerous array of electric charges into digital signals, often used as an image detector in a digital camera. Also known as charge coupled device.
charger - A device for storing energy in a battery.
Charlie - A North Atlantic Treaty Organization (NATO) phonetic alphabet code word representing the letter C. Used in radio communication, particularly when spelling out a call sign.
chassis - Typically a metallic enclosure or frame of an electrical instrument or other machine that forms the basic external shape (footprint) of the device, protects inside workings from unwanted intrusion, and shields the operator from potentially dangerous contact with internal components.
chassis ground - The common connection for all parts of a circuit that connect to the metal enclosure or chassis of the circuit. Chassis ground is usually connected to the negative terminal of the power supply.
Chebyshev filter - A type of low-pass filter that exhibits a very sharp cutoff (steep roll-off) and a ripple in its passband.
check - (1) The number of words or word equivalents in the text portion of a message. (2) The word count in the preamble of a formal traffic message. (3) The last two digits of the first year in which a operator was licensed, for logging contacts during some contests. (4) A test for communication quality, as in radio check, signal check, or audio check.
check in - To register one's station's presence on a net with a net control station. Also known as check-in; checking in.
check point - A person who is authorized by CQ Amateur Radio to verify that the contacts made by a ham toward an award are authentic. (See worked all zones (WAZ); seek you foreign country (CQ DX))
checksum - A method of detecting errors in digital data by including a calculated value with the data.
cheerleading - Slang for the practice of advertising, promoting, or broadcasting information about another ham radio station's frequency and location to aid other stations in making many contacts in a short period of time, which practice is generally prohibited during contesting. (See spotting; self-spotting)
chicken band - Slang for Citizen's Band.
chicken net - Slang for a net in which participants do little more than check in periodically (but is still useful for testing equipment, propagation, skill, etc.).
chief engineer (CE) - The person at a broadcasting station responsible for proper and legal operation of a station and maintenance of all required records.
chip - (See integrated circuit) Also known as chipset.
chirp - (CW term) A slight shift in transmitter frequency each time one keys a transmitter that results in a chirping sound. (See key clicks) Also known as CHIRP.
choke - An inductor that blocks higher-frequency alternating current in a circuit. Also known as filter choke.
choke balun - (See current balun)
choke filter - A type of low-pass filter that blocks radio frequency (RF) current.
chopper - (Archaic) (CW term) A rotary device used to modulate a Morse code (CW) signal to produce interrupted Morse code (ICW).
chordal hop - The radio wave propagation between two points by two or more successive refractions through the ionosphere before arriving at its destination, resulting in a signal that exhibits less loss than the same signal, had it traveled through the dense ground atmosphere twice.
circuit - A conductive path through which current can flow.
circuit breaker - (1) A protective component that opens or trips a circuit when an excessive current flow occurs. (2) A radio amateur operator who wants to join a contact that is already in progress.
circuit common - (See common)
circuit design - The process of circuit design can cover systems ranging from complex electronic systems all the way down to the individual transistors within an integrated circuit. For simple circuits, the design process can often be done by one person without needing a planned or structured design process, but for more complex designs, teams of designers following a systematic approach with intelligently guided computer simulation have become common.
circuit ground - (See signal ground)
circular polarization - an electromagnetic propagation mode in which the polarization, rather than being vertical or horizontal linear polarization, rotates as the wave moves from the source. (See elliptical polarization; horizontal polarization; vertical polarization)
circultor - A type of repeater duplexer that routes RF signals from the transmitter to the antenna, and from the antenna to the receiver, while preventing the signals from passing directly from transmitter to receiver, to reduce or eliminate intermodulation interference produced by another nearby transmitter.
Citizen's Band (CB) - A United States radio service having 40 assigned channels in the former amateur 11-meter (m) band (near 27 MHz). Available to United States citizens for personal or business use under strict power and antenna limitations over a few miles. Also known as Citizens Band Radio Service (CBRS).
Citizens Band Radio Service (CBRS) - (See Citizen's Band)
city power - (See household power)
Civil Air Patrol (CAP) - A volunteer affiliate of the United States Air Force. The CAP operates a national radio network of high frequency single sideband and very-high frequency radio repeaters.
clamp - (See limiter)
clarifier (CLAR) - A control on a transceiver to allow the receive frequency to be shifted from the transmit frequency by a small amount. On some radios it is called RIT. (See receiver incremental tuning)
class - An amateur radio license category or classification that defines the licensee's transmitting privileges, of which Technician, General, and Amateur Extra can currently be earned (but Advanced and Novice are still recognized. To prevent confusion, the term course more appropriately refers to a classroom experience, even online.
Class A amplifier - A linear amplifier that is characterized by low distortion, and therefore appropriate for amplifying phone signals, in spite of being relatively inefficient.
Class B amplifier - A type of amplifier that is much more efficient than a Class A amplifier because it operates on less than the full (greater than 180° and less than 360°) signal cycle.
Class C amplifier - A type of amplifier that is much more efficient than a Class A amplifier because it operates on less than the full (greater than 180° and less than 360°) signal cycle.
Class D amplifier - A non-linear amplifier that is characterized by high efficiency, and therefore appropriate for amplifying CW modulated signals, but not those of single-sideband.
Class X - (See X-class)
clear - (1) A term used to indicate that a radio station has finished transmitting. (2) The description of a frequency or channel that appears to be free of transmissions (available for use) at the moment.
climbing harness - (See fall arrest)
clip distortion (See clipping)
clipping - Overdriving an amplifier circuit, causing the signal to drop out on voice peaks. Also known as clip-distortion; flat topping; flat-topping.
clockwise (CW). A curve corresponding in direction to the movement of the hands of an analog clock.
cloning - Duplicating the memory contents of a radio into another radio.
closed circuit - An electrical circuit with an uninterrupted path for the current to flow. Turning a switch on, for example, closes or completes the circuit and allows current to flow. Also known as complete circuit.
closed repeater - (Repeater term) A repeater that restricts access to those who know a special code. (See open repeater)
closing - (1) When a station ends its operations and shuts down. (2) When a frequency can no longer support propagation to a desired station or location.
cloud warmer - (Archaic) An antenna that radiates most of the transmitted energy nearly straight up. (See near vertical incidence skywave) Also known as cloud-warmer; cloudwarmer.
clover - A phase shift keying (PSK) mode that allows full duplex communication. (See phase shift keying version 31)
club - (See Amateur Radio Club)
club station - In the United States, special call signs may be made available for clubs, and are frequently used at a club station established for use by the club's members.
club trustee - (See trustee)
clustering - (See spotting)
co-channel interference - Interference from stations on frequencies adjacent to the desired signal.
coax - (See coaxial cable)
coax switch - (See antenna switch)
coaxial cable - A type of transmission or feed line with one conductor inside the other used for radio and data transmission. Coaxial cable consists of a single center conductor surrounded by a dielectric, often polyethylene or foam polyethylene, but sometimes air. The dielectric is then enclosed by a tubular conductor which is then covered by a plastic jacket. Also known as coax.
coaxial capacitor - An electrical component (part of a class of capacitor called a feed-through capacitor) made of an uninterrupted wire or other conductor completely surrounded by a dielectric material, which is then completely wrapped in a cyclindrical metal sleeve, such that all three pieces share a common axis along the length of the wire; the wire at the center typically used to conduct direct current (DC) supply current in a circuit, while the sleeve is connected to ground, thus filtering out high-frequency noise (such as alternator noise) in the DC path. Also known as feed-through capacitor; feedthrough capacitor.
code - (See Morse code)
Code of Federal Regulations (CFR) - A code that covers the operating rules and regulations for the amateur radio service in the United States.
code-division multiple access - (See spread spectrum multiple access)
coded access - (Repeater term) A method of restricting access to a repeater station to amateur radio stations that begin their transmission with a special sequence of tones.
code practice oscillator (CPO) - (CW term) An oscillator used with a key and either headphones or a loudspeaker to practice sending and receiving Morse code (CW).
code plug - A binary file that contains transceiver configuration information, plus programming frequencies, offsets, tones, power levels, timeout values, and other settings for the proper operation of a particular radio model, and so-called because originally much of the settings (code) were hard-wired on a small device (plug) that you could insert into a compatible transceiver, to perform the configuration and programming.
coherent continuous wave (CCW) - (CW term) A Morse code (CW) technique that employs stable and precisely calibrated transmitters keyed at a known clock rate. This allows receivers to use extremely narrow band filtering that increases the signal-to-noise ratio (SNR) to a usable point, even if the sending rate is very slow.
coil - A conductor wound into a series of loops. (See inductor)
coil-choke balun - A multi-turn coil in a length of coaxial cable intended to provide an inductive reactance and thus reduce currents flowing on the outside of the shield. (See balun)
cold solder joint - A poorly soldered union of two or more electrical conductors, often resulting in an unsound connection or intermittent contact, and can have a grainy appearance. Also known as bad solder joint.
collector - (See transistor)
collinear antenna - Multiple antennas arranged such that their primary radiating elements are positioned along a common line, to form an antenna whose gain is greater than that of each section alone.
collision - A condition that exists when two or more packet radio stations simultaneously attempt to transmit on the same frequency.
color code - A system of numerical values that are assigned to various colors. Colored stripes are painted on the body of resistors and sometimes other components to show their values. Also known as color-code; colorcode.
Colpitts oscillator - An oscillator circuit in which the feedback is provided by a signal from a portion of the tuned circuit set by a voltage divider. Invented in 1918 and patented 1927 by American engineer Edwin H. Colpitts.
combiner - A device or circuit that brings together two or more radio frequency (RF) signals (often of differing frequencies within the same band) into one signal, to be transmitted through an antenna or forwarded to another circuit or stage for further processing (not to be confused with diplexer), often used as part of a repeater site. Also known as RF combiner; RF splitter.
commercial - A type of local two-way radio communication for use in corporate, industrial, or educational environments, such as construction sites, warehouse stores, mass transit vehicles, and school buses. Also known as business band.
Commission Registration System (CORES) - An agency-wide registration system for anyone filing applications with or making payments to the Federal Communications Commission (FCC).
common - The term for the shared reference for all voltages in a circuit. Also known as circuit common.
common mode - Currents that flow equally on all conductors of a multi-conductor cable, such as speaker wires or telephone cables. This type of connection is sometimes intentionally used for signaling on a balanced telephone line, but is generally undesired in amateur radio systems.
common-mode choke - (See radio-frequency choke)
common-mode current (CMC) - Electric behavior in a two-conductor cable or other transmission line such that the current in one conductor is not perfectly equal and opposite that of the other conductor, resulting in energy radiation produced by the difference in the currents, often the cause of feedline radiation. Also known as antenna current; common-mode signal; imbalance current; secondary-mode current.
communications - The means of connection between people or places. In particular, the means of sending or receiving information, such as by amateur radio, over telephone lines, or by computers.
communications emergency - A situation in which communication is required for immediate safety of human life or protection of property.
community television - (Archaic) The precursor to cable television. (See cable television)
compact disc (CD) - An optical disk used to store digital data.
companding - A modulation technique (named from compressing - expanding) that involves compressing an audio signal prior to transmission, then expanding (decompressing) it at the receiver to improve the signal-to-noise ratio of the signal. Also known as companded; compander.
comparator - (See voting repeater system)
complementary-symmetry metal-oxide semiconductor (CMOS) - A technology or a chip built using such technology for making low-power integrated circuits.
complete circuit - (See closed circuit)
complex number - The sum of a real number and the imaginary unit multiplied by another real number, as in a + jb, with a and b being real numbers and j being the imaginary unit.
compliance - Conformance by a radio station owner on behalf of transmitting equipment and its operations to the Federal Communications Commission (FCC) safety limits of maximum human exposure to radio frequency (RF) fields (determination of which is known as a compliance evaluation or exposure evaluation, and similar determination following equipment change known as re-evaluation). Also known as compliance evaluation; exposure evaluation.
component - An electrical device that has a specific quantity of an electrical property, such as resistance, or that has a specific electrical function.
component signal - One of the signals that makes up a composite signal. (See composite signal)
composite signal - A signal made up of several individual component signals.
compression - (See gain compression; speech compression)
Computer Aided Tranceiver (CAT) - A standard created by Yaesu (formerly Vertex) to provide a serial interface between a computer and a transceiver that supports the protocol, to control functions such as frequency, mode, filtering, and setting memory. computer interface version five (CI-V) - A device allowing multiple radio control simultaneously that was developed by Icom.
concrete-encased electrode - A type of grounding whose main conductor is embedded in concrete or passes through a layer of concrete, to form a better connection (lower impedance) to earth ground than might otherwise be achieved, in poorly conductive soil or soil located in a naturally dry climate. Formerly called Ufer ground.
condenser - (Archaic) An old term for a capacitor. (See capacitor)
condenser microphone - (See electret microphone)
conditions (CNDX) - The prevailing state of the weather, ground, sea, or atmosphere at a particular time. (See band conditions)
conductance - The real component of admittance, or quantity of allowance for current flow in a circuit, expressed in siemens (S) and is the reciprocal of resistance in a purely resistive circuit.
conductor - A material that has a loose grip on its electrons in response to an applied voltage so that an electrical current can pass through it.
Conference of Postal and Telecommunications Administrations (CEPT) - CEPT was established in 1959 by 19 countries of Europe, that expanded to 26 during its first ten years and issues amateur radio licenses. CEPT's activities include co-operation on commercial, operational, regulatory, and technical standardization issues.
connection - (Archaic) An early term for a circuit design. (See circuit design)
connected - The condition in which two packet-radio stations are sending information to each other. Each is acknowledging when the data has been received correctly.
Contact Volunteer Examiner (CVE) - The Volunteer Examiner (VE) in charge of other VEs in a particular amateur radio examination session; the main contact between the Volunteer Examiner Coordinator (VEC) and the group of local examiners.
contesting - A competitive activity pursued by amateur radio operators. In a contest, an amateur radio station, that may be operated by an individual or a team, seeks to contact as many other amateur radio stations as possible in a given period of time and exchange information. Rules for each competition define the amateur radio bands, the mode of communication that may be used, and the kind of information that must be exchanged. The contacts made during the contest contribute to a score by which stations are ranked. Contest sponsors publish the results in magazines and on web sites.
continuous four-level frequency modulation - (1) A continuous four-level frequency modulation. (2) A data transmission mode standard created by Yaesu using frequency-shift keying (FSK) at two bits per baud to create its four frequency states.
continuous wave (CW) - A continuous wave is an unmodulated, uninterrupted radio frequency (RF) wave. However in common usage the term refers to international Morse code (CW) emissions or messages that are an interrupted wave. The name was given to an early method of radio transmission, in which a carrier wave was switched on and off. Information was carried in the varying duration of the on and off periods of the signal, for example by Morse code in early radio. (See carrier)
continuous wave filter (CW filter) - (CW term) A device used to narrow passband to improve reception of Morse code (CW) in crowded band conditions.
continuous-tone-coded squelch system (CTCSS) - (Repeater term) A continuous sub-audible low frequency tone that is added to a transmitted carrier to access many repeaters. Receivers set to the same low frequency tone can decode the signal. (See private line)
control code - Information in the form of data or tones used to adjust a station under remote control.
control link - The means by which a control operator can make adjustments to a station under remote control.
control operator - An amateur radio operator responsible for the proper operation of a licensed radio station. The control operator has broad authority to take any action deemed necessary to insure that the station is being operated within Federal Communications Commission (FCC) regulations per the terms of the license.
control point - The locations at which the control operator function is performed.
controlled environment - Any area in which a radio frequency (RF) signal may cause radiation exposure to people who are aware of the radiated electric and magnetic fields and who can exercise some control over their exposure to these fields. The Federal Communications Commission (FCC) generally considers amateur radio operators and their families to be in a controlled RF exposure environment to determine the maximum permissible exposure levels. (See uncontrolled environment)
controller - (Repeater term) The control system within a repeater. It usually includes turning the repeater on and off, timing transmissions, sending the identification signal, controlling the auto patch, and continuous tone coded squelch system (CTCSS) encoder/decoder.
conventional current - (See current)
conversion - The number of intermediate frequency (IF) circuits in a receiver. (See superheterodyne)
coordinator - A non-governmental group that works to voluntarily assign frequencies to users in order to prevent interference, especially for repeater stations.
coordinated repeater station - An amateur repeater station for which the transmitting and receiving frequencies have been recommended by the recognized repeater coordinator.
Coordinated Universal Time (UTC) - (See Universal Time Coordinate) Successor to Greenwich Mean Time (GMT).
copy - (1) A term used as a question, as in "Did you understand all?" (2) A term used as a statement as in "I understood all." (3) An indication of how well communications are received, as in "I have a good copy on you."
copying - A term used to indicate one is monitoring as in "I was copying the mail," meaning "I was listening in on the conversation."
core - In an inductor, it is the material or space used in the center of an inductor coil, where the magnetic field is concentrated.
corner frequency - (See cutoff frequency)
corona ball - A round ball placed at the top of a whip antenna to minimize static discharge. Its use, purpose, and importance is often over-looked. Also known as solar coronal hole.
corona hole - Sunspot activity that may lead to enhanced VHF and 10-meter propagation.
coronal mass ejection (CME) - Massive burst of charged solar particles, which take 20 to 40 hours to reach earth after being discharged, disturbing high frequency (HF) and Global Positioning System (GPS) communication, and affecting other radio wave propagation.
coulomb (C) - The basic unit of electrical charge. A coulomb is 1 ampere second, or 6.25 x 1012 electrons, thus 1 ampere equals the flow of 1 coulomb of electrons per second.
counterclockwise (CCW) - In the opposite direction to the way in which the hands of an analog clock move. Also known as counter clockwise.
counterpoise - One or more wires in a network insulated from the ground to reduce loss resistances that might occur when a quarter-wave antenna is connected to poorly conducting earth. It acts as a condenser plate with high capacity to earth, with the result of lower loss in the antenna system. (See radials)
country code - A short alphabetic or numeric geographical code (geocodes) developed to represent a country and its dependent areas, for use in data processing and communications. (See grid square)
coupling - The physical association or connection between two systems, to transfer energy or information between them.
course - Refers to a classroom experience, even online.
courtesy beep - (See courtesy tone)
courtesy tone - (Repeater term) A tone or beep transmitted by a repeater to indicate that it is okay for the next station to begin transmitting. The courtesy tone is designed to allow a pause between transmissions on a repeater, so other stations can call. It also indicates that the time-out timer has been reset. Also known as courtesy beep.
covenants, conditions, and restrictions (CC&R) - An extensive set of rules drawn up by homeowner's associations and their lawyers that, among other things, typically restrict or completely prohibit a homeowner from having most forms of antennas on his or her property. Such regulations are formed and placed upon the property before the home is initially sold, and typically remains in effect for the life of the home. Also known as CC&Rs; CCRs.
coverage - (Repeater term) The geographic area for which the repeater provides communication.
CQ - seek you - A radiotelegraph code meaning "Calling any amateur radio station," the general call when requesting a conversation with anyone. The call may be sent in Morse code (CW), phone, or in some digital modes. The term also refers to the etiquette on high-frequency (HF) bands where you'll talk with anyone. It is, however, frowned upon on very-high frequency (VHF) and ultra-high frequency (UHF) where efficiency (minimum communication) is the goal.
CQ Amateur Radio Magazine - A quarterly magazine for active amateur radio operators that focuses on all aspects of very-high frequency (VHF) and ultra-high frequency (UHF) amateur radio.
CQ DX - seek you foreign country - A radio communications term used for "Calling any amateur radio station," the general call when requesting a conversation only with someone in a foreign country.
CQ VHF Magazine - A quarterly magazine that serves ham radio operators whose operational and technical interests lie above 50 megahertz (MHz). The magazine focuses on radio technology, products, and activities that exist on 6 meters, 2 meters, 440 megahertz (MHz) and above.
critical angle - The angle at which a radio signal is refracted in the ionosphere. Lower angles generally result in greater distance transmissions.
CQ Zone - Any one of 40 geographic areas of the world, as defined and named numerically by CQ Amateur Radio for the purpose of obtaining specific awards, such as Worked All Zones (WAZ).
craft - The hobby, service, skill, education, endeavor, design, building, and/or art of amateur radio participation, promotion, or activity.
critical frequency - The highest frequency at which a vertically incident radio wave will return from the ionosphere. Above the critical frequency, radio signals pass through the ionosphere instead of returning to Earth.
cross band - The process of transmitting on one band and receiving on another. For example, a repeater might receive a signal on 70 centimeters (cm) and retransmit it at 2 meters (m). Also known as cross-band; crossband.
cross modulation - The undesirable result from the modulation of one strong signal being transferred onto other signals being received, often resulting in hearing an unintended station in the background of the sound from the intended station. Also known as cross-modulation.
cross-band repeat (XBR) - A mode in many dual-band radios where a radio transmits on one band, an cross-band repeater transmits the received signal on another band, which is heard back by the radio on the other end. Also known as crossband repeat.
cross-band repeater (CBR) - (Repeater term) A repeater that receives incoming signals and re-transmits them on different bands.
crossed field antenna (CFA) - A controversial type of compact-sized antenna intended to exhibit the same efficiency as conventional antennas.
crosstalk - The typically undesirable presence of a signal in a circuit or radio medium, due to unintentional coupling between the receiver and the signal source. Also known as cross-talk.
crystal - A quartz or similar material that has been ground to produce natural vibrations of a specific frequency.
crystal (XTAL) - A piezoelectric device that tends to resonate at a frequency dependent on its material, dimensions, and temperature. (See piezoelectric)
crystal filter - A network of piezoelectric crystals used to obtain high rejection of unwanted signals. (See piezoelectric)
crystal ladder filter - An electronic filter that uses quartz crystals for its resonators, resulting in narrow bandwidth and steep skirts.
crystal oscillator - A device that uses a quartz crystal to keep the frequency of a transmitter constant.
crystal radio - A radio receiver that uses a quartz crystal or diode as a detector and is powered completely by radio waves that arrive at its antenna.
crystal-controlled transmitter - A type of transmitter that consists of a crystal oscillator followed by driver and power amplifier stages.
cubical-quad antenna - An antenna built with its elements in the shape of four-sided loops. In 1957 James Sherriff McCaig patented the cubical two-element multi-band quad antenna. Also known as quad antenna.
current - A flow of electrons in an electrical circuit. Also known as conventional current. (See ampere; electric current)
current balun - A transformer or choke designed to force the currents on the two leads of a transmission line to be equal and opposite. Also known as choke balun.
current location (QTH) - Your current location (often in latitude and longitude coordinates).
cut out - Slang for intermittent audio or signal continuity during transmission. Also known as cutting out.
cut numbers - A system of sending numbers by way of Morse code (CW) by substituting shorter letter characters for the longer number characters.
cutoff frequency - (1) The frequency at which energy through a system or circuit begins to be attenuated from one frequency to another by 3 decibles (dB) (output is -3 dB, or half the strength of the input signal). Also known as corner frequency. (2) The frequency below which a radio wave is unable to penetrate a layer of the ionosphere by reflection at an incidence angle required for radio frequency (RF) transmission between two given points.
cycle - One complete repetition of a repeating waveform, such as the sine wave.
cycles per second (CPS) - (Archaic) (See hertz)
cyclic redundancy check (CRC) - The code used in a digital communication protocol to detect an unintentional alteration of transmitted data by comparing a computed check of the received data with the check that was received in the transmission.

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D layer - The lowest region of the ionosphere. The D-layer contributes very little to short-wave radio propagation and acts mainly to absorb energy from radio waves as they pass through it. This absorption has a significant effect on signals below about 7.5 megahertz (MHz) during daylight. Also known as D region.
D-RATS - A free, easy to use, multi-platform software program for data communications with D-STAR devices or through the Internet.The software can be run onWindows, MacOS and Linux/UNIXcomputers.
damped oscillations - (Archaic) Radio frequency pulses such as those produced by a spark transmitter which typically are a series of short bursts of radio frequency energy that decay in amplitude with time. Also known as damped waves.
damped waves - (See damped oscillations)
dark side of the moon - Morse code (CB) slang for a location that is within the shadow of a repeater or other radio frequency (RF) signal source. Also known as black hole.
data - Computer-based communication modes, such as packet radio, that can be used to transmit and receive computer files or digital information. Short for digital communication mode. Also known as data emission; digital mode.
data communications - The transfer of data between two or more locations.
data loop antenna - A variation of the cubical quad with triangular elements.
data mode - A digital computer-to-computer communication, such as by packet radio or radioteletype (RTTY), in which information is exchanged as data characters or digital information.
datagram - A basic transfer unit associated with a packet-switched network in which the delivery, arrival time, and order of arrival are not guaranteed by the network service.
de-emphasis - A network to decrease the amplitude of higher audio frequencies with respect to that of lower frequencies. Also known as deemphasis.
dead air - A period of silence during a transmission by a mode (such as amplitude modulation (AM) or frequency modulation (FM) that sends a carrier signal, or moment between transmissions of a mode (such as single sideband (SSB) that does not.
dead carrier - Slang for transmission of an un-modulated carrier signal, which is simply a sine wave of a particular frequency, similar to dead air. Also known as open carrier, although an open carrier is often thought to be accidental while a dead carrier is typically a deliberate transmission, such as for testing, and deadkey by Citizen's Band (CB) operators).
dead end - (Archaic) The unused part of a tapped inductor beyond the tap in use. Letting unused turns float was a source of various problems in early radio frequency (RF) circuit design. (See tap)
dead full quieting (DFQ) - (Repeater term) A condition where there is no noise behind the signal.
dead key - Slang for transmission of an un-modulated carrier signal, which is simply a sine wave of a particular frequency, similar to dead air. Also known as open carrier, although an open carrier is often thought to be accidental while a dead carrier is typically a deliberate transmission, such as for testing, and deadkey by Citizen's Band (CB) operators).
dead zone - (See skip zone)
deca- (da-) - (See deka-)
decameter band - (See high frequency)
decameter wave - (See high frequency)
deci- (d-) - One tenth, or the metric prefix for 10-1, or divide by 10.
deceptive signals - Transmissions that are intended to mislead or confuse those who may receive the transmissions. For example, distress calls transmitted when there is no actual emergency are deceptive signals. Also known as false signals.
decibel (dB) - A unit used to measure the intensity of a sound or the power level of an electrical signal by comparing it with a given level on a logarithmic scale. One decibel (dB) equals 10log (power ratio) or 20log (voltage or current ratio). The term dB comes from a logarithmic unit of measurement, called a bel (B), that was invented by Bell Labs and named after Alexander Graham Bell. One bel is defined as a power ratio of ten, or ten times the power. Although the dB is defined with respect to power, it has become common practice to also use it to express voltage or current ratios, in which case it is defined as 20log.
decibels above a dipole antenna (dBd) - A unit of radio frequency (RF) power in decibels compared to a dipole antenna.
decibels above an isotropic antenna (dBi) - A unit of radio frequency (RF) power in decibels compared to an isotropic antenna.
decibels of the measured power (dBm) - A decibel measure, 1 mW with a load impedance of 600 Ohms (0dBm equals 1 mW). It is used for low-power transmissions.
decibels microvolt (dBμV) - A decibel measure relative to 1 microvolt (μV).
decibels optical gain (dBo) - A decibel measure relative to light transmission and is an unofficial term used by some amateurs working with transmission of data using light.
decibels to a carrier (dBc) - In terms of radio frequency (RF) signals, dBc is the power ratio of a signal to a carrier signal, expressed in decibels.
decimation - The process of reducing the effective sample rate of a signal by removing samples; for example, interpolate a digital signal by three, then decimate it by four, to adjust its sampling rate by a factor of 3/4.
decimator - A device or circuit that uses an anti-aliasing filter to perform the digital signal processing function of decimation; that is, reduces the sampling rate of a signal. Also known as digital decimator.
decoding - The process of returning the signal to its original form. (See encoding)
decrement - (Archaic) A parameter of a spark- or damped-wave transmitter that denotes how rapidly the amplitude of the radio frequency (RF) wave decreases. If damping is too quick, you get a series of very short pulses that are very broad.
decryption - The process of reversing the enconding process. (See encryption)
degree - A measure of angle or phase. There are 360 degrees in a circle or cycle. (See cycle)
deka- (da-) - One ten, or the metric prefix for 10, or times 10. Also known as deca-.
delay - The time a scanner radio pauses on a channel to await another transmission.
Delta - A North Atlantic Treaty Organization (NATO) phonetic alphabet code word representing the letter D. Used in radio communication, particularly when spelling out a call sign.
delta loop antenna - Variation of the quad antenna, but with three sides per element, each side (leg) being 1/3-wavelength long for a symmetrical delta loop.
delta match - An impedance matching technique that matches a higher-impedance transmission line with a lower-impedance antenna by connecting the feedline to the driven element in two places spaced a fraction of the intended wavelength each side of the element center. Also known as delta matching system; delta matching network.
demodulate - To recover information from a modulated signal by reversing the process of modulation. (See modulate) Also known as demodulation.
deprecated - Not supported or diminished in value.
desensitization - The reduction of receiver sensitivity due to overload from a nearby transmitter. Also known as desense; desensing; de-sense.
desense - (See desensitization)
designator - Letters or numbers used to identify a specific electronic component.
destinate - Citizen's Band (CB) slang for having arrived at a particular location. Also known as destinated.
detect - (1) To determine the presence of a signal. (2) To recover the information directly from a modulated signal.
detector - The stage in a receiver in which the modulation, voice, or other information is recovered from a modulated radio frequency (RF) signal.
detune - The opposite of tune, or action of deviating from a tuned state, also known as a mis-match.
deviation - The change in frequency of a frequency modulation (FM) carrier because of a modulating signal. Also called carrier deviation; frequency deviation.
deviation ratio - The ratio between the maximum change in radio frequency (RF) carrier frequency and the highest modulating frequency used in a frequency modulation (FM) transmitter. (See modulation index)
dielectric - (1) The insulating material in which a capacitor stores electrical energy. (2) A non-conductive material used to separate the center conductor and shield (conductor) in coaxial cable that is typically made of foam or plastic and that can be polarized by an applied electric field.
differential phase shift keying (DPSK) - A form of binary phase shift keying (BPSK) where only data transitions are transmitted.
differential-mode circuit - The circuit formed by two conductors in which the current leaves on one and returns on the other, the typical desired circuit. Also known as differential-mode signal.
diffract - To alter the direction of a radio wave as it passes by edges of or through openings in obstructions, such as buildings or hills.
digipeater - (Repeater term) A type of repeater station that retransmits or forwards digital messages. Short for digital repeater.
digital audio broadcasting (DAB) - A standard for digital broadcast radio using Orthogonal Frequency Division Multiplexing (OFDM) between 174 to 240 MHz and 1452 to 1492 MHz, adopted primarily by countries in Europe and Asia Pacific.
digital communication - A computer-based communication mode; communication by transmission and reception of digitized information, called digital radio when using radio waves as the medium and formatted in an amateur radio mode. (See data)
digital data - Discrete, discontinuous binary digits. In comparison, analog data consists of continuous waves that vary or fluctuate infinitely within a range.
digital decimator - (See decimator)
digital filter - (See filter)
digital mode - (See data)
digital mobile radio (DMR) - An open radio standard for time-division multiplexing two digital voice signals on a 12.5 kHz repeater channel, originally used by Professional Mobile Radio, but widely adopted by many amateur radio manufacturers for phone, packet, and trunking applications.
digital multimeter (DMM) - A multimeter that displays its readings digitally (that is, with decimal digits).
digital mobile radio (DMR) - A technique for time-multiplexing two digital voice signals on a single 125 KHz repeater channel.
digital mode - (See data mode)
digital multimeter (DMM) - (See multimeter)
digital radio - Communication by transmission and reception of digitized information over radio waves using an amateur radio mode.
digital radio mondiale (DRM) - High-definition digital transmission system used by commercial shortwave broadcast stations.
digital repeater - (See packet radio repeater.
digital signal - (1) A signal, usually electrical, that can only have certain specific amplitude values, or steps, such as 0 and 1 or ON and OFF. (2) On the air, a digital signal is the same as a data mode signal. (See data mode)
digital signal processor (DSP) - Used to convert an analog signal to digital form and using a microprocessor to process the signal in some way, such as filtering or reducing noise. The mathematical manipulation of an information signal to modify or improve it in some way, it is characterized by the representation of discrete time, discrete frequency, or other discrete domain signals by a sequence of numbers or symbols and the processing of these signals. It is used to improve the signal-to-noise ratio for cleaner and more legible communications.
digital signal processing (DSP) - The numerical manipulation of a radio signal to prepare it for transmission or to filter the noise from it.
digital signal processor (DSP) - The specialized microprocessor that filters noise from a radio signal by converting the signal from analog to digital and using digital signal processing methods.
Digital Smart Technologies for Amateur Radio (D-STAR) - An open protocol digital voice and data protocol specification for amateur radio. The system was developed in the late 1990s by the Japan Amateur Radio League and uses minimum-shift keying in its packet-based standard.
digital synthesizer - (See direct digital synthesizer)
digital tone coded squelch (DTCS) - (See digital-coded squelch)
digital voltmeter (DVM) - (See multimeter)
digital-coded squelch (DCS) - A selective calling system, it is a digital form of continuous tone coded squelch system (CTCSS). Instead of sending a continuous audio tone however, it transmits a low level digital signal. Also known as Digital Private Line (DPL), A Motorola trademark..
digital-message device - See electronic-message unit.
digital-to-analog converter (DAC) - A device that converts digital signals into analog signals. Also known as D/A; D-to-A.
diode - An electronic component that allows electric current to flow in only one direction. Also known as silicone diode.
dip meter - A device used to determine the resonant frequency of an electronic circuit. Also known as grid-dip meter.
diplex - Circuitry that can process two signals without combining them. (See half-wave dipole)
diplexer A frequency splitting and isolation device, typically used to couple two transceivers to a single or dual-band antenna, thus allowing one to receive on one transceiver and transmit on the other transceiver. A typical application is to put 2 meter (m) and 440 megahertz (MHz) transceivers into a dual band antenna for satellite work. Thus, it allows a dual-band radio to use a single dual-band antenna.
diode - The electronic semiconductor component (often employed as a rectifier) that allows current to flow in only one direction through it (the ordinary semiconductor diode type also known as a silicon diode and junction diode), and whose two electrodes are called the anode and the cathode, the cathode end being identified with a stripe; other types of diodes include the Zener diode, the Schottky diode, the tunnel diode, the varactor diode, and the PIN diode.
dip - (See dual in-line package)
dip meter - An instrument that measures the resonant frequency of a radio frequency (RF) circuit. Also known as grid dip meter; grid dip oscillator.
diplexer - A device that allows a single dual-band transceiver to operate on two different antennas that support different bands, or two transceivers of different bands to operate on a single dual-band antenna, or two transceivers of different bands to operate two different antennas using the same feedline (not to be confused with splitter or combiner, both of which normally function on the same band or set of frequencies, or duplexer).
dipole antenna - A simple common type of wire antenna, usually center fed with coaxial cable. (See half-wave dipole)
dipole center insulator - (See center insulator)
direct conversion - A type of receiver that recovers the modulating signal directly form the modulated radio frequency (RF) signal.
direct current (DC) - An electric current flowing in one direction only in a wire. Sometimes written as dc.
direct current ground (DC ground) - A connection point directly to a chassis or battery ground to prevent build-up of hazardous DC voltage.
direct current resistance (DC resistance) - (See resistance)
direct current voltage (DC voltage) - A voltage with a constant polarity.
direct detection - A device acting as an unintentional receiver by converting a strong radio frequency (RF) signal directly to voltages and currents internally, usually resulting in RF interference to the receiving data.
direct digital synthesizer (DDS; DDFS) - An electronic circuit or device used for synthesizing an arbitrary waveform (method known as direct digital synthesis) from a single, fixed-frequency reference clock, and whose lookup tables contain amplitude values that represent an output waveform, such as a sine wave. Also known as direct digital frequency synthesizer.
direct FSK - A type of frequency-shift keying (FSK) modulation in which the digital signal is applied to the transmitter variable-frequency oscillator (VFO) for a typically frequency modulation (FM) signal.
direct path - The route that a transmitting antenna's signal takes directly to a receiving antenna without interference. (See reflected path)
direct radio - (See talk-around)
direct sampling - A method of digital signal processing that involves placing an analog-to-digital converter as close as possible to the incoming signal, reducing or eliminating the need for signal down-conversion, essentially replacing the receiver superheterodyne circuitry, the term direct indicating an attempt to digitize the incoming analog signal directly (without modification) before presenting the signal for further processing (filtering, mixing, demodulation, etc.).
direct-sequence spread-spectrum (DSSS) - The technique of spread-spectrum communication that uses a high-speed binary bit stream to shift the phase of the transmitted signal carrier frequency. Also known as direct sequence spread-spectrum.
direct wave - A radio signal propagated by way of line of sight.
directed net - A net that is under the direction of a net control station, meaning that all communication during the net is directed to and regulated by Net Control unless otherwise requested.
direction finding (DF) - (See amateur radio direction finding)
directional antenna - An antenna that radiates greater power in one or more directions allowing for increased performance on transmit and receive and reduced interference from unwanted sources.
directional wattmeter - (See wattmeter)
directionality - Slang for (or layman version of) directivity, as it relates to an antenna.
directivity - A measure of how much of the energy from an antenna is radiated in a particular direction.
director - A parasitic element on a Yagi antenna and some other antennas in front of the driven element that focuses the radiated signal in the forward direction. (See Yagi)
discharge - To extract energy from a battery or cell.
discone antenna - A type of omnidirectional antenna (version of biconical antenna) that consists of a disc on top and downwardly open cone underneath, both made from sheet metal or sets of rods, but separated from each other by an insulator.
discriminator - (See frequency discriminator)
dish antenna - A highly directional antenna, parabolic in shape, often used at microwave frequencies, that uses reflections to focus radio frequency (RF) signals.
dissipator - (See lightning dissipator) Also known as dissipater.
distant station (DX) - (1) On high-frequency (HF) radio, it is normally used to refer to a station on another continent or in an exotic location. (2) To contact a distant station. (3) (Archaic) Distant Station Century Club (DXCC) - An American Radio Relay League (ARRL) award for verified contacts with 100 countries or more.
distant station expedition (DXpedition) - Radio expedition to remote, unusual, and rare locations.
distant station operator (DXer) - An amateur radio operator who actively pursues contacting distant and rare amateur radio stations. The term is also applied to short wave listeners.
distortion - An undesirable modification of an audio or radio frequency signal, which can result in spurious emissions.
distress call - A transmission that signals a life-threatening situation. Most commonly referred to as an SOS or mayday call. (See SOS and mayday)
distress frequency - A frequency or channel specified for use in distress calling. The radiotelephone distress frequencies are 2.182 megahertz (MHz) and 156.8 megahertz (MHz). The survival craft and maritime distress frequency is 243 megahertz. The general aviation distress frequency is 121.5 megahertz.
District - (Archaic) An American Radio Relay League (ARRL) organizational unit in the 1920s just below the division level and administered by a District Supervisor.
District Emergency Coordinator (DEC) - An appointee of the American Radio Relay League (ARRL) who supervises the efforts of local Emergency Coordinators in a defined district.
dither - A small amount of noise added to the input signal to allow more precise representation of the signal over time.
diversity reception - (See voting repeater system) Also known as diversity operation; diversity combining.
dogbone insulator - The non-conductive component that physically connects two or more items that should not be connected electrically, such as radiating elements, guy wires, and structural braces, typically part of an antenna system. Also known as dog bone insulator; dog-bone insulator.
do-it-yourself (DIY) - A term that refers to building your own ham radio gear, especially antennas. Also known as homebrew.
DominoEX - A digital mode that uses a variant of multi-frequency-shift keying (MFSK) known as incremental frequency keying (IFK) for transmission of information. It works by sending short transmissions of 18 different tones, called symbols, one at a time, each carrying four bits of data. DominoEX is twice as fast as phase shift keying version 31 (PSK31), as well as more sensitive. It was designed by Murray Greenman ZL1BPU and means Domino from scratch. (See frequency-shift keying)
dope - To add an impurity to a semiconductor to produce a desired electrical characteristic. An N-type material is created if adding the impurity results in more electrons being available to flow as current. A P-type material results of fewer electrons are available.
Doppler shift - The change in frequency of a wave, or other periodic event, for an observer moving relative to its source or a source moving relative to an observer. It was named for the Austrian physicist Christian Doppler, who proposed it in 1842 in Prague. Also known as Doppler effect.
double - (1) The unintentional or deliberate interference of one ham radio operator with another, by transmitting at the same frequency simultaneously, usually resulting in both parties sounding mostly unintelligible (note that this term applies more to frequency modulation (FM) transmissions on 2-meter and 70-cm bands than to SSB transmissions on HF bands, in which case the result is usually more of a pileup). (2) The action of transmitting at the same time as another operator on the same frequency.
double extended Zepp antenna - (See extended double Zepp antenna)
double sideband (DSB) - In conventional amplitude modulation (AM) transmission, the carrier and both sidebands are present. Also known as double-sideband.
double Zepp antenna - A center-fed dipole antenna of two half-wave horizontal elements that attach to the feedline through a quarter-wave vertical radiating element and often constructed from ladder line, making the appearance of two back-to-back Zepp antennas. Also known as center fed Zepp antenna; centerfed Zepp antenna.
double-bazooka - An extremely broad-banded half-wave antenna that can operate efficiently across an entire amateur radio band with little change to the standing-wave ratio (SWR). The design eliminates the need for antenna matching baluns and can be fed directly with 50 Ohm coaxial cable.
double-extended Zepp antenna - A 1-1/4 wavelength long dipole. It provides about 3 decibels (dB) gain over a half wavelength dipole by narrowing the main beam perpendicular to the dipole wires. Zepp stands for Zeppelin. (See Zepp antenna)
double-pole, double-throw (DPDT) - A switch that has six contacts. The DPDT switch has two center contacts which can be connected to one of two other contacts. (See switch)
double-pole, single-throw (DPST) - A switch that connects two contacts to another set of contacts. A DPST switch turns two circuits on or off at the same time. (See switch)
double-sideband amplitude modulation (DSB-AM) - In some forms of amplitude modulation (AM), the carrier may be removed, producing double sideband with suppressed carrier (DSB-SC). An example is the stereophonic difference (L-R) information transmitted in stereo frequency modulation (FM) broadcasting on a 38 kilohertz (kHz) subcarrier.
double-sideband, suppressed-carrier (DSB-SC; DSBSC) - A Form of amplitude modulation in which both sidebands are present, but the carrier signal has been suppressed.
doublet antenna - (1) A center-fed dipole antenna of two half-wave horizontal elements that attach to the feedline through a vertical ladder line. Note: the doublet antenna seems to be identical to the double Zepp antenna, except in the doublet the quarter-wave vertical section is allegedly not supposed to radiate. (2) A classification of antenna, whose radiating elements are a pair of conductors that form an open DC circuit, of which the dipole is an example.
doubling - (Repeater term) On a repeater, if two stations transmit simultaneously, the signals mix in the repeater's receiver and results in a raspy signal. Frequency modulation (FM) has a characteristic whereby the stronger signal captures and overrides the weaker one.
down in the mud - (See mud)
down-conversion - (1) The process of modifying a signal by changing it to a lower frequency, allowing for convenient signal manipulation by analog circuitry, one step in the superheterodyne process, and integral to frequency-division multiplexing. (2) The process of modifying a signal by changing it to a lower frequency band, thereby extending the frequency spectrum available to a transceiver. Also known as down conversion; downconversion.
down-converter - A device to take higher frequencies, and lower them to appear at a lower frequency, for reception. Also known as down converter; downconverter.
downlink - Transmitted signals or the range of frequencies that a repeater or satellite transmits to a user. It is the opposite of uplink. (See satellite downlink; uplink) Also known as down link; down-link.
drain - (See transistor)
drift - Slow, gradual change in the frequency of a transmitter or receiver.
drive - (1) The quantity of power applied to the input of an amplifier, and known as overdrive if the quantity exceeds the amplifier's specification or capability. (2) The quantity of signal strength (typically power, also known as minimum drive, or voltage) applied to a circuit sufficient to enable its primary function, such as amplification, filtering, or switching. Also known as overdrive; over-drive.
driven element - The part of an antenna that connects directly to the feed line. Also known as active element. (See Yagi)
driver - The amplifier stage immediately preceding a power amplifier in a transmitter.
drop out - Slang for abrupt termination of audio or signal transmission. Also known as drop off; dropping out; dropoff; dropout.
drop-out delay - (See carrier delay)
dropout timer - (See timeout timer)
dropping out - (Repeater term) A repeater requires a minimum signal in order to transmit so when a signal does not have enough strength to keep the repeater transmitting, it drops out.
dry contacts - A switch or relay whose contacts are isolated from both power and ground.
dual bander - The term can be applied to either an antenna or transceiver, usually a combination of 2 meters (m) and 70 centimeters (cm).
dual in-line package - A type of through-hole electronic component package for integrated circuits made with two parallel rows of connecting pins on opposite sides of the package.
dual-band antenna - An antenna designed for use on two different amateur radio bands.
dual-tone multi-frequency (DTMF) - Used to transmit/receive numeric information such as a touch-tone phone number, a PIN, and remote radio control commands.
dual-watch - A receiver feature that allows the listener to monitor two different frequencies simultaneously. Also known as dual watch; dualwatch.
duck - (See rubber duck antenna)
ducting - (See tropospheric ducting)
dummy antenna- A station accessory that allows testing or adjusting transmitting equipment without sending a signal out over the air. It is a device that allows a dual-band radio to use a single dual-band antenna. A non-radiating 50 Ohm load connected to a transmitter replaces an antenna for testing purposes. Also known as dummy load; phantom antenna.
dummy load - (See dummy antenna)
dupe - A duplicate contact, such as happens in radio contesting.
duplex - (1) (Repeater term) A mode of operation in which the transmit and receive frequencies are different. (2) A mode of communication in which a user transmits on one frequency and receives on another frequency simultaneously. This is in contrast to half-duplex transmission in which the user transmits at one time and receives at another time. Also known as full duplex. (See half-duplex; simplex)
duplexer - (Repeater term) A device that allows the transmitter and receiver to share a single antenna.
duty cycle - A measure as a percent of the amount of time a transmitter is operating at full output power during a single transmission. A lower duty cycle means less radio frequency (RF) radiation exposure for the same peak envelope power (PEP) output. (See duty factor) Also known as duty factor.
duty factor - A measure as a fraction of the amount of time a transmitter is operating at full output power during a single transmission. A lower duty factor means less radio frequency (RF) radiation exposure for the same peak envelope power (PEP) output. (See duty cycle)
DX - Distant, foreign countries.
DX Century Club (DXCC) - A sponsored club of the American Radio Relay League (ARRL) by which membership is allowed only after showing proof of having made distant station (DX) contact with at least 100 different countries.
DX window - A sub-band specified by a voluntary band plan that is reserved for distant station operation (DXing), and should not be used for contacts between stations within the forty-eight contiguous United States.
DXCC Entity - The location of an amateur station officially recognized by the American Radio Relay League (ARRL) with whom another station in a different entity can make a verifiable distant station (DX) contact for contesting and other ham radio purposes. Also known as DXCC Zone; DXCC Country; DSCC List; DSCC Prefix.
DXing - The hobby of making DX contacts with distant radio stations, particularly those located outside one's own country. Also known as chasing DX; DX-ing; DX'ing.
DXpedition - Slang for a ham radio operator (also called a DX chaser) who makes distant station (DX) contacts with distant radio stations (DXing), on a regular basis as a hobby. Also known as DX-pedition; DX'pedition.
dynamic host configuration protocol (DCHP) - A protocol by which a machine can obtain an Internet Protocol (IP) number and other network configuration information from a server on a local network.
dynamic microphone - A microphone element in which the diaphragm is tied to a coil of wire surrounding a permanent magnet. Also abbreviated dynamic mic.
dynamic range - The ratio of the strongest to the weakest signal that a system can respond to within a specified level of distortion.
dyne (dyn) - A unit of force that, acting on a mass of one gram, increases its velocity by one centimeter (cm) per second every second along the direction that it acts. (See newton)

To the top!   E

E-layer - The region of the ionosphere found approximately 55 to 90 miles above Earth, the second lowest ionospheric layer. This region fades away a few hours after sunset. The main impact of the E-layer on radio propagation is to absorb energy from signals passing through it. Although sporadic, E propagation makes possible distant communication on frequencies above 30 megahertz (MHz). Also known as E region.
e-mail - (See email)
E-plane - A flat geometric surface defined by the electric wave component of an electromagnetic wave in a particular direction, also known as the vertical plane or elevation plane of a vertically polarized antenna, or the horizontal plane or azimuthal plane of a horizontally polarized antenna. Also known as E plane.
E-skip - Sporadic E-layer ionospheric propagation.
earphones - (See headphones)
early-out - Slang for announcement or request to check into a net then leave prior to its conclusion, to alert the net control station that the operator should not be called upon at a later time in the net. Also known as early; in-and-out; out after roll; out after roll-call; out after roll call; short-time; short time.
earth ground - (See ground)
earth grounding system - A set of usually buried conductors often arranged radially and in combination with metal ground rods driven into the soil. Designed to provide a low-resistance ground connection for systems or equipment. (See ground)
earth station - An amateur radio station located on, or within 50 km of, the Earth's surface and intended for communication with space stations or with other Earth stations by means of one or more other objects in space.
earth-moon-earth (EME) - A method of communicating with other stations by reflecting radio signals off the Moon's surface. Also known as moonbounce.
Echo - A North Atlantic Treaty Organization (NATO) phonetic alphabet code word representing the letter E. Used in radio communication, particularly when spelling out a call sign.
EchoLink - A softward program that uses a network protocol called voice over Internet Protocol (VoIP) that allows worldwide connections to be made between stations, from computer to station, or from computer to computer. There are more than 100,000 registered users in more than 125 countries worldwide.
Edison effect - (Archaic) Thomas A. Edison discovered the electron flow from a glowing cathode to an anode in an evacuated glass bulb that was called the Edison-effect. This led to the development of the vacuum tube.
effective isotropic radiated power (EIRP) - The quantity of power required to transmit a signal in all directions equally, from a theoretical spherically radiating source (total power radiated from an isotropic source, as observed by a distant receiver, making EIRP = ERP × 1.64, or EIRP is ERP + 2.15 dB).
effective radiated power (ERP) - Station output, including the transmitter, antenna, and everything in between, when considering transmitter power and system gains and losses.
efficiency (η) - The measure of a system output compared with its input, expressed as a ratio or percentage; as it relates to electric power, it is defined as the useful power output divided by the total power input to a circuit or device; for example, the efficiency of a radio frequency (RF) power amplifier can be calculated by dividing the RF output power by the direct current (DC) input power/ egress - The leakage of radio-frequency interference (RFI) and audio-frequency interference (AFI) out of the vehicle's various electrical circuits into some other electrical circuit where it is unwanted.
egg insulator - The non-conductive component that physically connects two or more items that should not be connected electrically, such as radiating elements, guy wires, and structural braces, but provides for the connection in such a way that, should the insulator become damaged or be destroyed, the conductors will maintain their structural connection after their electrical separation is compromised; typically part of an antenna system. (See dogbone insulator)
EH antenna - Specially designed crossed field antenna that produces electric (E) waves and magnetic (H) waves that travel both in phase and perpendicular to each other, to improve efficiency, thereby allowing for a smaller construction while maintaining the performance of conventional antennas.
electret - A stable dielectric material that produces an electrostatic field originating from a permanently embedded static electric charge (unlike a magnet, which produces a magnetic field).
electret microphone - A type of electrostatic capacitor-based microphone (sometimes called an electret condenser microphone as a result), that eliminates the need for a polarizing power supply by using permanently charged electret material.
electret condenser microphone - (See electret microphone)
electric field - An electric field exists in a region of space if an electrically charged object placed in the region is subjected to an electrical force; it is an invisible force of nature.
electrical current A flow of electric charge. Electric charge flows when there is voltage present across a conductor. It is the opposite of current, or conventional current. (See current)
electric shock - The physiological reaction or injury caused by current flowing through body tissue, and can range in severity from a barely perceptible tingling sensation to electrocution. Also known as shock.
electrical grid - An interconnected network (often shortened the grid) of transmission lines that deliver AC electrical power from multiple sources to the many consumers that require it, and is the primary source of commercially available household power to homes, businesses, and facilities. Also known as line voltage.
electrical service - The distribution box and meter, typically located outside a building, for providing household power from the power company or electrical grid to the building or facility.
electrically erasable programmable read-only memory (EEPROM) - A type of non-volatile memory used in computers and other electronic devices to store small amounts of data that must be saved when power is removed, for example, calibration tables or device configuration.
electrically programmable read-only memory (EPROM) - A type of non-volatile memory chip that retains its data when its power supply is switched off.
electrode - (1) An electrical conductor used to make contact with a nonmetallic part of a circuit, such as a semiconductor, an electrolyte, or a vacuum. (See anode and cathode) (2) An electrical contact or connection point.
electrolysis - An electrochemical process in which a current passed through a solution between electrodes of different metals results in the transfer of molecules of one material into the solution and then often to the other electrode. This is the process by which electroplating is performed. It also can happen if two dissimilar metals are in contact in the presence of water.
electrolytic capacitor - A high-capacitance capacitor used in power supply filters and other applications. Unlike many capacitors, the positive terminal is marked and must be connected to the positive terminal. (See electrolyte)
electromagnetic compatibility - The ability of an eletrical device or system to function acceptably in its electromagnetic environment, by limiting unintentional rafio frequency (RF) generation, propagation, and reception of electromagnetic energy.
electromagnetic interference - Interference sometimes caused by battery chargers and inverters.
electromagnetic force (EMF) - The fundamental force that is associated with electric and magnetic fields and is responsible for atomic structure, chemical reactions, the attractive and repulsive forces associated with electrical charge and magnetism, and all other electromagnetic phenomena. It is carried by the photon.
electromagnetic interference (EMI) - A disturbance that affects an electrical circuit due to either electromagnetic induction or electromagnetic radiation emitted from an external source. Also known as radio-frequency interference (RFI).
electromagnetic pulse (EMP) - An extremely high-energy magnetic field, such as the current flow caused by a lightning strike or nuclear explosion.
electromagnetic radiation - The propogation of radiant energy, including infrared, visible light, ultraviolet, radio frequency, gamma and X-rays, through space and matter.
electromagnetic spectrum - A graphic representation of a range of frequencies from 60 hertz (Hz) electrical current, through radio waves, visible light, ultra violet light, X-rays, and Gamma rays.
electromagnetic wave - The electric field and magnetic field moving through space or a transmission line.
electrolyte - A liquid or semi-liquid paste material used in high-capacitance capacitors.
electromagnetic compatibility (EMC) - The ability of an eletrical device or system to function acceptably in its electromagnetic environment, by limiting unintentional RF generation, propagation, and reception of electromagnetic energy.
electromagnetic interference sleeves (EMI sleeves) - Ferrite beads or tubes slipped over wires to insert inductance with the intent of attenuating unwanted high-frequency signals. They are usually enclosed in a snap-on plastic cover so they can be easily placed over existing wiring without the need to splice into the wiring and act like chokes. When properly applied, reduce or eliminate radio-frequency interference (RFI) ingress and egress. Also called split beads.
electromotive force (EMF) - The energy per unit of charge, measured in volts, that pushes a current through a circuit.
electron - A negatively-charged particle, normally found in an area surrounding the nucleus of an atom. Moving electrons make up an electrical current.
electron tube - (Archaic) (See vacuum tube)
Electronic Code of Federal Regulations (e-FCR) - A regularly updated, editorial compilation of Code of Federal Regulations (CFR) material and Federal Register amendments produced by the National Archives and Records Administration's Office of the Federal Register (OFR) and the Government Printing Office (GPO).
Electronic Components Industry Association (ECIA) - The organization that manages the maintenance of all existing interconnect, passive, and electro-mechanical (IP&E) standards for the Electronic Industries Association (EIA) as of February 2011.
electronic current - In electronic circuits, the reference current directions are often chosen so that all currents are toward ground. This often matches conventional current direction, because in many circuits the power supply voltage is positive with respect to ground. It is the opposite of conventional current. (See current)
Electronic Industries Association (EIA) - (Archaic) An organization that assigned maintenance of all existing interconnect, passive, electro-mechanical (IP&E) standards. The EIA ceased operation in February of 2011 and their standards are now managed by the Electronic Components Industry Association (ECIA).
Electronic Industries Association 232 (EIA232) A standard of the Electronic Industries Association (EIA) defining a serial computer connection arrangement. The standard specifies pin-outs for a 25-pin (DB25) and 9-pin (DB9) subset, signal relations, voltage levels, and maximum cable lengths. The EIA changed the name from RS-232 to EIA232 and some signal lines were renamed and various new ones were defined, including a shield conductor. The EIA ceased operation in February of 2011 and their standards are now managed by the Electronic Components Industry Association (ECIA).
electronic keyer - (See keyer)
Electronic QSL Card Centre ( - A website for sending and receiving QSL cards online.
electronic mail (email) - A method of exchanging digital messages from an author to one or more recipients. Also called e-mail.
electronic-message unit (EMU) - (Archaic) Used in combination with an existing radio set, it allowed secure messages to be sent between Special Operations units of the British Army and was usually contained in a special slot but could also be used stand-alone, powered by a simple 9V-volt battery. It had a 20-button numeric key pad and used two digits to represent letters and other characters. Also known as digital-message device.
Electronics Illustrated Magazine - (Archaic) An American magazine started in May 1958 by Fawcett Publications, the publishers of Mechanix Illustrated. The magazine was published monthly from 1959 to 1961 then bi-monthly until November 1972.
electrostatic discharge (ESD) - The sudden flow of static electricity (of which lightning is an extreme example) between two or more electrically charged objects when the difference in charge potential overcomes the ability to prevent (by distance or material type) the transfer of energy.
element - (1) An arrangement of metallic conductors of an antenna, electrically connected to a receiver, transmitter, or transceiver, to radiate or receive radio waves. (2) A pool of questions for an amateur radio exam. (3) A dot or dash in Morse code (CW). (See Keplerian elements)
elephant - (Repeater term) A repeater that receives further than it can transmit a signal. (See alligator)
elevation - (1) The angle that an antenna, often a beam antenna, makes with the horizon. (2) How high an object or place or station is above sea level. (See above sea level)
elevation pattern - A graph showing how an antenna radiates and receives at different vertical angles. (See radiation pattern)
eleven meters - (CW term) Currently the Citizen's Band (CB), a United States radio service having 40 assigned channels that once was an amateur radio band. (See Citizen's Band)
elmer - A mentor or teacher who is an experienced operator who tutors newer operators. The term first appeared in QST Magazine in a March 1971 "How's DX" column by Rod Newkirk.
elliptical filter - A signal filter that produces a response with a very narrow transition band (very sharp transition), coupled with equal ripples in the passband and stopband sides.
elliptical polarization - The polarization of electromagnetic radiation in which the travel path of the electric field describes an ellipse in relation to the direction of travel. (See circular polarization; horizontal polarization; vertical polarization)
emergency - An incident of unusual or serious concern, alarm, or danger, often associated with a situation that has compromised, or poses an immediate risk to health, life, property, or environment.
Emergency Alert System (EAS) - A system where at first an alert tone is transmitted, followed by specific instructions regarding the receivable frequency in case of a national or local emergency. The EAS superseded the Emergency Broadcast System (EBS) in 1994.
Emergency Broadcast System (EBS) - (Archaic) A system where at first an alert tone is transmitted, followed by specific instructions regarding the receivable frequency in case of a national or local emergency. Superseded by the Emergency Alert System (EAS) in 1994. (See Emergency Alert System)
emergency communication (EMCOMM; EMCOM) - In times of crisis and natural disasters, amateur radio is often used as a means of emergency communication when wireline, cell phones, and other conventional means of communication fail.
Emergency Coordinator (EC) - An appointee of the American Radio Relay League (ARRL) who prepares for, and engages in management of communications needs in disasters.
emergency locator transmitter (ELT) - A device (beacon) that transmits a signal to indicate location or position during a time of emergency or distress.
Emergency Operation Center (EOC) - A central command and control facility responsible for carrying out the principles of emergency preparedness and emergency management (disaster management functions at a strategic level in an emergency situation) and ensuring the continuity of operation of a company, political subdivision, or other organization.
Emergency Response Communications (ERC) - A department of the Latter Day Saints (LDS) Church responsible for emergency communication and its preparation and training.
emergency traffic - Messages with life and death urgency or requests for medical help and supplies that leave an area shortly after an emergency. (See traffic)
Emergency War Powers - (See War Powers Act)
emission - Transmission of a signal from an amateur radio station.
emission mode - (See mode)
emission privilege - Permission to use a particular emission type, such as Morse code (CW) or voice.
emission types - The different modes authorized for use on the amateur radio bands. Examples are frequency modulation (FM), Morse code (CW), radioteletype (RTTY), and single sideband (SSB).
emitter - (See transistor)
emphasis - (1) The modification of the amplitude-versus-frequency characteristics of a signal to reduce the adverse effects of noise, using a pre-emphasis network to increase (boost) the amplitude of higher audio frequencies with respect to that of lower frequencies, and a de-emphasis network to decrease the amplitude of higher audio frequencies with respect to that of lower frequencies. Also known as pre-emphasis; preemphasis. (2) The encoding of a message, transmission, or its information, such that it can only be read or understood by a receiver that is capable of decoding, or authorized to decode, the message.
enameled copper wire - Wire in which the insulation is a thin coating of enamel. Often used for inductors, transformers, or electromagnets.
encoding - Changing the form of a signal into one suitable for storage or transmission. (See decoding)
end-fed - A type of antenna design whose feedline connects to one end of a radiating element, as in those of a monopole, J-pole, or even a random wire configuration. Also known as end-fed half-wave (EFHW).
end-fed Zepp antenna - (See Zepp antenna) Also known as endfed Zepp antenna.
encryption - The transmitting of a cryptic form so that only certain people understand what has been sent. (See decryption)
energy - The ability to do work or the ability to exert a force to move an object.
entity - (See DXCC Entity)
envelope - The outline of a radio frequency (RF) signal formed by the peaks of the individual RF cycles.
equivalent isotropic radiated power - (See effective isotropic radiated power)
equivalent series resistance (ESR) - The total alternating current (AC) resistance effect of an electrical component or circuit (device) at a given frequency, as though the resistance is in series with the device.
Esaki diode - (See tunnel diode)
ether - An old theory for the medium once believed to conduct radio waves. The existence of the ionosphere was first discovered by the English physicist, Appelton in 1924.
European Conference of Postal and Telecommunications Administration (CEPT) - An agreement between the United States and European nations to allow American amateurs to operate legally within participating countries without a special license or permit.
evaluation - (See compliance)
event - (See special event)
exposure evaluation - (See compliance)
exalted-carrier reception - A reception technique where the carrier produced by a receiver's beat frequency oscillator (BFO) circuit or product detector is used to replace the carrier of an amplitude modulation (AM) signal for better reception.
exalted-carrier single sideband (ECSS; ECSSB) - A method of using single sideband to tune amplitude modulation (AM) broadcasts.
exam session - The formal and official arrangement to assess a candidate for licensing knowledge and qualification through an amateur radio examination. Also know as examination session.
excessive deviation - (See overdeviation)
excessive drive - The signal strength (typically power or voltage, known as drive) applied to a circuit greater than the amount the circuit can tolerate, possibly resulting in clipping (on single sideband), malfunction, overload, or even permanent damage.
exchange - The passing of all necessary information between two stations during a contact.
exciter - (1) A device or circuit that drives the final amplifier of a transceiver or power amplifier. (2) A once-popular device or circuit of a tube transmitter that combines an oscillator with the modulator to create its output signal.
Experimenters' Section (X Section) - (Archaic) A QST magazine department in the 1920s.
exposure evaluation - (See compliance)
extended binary coded decimal interchange code (EBCDIC) - An 8-bit character encoding used mainly on International Business Machines Corporation (IBM) mainframes and their midrange computer operating systems.
extended double Zepp antenna - A center-fed dipole antenna of two 5/8-wave horizontal elements that attach to the feedline through a quarter-wave vertical radiating element often constructed from ladder line, making it a little longer than the double Zepp antenna.
extended-coverage receiver - A receiver that tunes frequencies from around 30 megahertz (MHz) to several hundred megahertz or into the gigahertz (GHz) range. Also known as wide-range receiver.
Extra - (See Amateur Extra)
extraordinary wave - One of two types of elliptically polarized radio waves that results from the interaction with the ionosphere and the one that is polarized by the influence of earth's magnetic field. Also known as X-wave.
extremely high frequency (EHF) - A frequency in the range of 300 to 30,000 megahertz (mHz) or 30 to 300 gigahertz (GHz). Also known as XHF.
extremely low frequency (ELF) - Radio waves of electromagnetic radiation with frequencies from 3 to 300 hertz (Hz), and corresponding wavelengths from 100,000 to 1000 kilometers (km). Also known as XLF.
eyeball - Slang for a face-to-face contact between two ham radio operators. Also known as eyeball QSO; face-to-face.
ezine - A magazine on the world wid web (WWW), usually in Portable Document Format (PDF). Also called e-zine. (See Portable Document Format)

To the top!   F

F connector - A connector found on 440 MHz and 1.2 GHz antenna circuits.
F layer - The region of the ionosphere found approximately 90 to 400 miles above Earth and which is responsible for most long distance propagation on frequencies below 30 megahertz (MHz). The F-layer refracts radio waves and returns them to Earth. During the daytime, especially in the summer, solar heating can cause the F-layer to split into two separate layers, the F1-layer and the F2-layer. Also known as F region.
face-to-face (F2F) - Slang for an in-person contact meeting between hams without the use of radios. Also known as eyeball QSO.
facsimile (fax) - A digital mode for transmitting text and images.
factory reset - (See reset)
fading - Signal reduction due to atmospherics. Also known as freak.
Fahnstock clip - (Archaic) A metal spring clip shaped like the letter R with a small loop at the center. Often used for the connection of antenna and ground leads in early radio equipment.
fall arrest - A type of climbing harness designed to safely stop a climber who is already in process of falling, and one of the major forms of fall protection. Also known as fall arrester; fall arrestor; climbing harness.
false signals - (See deceptive signals)
Family Radio Service (FRS) - A walkie-talkie radio system authorized in the United States since 1996 and intended for short-range communication by family members. Short-range handheld radios can be used in this system without a license. The service uses channelized frequencies around 462 and 467 megahertz (MHz) in the ultra-high frequency (UHF) band. It does not suffer the interference effects found on Citizen's Band (CB) at 27 megahertz (MHz), or the 49 megahertz (MHz) band also used by cordless phones, toys, and baby monitors. FRS uses frequency modulation (FM) instead of amplitude modulation (AM).
fan antenna - (Archaic) A popular antenna in the 1920s, it is multiple vertical wires that spread out as they are strung up from ground level, fed at the common point at the bottom, insulated and supported by a horizontal wire at the top.
fan dipole antenna - A type of multiband dipole antenna in which multiple parallel radiating elements join at a common point on each side, or in which the radiating elements spread out radially from the common points, like with a cat's whisker antenna. Also known as parallel fan dipole antenna.
far field (of an antenna) - That region of the electromagnetic field surrounding an antenna where the field strength as a function of angle (the antenna pattern) is essentially independent of the distance from the antenna. In this region the field has a predominantly plane-wave character, locally uniform distributions of electric field strength, and magnetic field strength are in a plane perpendicular to the direction of propagation. Also known as far-field; free-space region.
farad (F) - The basic unit of capacitance, it is the charge in coulombs that a capacitor will accept for the potential across it to change 1 volt. The term was coined by Josiah Latimer Clark in the year 1861 in honor of Michael Faraday. (See coulomb)
Farnsworth - (CW term) A method of sending Morse code (CW) characters when learning. Example characters are sent at 13 words per minute but the spacing is adjusted so that the overall code speed is 5 words per minute.
fast Fourier transform - The digital process applied to I and Q signals in order to recover the baseband modulation information, essentially converting the digital signals from the time domain to the frequency domain.
fast blow - (See fuse)
fast Fourier transform (FFT) - A digital technique to interchange frequency and time domain data. Named after the first man to work on the technique, Joseph Fourier.
Federal Aviation Administration (FAA) - An agency of the federal government responsible for regulating every aspect of civil aviation, including the construction and operation of airports and air traffic management.
fast-scan television (FSTV) - (See amateur television)
Federal Communications Commission (FCC) - The governmental body that regulates wireless communications in the United States, including amateur radio.
Federal Radio Commission (FRC) - (Archaic) The precursor to the Federal Communications Commission (FCC) created by the Radio Act of 1927.
Federal Registration Number (FRN) - An identification number assigned to an individual by the Federal Communications Commission (FCC) to use when performing license modification or renewal.
feed line - (See transmission line) Also known as feedline.
feed-line coupler - (See antenna tuner). Also known as feedline coupler.
feed-line loss - (See transmission-line loss)
feed impedance - The resistance and sometimes reactance as seen at the connection point of an antenna.
feed point - The part of an antenna at which connections are made. The connections are usually to a transmission line that runs from the antenna to the radio equipment. Also known as feedpoint; antenna feed.
feed point impedance - The ratio of radio frequency (RF) voltage to current at the feed point of an antenna.
feeder - Short (primarily British) term for feedline. (See transmission line)
ferrite - A ceramic material with magnetic properties used in inductors. Ferrite is often formed into beads or cores so that it may be placed on cables, forming an electronic radio frequency (RF) choke.
ferrite choke - A type of choke that uses a ferrite ceramic core to suppress high frequency noise in circuits; while ferrite chokes and ferrite beads are usually regarded as the same electrically, ferrite beads often refer to the ferrite ceramic core without the wire inductor winding. Also known as ferrite bead; snap-on ferrite choke.
fiber optics - The field of applied science and engineering concerned with the design and application of optical fibers. (See optical fiber)
Field Day - An annual American Radio Relay League (ARRL) sponsored event in which temporary amateur radio stations are set up, usually in a public place, to communicate with as many stations as possible.
field strength - A measure of the intensity of an electric or magnetic field. Electric fields are measured in volts per meter and magnetic fields in amperes per meter.
field-effect transistor (FET) - A transistor that uses an electric field to control the shape and hence the conductivity of a channel of one type of charge carrier in a semiconductor material. An FET has three electrodes, a gate, a drain, and a source. (See transistor)
field-programmable gate array (FPGA) - Programmable integrated circuit designed to be configured by a customer after being manufactured, to create complex logic functions in a single integrated circuit. Also known as pin grid array.
field-strength meter - A test instrument used to show the presence of radio frequency (RF) energy and the relative strength of the RF field. Also known as field strength meter.
feed-through capacitor - (See coaxial capacitor) Also known as feedthrough capacitor.
filament - The heating element of a vacuum tube.
filter - A circuit or device that will allow some signals to pass through it but will greatly reduce the strength of others. An active filter uses amplifier circuits or components. A passive filter is constructed entirely from resistors, capacitors, and inductors. A digital filter performs the filtering functions on digital data.
filter choke - (See choke)
filter skirt - (See transition band)
final - (1) The final transistor(s), or in the early days, vacuum tubes, in an amplifier. (2) Slang for the last transmission in a contact before singing off. (3) Short for final amplifier, especially the transistor or tube used for power amplification.
final amplifier - A device or circuit placed in a transmitter where the output signal meets the feedline, and can be little more than a transistor in the amplifier stage of a high tension (HT) or as large as a separate power amplifier unit.
finite impulse response (FIR) - A type of digital signal processing filter whose impulse response is finite, in that it will eventually reach zero, resulting in a filter that is easier to design, and delays all frequency components of the signal by the same amount.
fire bottle - (Archaic) (See vacuum tube)
firmware - Operating instructions for microprocessors that are stored in non-volatile memory. It remains even when power is turned off.
First Class CW Operators Club (FOC) - A club in the United Kingdom that promotes good Morse code (CW) operating, activity, friendship, and socializing by way of its worldwide membership of approximately 500.
fist - (1) (CW term) Early spark transmitters showered the operator with sparks so Marconi's key lever was lengthened and the padded end was beaten with the fist of the operator to send dots and dashes. (2) (CW term) A Morse code (CW) operator's reference to another operator's keying characteristic.
FISTS - A club founded by Geo Longden G3ZQS in 1987 to promote the use of Morse code (CW) transmission mode. FISTS refers to an individual's sending style to send Morse code (CW) dots and dashes.
five-by-five - An audio and radio frequency (RF) signal report used primarily in non-amateur radio communication to indicate "loud and clear." Also known as five-and-five; 5 by 5; 5-5; five-five.
five-by-nine - An audio and radio frequency (RF) signal report using the readability, strength, tone (RST) system to indicate "loud and clear." Also known as 5 by 9; 5-5; five-five.
five-over-nine - Received signal that is 5 desible (dB) greater than S9 on the S meter, that assumes a readability level of 5. Also known as 5 over 9.
fixed resistor - An electronic component specifically designed to oppose or control current through a circuit. The resistance value of a fixed resistor cannot be changed or adjusted.
fixed station - A station that always operates from a constant, specified land location. (See base station) Also known as fixed-station.
flash conversion analog-to-digital - A type of analog-to-digital (ADC) that uses a linear voltage ladder and a comparator to measure the input voltage with respect to successive reference voltages.
flat braid - (See ground braid)
flat strap - (See ground strap)
flat topping - Over-modulating so as to distort a waveform. (See clipping) Also known as flat-topping.
float voltage - The voltage at which a battery is maintained after being fully charged, to compensate for self-discharge, and which can vary significantly between battery types.
floating ground - A type of ground that is not electrically connected with the Earth, such that its electric potential can differ from that of earth ground.
flutter - The rapid variation in the signal strength of a station, usually due to propagation variations.
FME connector - The model name for a common 50 Ω (primarily RG-58) coaxial cable feedline connector used for very high frequencies (VHF) in mobile applications.
foldback - A device (power supply, amplifier, or transmitter of a transceiver) output circuit that attempts to limit the amount of current being drawn by the load, to help protect the device from overload. Also known as fold back.
folded dipole antenna - A dipole antenna utilizes two parallel and end connected half-wavelength wires. The feed line connects to only one of the wires. Because of the antenna's current distribution, the feed impedance is increased, typically by a factor of four. This antenna is used to provide a low standing-wave ratio (SWR) match to an open wire feed line at the dipole's resonant frequency.
for example (e.g.) - An abbreviation for the Latin phrase exempli gratia. Form 605 - An Federal Communications Commission (FCC) form that serves as the application for the amateur radio license, or for modifications to an existing license.
formal traffic - (See traffic)
forward error correction (FEC) - A mode that sends all data twice with an interleaving technique to reduce errors from impulse noise and static crashes.
forward power - Power in a transmission line traveling from a transmitter toward a load or antenna.
fox hunt - (See amateur radio direction finding) Also known as foxhunt; foxhunting; fox hunting.
Foxtrot - A North Atlantic Treaty Organization (NATO) phonetic alphabet code word representing the letter F. Used in radio communication, particularly when spelling out a call sign.
Franke-Taylor, 4-FSK (FT4) - A type of frequency-shift keying (FSK) data transmission protocol, specifically, audio-frequency shift keying (AFSK) modulation, designed to support very weak signal communication by decoding signals many decibles (dB) below the noise floor (low signal-to-noise conditions) using forward error correction (FEC), is less sensitive than JT9 or JT65, but transmitting at 6-second intervals, which is 2.5 times faster than FT8 in contact completion.
Franke-Taylor, 8-FSK (FT8) - A type of frequency-shift keying (FSK) data transmission protocol (specifically, audio-frequency shift keying (AFSK) modulation) designed to support very weak signal communication by decoding signals many decibles (dB) below the noise floor (low signal-to-noise conditions) using forward error correction (FEC), is less sensitive than JT9 or JT65, but transmitting at 15-second intervals, which is four times faster in contact completion.
freak - (See fading)
free-space region - (See far field of an antenna)
frequency - The number of complete wave cycles of an alternating current that occur per second. The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency.
frequency bands - A group of frequencies where amateur radio communications are authorized. (See band)
frequency coordination - (Repeater term) Allocating repeater input and output frequencies to minimize interference between repeaters and to other users of the band.
frequency coordinator - (Repeater term) An elected individual or group that recommends repeater frequencies to reduce or eliminate interference between repeaters operating on or near the same frequency in the same geographical area.
frequency counter - A test instrument that measures and displays the frequency of signals or the repetition rate of pulses.
frequency deviation - (See deviation)
frequency discriminator - A circuit that delivers an output voltage that is proportional to the deviations of a signal from a predetermined frequency value. It is a type of detector used in some frequency modulation (FM) receivers.
frequency division multiple access (FDMA) - A method of accessing a particular data channel of a frequency-division multiplexing transmission system that requires high-performance filters for reliable communication.
frequency modulated phone - The type of frequency modulation (FM) signals used to communicate by voice (phone) over most repeaters. FM is a method of combining a radio frequency (RF) carrier with an information signal, such as voice. The voice information, or data, changes the RF carrier frequency in the modulation process. FM broadcast stations and most professional communications (fire, police, taxi) use FM. FM phone is the most popular amateur mode on very-high frequency (VHF) and other frequency bands.
frequency modulation (FM) - The process of adding information to a rafio frequency (RF) signal or carrier by varying its frequency. Part of the modulation index.
frequency privileges - The permission to use a particular group of frequencies.
frequency response - Radio spectrum frequency response can refer to measurements of antenna systems, coaxial cable, twisted-pair cable, video switching equipment, and wireless communications devices.
frequency synthesis - A tuning method in transmitters and receivers that uses a few piezoelectric crystals to generate a wide range of frequencies.
frequency drift - An undesirable and arbitrary change in oscillator nominal frequency, often due to temperature variation and component aging.
frequency modulation - A method of combining an information signal (your voice, Morse code (CW), data packets, etc.) with a radio frequency (RF) signal of constant amplitude, so that the frequency of the output signal varies with the information signal.
frequency multiplier - (See multiplier)
frequency-division multiple access (FDMA) - A method of accessing a particular data channel of a frequency-division multiplexing transmission system that requires high-performance filters for reliable communication.
frequency synthesis - The creation of multiple frequencies (synthesized frequencies) or bands from a single reference (often a crystal oscillator-based) frequency signal, rather than from a continuously-tunable oscillator circuit or multiple crystals, the two primary methods being phase-locked loop synthesis and direct digital synthesis. Also known as synthesized frequency.
frequency-division multiplexing (FDM) - A technique by which the total bandwidth available in a communication medium is divided into a series of non-overlapping frequency sub-bands, each of which is used to carry a separate signal. This allows a single transmission medium, such as a cable or optical fiber, to be shared by many signals. An example of a system using FDM is cable television, in which many television channels are carried simultaneously on a single cable.
frequency-hopping spread spectrum - The technique of spread-spectrum communication in which the carrier frequency of the transmitted signal is changed very rapidly according to a particular sequence that is also used by the receiving station. Also known as frequency hopping spread spectrum.
frequency-modulation capture effect - The ability of a frequency modulation (FM) signal that is stronger than others on the same channel to completely take over the channel to the exclusion of the weaker signals.
frequency-shift direction (FST-D) - (Repeater term) Enables access of repeaters.
frequency-shift keying (FSK) - A form of digital frequency modulation used especially in facsimile, data, and telegraph transmission in which the modulating wave shifts transmitter frequency to represent the bits of digital data. Also known as shift keying.
frequency-shift keying, 441 baud (FSK441) - A type of multi-frequency-shift keying (MFSK) data transmission mode (protocol) at 441 baud, designed to support communication using meteor scatter events.
Fresnel zone - The roughly ellipsoidal (football-shaped) region of space between a transmitter and a receiver defined by potential object (obstruction) locations lying off the line-of-sight, resulting in possible constructive (aided by in-phase) or destructive (attenuated by out-of-phase) interference patterns, as in multipath, often resulting in picket-fencing and other irritating sound effects.
Friendship Award (FA) - (Archaic) An award given by the American Radio Relay League (ARRL) whose purpose was to encourage friendly contact between radio amateurs (hams) and thereby discover new friends through personal communication with others. It was discontinued in 2004.
front end - A generic term for all the receiver circuitry between the antenna system and the mixer; typically, all the components in the receiver that process the original incoming radio frequency (RF) signal before it is converted to a lower intermediate frequency. Also known as front-end; RF front-end.
front-end filter - The portion of a receiver front end that provides a band-pass filter, to reduce strong, out-of-band signals and image response. Also known as front end filter.
front-end overload - Interference to a receiver caused by a strong signal that overpowers the receiver radio frequency (RF) amplifier, or front end. Front-end overload results in distortion of the desired signal and the generation of unwanted spurious signals within the receiver. (See receiver overload) Also known as front end overload.
front-to-back ratio (F/B) - The ratio of an antenna's gain in the forward direction to that in the opposite direction. (See front-to-side ratio)
front-to-side ratio (F/S) - The ratio of an antenna's gain in the forward direction to that at right angles to the forward direction. (See front-to-back ratio)
full break-in - (CW term) Allows a station to break into the communication without waiting for the transmitting station to finish. Also known as full break in.
full duplex - (See duplex) Also known as full-duplex.
full gallon - (See gallon)
full quieting - (Repeater term) A phenomenon of frequency modulation (FM) transmissions where the incoming signal is sufficient to engage the receiver limiters, thus eliminating the noise due to amplitude fluctuations.
full-wave bridge rectifier - A circuit that converts alternating current (AC) to direct current (DC) and that uses four diodes that do not require a center-tapped transformer. (See tap) Also known as bridge rectifier.
fundamental - The lowest frequency to which a harmonic is related. (See harmonic)
fundamental overload - Radio frequency (RF) interference caused when a strong RF signal exceeds a receiver's ability to reject it. Also known as overload; RF overload.
fuse - A thin metal strip mounted in a holder. When too much current passes through the fuse, the metal strip melts and opens the circuit. Fuses are rated in amperes and voltage and time to activate such as fast blow or slow blow.
Fusion - (See System Fusion)

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GaAs field-effect transmitter (GaAs FET) - A gallium arsenide (GaAs) field-effect transistor (FET) is a specialized type of field-effect transistor that is used in amplifier circuits at very-high, ultra-high, and microwave radio frequencies. This spans the electromagnetic radiation spectrum from approximately 30 MHz up to the infrared band.
G5RV antenna - A simple 20-meter (m) dipole antenna that is 102 feet long and uses a short length of open-wire transmission line to provide a match to 50-ohm coaxial cable. It is also popular as a multi-band antenna but suffers high loss in the 50-Ohm cable on some bands. It was invented in 1946 by Louis Varney.
G5RV Junior - A version of the G5RV antenna physically shortened for space restrictions, and typically limited to 40 meters (m) and higher.
gain - (1) In general, the ratio of the output to input signal (can be voltage, current, or power) strength change by a circuit or device, often measured in decibles (dB) or similar unitless designation. (2) The ratio of the quantified tendency of an antenna to focus more of its radiated signal strength or reception ability in one direction than that in other directions, often expressed as a ratio of the radiated signal strength of the antena in the direction of maximum radiation to that of a reference antenna (another way to look at it is the ratio of the amount of power required by an isotropic radiator with respect to the amount of power required by a particular antenna to produce the same field strength at a point, expressed in decibels above an isotropic antenna (dBi), or the ratio of the amount of power required by a dipole antenna with respect to the amount of power required by a particular antenna to produce the same field strength at a point, expressed in decibels above a dipole antenna (dBd). (3) The quantified ability of a transistor to produce an output signal (voltage or current) that is proportional to a weaker input signal. (4) The quantified ability of an amplifier to increase signal strength (power) at its output, compared with that of its input, often measured in decibles (db) (or decibels of the measured power (dbm), depending on amplifier type).
gain antenna - Slang or nickname for an antenna that exhibits a gain greater than 0 decibels above a dipole antenna (dBd) (typically much greater than zero, such as 6 dBd or 9 dBd), without regard to directivity.
gain compression - Ratio of the amount of nonlinear amplifier gain (distortion due to saturation) with respect to its ideal linear gain, expressed in decibles (db), and often associated with receivers that have a wide dynamic range (not to be confused with dynamic range compression, a desirable audio process).
gallium arsenide (GaAs) - A compound of the elements gallium and arsenic. It is a high-speed semiconductor and is used in the manufacture of devices such as microwave frequency integrated circuits, monolithic microwave integrated circuits, infrared light-emitting diodes, laser diodes, solar cells, and optical windows.
gallon - (1) Fifteen-hundred watts peak envelope power (PEP). (2) One thousand watts Morse code (CW). (3) Slang for transmitter output power.
gamma match - A kind of impedance matching arrangement in which a rod is used to tap into one side of a dipole-antenna element to allow attachment of coaxial cable to the appropriate impedance point of the antenna. Often used in directional array antennas such as Yagis. (See tap)
gassy tube - A vacuum tube into which some air molecules have penetrated, possibly changing some of the tube characteristics.
gate - (See transistor)
gateway - (1) A station that serves to connect one network of stations with the Internet or another network of stations. (2) A hardware or software setup that translates between two dissimilar protocols.
gauge - (See American wire gauge)
Gaussian minimum-shift keying (GMSK) - A form of minimum-shift keying (MSK) data transmission in which the data stream is shaped with a Gaussian filter prior to modulation.
gear - (1) Slang or short for any kind of ham radio equipment. (2) Slang or short for any kind of equipment.
gel cell - A small sealed lead-acid rechargeable battery that uses a gel instead of a liquid electrolyte. It is often used as backup power in applications.
General - (See General Class)
general-coverage receiver - A receiver used to listen to a wide range of frequencies. Most general-coverage receivers tune from frequencies below 550 to 1700 kilohertz (kHz), the standard-broadcast amplitude modulation (AM) band, to at least 30 megahertz (MHz). They are capable of operation in several different modes, including amplitude modulation (AM), Morse code (CW), and single sideband (SSB). These frequencies include the shortwave-broadcast bands and the amateur radio bands from 160 to 10 meters (m). (See extended-coverage receiver)
General Certification Rule (GCR) - Most award sponsors allow GCR in lieu of actually wanting to see one's cards and usually means getting the signatures of two witnesses who certify that the holder possesses the cards and that the information stated on the application is correct.
General Class - The most common mid-level of amateur radio license, it allows for cross-country and worldwide communication. In addition to the Technician privileges, General Class operators are authorized to operate on any frequency in the 160-, 30-, 17-, 12-, and 10-meter (m) bands. They may also use significant segments of the 80-, 40-, 20-, and 15-meter bands. The General Class license does not require familiarity with Morse code (CW).
General Conference on Weights and Measures (CGPM) - The senior of the three Inter-governmental organizations established in 1875 under the terms of the Metre Convention to represent the interests of member states. The treaty, which also set up two further bodies, the International Committee for Weights and Measures (CIPM) and the International Bureau of Weights and Measures (BIPM), was drawn up to coordinate international metrology and to coordinate the development of the metric system.
general coverage - A feature attributed to a receiver that can accept and demodulate radio-frequency signals outside the amateur bands, specifically (typically) 100 kilohertz (kHz) to 30 megahertz (MHz), often for shortwave listening.
general-coverage receiver - A receiver used to listen to a wide range of frequencies. Most general-coverage receivers tune from frequencies below the standard-broadcast band to at least 30 MHz. These frequencies include the shortwave-broadcast bands abd the amateur bans from 160 to 10 meters.
General Mobile Radio Service (GMRS) - A licensed North American land-mobile frequency modulation (FM) ultra-high frequency (UHF) radio service designed for short-distance two-way communication for family use within a city or region. It requires a license in United States but can be used license-free in Canada.
generator - A device that uses a motor to convert mechanical energy into alternating current (AC) or direct current (DC) electrical energy.
geographical codes (geocodes) - A code to identify a point or area on the surface of the Earth. (See country code)
geomagnetic index - The semi-logarithmic quantification of disturbances in the earth's magnetic field, denoted primarily by the K-index (0 through 9), which can vary throughout the day (an indicator of the short-term stability of the earth's magnetic field), and often accompanied by the A-index (0 through 400), which is a daily average (an indicator of the long-term stability of the earth's magnetc field); because measurements of these values could vary between earthly locations, the planetary (meaning global) KP-index and AP-index are often provided instead; disturbances such as geomagnetic storms can affect high frequency (HF) radio communication greatly, with generally the higher the index the more HF communication is degraded. Also known as geomagnetic indices; K-index; K index; KP-index.
geomagnetic storm - The temporary disturbance in the earth's magnetosphere, resulting in both degraded high-latitude high -frequency (HF) propagation and auroras, which can reflect very-high frequency (VHF) signals.
geometrical horizon - (See horizon) Also known as geometric horizon.
Get on the Air (GOTA) - A category in the annual American Radio Relay League (ARRL) Field Day event. The GOTA station may be operated by a Technician and generally inactive amateur radio operators under their existing operating privileges, or under the direction of a control operator with appropriate privileges, as necessary. Non-licensed persons may participate under the direct supervision of an appropriate control operator.
giga- (G-) - One billion, the metric prefix for 109, or times 1,000,000,000.
gigahertz (GHz) - One billion (1,000,000,000) hertz (Hz).
gin pole - A supported device that uses a pulley or block and tackle on its upper end for lifting tower sections or antennas. It derives from gyn, which is an improvised three legged lifting device used on sailing ships.
Global Positioning System (GPS) - An accurate worldwide navigational and surveying facility based on the reception of signals from an array of orbiting satellites.
go-kit - A pre-packaged collection of equipment or supplies kept at hand to allow a radio operator to quickly report where needed in time of need.
go ahead - (See over)
Golay-teleprinting over radio (G-TOR) - A digital frequency-shift keying mode that offers faster data transfer rate than PACTOR (Latin for the mediator). G-TOR is a trademark of Kantronics, Inc. and was devised by M. Golay. It is rarely used by amateur radio operators.
Golf - A North Atlantic Treaty Organization (NATO) phonetic alphabet code word representing the letter G. Used in radio communication, particularly when spelling out a call sign.
Government Printing Office (GFO) - An agency of the legislative branch of the United States federal government, the office prints documents produced by and for the federal government, including the Supreme Court, the Congress, the Executive Office of the President, executive departments, and independent agencies.
grace period - The time Federal Communications Commission (FCC) allows following the expiration of an amateur radio license to renew that license without having to retake an examination. Those who hold an expired license may not operate an amateur radio station until the license is reinstated.
grant - Authorization given by the Federal Communications Commission (FCC).
gray line - A band around the Earth that separates daylight from darkness. It is a transition region between day and night. One of the many types of propagation paths. Also known as grey line.
great-circle route - The shortest path by radio between any two points on Earth.
green stamp - A United States dollar bill sent along with a QSL card instead of an International Reply Coupon (IRC) to offset postage costs of the return card.
Greenwich Mean Time (GMT) - (See Universal Time Coordinate)
grid - (1) The portion of a vacuum tube that controls the flow of electrons internally from the cathode to the anode (plate), or in other words, the flow of current internally from the anode to the cathode, and usually includes a control grid, screen grid, and suppressor grid. Also known as screen grid. (2) Slang or short for electrical grid. Also known as supressor grid.
grid current - (See vacuum tube)
grid locator - A locator in the Maidenhead Locator System, named after the town outside London where it was first conceived by a meeting of European very-high frequency (VHF) managers in 1980. It is a shorthand means of describing the operator's general location anywhere on the Earth in a manner that is easy to communicate over the air. The entire globe is divided into grid rectangles. Each subsquare is designated by the addition of two letters after the grid square and measure 2.5 minutes latitude by 5 minutes longitude, roughly corresponding to 3 by 4 miles in the continental United States. For example, Meadow Hills, Aurora, Colorado 80014 is located in grid DM79op. Also known as grid square; QTH locator.
grid-dip meter - (See dip meter)
grid-dip oscillator - (See dip meter)
ground - To connect an electrical device with the earth, it is a common zero-voltage reference point. Grounds fulfill three distinct functions: (a) A safety ground to protect from a shock hazard if one of the mains or high voltage power supply wires contacts the chassis due to some kind of fault. (b) A lightning ground for lightning protection. (c) a radio frequency (RF) ground, required only for certain types of antennas that require current flow to ground to complete the antenna circuit. Also known as earth ground; ground potential.
ground braid - A cable typically made of braided tinned copper or braided copper for bonding, which ensures two points (such as radio equipment) being connected have the same electric potential, which ideally is earth ground potential. Also known as flat braid; braid, braided strip; grounding braid.
ground bus - A thick, heavy plate or bar (busbar) that provides a common connection point for the chassis ground of multiple pieces of equipment, and that is typically bonded with earth ground. (See power bus)
ground connection - A connection made to the earth for electrical safety. This connection can be made inside to a metal cold-water pipe or outside to a ground rod.
ground potential - (See ground)
ground rod - A copper or copper-clad steel rod that is driven into the earth to create a ground to electrical equipment. A heavy copper wire from the ham shack connects all station equipment to the ground rod. Also known as rod.
ground strap - Flat ribbon conductor made of copper (often called flat strap or copper strap) for grounding equipment in your shack to minimize losses in your radio frequency (RF). Also known as strap.
grounding system - (1) A system of interconnected wires, straps, rods, and cabling that provides a stable electrical reference to ground (preferably earth ground). (2) The practice of providing or ensuring a connection to ground potential. Also known as copper strap; grounding strap; flat strap.
ground wave - An electrical wave traveling directly from the transmitter to the receiving station without bouncing off the ionosphere. Also known as surface wave.
ground-fault interrupter (GFI) - A breaker that opens a circuit when an imbalance of current flow is detected between the hot and neutral wires of an alternating current (AC) sending current flowing along an unintended path, possibly through water or through a person. Also known as ground-fault circuit interrupter (GFCI) (See circuit breaker)
ground-plane antenna - (1) An omni-directional vertical antenna built with the central radiating element one-quarter-wavelength long and several radials extending horizontally from the base. The radials are slightly longer than one-quarter wave, and may droop toward the ground. Ground-plane antennas require a ground plane in order to operate properly. (2) A flat or nearly flat horizontal conducting surface that acts as an electrical mirror and serves as part of an antenna, to reflect the radio waves from the other antenna elements. The plane does not necessarily have to be connected to ground. Ground planes are particularly used with monopole antennas.
ground-wave propagation - The method by which radio waves travel along the Earth's surface, even beyond the horizon.
grounding - Placing an electrical connection to the earth.
group calling - One-to-many form of communication. (See individual calling)
group frequency method - (Archaic) Using a tuning capacitor in the headphone circuit to select a specific spark tone.
guy rope - A rope used to support a tower or mast.
guy wire - A wire used to support a tower or mast.

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half-duplex (HDX) - (Repeater term) A communication mode in which a radio transmits and receives on two different frequencies but performs only one of these operations at any given time. (See duplex and full duplex).
half-power bandwidth - (See 3 dB bandwidth) Also known as half duplex.
half-wave dipole antenna - A basic half-λ is a dipole antenna approximately a half wavelength long, usually fed by connections to each side of the center with a ladder-type open feeder. It is often used as an antenna itself, it is also a reference standard for other antennas. It is a popular antenna with amateur radio operators. The λ is a Greek small lambda. (See dipole)
half-wave rectifier - A circuit or device that converts (rectifies) exactly half of the input waveform, instead of the entire signal (see full-wave rectifier), into direct current (DC). Also known as half-wave rectification.
ham - An informal term for an amateur radio operator licensed to operate an amateur radio station. By extension, ham radio refers to amateur radio in general. (See ham radio)
ham bands - The Federal Communications Commission (FCC)-authorizes amateur radio bands used in the United States. There are 27 in all with the most popular being the 70-centimeter (cm) and 2-meter (m) amateur radio bands.
ham cave - (See shack) Also known as hamcave.
ham net - (See net) Also known as hamnet.
ham police - (See Amateur Auxiliary)
ham radio - The use of designated radio frequency spectrum for purposes of private recreation, non-commercial exchange of messages, wireless experimentation, self-training, and emergency communication. A synonym is amateur radio. In the United Kingdom, the term ham radio was deprecated in the 1970s because amateurs were self-conscious and a bit offended by the image of them created by Tony Hancock in his famous Radio Ham episode. In the United States, there used to be a magazine called Ham Radio but they had never heard of Tony Hancock so they were much less stuffy about it. The term ham radio started as a pejorative, mocking amateur radio operators with a 19th century term for being bad at something, like ham actor or ham-handed. It had already been used for bad wired telegraph operators, who (like a ham-fisted boxer) presumably was seen with hands as clumsy as if they were hams. Subsequently, it was coopted by the community itself, which adopted it as a welcome moniker. Other, more entertaining explanations have grown up throughout the years, but are apocryphal. Amateurs increasingly adopted the word ham to describe their hobby and themselves after 1919. (See amateur radio)
ham-bands-only receiver - A receiver designed to cover oly the bands used by amateurs. Usually refers to the bands from 80 to 10 meters, sometimes including 160 meters.
Ham Radio Magazine - (Archaic) A monthly amateur radio enthusiast magazine published in the United States from February 1968 to June 1990. At the 1990 Dayton Hamvention it was announced that Ham Radio had been sold to the publishers of CQ Amateur Radio. The June 1990 issue was the 268th and final issue published where subscribers were told of the sale and that they would receive CQ in the future.
ham shack - (See shack) Also known as hamshack.
ham-band receiver - A receiver designed to cover only the bands used by amateur radio operators. Usually refers to the bands from 80 to 10 meters (m), sometimes including 160 meters. Also known as ham-bands-only receiver.
ham-in-a-can - (1) Slang for a ham radio station, including transceiver, battery, and antenna, along with other support gear, that is built into a portable carrying case. (2) Slang for ham radio equipment that's been installed on, or attached to, a computer dedicated as a digital station for communication using the Automatic Packet Reporting System (APRS), D-STAR, or other data modes.
HamCation - A specific and unusually large hamfest held annually in Orlando, Florida.
HamCon - (See hamfest) Also known as Ham-Con.
hamfest - An informal flea market for a scheduled gathering of amateur radio operators. Often includes presentations, workshops, exam sessions, and sellers of computer equipment, electronic equipment, ham radio equipment, and all the accessories. Also known as hamvention; swap meet; swapmeet.
hamspeak - Language, terminology, and slang used among ham radio operators, hobbyists, and enthusiasts. Also known as ham speak.
hamvention - (See hamfest)
hand-held transceiver (HT) - (Repeater term) A small, lightweight portable transceiver that operates in the 70 centimeter (cm) and 2 meter (m) amateur radio bands. Self-contained hand-held radios include an antenna and battery and transmit at low power.
Handie-Talkie - A hand-held radio used in lieu of a walkie-talkie to distinguish licensed amateur radio operators from Citizen's Banders (CBers). It is a Motorola trademark.
handle - (1) Morse code (CB) slang for nickname. (2) Older slang for first name.
Handy's Handbook - (Archaic) The first edition of The Radio Amateur's Handbook, edited by the American Radio Relay League (ARRL) Communications Department Manager F. E. Handy and published in 1926. It was commonly referred to as Handy's Handbook in the late 1920s.
handy talky - Transceivers that operate in the 70-centimeter (cm) and 2-meter (m) amateur radio bands. (See hand-held transciever) Also known as handy-talkie; handy-scratchy.
hang time - (Repeater term) The short period following a transmission that allows others who want to access the repeater a chance to do so. A courtesy tone sounds when the repeater is ready to accept another transmission. Also known as hangtime.
hard line - A type of coaxial cable that consists of a solid outer conductor instead of braid, resulting in very low loss, typically used in repeater applications. Also known as hardline; hard-line.
harmful interference - Malicious interference that seriously degrades, obstructs, or repeatedly interrupts a radio communication service operating in accordance with the Radio Regulations. (See malicious interference) Also known as willful interference.
harmonic - (1) A multiple of a fundamental frequency. These signals from a transmitter or oscillator occur on whole-number multiples, such as 2×, 3×, 4×, etc., of the desired operating frequency. (2) Older slang for the child of a ham.
Hartley oscillator - An oscillator circuit that generates a waveform using positive feedback supplied through a tapped coil, and is one of (at least) three primary oscillator circuits used in amateur radio equipment, commonly in a variable-frequency oscillator (VFO) circuit.
header - The first part of a digital message containing routing and control information about the message. (See preamble)
headphones - A pair of speakers held against or inserted into each ear. A headset or boomset combines headphones with a microphone for additional convenience. Also known as head phones.
headset - (See headphones)
health and welfare traffic - Messages about the well being of individuals in a disaster area. Such messages must wait for emergency and priority traffic to clear, and results in advisories to those outside the disaster area awaiting news from family and friends.
heat sink - The heavy fins on the back of a transmitter to dis-sipate heat buildup.
hecto- (h-) - One hundred, or the metric prefix for 102, or times 100. Also known as hecta- (h-).
height above average terrain (HAAT) - A measure of how high an antenna site is above the surrounding landscape. It is officially measured in meters (m), even by the Federal Communications Commission (FCC) in the United States because Canada and Mexico, both of which use metric, have extensive border zones where international stations can be received on either side of the international boundaries.
height above sea level (HASL) - A measurement of how high an antenna site is above sea level, often used for mountaintop stations such as repeaters and portable operations to describe their elevation. Measured in either feet (ft) or meters (m) depending on the country.
Heliax - A brand name of a very low-loss, rugged, and relatively expensive hard line coaxial cable, often characterized by a corrugated outer shield and a low-density foam (often abbreviated LDF in product names) or air dielectric. Also known as Andrew Heliax; Andrew cable.
Hellschreiber (Hell) - light, bright, or clear writer - A digital mode for sending and receiving text using facsimile technology. Named for the inventor, a German engineer named Rudolph Hell, who patented this early method of facsimile sending in 1929. Also known as Feldhellschreiber; Feld-Hell.
henry (H) - The International System of Units (SI) derived unit of inductance named in honor of Joseph Henry, the American scientist who discovered electromagnetic induction independently of and at about the same time as Michael Faraday in England. (Plural is "henrys," not "henries.")
hertz (Hz) - The International System of Units (SI) unit of frequency defined as the number of cycles per second of a periodic phenomenon. One hertz equals one complete cycle per second. One of its most common uses is the description of the sine wave, particularly those used in radio and audio applications. It is named for Heinrich Rudolf Hertz, who was the first to conclusively prove the existence of electromagnetic waves.
heterodyne - Signals at the output of a mixing or modulating process.
hi hi - ha ha - The Morse code (CW) equivalent of a laugh. In Morse code, hi hi sounds like someone chuckling, that is, dot dot dot dot   dot dot. Although used in Morse code, it actually has carried over to phone as well, although absolutely no one knows why someone must say "hi hi" or even spell it out as "aich-eye-aich-eye;" why not just laugh!
high frequency (HF) - The frequency range of 3 to 30 megahertz (MHz). Normally, the 1.9 MHz or 160-meter (m) band is also included. Also known as decameter band; decameter wave; short wave.
High Speed Multimedia (HSMM) - An American Radio Relay League (ARRL) working group and individual amateur effort as well. Primary to high-speed voice, video, and data transmission on the amateur allocations within the 2.4 gigahertz (GHz) and 5.8 gigahertz (GHz) bands using commonly available WiFi equipment with high-gain directional antennas. Also known as high-definition television (HDTV) - When transmitted at two megapixels per frame, HDTV provides about five times as many pixels as standard-definition (SD) television.
high-frequency bands (HF bands) - Amateur radio bands in the region of the radio frequency (RF) spectrum from 3 to 30 megahertz (MHz). There are bands at approximately 80, 30, 20, 17, 15, 12 and 10 meters (m) in this region.
high-frequency scatter - Propagation of radio signals as they are scattered into the skip zone through several different radio wave paths, often resulting in a wavering or distorted sound. Also known as scatter propagation.
high-pass filter (HPF) - An electronic filter that passes high-frequency signals but attenuates or reduces the amplitude of signals with frequencies lower than the cutoff frequency.
high-performance software-defined radio (HPSDR) - An open-source, "GNU's Not Unix," pronounced as one syllable with a hard g (GNU) type hardware and software project defining next-generation software-defined radio by a more modular approach (using a common bus).
high-speed meteor scatter (HSMS) - A software program for meteor scatter communication. Also known as meteor scatter.
high-speed multimedia radio (HSMM) - A wireless high-speed data network (mesh) over amateur radio frequencies using commercial off-the-shelf hardware such as a wireless fidelity (WiFi) router or D-STAR equipment, for use in Amateur Radio Emergency Data Network (AREDN).
high tension (HT) - Voltage levels over 500 volts.
hinternet - (See high-speed multimedia)
hit the repeater - (Repeater term) Slang for access the repeater or communicate with the repeater, in an effort to make use of a repeater's repeat and other functions (such as Internet Radio Linking Project IRLP) or autopatch).
hold the repeater - (Repeater term) Slang for keep the repeater open or maintain repeater access, in an effort to maintain continuous use of a repeater's repeat and other functions (such as Internet Radio Linking Project (IRLP) or autopatch.
hole - A lack of an electron at a position where one could exist in an atom or atomic lattice of a doped semiconductor material.
hole-mount - (See through-hole mount)
holiday-style - Slang for a relatively relaxed station operating plan (typically in reference to a DXpedition or special event station), in which on-air operation might be seccondary to the intended journey, or that making contacts is not the station's first priority (the station will operate as time permits, in between activities, for example); often synonymous with vacation-style.
hollow state - (Archaic) A slang term for equipment that uses vacuum tubes.
Home Call Area - Of the 10 Federal Communications Commission (FCC) Regions in the United States, the one in which you resided upon issuance of your amateur radio license. For years, the Federal Communications Commission (FCC) required licensees to change call signs when they moved to a different call area, a requirement that is no longer in effect.
homebrew - Slang for home-built, do-it-yourself, noncommercial radio equipment.
homeowner association (HOA) - A corporation established by a real estate developer to market, manage, and sell homes and lots in a residential subdivision, which management can include enforcement of applicable covenants, conditions, and restrictions (CC&Rs) that limit the installation of ham radio equipment honeycomb coil - (Archaic) An inductor wound with turns that weave in and out radially so that adjacent windings are never parallel and thus minimizes the distributed capacitance of the coil.
hop - Communication between stations by reflecting the radio waves off of the ionosphere. (See sky-wave propagation)
horizon - (1) Perceived boundary between earth and sky from a given height. Also known as true horizon. (2) geometrical horizon: A calculated boundary between a spherical body (such as a star, planet, or moon, but in most applications, a spherical earth) and its sky, assuming ideal. Also known as true horizon. (3) radio horizon: The distance over which two stations can communicate by direct path, also known as line-of-sight propagation when applied to signals of frequencies higher than 30 megahertz (MHz), approximately 15 percent greater than the geometrical horizon because of downward bending caused by atmospheric density variations. (4) visual horizon/visible horizon: The apparent line or circle that separates the earth from the sky, whose distance is approximately 8 percent greater than the geometrical horizon because of downward bending caused by atmospheric density variations. Also known as skyline.
horizontal loop - (See skywire antenna)
horizontal polarization - An alignment of a signal's electric field parallel to the level surface of the earth (actually, perpendicular to the vector force of Earth's gravity), and a signal with such an alignment is said to be horizontally polarized. (See elliptical polarization; circular polarization; vertical polarization)
horizontally polarized antenna - An antenna in which the electric field lines are horizontal. This is generally the case for dipole or Yagi antennas with horizontal elements.
horizontally polarized wave - An electromagnetic wave with its electric lines of force parallel to the ground.
hot - (1) Slang for wire or other conductor in a particularly alternating current (AC) electrical system that has electric potential relative to ground. (2) Slang for over-driven microphone that results in clipping. (3) Slang for excessive amount of radio frequency (RF) signal flowing in the radio cabinetry or housing.
hot mic - Slang for microphone that is turned on.
hot-carrier diode - (See Schottky diode) Also known as hot carrier diode.
hot-wire ammeter (HWA) - (Archaic) A device for measuring feed-line current and therefore antenna current. It was the common way of specifying radiation (rather than power in watts).
Hotel - A North Atlantic Treaty Organization (NATO) phonetic alphabet code word representing the letter H. Used in radio communication, particularly when spelling out a call sign.
house current - (See household power) Also known as house power.
household power - General-purpose household AC electrical power that is supplied to a home, business, or facility. Also known as AC power; city power; outlet power; street power; utility power; wall power.
hum - Unwanted and often constant low-frequency sound, characteristic of an unintended oscillation or ground loop within a circuit. (See power-line interference)
hyperscan - A very high scanning rate in a scanner receiver. Also known as turboscan.

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iambic - (CW term) A method of Morse code (CW) keying where the operator holds both paddles at same time and sends alternating dots and dashes.
iambic keyer - A dual-paddle telegraph key that requires a (typically sideways) squeezing action to produce Morse code (CW) tones, unlike a straight key. Also known as iambic paddle.
Icom Commputer Control Interface (CI-V) - Allows multiple radio control simultaneously.
identification (ID) - The identification of an amateur radio operator that announces the station's call sign every 10 minutes as and at the end of a conversation as specified by Part 97 of the Federal Communications Commission (FCC) Rules and Regulations. Conversations need not come to a halt when one identifies.
image - (1) A communication mode, such as amateur television (ATV) and slow-scan television (SSTV), used for transmitting analog pictures over radio waves, often for reporting severe weather information, location announcements, and individual identification. (2) A false signal produced in a superheterodyne receiver's circuitry.
image response rejection ratio (IMRR) - The ratio of intermediate frequency (IF) signal strength produced by the received signal with respect to that produced by the image response, expressed in decibels (dB).
image rejection - An undesirable signal generated when a superheterodyne receiver mixes a VFO frequency with a received signal to produce an IF signal; in other words, the unwanted signal is a "mirror image" of the receive signal in response to the mixing function.
imbalance current - See commode-mode current.
impedance - The opposition of both the electrical alternating current (AC) and direct current (DC) in a circuit. Impedance includes factors other than resistance, and applies to alternating currents. Ideally, the characteristic impedance of a feed line is the same as the transmitter output impedance and the antenna input impedance.
impedance matching - To design or adjust impedances of a circuit to be equal or the case in which two impedances are equal. The term usually refers to the point at which a feed line is connected to an antenna or to transmitting equipment. If the impedances are different, that is a mismatch. (See mismatch) Also known as match.
impedance transformation - Changing the voltage to the current ratio of a signal in a circuit. It can be done with a transformer or by making use of the transformational property of mismatched transmission lines.
impedance-matching device - Also called impedance matching unit. (See antenna tuner)
in-and-out - (See early out)
in-the-mud - (See mud)
in-phase - The description of two alternating current (AC) signals whose voltage values or current values reach their peak levels at the same time. (See in-phase / quadrature) Also known as in phase; inphase.
in-phase/quadrature (IQ data) - Two components of a modulated signal that reflect changes in the amplitude and phase of a sine wave; used for digital signal processing or in analysis. Also known as IQ; I and Q signal; quadrature phase.
incident - The situation, occurrence, or risk that poses a threat to health, life, property, or environment, and one that might require the services of an Incident Management Team or Incident Response Team Incident Commander (IC) - The highest-level leader in the National Incident Management System during a particular incident, and the person in charge of managing and coordinating all resources in conjunction with the incident.
Incident Management Team (IMT) - A group that identifies, analyzes, and corrects hazards to prevent a future re-occurrence.
Incident Response Team (IRT) - A group that identifies, analyzes, and corrects hazards to prevent a future re-occurrence.
increment steps - The discrete frequency steps tuned by a receiver using frequency synthesis.
incremental frequency keying (IFK) - A shift keying variant of multi-frequency-shift keying (MFSK) used for transmission of information. (See DominoEX and multi-frequency-shift keying)
India - A North Atlantic Treaty Organization (NATO) phonetic alphabet code word representing the letter I. Used in radio communication, particularly when spelling out a call sign.
indicator - Used to signal status audibly or visually, it is words, letters, or numerals appended to and separated from the call sign during station identification.
indirect frequency modulation (indirect FM) - (See phase modulation)
individual calling - One-to-one form of communication. (See group calling) Also called paging.
inductance - A measure of the ability of a coil to store energy in a magnetic field.
inductive coupling - The effect of two or more circuits not connected to each other being close enough that an AC current through one can result in an alternating current (AC) voltage across the others through mutual inductance.
inductive index (AL; AL) - The specification of an inductor core, dependent upon its material permeability, dimensions, and shape, expressed in inductance-per-square turn. Also known as inductance index.
inductive reactance - The imaginary quantity of opposition to current flow in a circuit (reactance) due to inductance, that varies with frequency and is expressed in ohms (Ω).
inductive time constant - (See time constant)
inductor - An electrical component, usually composed of a coil of wire wound on a central core. An inductor stores energy in a magnetic field and is usually composed of a coil of wire wound around a central core.
inductor core - A centrally located inductor section of greatest magnetic field concentration, highly dependent on material type, of which soft iron, powdered metals, ferrite, air, and some special alloys are among the most common. Also known as magnetic core; slug.
inductor tap - (See tap)
infinite impulse response (IIR) - A type of digital signal processing filter whose impulse response can be infinite, in that it might never reach zero, resulting in a filter that is generally easier to implement for a given set of passband rolloff requirements.
informal traffic - Messages handled informally on behalf of others without the benefit of a preamble. (See traffic and preamble)
information bulletin - A message directed only to amateur operators consisting solely of subject matter of direct interest to the amateur service.
infrared - Having a wavelength just greater than that of the red end of the visible light spectrum but less than that of microwaves. Infrared radiation has a wavelength from about 800 nanometers (n) to 1 milimeter (m), and is emitted particularly by heated objects.
infinite impulse response - A type of digital signal processing filter whose impulse response can be infinite, in that it might never reach zero, resulting in a filter that is generally easier to implement for a given set of passband rolloff requirements.
ingress - The absorption of radio-frequence interference (RFI) and audio-frequency interference (AFI( into a vehicle's or radio's electrical circuitry where it is unwanted.
input frequency - (Repeater term) A repeater's receiving frequency. To use a repeater, one transmits on the input frequency and receives on the output frequency.
input-offset voltage - The differential input voltage of an op-amp required to bring its open-loop output voltage to zero. Also known as input offset voltage.
input/output (I/O) - The communication between an information processing system, such as a computer, and the outside world — possibly a human or another information processing system. Inputs are the signals or data received by the system, and outputs are the signals or data sent from it.
insertion loss - A signal loss introduced by the addition of an electric component, such as a connector, filter, meter, switch, or feedline extension.
insulation-displacement connector (IDC) - A connector intended for use on flat ribbon-type cables.
insulator - A material whose internal electric charges do not flow freely, and which therefore does not conduct an electric current under the influence of an electric field.
integrated circuit (IC) - A single structure, such as a chip, containing multiple active devices that perform a function such as an op-amp, a number of logic gates, or a microprocessor.
intensity (I) - The symbol for current in an electric circuit, measured in amperes.
intercept point - (See third-order intercept point)
interconnect, passive and electro-mechanical (IP&E) - The non-active components in an electronic system. Interconnects are plugs and sockets. Passive components refer to resistors, capacitors, potentiometers, transformers, and inductors. Electromechanical covers mechanical relays and switches, as well as fans and power supplies.
interference - Anything that discrupts or modifies a radio signal; interruption or excessive noise in a radio transmission. (See harmful interference; malicious interference)
intermediate - (Archaic) The separator between a called and a calling station's call signs which in the 1920s was proposed to change depending on the countries involved during a contact. Also known as interval sign.
intermediate frequency (IF) - A frequency to which a carrier frequency is shifted as an intermediate step in transmission or reception. The IF is created by mixing the carrier signal with a local oscillator signal in a process called heterodyning, resulting in a signal at the difference or beat frequency. These frequencies are used in superheterodyne radio receivers, in which an incoming signal is shifted to an IF for amplification before final detection is finished. Most of the receiver's gain and selectivity are achieved at the IF stages. (See heterodyne)
intermediate-frequency shift (IF shift) - A function that electronically shifts intermediate frequency (IF) frequency from a center frequency, usually to eliminate interference.
intermediate frequency shift - A function that electronically shifts the IF frequency from a center frequency to reduce interference.
intermodulation (intermod) - A problem caused in the receiver of a radio by a nearby transmitter's spurious emissions that may fall on or very near to the receiver's receive frequency. In some cases, a perfectly clean transmitter (i.e., no spurious signals) can produce intermod if it overloads a receiver or if there is some other point for 3rd-order intercept. Intermod, which is close, but not necessarily right on, the receiver's frequency can cause the receiver to become less sensitive. Also known as desense; intermodulation distortion. (See desensitization) Also known as inter-modulation distortion.
intermodulation distortion (IMD) - (See intermodulation)
intermodulation interference (IMI) - The undesirable interference effect of intermodulation distortion.
International Amateur Radio Permit (IARP) - A document that allows foreign operation within North and South American treaty countries, other than the United States, without the need to obtain a license or permit.
International Amateur Radio Union (IARU) - An association of national amateur radio organizations created to represent amateur radio before the International Telecommunications Union (ITU). (See International Telecommunications Union)
International Civil Aviation Organization (ICAO) - An organization that promotes understanding and security through cooperative aviation regulation.
International Civil Aviation Organization spelling alphabet (ICAO spelling alphabet) - (See North Atlantic Treaty Organization (NATO) phonetic alphabet)
International Bureau of Weights and Measures (BIPM) - An international standards organization, one of three such organizations established to maintain the International System of Units (SI) under the terms of the Metre Convention.
International Committee for Weights and Measures (CIPM) - The eighteen persons from Member States of the Metre Convention appointed by the General Conference on Weights and Measures (CGPM) whose principal task is to ensure world-wide uniformity in units of measurement by direct action or by submitting proposals to the CGPM.
International Prototype Kilogram (IPK) - Commissioned by the General Conference on Weights and Measures under the authority of the Metre Convention (1875), the IPK is in the custody of the International Bureau of Weights and Measures (BIPM).
International Reply Coupon (IRC) - A coupon available at the post office and widely accepted worldwide, although not universally, as return postage for QSL cards.
International Space Station (ISS) - A habitable artificial satellite in low Earth orbit.
International System of Units (SI) - The modern form of the metric system.
International Telecommunications Union (ITU) - The organization of the United Nations (UN) that specifies worldwide guidelines concerning the use of the electromagnetic spectrum for communication purposes.
International Telecommunications Union phonetic alphabet (ITU phonetic alphabet) - (See North Atlantic Treaty Organization phonetic alphabet)
International Telecommunications Union Region - Any one of 3 major geographic world areas, as defined and named numerically by the International Telecommunications Union (ITU). Also known as ITU Region.
International Telecommunications Union Zone - Any one of 75 geographic areas of the world, as defined and named numerically by the International Telecommunications Union (ITU). Also known as ITU Zone.
International Telegraph Alphabet number 2 (ITA2) - A system in which characters are expressed using five bits that was used until the advent of the American Standard Code for Information Exchange (ASCII).
Internet - A global system of interconnected computer networks that use the standard Internet protocol suite, Transmission Control Protocol (TCP) and Internet Protocol (IP) to serve billions of users worldwide.
Internet Protocol (IP) - The principal communication protocol in the Internet protocol suite for relaying datagrams across network boundaries. (See Transmission Control Protocol)
Internet protocol suite (TCP/IP) - The set of communications protocols used for the Internet and similar networks, and generally the most popular protocol stack for wide area networks. (See Internet Protocol and Transmission Control Protocol)
Internet Radio Linking Project (IRLP) - (Repeater term) A system that uses a network protocol called voice over Internet Protocol (VoIP) to link repeaters. There are now over 1,000 repeaters around the world connected by the Internet through the amateur radio Internet radio linking project, 24 hours a day, 7 days a week.
Internet remote base - The control an amateur radio station remotely through a computer.
intermodulation distortion (IMD) - The undesirable signal generated by the amplitude modulation mixing of two or more signals with different frequencies, arising from system nonlinearities, and resulting in distortion and intermodulation interference with an excessively large bandwidth (not to be confused with harmonics).
intermodulation interference (IMI) - The undesirable interference effect of intermodulation distortion.
interplanetary magnetic field (IMF) - The portion of the solar magnetic field that is carried by the solar wind among the planets of the solar system (interplanetary space).
interpolation - The process of mathematically increasing the sample rate of a signal (upsampling); for example, interpolate a digital signal by three, then decimate it by four, to adjust its sampling rate by a factor of 3/4.
interrupted Morse code (ICW) - (Archaic) (CW term) A modulated Morse code (CW) signal using a chopper to pulse it. (See chopper)
interval sign - (Archaic) (See intermediate)
intrinsic - Meaning natural state, as it applies to semiconductors, material or portion (region) of material that has not been doped, but exists in its extremely pure form, opposite of extrinsic.
Inverse Square Law - The physical principle by which power density decreases as you get further away from a transmitting antenna. Radio frequency power density decreases by the inverse square of the distance.
inverted-L antenna - A type of monopole antenna whose vertical radiating element section is bent over and made parallel to the ground. Also known as inverted L antenna; inverted ell antenna.
inverted-V antenna - A type of dipole wire antenna in which the center is higher than the two ends. This is probably the most common way dipoles are installed today. Also known as inverted V antenna; inverted vee antenna.
inverter - A device that converts direct current (DC) power typically into 60Hz alternating current (AC) power.
inverting - A type of non-mode-specific linear transponder that re-transmits a received signal at the same passband offset from the end of its passband as that of the received signal, but on the opposite end of the passband (roughly mirrored image of the received signal).
ion - An electrically-charged atom or molecule in which the total number of electrons is not equal to the total number of protons, giving the atom a net positive or negative electrical charge.
ionization - The process of adding or stripping away electrons from atoms or molecules. Ionization occurs when substances are heated at high temperatures or exposed to high voltages and can lead to significant genetic damage in biological tissue.
ionizing radiation - Electromagnetic radiation that has sufficient energy to knock electrons free from their atoms, producing positive and negative ions. X-rays, Gamma rays, and ultraviolet radiation are examples of ionizing radiation. (See radiation)
ionosonde - A device that uses radio waves to examine the ionosphere and report optimum operating frequencies suitable for HF two-way communication.
ionosphere - A region of electrically charged or ionized gases high in the atmosphere. The ionosphere bends radio waves as they travel through it, returning them to Earth. Also known as sky-wave propagation.
ionospheric scatter - A form of scatter propagation in which radio waves are refracted by the E layer of the ionosphere, allowing for communication between 25 megahertz (MHz) and 100 MHz as a result of irregularities or discontinuities in that atmospheric region. Also known as ionoscatter.
ionospheric storm - A disturbed condition in the ionosphere caused by release of charged particles by the sun that results in high absorption and poor radio propagation on most frequencies.
ionoscatter - (See ionosphere scatter)
Islands On The Air (IOTA) - A popular Radio Society of Great Britain (RSGB) award for amateur radio operators, where the objective is to contact amateur radio operators transmitting from offshore islands throughout the world.
isolator - (See radio frequency isolator)
isotropic antenna - A theoretical antenna used as a reference for antenna gain measurements, and has no gain in any direction.

To the top!   J

J-antenna - (See J-pole antenna)
J-pole antenna - An omnidirectional vertical end-fed dipole antenna that is a mechanically modified version of the Zepp (Zeppelin) antenna. It consists of a half-wavelength radiator fed by a quarter-wave matching stub. This antenna does not require the ground plane that 1/4-wave antennas do to work properly. Also known as J-antenna.
jack - A female electrical connector designed to have a mating assembly inserted into it.
jam - To cause intentional interference with another radio signal. Also known as jamming.
Jamboree On The Air (JOTA) - An annual event in which about 500,000 Scouts and Guides all over the world make contact with each other by means of amateur radio.
Joe Taylor, 9 tones (JT9) - A type of MFSK data transmission protocol (specifically, AFSK modulation) designed to support very weak signal communication by decoding signals many dB below the noise floor using FEC. The software for this mode (WSJT) was written by Joe Taylor K1JT, the 1993 winner of the Nobel Prize in physics.
Joe Taylor 65 tones (JT65) - A type of MFSK data transmission protocol (specifically, AFSK modulation) designed to support EME, tropospheric scatter, and other very weak signal communication by decoding signals many dB below the noise floor using FEC. The software for this mode (WSJT) was written by Joe Taylor K1JT, the 1993 winner of the Nobel Prize in physics. Also known as JT-65.
Joe Taylor 65-High Frequency (JT65-HF) - Alternative extension to the JT65 data transmission protocol designed for communication on HF bands at very low power levels. The software for this mode (WSJT) was written by Joe Taylor K1JT, the 1993 winner of the Nobel Prize in physics.
Jones filter - A variable-bandwidth crystal lattice filter, used as part of a high frequency (HF) receiver intermediate frequency (IF) stage.
Jordan Sherrer-designed 8-FSK - A type of frequency-shift keying (FSK) data transmission protocol similar to Franke-Taylor, 8-FSK (FT8), but adds keyboard-to-keyboard text messaging.
joule (J) - The International System of Units (SI) unit of work or energy, equal to the work done by a force of one newton when its point of application moves one meter (m) in the direction of action of the force, equivalent to one 3600th of a watt-hour. Named for the British physicist James Prescott Joule.
jug - (Archaic) A synonym for a large transmitting vacuum tube. (See vacuum tube) Also known as klystron; magnetron; valve.
juice - (Archaic) An early common slang term for electric power service.
Juliet - A North Atlantic Treaty Organization (NATO) phonetic alphabet code word representing the letter J. Used in radio communication, particularly when spelling out a call sign.
jump off - Slang for an intention to leave the current conversation.
jumper - (1) A small piece of wire used to connect two parts of a circuit. In computers and other devices, a jumper may take the form of a smaller plastic piece with an internal conductor that fits over two circuit board posts. (2) A removable electrical component used for connecting two or more pins or posts that are installed on a printed circuit board or other surface, to make such a connection available. Also known as pigtail.
junction diode - (See semiconductor diode)
junction field-effect transistor (JFET) - A field-effect transistor that can be used as an electronically-controlled switch or as a voltage-controlled resistance. Electric charge flows through a semiconducting channel between source and drain terminals and by applying a reversed-bias voltage to a gate terminal. The channel had reached the pinch-off voltage, so that the electric current is impeded or switched off completely. (See varactor)
junction transistor - (See bipolar junction transistor)
junkbox - A slang word for the collection of spare parts and miscellaneous items kept by an amateur radio operator or hobbyist.
jury rig To fix in an unorthodox manner.

To the top!   K

K-index - A measure of the Earth's magnetic field as measured at Boulder, Colorado. Propagation conditions improve with lower measurement numbers.
K9YA Telegraph Magazine - A magazine offering the amateur radio community a no-cost, high-concept publication covering a number of topics unavailable elsewhere and in providing a welcoming venue and readership to first-time writers. It is an ezine first published in January 2004.
Keep It Simple, Stupid (KISS) - A protocol for communicating with a serial terminal node controller (TNC).
Keplerian data sets (keps) - Data showing you everything about a sattelite and allowing you to "find" any satellite there is.
Keplerian elements - Numeric parameters describing a satellite's orbit that can be used to compute the position of the satellite at any point in time. Named for Johannes Kepler and his six laws of planetary motion.
kerchunk - (Repeater term) The sound made when a brief transmission activates a repeater.
kerchunker - (Repeater term) An operator that activates a repeater station by transmitting on its input frequency without speaking.
kerchunking - (Repeater term) Activating a repeater without identifying or modulating the carrier.
key - (1) (CW term) A manually operated switch device that turns a transmitter on and off to send Morse code (CW). Also called a straight key or telegraph key. (2) To press a key or button. Also called cootie key; slap key; telegraph key.
key click - A spurious signal generated when a transmitter is turned on or off that is heard as a click by stations on nearby frequencies. Also known as Chirps.
key up - (1) To activate a transmitter. (2) (Repeater term) To turn on a repeater by transmitting on its input frequency. Also known as key-up.
keyboard-to-keyboard - A digital mode intended for operators to exchange text messages as characters are entered.
keyer - (1) (CW term) A device used to send Morse code (CW) semi-automatically and more accurately. It connects to a key and forms a continuous string of dots and dashes, depending on which lever of a connected paddle is pressed. Also known as electronic keyer. (2) (CW term) A person who sends Morse code.
kilo (k) - One thousand, or the metric prefix for 103, or times 1,000.
Kilo - A North Atlantic Treaty Organization (NATO) phonetic alphabet code word representing the letter K. Used in radio communication, particularly when spelling out a call sign.
kilocycle (kc) (Archaic) A thousand cycles per second. Replaced by kilohertz (kHz). (See kilohertz)
kilogram (kg) - The base unit of mass in the International System of Units (SI) defined as being equal to the mass of the International Prototype of the Kilogram (IPK).
kilohertz (kHz) - One thousand (1,000) cycles per second. (See hertz)
kilometer (km) - A unit of length in the metric system, equal to one thousand meters (m). Also known as kilometre.
kilowatt (KW) - One thousand (1,000) watts.
kilowatt-hour meter (kWh meter) - A device used to measure electrical consumption over time. Often used by power companies to establish usage for billing purposes.
klystron - A specialized vacuum tube that uses velocity modulation in high-power very-high frequency (VHF), ultra-high frequency (UHF), and microwave television and radar amplifiers and transmitters.
knife-edge - The result of the alteration of radio waves if the dimensions of a diffraction edge is small in terms of a wave's wavelength. (See diffract) Also known as knife edge; knife-edging; knife edging.

To the top!   L

L band - A synonym for the 23-cm band.
L network - A two-element, generally passive network, with one series element and one shunt element. The circuit diagram resembles the letter L.
LC circuit - An electric circuit consisting of an inductor, represented by the letter L, and a capacitor, represented by the letter C, connected together. Also known as tank circuit.
LC oscillator - An oscillator using an inductor and a capacitor connected to determine its oscillating frequency.
ladder line - (See open-wire line)
lag - The waveform in which positive chnge occurs last in comparing two waveforms.
lamp - An electric device capable of producing (typically incandescent) light.
land mobile radio (LMR) - (See professional mobile radio)
land mobile radio system (LMRS) - A person-to-person voice communication system consisting of two-way radio transceivers (an audio transmitter and receiver in one unit) which can be stationary (base station units), mobile (installed in vehicles), or portable (handheld walkie-talkies).
landline - A dedicated leased or dial-up telephone line, often used to provide control connectivity to a remote repeater station.
lead - (1) A wires or connection point on an electrical component or a probe and cable that is used to connect test instruments to the devices being measured. (2) The waveform in which change in the positive direction occurs first when comparing two waveforms.
lead acid - The oldest type of rechargeable battery most commonly used in automobiles and marine applications. As some batteries can deliver large amounts of current instantaneously and contain sulphuric acid, these must be handled with caution.
least significant bit (lsb) - The bit in a binary number that is of the lowest numerical value.
legal limit - The highest amount of transmitter power (PEP) allowed by the Federal Communications Commission (FCC) for amateur use, or 1500 watts or 1.5 kilowatts (kW).
Leyden jar - A crude passive electrical device once used for temporarily holding a high-voltage (estimated 20 kilovolts (kV) to 60 kV) electric charge, and original complete forerunner of the modern capacitor, consisting basically of a sheet of foil that lines the inside of a glass jar, connected to a rod or other conductor that protrudes through the lid (and often topped by a corona ball to prevent or slow atmospheric charge leakage), plus another sheet of foil that wraps around the outside of the glass jar. Also known as Leiden jar.
lid - (CW term) A synonym for an inept radio operator — one who does not follow proper procedures, sends sloppy Morse code (CW), has very poor practices, and has bad manners.
light-emitting diode (LED) - A semiconductor light source, LEDs are used as indicator lamps in many devices and are increasingly used for other lighting.
lightning - A sudden electrostatic discharge, normally during an electrical storm, between electrically charged regions of a cloud, between a cloud and another cloud, or between a cloud and the ground, often referred to as a strike, and is a form of arcing.
lightning arrestor - A device used on buildings, electrical power systems, and telecommunications systems to protect the insulation and conductors of the system from the damaging effects of lightning. The typical lightning arrester has a high-voltage terminal and a ground terminal. When a lightning surge (or switching surge, which is very similar) travels along the power line to the lightning arrester, the current from the surge is diverted through the arrestor, in most cases to earth. Also known as arrestor; RF lightning arrestor; RF protector.
lightning dissipator - A type of omnidirectional antenna (version of biconical antenna) that consists of a disc on top and downwardly open cone underneath, both made from sheet metal or sets of rods, but separated from each other by an insulator. Also known as lightning dissipater.
lightning protection - Methods to prevent lightning damage to one's house and equipment, such as unplugging the equipment, disconnecting the antenna feed lines, and using a lightning arrestor that is placed where wires enter a structure, preventing damage to electronic instruments within and ensuring the safety of individuals near them.
liquid-crystal display (LCD) - A device for displaying graphics or characters by passing light through a liquid crystal between patterns of electrodes. The light transmission is changed from transparent to opaque with the application of voltage. Also known as liquid crystal display.
Lima - A North Atlantic Treaty Organization (NATO) phonetic alphabet code word representing the letter L. Used in radio communication, particularly when spelling out a call sign.
limiter - (1) An amplifier in a frequency modulation (FM) receiver that makes the receiver less sensitive to amplitude variations and pulse noise. (2) A type of circuit that prevents a signal's amplitude from exceeding a fixed limit. (See automatic noise limiter. Also known as clamp; limiting.
line - (1) Any visible or imaginary path defined or identified for propagation purposes, such as gray-line or line-of-sight. (2) Any conductor of electrical energy, such as a transmission line or power line or ground line. (3) A pathway for communication (communication line), such as a telephone landline. (4) A row of characters forming a text message. (See feed line; power line; scan line)
line A - An imaginary line roughly parallel to, and south of, the United States-Canadian border, north of which amateur stations are not permitted to transmit between 420 and 430 megahertz (MHz).
line amplifier - An amplifier whose output preserves the input waveform, and is usually a Class A amplifier. Also known as linear; power amplifier.
line isolator - (See radio frequency isolator)
line noise - (See power line noise)
line-of-sight (LOS) - The term used to describe very-high frequency (VHF) and ultra-high frequency (UHF) propagation in a straight line directly from one station to another. Also known as "line-of-sight propagation."
linear - To act on a signal such that the result is a replica of the original signal at a different scale.
linear amplifier - (See amplifier)
linear power supply - A type of power supply that converts electrical alternating current (AC) power to direct current (DC) power directly, without pulsing the energy during the conversion process, and is typically much heavier and less efficient than a switching power supply, but also typically less (electrically) noisy.
linear transponder - (See transponder)
ling distance (LD) - (Archaic) A precursor to distant station (DX). (See distant station)
link - A communication connection, typically by internet, radio waves of a much higher frequency, or being directly wired, between two repeaters or between one station and another, each point connected this way being called a node.
lip mount - A type of antenna mount that combines an antenna attachment method with a fixture connection for installation on the edge of a sheet metal body, such as that of a vehicle trunk or metal cabinet or enclosure. Also known as lip-mount; trunk-lip mount.
listen out - Slang for continue listening on this frequency until the end of the conversation.
lithium ion (Li-Ion) - A type of rechargeable battery that has better capacity than Ni-Cad (Nickel-Cadmium), Ni-MH (Nickel-Metal Hydride), etc., with no memory effect after repeated non-full charge/discharge cycles.
lithium iron phosphate (LiFePO4 - A type of rechargeable battery that offers a longer lifetime than do other battery types, is safer, exhibits little or no memory effect, and is known for high energy density compared with that of other batteries, and relative low weight but high cost and high and constant charge/discharge rate compared with that of Li-ion batteries. Also known as lithium ferrophosphate (LFP).
lithium-ion-polymer (Li-Po) - A type of lithium-ion rechargeable battery that either contains a polymer electrolyte or is encased in a polymer package, and exhibits little or no memory effect. Also known as lithium-polymer; LiPo; LiPol.
Litzendraht wire (Litz wire) - (Archaic) A bundle of stranded wire with each strand insulated from one another to reduce alternating current (AC) resistance due to skin effect by increasing surface area. The term comes from Litzendraht, German for braided, stranded, or woven wire.
load - (1) A device or system to which elelctrical power is delivered, such as an antenna or a heating element. (2) The amount of power consumed or that can be safely dissipated, such as a 50-watt load.
loaded dipole antenna - An electrical half-wavelength antenna shortened by the substitution of series inductance or shunt capacitance in place of antenna length.
loading coil - An inductance inserted into an antenna that lowers its resonant frequency allowing for a shorter antenna. Also known as inductor; resonator.
lobe - An area in the radiation pattern of an antenna where the radiation is at maximum. The main or major lobe has the greatest strength for the entire pattern. The side lobes of the far field radiation pattern of an antenna are located at an angle to the main lobe.
local area network (LAN) - A small computer network generally limited to a small geographical area. This is usually within the same building or a single floor of a building.
local control - A control operator who directly manipulates the operating adjustments in a station to achieve compliance with Federal Communications Commission (FCC) rules.
Local Government Liaison (LGL) - An appointee of the American Radio Relay League (ARRL) who monitors local government dockets consistently, offers local, organized support quickly when necessary, and is known in the local amateur community as the point man for local government problems.
local oscillator (LO) - A receiver circuit that generates a stable, pure signal used to mix with the received radio frequency (RF) to produce a signal at the receiver intermediate frequency (IF).
log - (1) The documents of an amateur radio station that detail operation of the station. They can be used as supporting evidence and for troubleshooting interference-related problems or complaints. (2) The recording of amateur radio contacts. Although it is no longer mandatory by Federal Communications Commission (FCC), it is required for contesting.
log-periodic dipole array (LPDA) A broadband, multi-element, directional, narrow-beam antenna that has impedance and radiation characteristics that are regularly repetitive as a logarithmic function of the excitation frequency.
logger - A person who assists the operator of a contest or event by recording the contact details.
Logbook of the World (LOTW) - An online database implemented by the American Radio Relay League (ARRL) to provide a contact verification service for ham radio operators toward awards.
logging software - A computer log of contacts, used for QSL card con-firmations on contacts.
lollipop - A ham radio term for an Astatic D-104 microphone.
Long Interval Tone Zero (LiTZ) - A loosely defined alert method within the Wilderness Protocol in which a person in need of help can issue an alert by pressing and holding the Ø (zero) key on a transmitter keypad for three or more seconds to send a dual-tone multi-frequency (DTMF) tone that can open a repeater that supports the protocol, or at the very least can alert another ham who might be monitoring the frequency. Also known as Long-tone Zero; Long Tone Zero.
long wave (LW) - The frequency range of 150 to 300 kilohertz (kHz), although this term is often used to mean any radio signal lower than 540 kilohertz (kHz). Also known as longwave.
long-wire antenna - (See random wire antenna)
long-range navigation (LORAN) - Originally developed for navigation over the Atlantic, the original LORAN system used longer wavelengths for longer range.
loop antenna - (1) A small receiving antenna usually designed for indoor use and tuning frequencies below 5 megahertz (MHz). It is constructed with elements that are continuous lengths of wire or tubing. (2) A point of maximum voltage of current on an antenna.
loop skywire - (See skywire antenna)
loss - The reduction in (attenuation of) signal strength; negative gain.
loss of signal (LOS) - A condition that occurs when a satellite becomes invisible to the antenna as it goes below the horizon.
loss resistance - (See motional resistance)
loud and clear - Your audio is strong and perfectly understandable.
loudspeaker - (See speaker)
low band - Slang for high frequency (HF). Also known as lowband.
Low Earth Orbit (LEO) - A satellite in Low Earth Orbit is an Earth-centred orbit with an altitude of 1,200 miles or less whose pass time will vary from two to six minutes.
low frequency (LF) - The frequency range of 30 to 300 kilohertz (kHz).
low power operation (QRP) - Usually 1 watt or less.
low-angle radiation - The primary or average radio frequency (RF) field of an antenna system that is radiated at a relatively low predetermined angle, with respect to level ground. (See far-field)
low-density foam (LDF) - A model name/prefix for a common type of dielectric used in Heliax cable and other hard-line versions of feedline.
low-frequency experimental radio (LowFER) - A synonym for one who experiments at very low frequencies, typically on 1750 meters (m), which is 160 to 190 kilohertz (kHz) and can be used under Federal Communications Commission (FCC) Part 15 which covers radio-frequency devices. Also known as LOWFER.
low-noise amplifier (LNA) - An electronic amplifier circuit for very weak RF signals, such as those that are received from a feedline and its attached antenna, and typically used in the front end of a receiver circuit.
low-pass filter (LPF) - A filter that allows signals below the cutoff frequency to pass through and attenuates signals above the cutoff frequency. (See cutoff frequency) Also known as low pass filter.
lower sideband (LSB) - (1) In an amplitude modulation (AM) signal the sideband located below the carrier frequency. (2) The common single-sideband operating mode on the 40-, 80- and 160-meter (m) amateur radio bands. (See sideband) Also known as lower sideband.
lowest usable frequency (LUF) - The lowest frequency that can support propagation between two points.

To the top!   M

machine - (1) Repeater term) Slang term for an automatic repeater station. (2) (Archaic) Infrequently used slang for rig.
magic band - A synonym for the 6-meter (m) band, or 50 to 54 megahertz (MHz), due to its unpredictable propagation. During band openings you can work the world with just 10 watts or less.
magnetic core - (See inductor core)
magnetic field - A mathematical description of the magnetic influence of electric currents and magnetic materials. A magnetic field exists in a region of space if a magnet or an electrical current is subjected to a magnetic force.
magnetic loop antenna - A type of antenna whose radiating element is bent into a roughly rectangular or curved into a roughly circular shape, to be operated from within a relatively small area, such as a house or backyard.
magnetic mount - (Repeater term) A magnetic base that permits quick installation and removal of an antenna from a motor vehicle or other metal surface. Also known as mag mount; mag-mount; magmount; magnetic-mount.
magnetosphere - An area of space near the earth in which the behavior of charged particles are often controlled by the earth's magnetic field.
magnetron - (See vacuum tube)
magnetron oscillator - A high-power ultra-high frequency (UHF) or microwave oscillator made from a diode vacuum tube with a specially shaped anode surrounded by a permanent magnet, to create an interaction between the resulting stream of electrons and the magnetic field.
Maidenhead Locator System - A geographic coordinate system of grid squares drawn on maps of the Earth and used by amateur radio operators. It was named after the town outside London where it was first conceived by a meeting of European very-high frequency (VHF) managers in 1980. (See grid square)
main lobe - (See lobe)
mains electricity - The general-purpose alternating-current (AC) electric power supply. Also known as mains power.
malicious interference - Harmful nterference that seriously degrades, obstructs, or repeatedly interrupts a radio communication service operating in accordance with the Radio Regulations. (See harmful interference)
Marconi, Guglielmo - An Italian inventor and engineer, labeled by many as the Father of Wireless Telegraphy, the Father of Radio, and even credited with the invention of the radio, was known especially for his pioneering work on long-distance radio transmission.
marine high-frequency radio channels - Channels assigned by international agreement for use by recreational or commercial vessels beyond the range of coastal very-high frequency (VHF) operation. There are channels assigned near 2, 4, 6, 8, 11, 13, 17 and 22 megahertz (MHz).
maritime mobile - Amateur radio operation from aboard a marine vessel.
maritime station - A two-way radio unit aboard a ship or a station on land that communicates with ships.
mark - The higher frequency of a binary frequency-shift keying (BFSK) data signal, identifying the 1 bit.
mark frequency - In frequency-shift keying, the higher of the two frequencies used. (See space frequency)
MARS/CAP modification - Modification made to a transceiver, enabling transmissions outside the frequency limits of the amateur bands, originally for use on military bands used by Military Auxiliary Radio System (MARS) and Civil Air Patrol (CAP) operation, but can also extend to bands reserved for General Mobile Radio Service (GMRS), Family Radio Service (FRS), Multi-Use Radio Service (MURS), Maritime, Aviation, and other communication.
mass-produced rig (MPR) - A radio that is produced in large quantities. The term is often used to describe radios that are not originally purchased in kit form.
mast - The bottom section of a center-loaded antenna. Common mast materials include aluminum, stainless steel, copper plated steel, and fiberglass covered copper.
master oscillator, power amplifier (MOPA) - A configuration that inserts an amplifier stage between the oscillator and the antenna which prevents changes in the loading presented by the antenna from altering the frequency of the oscillator.
match - (See antenna match; impedance matching)
matchbox - (See antenna tuner)
matching coil - A small coil attached at the base of a mobile high-frequency (HF) antenna. It uses capacitive reactance from the antenna to form an inductor/capacitor (LC) network which transforms the antenna's input impedance to that of the feed line.
Maxim, Hiram Percy - An American radio pioneer and inventor who founded the American Radio Relay League (ARRL) in response to the lack of relay stations that could pass messages via amateur radio at the time.
maximum authorized transmitting power - No more than the maximum transmitter power by an amateur station necessary to carry out the desired communications.
maximum permissible exposure (MPE) - The highest power or energy density that is considered safe, that is, that has a negligible probability for creating damage in the human body. Limits are based on whole-body specific absorption rate (SAR) values. The Federal Communications Commission (FCC) Rules establish maximum permissible exposure values for humans to radio frequency (RF) radiation. (See specific absorption rate)
maximum symbol rate - (See baud)
maximum useable frequency (MUF) - The highest-frequency radio signal that will reach a particular destination using sky-wave propagation, or skip. The MUF may vary for radio signals sent to different destinations.
mayday - From the French m'aidé; m'aider; m'aidez for help me, mayday is used when calling for emergency assistance in voice modes. (See distress call)
mean power - (See average power)
mechanical filter - A filter that uses a network of mechanical piezoelectric elements to obtain high rejection of unwanted signals. (See piezoelectric)
medium frequency (MF) - The frequency range of 300 to 3,000 kilohertz (kHz).
medium-wave-frequency experimental radio (medfer) - Experiments with radio communications at low frequencies such as those on the edges of the amplitude modulation (AM) broadcast band.
medium wave (MW) - The frequency range of 300 to 3,000 kilohertz (kHz). Also used for the amplitude modulation (AM) broadcast band from 530 to 1710 kilohertz (kHz). This range includes the 160-meter (m) amateur band, the AM broadcast band, and the 2182 kilohertz (kHz) marine radiotelephone band.
mega (M) - One million, the metric prefix for 106, or times 1,000,000.
megacycle (mc) - (Archaic) (See megahertz)
megahertz (MHz) - One million (1,000,000) cycles per second.
megawatt (MW) - One million (1,000,000) watts of transmitter power.
memory bank (bank) - A set of memory channels organized into a group.
memory channel - Frequency and mode information stored by a radio and referenced by a number or alphanumeric designator.
memory effect - A situation in which rechargeable batteries such as Ni-Cad and Ni-MH types may be temporarily getting less capacity as a result of repeated non-full charge/discharge cycles. Li-Ion batteries are free from this effect.
memory mode (MR) - A mode that allows the operator to tune from channel to channel. Also known as channel mode.
menu - A list of selectable control or configuration functions or options.
mesh network - Slang for high-speed multimedia radio.
message forwarding system - A group of amateur stations participating in a voluntary, cooperative, interactive arrangement where communications are sent from the control operator of an originating station to the control operator of one or more destination stations by one or more forwarding stations.
metal-oxide semiconductor field-effect transistor (MOSFET) - A type of active solid-state device often used as an amplifier or switch.
metal-oxide varistor (MOV) - An electronic component whose resistance varies with the applied voltage across it, of which the metal-oxide varistor (MOV) is the most common.
meteor-scatter operator - One who uses the ionized trails produced by meteors to scatter and reflect radio signals.
meteor scatter - Ionized trails of meteors used as a radio reflecting media. (See meteor scatter)
meter - An instrument that displays a numeric value as a number or as the position of an indicator on a numeric scale.
meter (m) - The International System of Units (SI) symbol m, it is the fundamental unit of length. Originally intended to be one ten-millionth of the distance from the Earth's equator to the North Pole (at sea level), its definition has been periodically refined to reflect growing knowledge of metrology. Since 1983, it has been defined as the length of the path travelled by light in vacuum during a time interval of 1/299,792,458 of a second. Also known as metre.
method of moments - The numerical computational method of solving linear partial differential equations that have been formulated as integral equations (in boundary integral form), useful for modeling antenna radiation patterns.
Metre Convention - An international treaty, signed in Paris on 20 May 1875 by representatives of seventeen nations that set up an institute for the purpose of coordinating international metrology and for coordinating the development of the metric system.
metric prefixes - A series of terms used in the metric system of measurement. Metric prefixes are used to describe a quantity as compared to a basic unit. The metric prefixes are indicated by multiples of 10.
metric system - A system of measurement developed by scientists and used in most countries of the world that use a set of prefixes that are multiples of 10 to indicate quantities larger or smaller than the basic unit. (See General Conference on Weights and Measures and Metre Convention)
mic fright - Being reluctant to make one's first radio contact.
micro (μ) - One millionth, or the metric prefix for 10-6, or divide by 1,000,000.
microcontroller - A computer on a single integrated circuit designed for embedded (complete, self-contained) applications, and which can replace complex digital circuitry.
microfarad (μF) - One millionth (10-6) of a farad. The μ is a Greek small mu. (See farad)
microphone (MIC, mike) - An acoustic-to-electric transducer or sensor that converts sound into an electrical signal. Abbreviated as mic or mike.
microphone gain (MIC gain) - (1) Sensitivity of a microphone amplifier circuit. (2) Control that allows modification of the amount of microphone signal amplification.
microphone to you - (See over)
microphonics - An electrical or signal noise resulting from the mechanical vibration of charged component parts, similar to the way a microphone transforms audio vibrations into electrical signals; for example, an undesirable change in oscillator frequency due to mechanical vibration.
microprocessor - A computer on a single integrated circuit designed for general purpose applications, such as a personal computer.
microsecond (μs) - An International System of Units (SI) unit of time equal to one millionth of a second, or 10−6, or 1/1,000,000.
microstrip - A type of transmission line that can be constructed as a precision printed circuit board lead separated from a ground plane by a dielectric substrate to provide constant impedance interconnects at microwave frequencies.
microwave - The region of the radio spectrum above 1,000 megahertz (MHz), or 1 GHz.
microwave bands - A division of the range of frequencies above 1,000 megahertz (MHz), or 1 GHz, into a series of bands.
mike - An abbreviation for microphone. (See microphone)
Mike - A North Atlantic Treaty Organization (NATO) phonetic alphabet code word representing the letter M. Used in radio communication, particularly when spelling out a call sign.
mil - One thousandth (1/1,000) of an inch.
Military Auxiliary Radio System (MARS) - Formerly Military Affiliate Radio System and Auxiliary Amateur Radio System, is a system for military-affiliated amateur radio operators who provide free communication for overseas G.I.s and other federal services. The letters G.I. were used to denote equipment made from galvanized iron during World War I. In that same war, G.I. started being interpreted as Government Issue, and it was used from then on as an adjective for anything having to do with the Army.
military time - Alternate term for 24-hour clock, in which local time is represented by twenty-four equal-length but uniquely designated time periods per day.
mill - A special typewriter used by radio operators to copy messages.
milli (m) - One thousandth, or the metric prefix for 10-3, or divide by 1,000.
milliampere (mA) - One thousandth (1/1,000) of an ampere.
milliampere hour (mAh) - One-thousandth (1/1,000) of an ampere hour, commonly used to describe the energy charge that a battery will hold and how long a device will run before the battery needs recharging.
milliwatt (mW). One thousandth (1/1,000) of a watt. A derived unit of power in the International System of Units (SI), named after the Scottish engineer James Watt. The unit, defined as one joule (J) per second, measures the rate of energy conversion or transfer. (See watt)
minimum discernable signal (MDS) - (See sensitivity)
minimum-shift keying (MSK) - A type of frequency-shift keying (FSK) data transmission that uses a continuous-phase method of modulation by encoding each bit as a half sinusoid.
minimum-shift keying, 144 MHz (MSK144) - A type of brief frequency-shift keying (FSK) data transmission mode used for meteor scatter propagation at 50 megahertz (MHz) or higher frequencies.
minimum-shift keying, 144 MHz Short (MSK144 Sh) - A protocol used for communication at 144 megahertz (MHz) or higher.
MININEC - A variation of the National Electrical Code (NEC) design modeling and radiation pattern simulation software. Also known as mini-NEC.
mismatch - A condition that happens when a feed line is connected to an antenna or to transmitting equipment and the impedances are different. (See impedance match) Also known as mis-match.
mixer - A circuit that takes two or more input signals, and produces an output that includes the sum and difference of those signal frequencies.
mixing - The act of combining an RF signal of one frequency with a signal of an intermediate frequency, to create a new signal (often, the product, as in modulation), for which further manipulation and amplification are easier to design for and work with.
mnemonic - A pattern of letters, ideas, or associations that assists in remembering something.
mobile - (1) A transceiver that is usually too large to normally carry around by hand, but small enough to install in a vehicle; can also refer to any transceiver in your vehicle, regardless of size. (2) Operating an amateur radio from a vehicle.
mobile device - (See mobile station)
mobile flutter - (Repeater term) A synonym for a condition experienced on very-high frequency (VHF) and above where a signal rapidly fluctuates in amplitude experiencing multi-path interference causing a sound akin to rubbing a stick on a picket fence. If a repeater user's signal isn't strong enough to maintain solid access to the machine's input, such as when operating from a vehicle passing beneath underpasses or through hilly terrain, the signal would be hard to copy because of a pronounced, rapid fluttery or choppy characteristic. Also called picket fencing.
mobile operation - Radio communications conducted while in motion or during halts at unspecified locations.
mobile station - A radio transmitting device designed to be mounted in a vehicle or in a boat, plane, motorcycle, truck, recreational vehicle, etc., that can be used while the vehicle is in motion or at various stops. A push-to-talk (PTT) switch activates the transmitter. As a class of transceiver, mobile units fall between hand-held (5 watts or less) and base stations in both physical size and transmitted power. These units typically operate from the vehicle's battery and often transmit 50 watts or more using a vertical antenna mounted to use the metal vehicle body as a ground plane.
mode - (1) The combination of a type of information and a method of transmission. For exmple, frequency modulation (FM) radiotelephony or frequency modulation (FM) phone consists of using FM modulation to carry voice information. (2) A form of a radio emission, such as amplitude modulation (AM), frequency modulation (FM), or single sideband (SSB). (3) The combination of a satellite's uplink and downlink bands.
mode-restricted - Portions of the amateur radio bands in which only ceertain emission types are allowed.
modem - See modulator/demodulator.
Modern Electrics Magazine - (Archaic) A technical magazine for the amateur radio experimenter that was created by Hugo Gernsback and began publication in April 1908. The magazine was initially intended to provide mail-order information for radio parts and to promote the amateur radio hobby. The magazine was sold in 1913, and ceased publication with the December 1913 issue.
modulate - The process of adding information to a radio frequency (RF) signal or carrier by varying its amplitude, frequency, or phase. (See demodulate)
modulated continuous wave (MCW) - (CW term) Sending Morse code (CW) over an amplitude modulation (AM) transmitter using an audio tone.
modulation - The process of varying a radio frequency (RF) carrier in some way, for example, the amplitude or the frequency, to add an information signal to be transmitted.
modulation envelope - A signal created by connecting the peak values of a modulated signal, a boundary curve that encapsulates a modulated waveform of a radio frequency (RF) signal.
modulation index - (Repeater term) (See amplitude modulation; frequency modulation, phase modulation
modulator/demodulator (modem) - A device that modulates a radio signal to transmit data and demodulates a received radio signal to recover transmitted data.
modem - A device (from modulator/demodulator) that can encode (modulate) an audio or data signal for transmission, and decode (demodulate) a received signal into an audio or data signal.
Molex connector - A nylon-supported two-pin (or more) connector often used for power connections. The connector was pioneered by the Molex Connector Company.
Molex T connector - (See T connector)
monitor mode - One type of packet radio receiving mode. In monitor mode, everything transmitted on a packet frequency is displayed by the monitoring terminal node controller (TNC). This occurs whether or not the transmissions are addressed to the monitoring station.
monitoring - (1) To listen to radio voice or Morse code (CW) signals without transmitting. (2) To disable a radio's squelch to listen for weak signals.
monoband antenna - An antenna suitable for operation on just one band of frequencies.
monolithic microwave integrated circuit (MMIC) - An integrated circuit that performs functions such as mixing, filtering, and amplifying at microwave (300 megahertz (MHz) to 300 gigahertz (GHz)) frequencies.
monopole antenna - A vertical antenna that is typically connected to the inner conductor of a coaxial transmission line (or a matching network) and the shield of the transmission line is connected to ground.
monostable multivibrator - A circuit whose signal switches momentarily to the opposite binary state, then returns to its original state after a set time. Also known as one-shot.
moonbounce - (See earth-moon-earth) Also known as moon bounce.
Morse code (CW) - (CW term) A method of transmitting text information as a series of on-off tones, lights, or clicks that can be directly understood by a skilled listener or observer without special equipment. In amateur radio and military communications, the terms and Morse code and CW are used interchangeably, despite the distinctions between the two. In 1838 Samual F.B. Morse and his friend Alfred Vail developed the Morse Code. (See continuous wave) Also known as code.

A• ―
B― • • •
C― • ― •
D― • •
F• • ― •
G― ― •
H• • • •
I• •
J• ― ― ―
K― • ―
L• ― • •
M― ―
N― •
O― ― ―
P• ― ― •
Q― ― • ―
R• ― •
S• • •
U• • ―
V• • • ―
W• ― ―
X― • • ―
Y― • ― ―
Z― ― • •        

1• ― ― ― ―
2• • ― ― ―
3• • • ― ―
4• • • • ―
5• • • • •
6― • • • •
7― ― • • •
8― ― ― • •
9― ― ― ― •
O― ― ― ― ―

1. The length of a dot is one unit.
2. A dash is three units.
3. The space between parts of the same letter is one unit.
4. The space between letters is three units.
5. The space between words is seven units.

Morse code abbreviation - An abbreviation or shortened version (one to four characters) of a commonly used word, originally for brevity in sending a message by Morse code (CW), but also used in phone as part of the spoken or written ham vocabulary.
motional capacitance - The effective capacitance in the series leg of the equivalent circit for a crystal oscillator.
motional inductance - The effective inductance in the series leg of the equivalent circit for a crystal oscillator.
motional resistance - The effective resistance in the series leg of the equivalent circit for a crystal oscillator. Also known as loss resistance.
motorboating - Slang for an undesirable low-frequency feedback resulting in a motorboat sound on the audio.
mount - (1) A method of attaching an antenna to a vehicle, such as with magnets, to the trunk, hood, or mirror. (See antenna mount) (2) To install, attach, or connect one piece of equipment to another, either directly or by means of a bracket, cage, or other assembly.
MP73-N - A digital narrow band slow-scan television (SSTV) program mode.
mud - Slang for at or below the current receiver noise level, often used as part of down in the mud, or simply, in the mud. Also known as down-in-the-mud; in-the-mud.
multi-band - A superset of terms that define both transmission and reception support for more than one band, such as dual-band (two bands), tri-band (three bands), and quad-band (four bands).
multi-band antenna - An antenna suitable for operation on several different bands of frequencies, usually using a single transmission line. Also known as multiband antenna.
multi-band transceiver - A transceiver that can transmit and receive radio frequency (RF) signals on more than one band.
multi-band trap antenna - An antenna in which parallel resonant circuits, called traps, are used to isolate certain sections to operate only on some frequencies. This results in an antenna that can operate on multiple bands. (See trap)
multi-contact, 4mm (MC4 connector) - The model name for a water-resistant and high-voltage direct current (DC) power connector that is easy to connect but intentionally difficult to disconnect (to prevent accidental disconnection), commonly used for connecting solar panels together.
multi-hop - A radio signal refracted more than one time between the transmitting and receiving stations.
multi-mode transceiver - A transceiver capable of amplitude modulation (AM), Morse code (CW), frequency modulation (FM), and single sideband (SSB) operation. Also known as multi-mode radio.
multi-path interference - A condition when reflected propagation signals partially cancel. (See mobile flutter)
multi-path propagation - Propagation by means of multiple reflections. When the reflected signals partially cancel, it is referred to as multi-path interference. (See mobile flutter)
Multi-Use Radio Service (MURS) - An unlicensed two-way radio service similar to Citizens Band (CB). Established by the U.S. Federal Communications Commission in the fall of 2000, MURS created a radio service allowing for unlicensed (Part 95) operation, with a power limit of 2 watts.
multiband - Superset of terms that define both transmission and reception support for more than one band, such as dual-band (two bands), tri-band (three bands), and quad-band (four bands). Also known as multi-band; quad-band; quad band; quadband; tri-band; tri band; triband.
multicoupler - A device that distributes a received RF signal (typically by frequency) to a variety of receivers, often as part of a repeater site. Also known as multi-coupler; splitter.
multilateral agreement - A set of rules agreed upon by two or more countries to authorize amateur radio operation in all applicable countries by a person who is not a citizen of (alien to) one or more of those countries. Also known as multi-lateral agreement; multilateral arrangement; multilateral operating agreement.
multimeter - An electronic test instrument used to measure current, voltage, and resistance in a circuit. The term describes all meters capable of making these measurements. Also known as volt-ohm-milliammeter; vacuum-tube voltmeter. If the numeric display is digital, the instrument may also be called a digital multimeter or digital voltmeter.
multimode - Capable of Morse code (CW), frequency modulation (FM), and single sideband (SSB) operation modes. Also known as multi-mode.
multipath - A type of interference or distortion caused by a signal arriving at a receiver from different-length paths at slightly different times, resulting in part of the signal from one path canceling part of the signal from another (destructive interference), or enhancing part of the signal from another (constructive interference). Also known as multi-path.
multiple receiver - (See voting repeater system) Also known as multi-receiver.
multiple-frequency-shift keying (MFSK) - A technique for transmitting digital data using multiple tones, extending the radioteletype (RTTY) two-tone technique to many tones, usually, but not always, one tone at a time. (See frequency-shift keying) Also known as multi-frequency-shift keying.
multiplier - A circuit in a frequency modulation (FM) transmitter that generates a harmonic (multiple) of a lower frequency signal to produce the desired operating frequency. Also known as frequency multiplier.
multiple-dipole antenna - Two or more separate dipole antennas connected to the same feed point to provide multi-band operation on the same feed line.
multiple-protocol controller (MPC) - A device that can act as a terminal node controller (TNC) for several protocols.
mutual inductance - A magnetic coupling between two inductors that allows current flowing in one inductor to cause (induce) current to flow in the other nearby inductor, which a transformer exhibits when an alternating-current (AC) voltage presented across its primary winding results in a voltage appearing across its secondary winding.

To the top!   N

N connector - A classification for a 50 ohm (Ω) weatherproof connector used on coaxial cable feedlines for ultra-high frequency (UHF) operation up to full legal amateur radio power levels, featuring low loss, constant impedance, and waterproof operation. It was one of the first connectors capable of carrying microwave-frequency signals, and was invented in the 1940s by Paul Neill of Bell Labs, after whom the connector is named. Also known as type N connector; type-N connector.
N-doped - An N-type junction that is doped with electrons. A P-N junction (or N-P junction) is formed by creating two substrate materials of P-type and N-type on a semiconductor. A diode is formed with a P-N junction. (See P-doped)
N-type - A type of doped semiconductor material that contains excess electrons in the outer shell of electrons (larger electron concentration than hole concentration), resulting in a net negative charge and making electrons the majority current carriers in this type of material. (See dope)
nano (n) - One billionth, or the metric prefix for 10-9, or divide by 1,000,000,000.
nanofarad (nF) - A farad is the charge in coulombs that a capacitor will accept for the potential across it to change 1 volt. One nanofarad (nF) is equal to one billionth (10−9) of a farad. (See farad)
narrow band (NB) - A channel in which the bandwidth of the message does not significantly exceed the channel's coherence bandwidth.
Narrow Band Emergency Messaging Software (NBEMS) - An open-source software that allows ham radio operators to reliably send and receive data using a computer and radio pair.
narrow band frequency modulation (NBFM) - A term used for when the significant energy in frequency modulation (FM) occupies the same bandwidth as ordinary amplitude modulation (AM) with the same modulating signal. Also known as NFM; N-FM.
narrow frequency modulation (NFM) - A receive mode that gives good results in congested frequency ranges.
National Aeronautics and Space Administration (NASA) - An independent agency of the United States government responsible for aviation and spaceflight.
National Archives and Records Administration (NARA) - An independent agency of the United States government charged with preserving and documenting government and historical records and with increasing public access to those documents, which comprise the National Archives.
National Bureau of Standards (NBS) - (Archaic) The precursor to the National Institute of Standards and Technology (NIST). (See National Institute of Standards and Technology)
narrow calling frequency - A subset of simplex calling frequencies that is recognized across the United States and reserved for incidental use, requesting non-urgent assistance, true emergencies, testing, and whose use in making casual or first-time contacts is encouraged.
National Contest Journal Magazine (NCJ) - A bimonthly magazine published by the American Radio Relay League (ARRL), with an independent volunteer editor. The magazine covers topics related to amateur radio contesting, is published in English, and draws its subscription base primarily from the United States and Canada.
National Electrical Code (NEC) - A set of guidelines governing electrical safety that includes antennas.
National Incident Management System (NIMS) - A system that identifies concepts and principles that answer how to manage emergencies from preparedness to recovery regardless of their cause, size, location, or complexity.
National Institute of Standards and Technology (NIST) - The United States government standards body for time, frequency, measures, and weights. Formerly known as the National Bureau of Standards.
National Oceanic and Atmospheric Administration (NOAA) - A scientific agency within the United States Department of Commerce focused on the conditions of the oceans and the atmosphere.
National Parks on the Air (NPOTA) - An event during 2016 in which portable ham radio stations located in pre-selected sites attempted to contact as many other NPOTA stations as they could, in conjunction with the National Park Service centennial celebration.
National Radio Quiet Zone (NRQZ) - The area in Maryland, Virginia, and West Virginia bounded by 39° 15' N on the north, 78° 30' W on the east, 37° 30' S on the south, and 80° 30' W on the west. This area is home of a number of high-sensitivity radio telescopes and equipment run by the National Aeronautics and Space Administration (NASA), National Security Agency (NSA), and others. There are restrictions on amateur radio beacons in this area; transmissions of any kind near certain facilities must be coordinated with the area frequency coordinator.
National Television System Committee (NTSC) - A standard for fast-scan analog color television signals.
National Traffic System (NTS) - An American Radio Relay League (ARRL) organized structure of local, regional, and national networks designed to deliver formal written message traffic, or radiograms, anywhere in the United States.
National Weather Service (NWS) - A service that provides weather, water, climate data, forecasts, and warnings for the protection of life and property and enhancement of the national economy.
natural wave - (Archaic) The resonant length of an antenna, usually one full wave.
Naval Communication Reserve (NCR) - (Archaic) A United States service for hams to serve in reserve duty in the 1920s and 1930s.
near field - The region of the electromagnetic field immediately surrounding an antenna where the reactive field dominates and where the field strength as a function of angle, or antenna pattern, depends upon the distance from the antenna. It is a region in which the electric and magnetic fields do not have a substantial plane-wave character, but vary considerably from point to point. (See plane-wave character)
near-vertical-incidence Skywave (NVIS) - (1) A propagation mode where signals are reflected back down from directly overhead. Useful for relatively short-distances, overcoming the limitations of the usual skip-zone distance. (See skip) Also known as near vertical incidence Skywave. (2) A type of antenna used primarily for short-range high frequency (HF) communication by directing much of its signal straight up. Also known as cloud warmer.
negative - (1) The part of an electric circuit that is at a lower electrical potential than another part designated as having zero electrical potential. (2) No; wrong; incorrect.
negative copy - Reporting an unsuccessful transmission.
negative feedback - The process in which a portion of the amplifier output is returned to the input, 180 degrees out of phase with the input signal, that improves linearity and reduces distortion.
negative offset - (Repeater term) (See offset)
negative resistance characteristic - Action of a material or device in which increased current results in reduced voltage drop. Often found in materials in the plasma state, such as within a lightning arc.
negative-positive-negative (NPN) - A transistor that has a layer of P-type semiconductor material sandwiched between layers of N-type semiconductor material.
net - A group of stations that meet on a specified frequency at a certain time. The net is organized and directed by a net control station operator, who calls the net to order, recognizes stations entering and leaving the net, and authorizes stations to transmit. Short for network, on air. Also known as ham net.
net control station (NCS) - A formal or directed net that manages its operation for a given session. The NCS operator calls the net to order at its designated start time, periodically calls for participants to join, listens for them to answer or check in, keeps track of the roster of stations for that particular net session, and generally orchestrates the operation of the net. (See net)
Net Manager (NM) - An appointee of the American Radio Relay League (ARRL) who is responsible for coordinating and supervising traffic handling activities in a section of the ARRL.
network - Several digital stations linked together to transmit data over long distances.
network, on air - (See net)
new Motorola mount (NMO) - A kind of screw-on mobile antenna mounting arrangement that provides a coaxial connection. It is the preferred mount for any very-high frequency (VHF) and ultra-high frequency (UHF) antenna. It is waterproof with or without the antenna attached, and can be installed from the outside. It is the mount of choice if maximum efficiency is to be maintained.
newbie - (See novice)
newton (N) - The International System of Units (SI) unit of force. It is equal to the force that would give a mass of one kilogram an acceleration of one meter (m) per second per second, and is equivalent to 100,000 dynes (dyn). It is named after Isaac Newton in recognition of his work on classical mechanics, specifically Newton's second law of motion. (See dyne and joule)
nickel-cadmium (NiCd) - A type of rechargeable battery using nickel oxide hydroxide and metallic cadmium as electrodes. The term is derived from the chemical symbols of nickel (Ni) and cadmium (Cd) or NiCd. The term NiCad is a registered trademark of the Saft company, although this brand name is commonly used to describe all NiCd batteries. Also known as Ni-Cd; nicad.
nickel-metal hydride (NiMH) - A type of rechargeable battery. It is very similar to the nickel–cadmium (Ni-Cad) cell. NiMH batteries use positive electrodes of nickel oxyhydroxide (NiOOH), like the nickle cadmium (NiCd), but the negative electrodes use a hydrogen-absorbing alloy instead of cadmium, being in essence a practical application of nickel–hydrogen battery chemistry. An NiMH battery can have two to three times the capacity of an equivalent size NiCd, and their energy density approaches that of a lithium-ion cell. Also known as Ni-MH.
nickels - A synonym used on distant station (DX) nets as a signal report of 5-by-5.
niner - The alternate way of speaking the numeral 9. Also known as 9er; 9-er.
node - (1) A point of minimum voltage or current on an antenna. (2) A remotely controlled terminal node controller/digipeater that is used as a connect point in packet radio.
noise - Unwanted elecromagnetic energy that can interfere with signal transmission or reception.
noise blanker (NB) - A circuit that provides noise reduction for impulse noise. Also known as blanker; noise blanker; noise-blanker.
noise bridge - A test instrument used to determine the impedance of an antenna system.
noise figure - The ratio in decibels (dB) of noise added to a signal by a device to the noise that would be in the signal if none were added. It especially applies to amplifiers.
noise floor - The average power of the sum noise from all noise sources. A weak signal must be above the noise floor to be discernible. Also known as theoretical noise.
noise reduction (NR) - A digital signal processing (DSP) feature that reduces unwanted signal noise.
noise squelch - (See carrier squelch)
nominal - By name only – for example, a D battery cell is typically labeled "1.5 volts" but might actually measure at 1.487 volts, so "1.5" is its nominal value.
non-inverting - A type of non-mode-specific linear transponder that re-transmits a received signal at the same passband offset from the end of its passband as that of the received signal, and on the same end of the passband.
non-ionizing radiation - An electromagnetic radiation that does not have sufficient energy to knock electrons free from their atoms. Radio frequency radiation is nonionizing. (See radiation)
non-volatile - Will maintain its stored information, even if its power is removed, especially in the case of computer memory.
noob - (See novice)
North American Low-power Morse-code Club (NAQCC) - A club promoting and encouraging Morse code (CW) proficiency on the amateur radio bands. Life membership is free.
North Atlantic Treaty Organization (NATO) - An intergovernmental military alliance based on the North Atlantic Treaty which was signed on 4 April 1949. The organization constitutes a system of collective defence whereby its member states agree to mutual defense in response to an attack by any external party.
North Atlantic Treaty Organization phonetic alphabet (NATO phonetic alphabet) - More accurately known as the International Radiotelephony Spelling Alphabet, it is code words assigned to the letters of the English alphabet so that critical combinations of letters and numbers can be pronounced and understood by those who transmit and receive voice messages by radio or telephone regardless of their native language or the presence of transmission static. The NATO phonetic alphabet is the most widely used spelling alphabet. Also known as ICAO phonetic alphabet; ICAO spelling alphabet; ITU phonetic alphabet, standard phonetics.

AAlfa (AL-fah)
BBravo (BRAH-voh)
CCharlie (CHAR-lee — SHAR-lee)
DDelta (DELL-tah)
EEcho (ECK-oh)
FFoxtrot (FAHKS-traht)
GGolf (GOLF)
HHotel (hoh-TELL)
IIndia (IN-dee-ah)
JJuliet (JEW-lee-et)
KKilo (KEE-loh)
LLima (LEE-mah)
MMike (MIKE)
NNovember (noh-VEM-ber
OOscar (OSS-kah)*
PPapa (pah PAH)
QQuebec (keh-BEHCK)
RRomeo (ROW-mee-oh)
SSierra (see-AIR-ah)
TTango (TANG-goh)
UUniform (YOU-nee-form — OO-nee-form)
VVictor (VIK-tah)*
WWhiskey (WISS-kee)
XX-ray (EKS-ray)
YYankee (YANG-key)
ZZulu (ZOO-loo)
* NOTE: The pronunciations for Oscar and Victor were
designed for speakers from all international languages.

northern lights - (See aurora)
notch filter - A band-reject filter with a very narrow stopband that passes all frequencies except those in a stopband centered on a center frequency. (See stopband)
November - A North Atlantic Treaty Organization (NATO) phonetic alphabet code word representing the letter N. Used in radio communication, particularly when spelling out a call sign.
Novice - (1) (Archaic) The Novice Class operator license was for persons who had passed a 5-word-per-minute Morse code (CW) examination and a basic theory exam. After the 1987 restructuring, privileges included four bands in the high-frequency (HF) range, or 3 to 30 megahertz (MHz), one band in the very-high frequency (VHF) range, or 30 to 300 megahertz (MHz), and one band in the ultra-high frequency (UHF) range, or 300 to 3,000 megahertz (MHz). This class was deprecated by the restructuring in the year 2000. (2) (Archaic) An early 1920s term for a broadcast listener, as distinguished from a radio amateur. (3) A new ham radio operator. Also known as newbie; noob; nube; rookie.
null - (1) To tune or adjust for a minimum response. (2) A position in the radiation pattern of an antenna where the radiation is zero or approaches zero.
number - Issue, as in this month's number of QST magazine.
Numerical Electromagnetics Code (NEC) - The popular antenna design modeling and radiation pattern simulation software that uses the method of moments approach for its calculations.
Numerical Electromagnetics Code variation (EZ-NEC; EZNEC) - A variation of the Numerical Electromagnetics Code (NEC) design modeling and radiation pattern simulation software.

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occupational exposure - (See controlled environment)
odd split - The unconventional frequency separation between input and output (I/O) frequencies. Also known as odball split. (See split)
odd-order intermodulation product - (See third-order intermodulation product)
oddball split - (See odd split)
off the air - Slang for "while not transmitting." (See on the air) Also known as off-air; off-the-air.
off wave - (Archaic) A term mostly used in the late 1920s and 1930s meaning operation outside the legal limits of an amateur band.
off-center-fed antenna (OFC) - A dipole wire antenna in which the feed wire is not attached in the middle. Also known as windom.
Office of Engineering and Technology (OET) - An office within the Federal Communications Commission (FCC_ that manages allocations of the electromagnetic spectrum and advises the Commission on technical and engineering matters.
Office of the Federal Register (OFR) - An office of the National Archives and Records Administration, it provides access to the official text of Federal Laws, Presidential Documents, and Administrative Regulations and Notices.
official - (1) A type of two-way radio communication for use in a government or medical environment, such as police (public safety), fire, Emergency Medical Services (EMS_, or hospitals.
Official Emergency Station (OES) - An appointee of the American Radio Relay League (ARRL) who is responsible for specific, pre-determined operational assignments during drills or actual emergency situations.
Official Observer (OO) - A former volunteer person or group (humorously referred to as the ham police) once appointed by the ARRL within the Amateur Auxiliary to observe and investigate technical irregularities and accidental, annoying, or egregious and repeated violations of the amateur radio rules before they come to the attention of the Federal Communications Commission (FCC).
Official Observer Coordinator (OOC) - An appointee of the American Radio Relay League (ARRL) who supervises the maintenance monitoring work of the section Official Observers, and coordinates special Amateur Auxiliary efforts with ARRL Headquarters.
Official Relay Station (ORS) - An appointee of the American Radio Relay League (ARRL) who functions in the community interest in case of emergency.
Official Traffic Station (OTS) - A position of the American Radio Relay League (ARRL) charged with maintaining communication with served agency shelters and with health and welfare traffic.
Office of Engineering & Technology (OET) - A branch of the Federal Communications Commission (FCC) that has developed guidelines for radio frequency (RF) safety.
offset - (Repeater term) The difference between the receive and transmit frequencies of a radio channel. On the 2-meter (m) amateur radio band these frequencies are 600 kilohertz (kHz) apart. In order to listen and transmit at the same time, repeaters use two different frequencies. If the output is above 147 megahertz (MHz) then the input is 600 kilohertz (kHz) above and is referred to as a positive offset. As a general rule, if the output frequency, or transmit of the repeater is below 147 megahertz (MHz) then the input frequency, or listening is 600 kilohertz (kHz) lower and is referred to as a negative offset.
offset direction (Repeater term) A sign of a repeater's offset, positive or negative, determined by offset = finput − foutput. Also known as shift direction. Also known as shift direction.
offset frequency - (Repeater term) Frequency difference between a repeater's receive and transmit frequencies. Also known as split.
ohm (Ω) - The basic unit of electrical resistance, used to describe the amount of opposition to current. One ohm is the resistance offered when a potential of one volt results in a current of one ampere. The Ω is a Greek capital omega. (See resistance) Also known as ohms.
Ohm's law - A formula for basic electronic calculation that gives a relationship between voltage (E), current (I) and resistance (R). The voltage applied to a circuit is equal to the current through the circuit times the resistance of the circuit (E = IxR, or I = E/R, or R = E/I). The law was named for George Simon Ohm, a German physicist and mathematician.
ohmmeter - A device used to measure electrical resistance.
ohmic resistance - (See resistance)
Olivia - A digital-mode software package using multiple frequency-shift keying carriers and intended for operation under weak-signal conditions.
old man (OM) - A friendship term for a friend, pal, or buddy, or any male operator.
old timer (OT) - A ham who has been around ham radio for a long, long time.
Old Timer's Club (OTC) - (Archaic) An American Radio Relay League (ARRL) club that recognized ham radio activity that had spanned 20 years or more. The club was discontinued in 2004.
omnidirectional antenna - An antenna that radiates and receives well in all horizontal directions.
on the air - Slang for actively transmitting. (See off the air; over the air; airwaves) Also known as on-the-air; on-air.
on the side - (CB term) Slang for an announcement that you need to leave the current conversation, but plan to listen when you can, so that you can rejoin the conversation later.
on-off keying (OOK) - (CB term) The simplest form of amplitude-shift keying (ASK) data transmission, which is simply the presence or absence of a carrier signal, and the type used in continuous wave (CW) operation to send Morse code messages.
one-shot - (See monostable multivibrator)
one-way communication - A transmission that is not intended to be answered. The Federal Communications Commission (FCC) strictly limits the types of one-way communication allowed on the amateur radio bands.
open band - A band that is available for skip communication.
open carrier - (See dead carrier)
open circuit - An electrical circuit that does not have a complete path, so current cannot flow through the circuit.
open net - A net that is available for any licensed ham to check in on, and one whose communication is not necessarily directed by a controlling station.
open repeater - (Repeater term) A repeater that can be used by all amateur radio operators who have licenses that authorize operation on the repeater frequencies. (See closed repeater)
open-sleeve dipole antenna - An antenna with one or more additional closely spaced wires placed parallel with but with no electrical to a simple dipole to create multiple resonant frequencies.
open squelch A squelch circuitry that has been disabled (open-circuited), so that all radio noise can be heard near the receiver frequency.
open-wire line (OWL) - A type of twin-lead balanced feedline consisting of two insulated wires held at a constant distance apart, either incased in plastic or constructed with insulating spacers placed at intervals along the line. Also known as ladder line; parallel-conductor line; twin-lead line.
opening - A condition that occurs when radio propagation is possible between two stations on the same frequency.
operate - The act of controlling radio station equipment to perform its intended function. Also known as operation.
operational amplifier (op-amp) - A direct current (DC)-coupled high-gain electronic voltage amplifier with a differential input and, usually, a single-ended output.
operator - (See control operator)
operator/primary station license - The operator portion of an amateur radio license gives permission to operate an amateur radio station. The primary portion of an amateur radio license authorizes an amateur radio station at a specific location and also lists the call sign of that station. Only one operator/primary station license grant may be held by any one person.
opposite sideband - (See reverse sideband)
optical fiber - A flexible, transparent fiber made of glass (silica) or plastic, slightly thicker than a human hair. It functions as a waveguide, or light pipe, to transmit light between the two ends of the fiber.
optical shaft encoder - A device that detects the rotation and position of a control by interrupting a light source with a patterned wheel.
opto-isolator - A tuning knob where an LED shines through an interrupter to signal a data pulse. Also known as optoisolator.
orbital period - The length of time a satellite makes a single revolution around the Earth.
Orbiting Satellite Carrying Amateur Radio (OSCAR) - The sattelite use of amateur radio frequency allocations to facilitate communication between amateur radio stations. These satellites can be used for free by licensed amateur radio operators for voice and data communication. Fully-operational satellites in orbit act as repeaters or linear transponders, or store and forward digital relays.
ordinary wave (O-wave) - One of two types of elliptically polarized radio waves (also known as an O-wave) that results from the interaction with the earth's magnetic field in the ionosphere, but behaves the same as without the influence the magnetic field. Also known as O wave.
orientation (OFDM) - Digital modulation technique using subcarriers at frequencies chosen to avoid intersymbol interference, for use in high-speed digital modes.
orthogonal frequency division multiplexing (OFDM) - A common modulation type used in high-speed multimedia (HSMM) work.
Oscar - A North Atlantic Treaty Organization (NATO) phonetic alphabet code word representing the letter O. Used in radio communication, particularly when spelling out a call sign. (Pronounced OSS-kah)
oscillate - To vibrate or generate a signal at a single frequency.
oscillation - The continuous generation of a periodic electric alternating current (AC) or electromagnetic signal.
oscillator (OSC) - A device or circuit that generates oscillating electric currents or voltages by nonmechanical means at a single frequency.
oscillation transformer – (Archaic) A transformer that forms the resonant circuit in a spark transmitter and couples to the antenna.
oscilloscope (O-scope) - An electronic test instrument used to observe wave forms and voltages on a cathode-ray tube (CRT). The tube displays time on the X-axis, amplitude on the Y-axis, and intensity of the CRT spot on the Z-axis. Also known as O scope; O-scope; oscope.
out - I have finished speaking and am not awaiting a reply, similar to clear.
out after roll - (See early-out) Also known as out after roll-call; out after roll call.
out-of-phase - The description of two alternating current (AC) signals whose voltage values or current values do not reach their peak levels at the same time. Also known as out of phase.
outdoor antena - (Archaic) (See aerial)
outlet power - (See household power)
output frequency - A repeater's transmitting frequency. To use a repeater, one must transmit on an input frequency, and receive on an output frequency.
over - A term used during a two-way communication to alert the other station that you are returning the communication back to them (although, not used on all frequencies or on repeaters). Other terms are go ahead, "microphone to you," and in Morse code (CW) the letter K is used as an invitation to transmit. The term is not actually necessary on 2-meter (m) frequency modulation (FM) repeaters, as the courtesy tone serves this function. Also known as over and out.
over the air - Slang for using radio waves as a means of communication. Also known as over the air waves; over the airwaves.
over-the-horizon (OTH) - (1) Radio wave propagation path over which signals are transmitted and received beyond the visual horizon by either reflection (bouncing) or refraction (bending). (2) A type of long-range radar (often called beyond the horizon) system that can detect targets much farther than ordinary radar.
overdeviation - A form of FM distortion (also called excessive deviation) in which the amplitude of the modulating signal produces a deviation that exceeds the receiver's bandwith, which is typically limited by the attenuating effect of the IF filter, often resulting in irritating receiver audio. Also known as over-deviation.
overdrive - (See drive) Also known as over-drive.
overload - (See fundamental overload)
overmodulation - A form of distortion in which the level of modulating signal exceeds the value necessary to produce 100% modulation, often resulting in flat-topping and excessive bandwidth. Also known as over-modulation.
overtone - An integer multiple of a frequency that is higher than the fundamental frequency (harmonics include the fundamental frequency).

To the top!   P

P-doped - A P-type junction that is doped with free holes or electron depletion. A diode is formed with a P-N junction. (See N-doped)
P-type - Type of doped semiconductor material that contains excess holes in the outer shell of electrons (larger hole concentration than electron concentration), resulting in a net positive charge and making holes the majority current carriers in this type of material. Also known as P-type.
P/N junction - A P/N junction (or N/P junction) is formed by creating two substrate materials of P-type and N-type inside a single crystal of semiconductor.
P5 North Korea - For distant station operators (DXers), a most unattainable contact or a non-existent station. The rarest call sign prefix as one of two countries worldwide (the other is 7O Yemen) to have had no licensed radio amateur service at all since 2002.
pi pad (π pad) - One of the possible configurations used in attenuators. (See attenuator)
packet - An amateur digital-data system that communicates using very-high frequency (VHF) and ultra-high frequency (UHF) frequencies.
Packet Bulletin Board System (PBBS) - A system that offers the ability to send and receive personal messages or bulletins intended for people around the world.
packet cluster - A network of automated packet radio stations for disseminating distant station (DX) and contest reports.
packet radio (PKT) - A form of packet-switching technology used to transmit digital data by way of radio or wireless communications links. For instance, with the AX.25 protocol, information is broken into short bursts, or packets, that also contain addressing and error-detection information.
packet radio repeater - A device dedicated to receiving, storing, then re-transmitting digital data packets. Also known as digipeater.
packet repeater - (See digipeter)
PACTOR - An evolution of amateur teleprinting over radio (AMTOR) and packet radio, it is a radio modulation mode used by amateur radio operators, marine radio stations, and radio stations in isolated areas to send and receive digital information by way of radio. The word pactor is Latin for the mediator. Also known as PACTOR-III; PACTOR 3.
paddle - (CW term) (1) A device used to send Morse code (CW) with an electronic keyer. (2) An alternate or short name for an entire Morse code keyer unit that features one or more paddles.
paging - (See individual calling)
pan adapter - An oscilloscope for monitoring a band of frequencies. Also known as pan-adapter; panadapter.
Papa - A North Atlantic Treaty Organization (NATO) phonetic alphabet code word representing the letter P. Used in radio communication, particularly when spelling out a call sign. (Pronounced pah-PAH)
parabola - A symmetrical open-plane curve formed by the intersection of a cone with a plane parallel to its side.
parabolic antenna - An antenna in the shape of a dish with a parabolic cross section.
parallel-conductor line - (See open-wire line)
parallel-tuned circuit - A circuit in which the capacitor and inductor are in parallel, and therefore have the same voltage.
parallel circuit - An electrical circuit in which the electrons follow more than one path in going from the negative supply terminal to the positive terminal.
parallel fan dipole antenna - (See fan dipole antenna)
parametric amplifier (paramp) - A highly sensitive low-noise amplifier that relies on varying the reactance parameter to achieve amplification, used for very-high frequency (VHF), ultra-high frequency (UHF), and microwave applications such as radar. Also known as reactance amplifier.
parasitic - Oscillations in a transmitter on frequencies other than the desired one that can produce spurious signals from the transmitter.
parasitic capacitance - (See stray capacitance)
parasitic-beam antenna - (See beam antenna)
parasitic-element antenna - An antenna element that affects the antenna performance by receiving and re-radiating energy from a driven element. Parasitic elements are not connected directly to the feed line. Also known as radiating element.
parasitic oscillation - An undesirable oscillation caused by feedback.
parasitic suppressor - A suppressor, designed to absorb sufficient energy to suppress unwanted very-high frequency (VHF) parasitic oscillations in a high-voltage high-frequency (HF) amplifier.
parawatch - (See dualwatch)
parity - An error detection method for digital data that counts the number of 1 bits in each data character. One bit added to each character, the parity bit, is used to indicate whether the correct number of 1 bits is odd or even.
Parks on the Air (POTA) - An award program for ham radio enthusiasts who successfully make contacts with other hams from one or more designated or candidate parks around the world.
parrot repeater - (See simplex repeater)
Part 15 - The section of the Federal Communications Commission (FCC) rules that permits operation of low-power transmitting devices likely to transmit or receive radio frequency (RF) signals without a license.
Part 15 - An unlicensed device that uses low-power radio signals.
Part 17 - Titled "Construction, Marking, and Lighting of Antenna Structures," it is a portion of the United States Government Code of Federal Regulations Title 47 that specifies and regulates construction, marking, and lighting of antenna structures.
Part 90 - (1) Titled Private Land Mobile Radio Services (LMRS), it is a portion of the United States Government Code of Federal Regulations Title 47 that specifies and regulates private (typically channelized narrowband) very-high frequency (VHF) and ultra-high frequency (UHF) radio operations such as public safety, commercial, Business Band, and pagers. (2) Federal Communications Commission (FCC) certification of commercial, official, and other non-amateur radios for use in non-amateur bands.
Part 95 - Titled "Personal Radio Services," it is a portion of the United States Government Code of Federal Regulations Title 47 that specifies and regulates personal (typically channelized) radio operations such as Morse code (CB), General Mobile Radio Service (GMRS), Family Radio Service (FRS), Multi-Use Radio Service (MURS), radio controlled (R/C), and medical devices.
Part 97 - The section of the Federal Communications Commission (FCC) rules that regulates the Amateur Radio Service. The fundamental purposes are expressed in the following principles: (a) Recognition and enhancement of the value of the amateur service to the public as a voluntary noncommercial communication service, particularly with respect to providing emergency communications. (b) Continuation and extension of the amateur's proven ability to contribute to the advancement of the radio art. (c) Encouragement and improvement of the amateur service through rules which provide for advancing skills in both the communication and technical phases of the art. (d) Expansion of the existing reservoir within the amateur radio service of trained operators, technicians, and electronics experts. (e) Continuation and extension of the amateur's unique ability to enhance international goodwill.
pass - The period during which signals from an orbiting satellite can be heard at a ground location.
passband - The range of frequencies or wavelengths that can pass through a filter without being attenuated. Also known as pass band; receiver passband.
passband tuner - A receiver circuit that permits adjusting the bandpass for best reception under different interference conditions. (See bandpass)
passband tuning (PBT) - A function to electronically reduce receiver interference by narrowing the intermediate frequency (IF) bandwidth.
passive filter - (See filter)
patch - (See auto patch; jumper)
path - The route taken by a signal from the transmitting station to the receiving station.
path noise - (Repeater term) The signal is so weak that the limiters have not engaged thus noise on the signal will be heard. This is sometimes referred to incorrectly as white noise. (See white noise)
pattern - (See radiation pattern)
peak-to-peak (P-P) - The distance measured between the greatest peaks of a periodically varying quantity, as in peak-to-peak voltage.
peak envelope power (PEP) - The average power of a radio frequency (RF) signal at the crest of the waveform which can be calculated by multiplying peak envelope voltage (PEV) by 0.707.
peak envelope voltage (PEV) - The maximum voltage on a transmission line during transmission.
peak filter - A band-pass filter with a very narrow passband which has a high Q factor compare with a notch filter.
peak inverse voltage (PIV) - The maximum voltage a diode can withstand when it is reverse biased or not conducting.
pecuniary - (Archaic) Payment of any type, whether money or other goods. Amateur radio operators may not operate their stations in return for any type of payment.
pentode - An electronic device, usually in the form of a vacuum tube, that has five electrodes (anode/plate, cathode, control grid, screen grid, and suppressor grid) plus a filament, and at one time often employed in an amplifier or oscillator circuit.
perigee - A point in the orbit of a satellite at which it is closest to the Earth. (See apogee)
period (Τ) - (1) The length of time in seconds taken by one cycle of a repeating waveform to pass a reference point. It is the reciprocal of frequency. The Τ is a Greek capital tau. (See frequency) (2) The length of time a satellite makes a single revolution around the Earth. Also known as orbital period.
permeability - A measure of the ability of a material to conduct magnetic flux relative to the ability of air to conduct magnetic flux (measure of the ability of a material to support the formation of a magnetic field within itself), and therefore determines the inductance of toroidal inductors, ferrite chokes, and other ferrite-core inductors.
permeability-tuned oscillator (PTO) - A variable-frequency oscillator (VFO) in which the frequency change is accomplished by way of an inductor with a movable slug rather than by way of a variable capacitor. Used with temperature compensated components, this oscillator provides a low-drift operation. Usually much more linear than a variable-frequency oscillator (VFO).
persistence - The length of time an image remains on a cathode-ray tube (CRT) screen after its beam is turned off.
personal - (CB term) Slang for first name.
personal computer (PC) - A computer designed for use by one person at a time.
personal mobile radio at 446 MHz) (PMR446) - A part of the UHF radio frequency range that is open without licensing for business and personal use in most countries of the European Union.
Personal Radio Service (PRS) - A classification of channelized VHF license-free radio services that are characterized by low-power and general availability, and include Morse code (CB), Family Radio Service (FRS), and Multi-Use Radio Service (MURS) systems.
phantom antenna - (Archaic) (See dummy antenna)
phase - A measure of position in time within a repeating waveform, such as a sine wave. Phase is measured in degrees or radians.
phase alteration line (PAL) - A television standard used in parts of Europe.
phase modulation (PM) - Similar to frequency modulation (FM), it is a form of modulation that represents information as variations in the instantaneous phase of a carrier wave. Modification in phase according to low frequency will give phase modulation. Part of the modulation index.
phase noise - A rapid, short-term, and random fluctuations (noise) in the phase of a waveform (also called phase jitter), expressed in decibles/hertz (dBc/Hz), often produced by phase variations in the reference oscillator signal, directly related to the short-term stability of the reference oscillator, and results in increased bandwidth required by the oscillator.
phase shift keying (PSK) - (See phase shift keying version 31)
phase shift keying version 31 (PSK31) - A method of digital modulation that shifts the transmitted signal's phase to represent the bits of digital data. It is a popular computer-generated radioteletype mode, used primarily by amateur radio operators to conduct real-time keyboard-to-keyboard informal text chat over the air. PSK31 occurs at 31.25 hertz (Hz) bandwidth. (See radioteletype (RTTY))
phase-locked loop (PLL) - An electronic circuit consisting of a variable frequency oscillator and a phase detector that can generate a wide range of frequencies in discrete steps such as 10 hertz (Hz). Also known as phase locked loop.
phasing harness - (See phasing line)
phasing line - A conductor (typically a cable) implemented on an antenna having multiple driven elements, such as an array, to ensure each driven element works in concert with the others to produce the desired antenna pattern (by ensuring the high frequency (HF) currents in all driven elements flow in phase and in the same direction. Also known as phasing harness.
phasor diagram - A graphical time-independent (time-invariant) complex value representation of a sinusoidal function, complete with amplitude and frequency, showing the phase relationship between circuit impedances and resistances at a given frequency.
phone - Another name for voice communication or voice modulation, it is an abbreviation for radiotelephone. (See radiotelephone)
phone emission - The Federal Communications Commission's (FCC) name for voice or other sound transmissions.
phone patch - (See autopatch)
phonetic alphabet - (See North Atlantic Treaty Organization phonetic alphabet)
phono connector - (See Radio Corporation of America connector)
photoconductivity - A phenomenon in which a material, such as a semiconductor, becomes more electrically conductive when exposed to (illuminated by) electromagnetic radiation such as visible or untraviolet light.
photodetector - A sensor of light or other electromagnetic energy.
photodiode - A type of photodetector capable of converting light into either current or voltage, depending upon the mode of operation. The common solar cell used to generate electric solar power is a large area photodiode.
photovoltaic (PV) - Related to the conversion of light energy into electrical energy using semiconducting materials that exhibit the photovoltaic effect.
photovoltaic cell - A solar cell that converts photons to electricity.
pi network - A once-popular filter circuit made from two L networks connected back-to-back with the inductors in series and the capacitors in shunt at the input and output, and that served as an antenna tuning unit with good harmonic attenuation.
pi-L network - A once-popular circuit made from a pi network with an additional series inductor on the output, and that served to match an external load impedance with that of a circuit or signal source, but has greater harmonic suppression than a pi network when used between a vacuum tube transmitter and its antenna.
picket-fencing - (See mobile flutter)
pico (p) - One trillionth, or the metric prefix for 10-12, or divide by 1,000,000,000,000.
picofarad (pF) - One trillionth (10−12) of a farad. A farad is the charge in coulombs that a capacitor will accept for the potential across it to change 1 volt. (See farad)
piezoelectric - Substances that are able to convert mechanical signals, such as sound waves, into electrical signals, and vice versa. They are therefore widely used in microphones, phonograph pickups, and earphones, and also to generate a spark for igniting gas.
piezoelectric effect - The ability of a substance to produce an electric charge when it is deformed physically.
pick it up - Slang for a directive to join the conversation in progress (also take one) by being the next station to transmit.
pick out - Slang for the ability to distinguish one signal from another.
pick up - (1) Slang for detect (discern). (2) Slang for collect (attract). (3) Slang for purchase or borrow or otherwise acquire (something not already in your possession). (4) Slang for retrieve.
pico (p) - Prefix, or units modifier, to indicate ÷ 1,000,000,000,000 or × 10-12.
Pierce oscillator An oscillator circuit that generates a waveform using positive feedback supplied through a quartz crystal, and is one of (at least) three major oscillator piezoelectric effect - The mechanical deformation of a material due to the application of a voltage or (conversely) the electric charge that accumulates in some solid materials in response to applied mechanical stress.
circuits used in amateur radio equipment.
piezoelectricity - The electric charge that accumulates in certain solid materials (such as crystals, certain ceramics, and biological matter such as bone, deoxyribonucleic acid (DNA) and various proteins) in response to applied mechanical stress.
pigtail - (See jumper)
pileup - Slang for the situation in which a large number of stations are trying to call the same distant station (DX) on the same frequency. Also known as pile up.
pill - (CB term) Older slang for a transistor, especially a power transistor in an amplifier.
pilot streamer - A column of ionized air that progresses downward at speeds of about 100 mph and establishes a path for a return lightning strike.
pilot tone - A 19 kilohertz (kHz) pilot tone added to a stereo broadcast to allow receivers to detect the presence of a stereo-encoded signal.
pin grid array (PGA) - A type of integrated circuit packaging, in which the pins are typically arranged in a square or rectangular array pattern.
PIN diode - An electronic semiconductor component that performs the same function as a silicon diode at low frequencies, but performs like a variable resistor or radio frequency (RF) switch at high frequencies, due primarily to its large region of intrinsic (normal, undoped semiconductor) material, its attenuation being controlled by a forward direct current (DC) bias current.
pinch-off voltage (VPO) - A condition in which the drain-source terminals of a field-effect transistor (FET) start to look like an open circuit, and no appreciable current flows even at high drain-source potentials. In practice there is always some residual current and the actual VPO measurement must make an allowance for this.
ping - A brief reception of a radio signal by way of meteor scatter radio wave propagation.
ping jockey - A nickname for meteor-scatter operator. (See meteor-scatter operator)
pink slip - Slang for written notification from a member of the Amateur Auxiliary for rules violation, which can be malicious or the result of equipment malfunction, or for exemplary operating behavior, in an attempt to help amateur radio operators self-police their compliance with the rules.
pirate - A station using an existing call sign and illegally operating on the air. (See bootlegger)
pirate radio - (See pirate)
plane-wave character - A locally uniform distribution of electric field strength and magnetic field strength in a plane perpendicular to the direction of propagation.
plate - Anode of a vacuum tube.
plate current - The quantity of current entering the anode of a vacuum tube.
plate tank - (Archaic) A resonant circuit at a vacuum tube amplifier's output frequency that is used to couple energy from the high-impedance plate or anode circuit to an antenna load.
plate transformer - (Archaic) A voltage step-up device that provides the high voltage to be rectified and filtered to supply a vacuum tube amplifier's plate circuit.
please acknowledge (PSE QSL) - A request for a reply to a contact or postcard.
plug - An male electrical connector designed to be inserted into a jack. (See jack)
plug-259 (PL-259) - Female antenna connector used on most high-frequency (HF) radios, it is a World War II threaded radio frequency (RF) connector design from an era when ultra-high frequency (UHF) referred to frequencies over 30 megahertz (MHz). Originally intended for use as a video connector in radar applications, the connector was later used for radio frequency (RF) applications. The term is often used for any compatible UHF cable plug and thus misnamed UHF. It mates the SO-239 socket. (See SO-239)
pocket beep - A beeping function, usually of a hand-held transceiver, when a specific signal is received.
PoE injector - A type of power sourcing equipment, device that supplies electric power to a PoE device through an Ethernet cable. Also known as Poe power injector.
point-contact diode - A type of diode constructed from a pointed metal wire (often called a cat's whisker) in contact with an n-type semiconductor or a crystal that contains n-type impurities, and can be used as a radio frequency (RF) detector.
polar coordinates - A two-dimensional coordinate system whose points are defined by distances from a reference point and angles from a reference direction, often with each distance representing a magnitude and each angle representing a phase.
polar orbit - A satellite orbit that passes over the North and South poles.
polarity - The orientation of an object or comparison of a value to some standard or convention that assigns the positive and negative. For example, a voltage can have a positive or negative value depending on what value of voltage is used as a reference.
polarization - The electrical-field characteristic of a radio wave. A radio wave can be horizontally, vertically, or circularly polarized. An antenna that is parallel to the surface of the earth, such as a dipole, produces horizontally polarized waves. One that is perpendicular to the earth's surface, such as a quarter-wave vertical antenna, produces vertically polarized waves. An antenna that has both horizontal and vertical polarization is said to be circularly polarized.
pole - A controlled current path or circuit in a switch.
pole-pig - A step-down transformer used by power transmission companies. Some surplus units can be reverse wired and used as the transformers in amateur radio high voltage supplies.
polychlorinated biphenyl (PCB) - A toxic material that might be present in some electronic components such as high-voltage capacitors and transformers Also known as PCBs.
portable designator - Additional identifying information added to a call sign specifying the station's location.
portable device - A radio transmitting device designed to be transported easily and to be set up for operation independently of normal infrastructure. For purposes of radio frequency (RF) exposure regulations, a portable device is one designed to have a transmitting antenna that is generally within 20 centimeters (cm) of a human body.
Portable Document Format (PDF) - A file format used to represent documents in a manner independent of application software, hardware, and operating systems.
portable station - An amateur radio station that is designed to be easily moved from place to place but can only be used while stopped. In Morse code (CW), portable operators may identify using /P. Portable stations differ from mobile stations in that large antennas or other structures must be folded or stowed away in order to move the station to a new location. While well-suited to field day or emergency/disaster operations, portable stations normally do not have a mobile station's ability to continue transmission while in motion.
positive - (1) The part of an electric circuit that is at a higher electrical potential than another point designated as having zero electrical potential. (2) Yes; right; correct.
positive-intrinsic-negative (PIN) - A photodiode with a large, neutrally doped intrinsic region sandwiched between P-doped and N-doped semiconducting regions. A PIN diode exhibits an increase in its electrical conductivity as a function of the intensity, wavelength, and modulation rate of the incident radiation.
positive-negative-positive (PNP) A type of bi-polar junction transistor that has a layer of N-type semiconductor material sandwiched between two layers of P-type semiconductor material. A small current leaving the base is amplified in the collector output. That is, a PNP transistor is on when its base is pulled low relative to the emitter.
positive offset - (Repeater term) (See offset)
post meridian (p.m.) - After noon.
pontential - An electric voltage level.
potentiometer - An electrical device in which the total resistance remains constant while resistance between end points is varied. The value of a potentiometer can be changed over a range of values without removing it from a circuit. Also known as pot; variable resistor.
pounding brass - (Archaic) Older slang for radio operation using Morse code (CB).
power (PWR) - (1) The rate at which energy is consumed, transferred, transformed, or used. Power is calculated in an electrical circuit by multiplying the voltage applied to the circuit by the current through the circuit, or P = IxE. (2) A transmitter setting or level designation that represents a particular output wattage quantity or range, such as 1, 2, 3, or low, medium, high or similar. (3) The action of applying energy to a device for an indeterminate amount of time. (4) A type of energy source. (5) Slang for operation at a power level greater than what is typically transmitted from a particular station.
power amplifier (PA) - An electronic amplifier used to convert a low-power radio-frequency signal into a larger signal of significant power, typically for driving the antenna of a transmitter. (See amplifier) Also known as RF power amplifier.
power bus - A single, relatively large conductor (distribution block) that provides power (sufficient current at the intended voltage) distribution to multiple devices (some distribution blocks provide both positive and negative sides to devices). (See ground bus)
power density - The strength of a radio frequency (RF) field measured as power per unit of area.
power factor - (Archaic) The cosine of the angle between voltage and current, so in resonance, it equals 1. Also known as apparent power; power factor; real power; true power; working power.
power line - Wire, cable, or other conductor used to provide AC household power from the grid to the electrical service at a home, business, or facility. Also called AC power line.
power line noise - Unwanted and typically constant low-frequency sound, characteristic of an unintended coupling with an alternating current (AC) power source, such as household power. Also known as line noise; power line hum.
power meter (PM) - (See wattmeter)
power over ethernet (PoE) - A type of power sourcing equipment, device that supplies electric power to a PoE device through an Ethernet cable. Also known as POE.
power sourcing equipment (PSE) - A device (such as an Ethernet switch) that provides electric power on an Ethernet cable. Also known as power-sourcing equipment.
power supply (PS) - A device with a circuit that provides a direct current (DC) output at some desired voltage from an alternating current (AC) input voltage.
power supply unit (PSU) - The source of electric energy for an electrical load; device used to deliver electric power to a radio or other device, the two most typical types for amateur applications being linear and switching, defined by their energy conversion methods.
power-sourcing equipment (PSE) - A device (such as an Ethernet switch) that provides electric power on an Ethernet cable.
power-line interference - Unwanted and typically constant low-frequency sound, characteristic of an unintended coupling with an AC power source, such as household power. Also known as power-line noise; AC line noise.
Powerpole - Brand name for a gender-neutral electrical (primarily DC) power connector widely used in ham radio applications, particularly go-kits and portable gear. Also known as Anderson Powerpole; Power Pole.
pre-emphasis - (See emphasis) Also known as preemphasis.
preamble - The header of a radiogram including message number, message type, originating station identification, time, and date originated.
preamplifier (preamp) - A receiving circuit that gives extra amplification to weak signals but at the cost of additional background noise and possible distortion. Preamplifier circuits are often included in a receiver and may be turned on or off. Also known as pre-amplifier.
precedence - A station category designator, for logging contacts during some contests.
precipitation static (P-static) - A type of static charge build-up due to rubbing against (triboelectric effect) or proximity to moisture (rain, fog, snow, or high humidity), as is common during thunderstorms and when aircraft fly through clouds. Also known as P static.
prefix - In the United States, each call sign has a one-letter prefix (K, N, W), or a two-letter prefix (AA-AL, KA-KZ, NA-NZ, WA-WZ), and a one-, two-, or three-letter suffix separated by a numeral (0-9) indicating the geographic region. For example, WØ is a prefix for Colorado, while the call sign might have a suffix of ZYX for a call sign of WØZYX.
preselector - A circuit that tunes a receiver's signal amplifying circuitry for maximum sensitivity on a desired frequency range. Also known as pre-selector.
President's War Emergency Powers - (See War Powers Act)
press-to-transmit - (See push-to-talk)
press release (PX) - (Archaic) An abbreviation used during the MacMillan polar expedition from 1923 to 1924.
primary - (1) The person who is an amateur radio station licensee (together with the transmitting equipment is known as a primary station), has the foremost responsibility for the proper operation of the station, and is the only person who can be designated as a control operator of an amateur station. (2) The input to a transformer, or its point of connection to a power or signal source (the output typically called the secondary). (3) A band or sub-band that is available (on a primary basis) to a specific group of users or operators who has priority use of the band over a secondary group. (4) A group or classification of users or operators that has been granted priority control (primary control) of a band or sub-band over that of a secondary group.
primary service - For each International Telecommunications Union (ITU) region, each frequency band allocated to the amateur service is designated as either a secondary service or a primary service. A station in a secondary service must not cause harmful interference to, and must accept interference from, stations in a primary service.
primary station license - (See operator/primary station license)
printed circuit board (PCB) - A board used to mechanically support and electrically connect electronic components using conductive pathways, tracks, or signal traces etched from copper sheets laminated onto a non-conductive substrate.
priority channel - A channel a scanner will immediately switch to when a signal is present.
priority traffic - Emergency-related messages, but not as important as emergency traffic.
priority watch - A reception mode in which a selected frequency is periodically checked even when the radio is tuned to another frequency.
private line (PL) - (Repeater term) A Motorola proprietary trademarked name for continuous-tone coded squelch system (CTCSS). (See continuous-tone coded squelch system)
private mobile radio (PMR) - A two-way voice, very-high frequency (VHF) and ultra-high frequency (UHF), communication system primarily used in the United Kingdom, similar to a land mobile radio system (LMRS) used in the United States, by both public safety and commercial operators.
Private Radio Bureau (PRB) - A group that administers the amateur radio services.
private line tone (PL tone) - former Motorola proprietary name of what we now call continuous-tone coded squelch system (CTCSS).
privileges - The frequencies and modes of communication that are permitted in an Federal Communications Commission (FCC) telecommunications service.
procedural signal - (CW term) One or two letters sent as a single character that do not represent text per se, but have a special meaning in transmission. They are generally not copied down, but are a form of control character. Amateur radio operators use procedural signals in Morse code (CW) contacts as a short way to indicate the operator's intention. Also known as proword; prosign.

A bar over the letters, such as AS for "Wait"
indicates that the letters are sent as one character.
• ― • ―Start mew line
• ― • ― •Message separator / telegram
• ― • • •Wait
― • • • ―Start new section / new paragraph
― • ― • ―Start of transmission
• • • • • • • •Error / correction
― • ―Invitation for any station to transmit
• • ― ― • •Please say again
― • ― ― •Invitation for named station to transmit
• • • ― • ―End of contact
• • • ― •Understood / verified
• • • ― ― ― • • •Start of distress signal
― • • •     ― • ―Break in conversation
― • ― •     • ― • •Closing down

product detector - A receiver circuit consisting of a beat frequency oscillator and additional circuitry for enhanced reception of Morse code (CW) and single sideband (SSB) signals.
programmable logic device (PLD) - A collection of programmable logic gates and circuits in a single integrated circuit; electronic component used for building reconfigurable digital circuits.
Project 25 (P25) - A suite of digital mobile radio communication standards designed primarily for official use by public safety (police, fire, Emergency Medical Services (EMS), etc.) in North America. Also known as APCO-25.
professional mobile radio (PR) - Person-to-person two-way radio voice communications systems which use portable, mobile, base station, and dispatch console radios. Also known as land mobile radio (LMR).
program - The action of setting your radio to a particular frequency, especially to communicate with a repeater, including setting the offset, tone, and power level, then possibly storing those settings in a memory channel. Also known as programming.
programmable gate array - (See field-programmable gate array)
programmable interface controller (PIC) - A family of Harvard architecture microcontrollers made by Microchip Technology, derived from the PIC1640 originally developed by General Instrument's Microelectronics Division.
programmable logic device (PLD) - A collection of programmable logic gates and circuits in a single integrated circuit; electronic component used for building reconfigurable digital circuits.
programmable read-only memory (PROM) - A form of digital memory where the setting of each bit is locked by a fuse or antifuse. Such PROMs are used to permanently store programs.
propagation - The behavior of radio waves when they are transmitted, or propagated, from one point on the Earth to another, or into various parts of the atmosphere. Radio propagation is affected by the daily changes of water vapor in the troposphere and ionization in the upper atmosphere, because of the effects of the Sun.
prosign - (See procedural signal)
protocol - A method of encoding, packaging, exchanging, and decoding digital data.
proton event - (See solar particle event) Also known as proton storm.
proword - (See procedural signal)
public exposure - (See uncontrolled environment)
Public Information Coordinator (PIC) - An appointee of the American Radio Relay League (ARRL) who is responsible for organizing, training, guiding, and coordinating the activities of each Public Information Officer (PIO) within an ARRL section.
Public Information Officer (PIO) - An appointee of the American Radio Relay League (ARRL) who establishes and maintains a list of media contacts in the local area, is a contact for local media, and carries out other duties as assigned by the ARRL.
pull out - Slang for action of distinguishing a station apart from the surrounding noise, enough to make a verifiable or meaningful contact with the station. Also known as pulled him out.
pull the big switch - A synonym for going off the air.
pulse modulation - A modulation method in which the timing, amplitude, and/or spacing of pulses of a transmitter's carrier are varied in order to convey information.
pulse waveform - A rectangular waveform made from narrow bursts of energy separated by periods of no signal.
pulse-code modulation (PCM) - A method used to digitally represent sampled analog signals. It is the standard form of digital audio in computers, compact discs, digital telephony, and other digital audio applications.
pulse-width modulation (PWM) - A method of encoding an information signal (your voice, data packets, etc.) into a pulsing radio frequency (RF) signal, so that the width of the output pulses varies with the information signal. Also known as pulse modulation.
push-pull amplifier - A linear amplifier that is characterized by low distortion, greater efficiency than a Class A amplifier, and reduces or eliminates even-order harmonics, and is therefore appropriate for amplifying phone signals. Also known as push pull amplifier.
push-to-talk (PTT) (1) A method of conversing on half-duplex communication lines, including two-way radio, using a momentary button to switch from voice reception mode to transmit mode using a thumb- or foot-activated switch. Also known as press-to-transmit. (2) A communication operation method that requires the press of a momentary switch or button to enable transmission of your voice.

To the top!   Q

Q code - An abbreviation for a common term used on the air, some of which can also be used as a question when followed by a question mark.
Q data - (See I/Q data)
Q line - The linear impedance matching transformer applied to an antenna to match its input impedance to the characteristic impedance of the feedline. Also known as Q-line; Q section.
Q signals - (CW term) Three-letter symbols specific to amateur radio beginning with Q to speed Morse code (CW) communication. They are similar to police 10 codes. Known in amateur radio as Q-codes.


Amateur radio operators use a subset of the full international Q-code. Here are the most common codes:

Code Question Answer
QRA What is the name (or call sign) of your station? The name (or call sign) of my station is ...
QRB How far are you from my station? The distance between our stations is ... nautical miles (or km).
QRG Will you tell me my exact frequency (or that of ...)? Your exact frequency (or that of ... ) is ... kHz (or MHz).
QRH Does my frequency vary? Your frequency varies.
QRI How is the tone of my transmission? The tone of your transmission is (1: good, 2: variable 3: bad)
QRK What is the readability of my signals (or those of ...)? The readability of your signals (or those of ...) is (1: bad ... 5: excellent).
QRL Are you busy? I am busy. (or I am busy with ... ) Please do not interfere.
QRM Do you have interference? I have interference.
QRN Are you troubled by static noise? I am troubled by static noise.
QRO Shall I increase transmit power? Please increase transmit power.
QRP Shall I decrease transmit power? Please decrease transmit power.
QRQ Shall I send faster? Please send faster (... words per minute).
QRS Shall I send more slowly? Please send more slowly (... words per minute).
QRT Shall I cease or suspend operation? I am suspending operation.
QRU Have you anything for me? I have nothing for you.
QRV Are you ready? I am ready.
QRX Shall I standby? / When will you call me again? Please standby. / I will call you again at ... (hours) on ... kHz (or MHz).
QRZ Who is calling me? You are being called by ... (on ... kHz (or MHz)).
QSA What is the strength of my signals (or those of ... )? The strength of your signals (or those of ...) is ... (1: very weak ... 5: very strong).
QSB Are my signals fading? Your signals are fading.
QSD Is my keying defective? Your keying is defective.
QSK Can you hear me between your signals (while transmitting), and if so can I break in on your transmission? I can hear you between my signals (while transmitting); break in on my transmission.
QSL Can you acknowledge receipt? I am acknowledging receipt.
QSM Shall I repeat the last telegram (message) which I sent you, or some previous telegram (message)? Repeat the last telegram (message) which you sent me (or telegram(s) (message(s)) numbers(s) ...).
QSN Did you hear me (or ...) on ... kHz (or MHz)? I did hear you (or ...) on ... kHz (or MHz).
QSO Can you communicate with ... direct or by relay? I can communicate with ... direct (or by relay through ...).
QSP Will you relay a message to ...? I will relay a message to ... .
QSS What working frequency will you use? I will use ... kHz (or MHz).
QSU Shall I send or reply on this frequency (or on ... kHz (or MHz))? Please send or reply on this frequency (or on ... kHz (or MHz)).
QSV Shall I send a series of "V" on this frequency (or on ... kHz (or MHz))? Please send a series of "V" on this frequency (or on ... kHz (or MHz)).
QSX Will you listen to ... on ... kHz (or MHz)? I am listening to ... on ... kHz (or MHz).
QSY Shall I change transmission frequency (to ... kHz (or MHz))? Please change transmission frequency (to ... kHz (or MHz)).
QSZ Shall I send each word or group more than once? Send each word or group twice (or ... times).
QTC How many telegrams (messages) have you to send? I have ... telegrams (messages) for you (or for ...).
QTH What is your position in latitude and longitude (or according to any other indication)? My position is ... latitude, ... longitude.
QTR What is the correct time? The correct time is ... hours.

QEX Magazine - A bimonthly magazine published by the American Radio Relay League (ARRL) that covers topics related to amateur radio and radiocommunication experimentation. The magazine features advanced technical articles on the theory, design, and construction of radio antennas and equipment and is published in English with a worldwide subscription base.
QSL Bureau - A United States international amateur organization set up by American Radio Relay League (ARRL) to process QSL cards between countries that provides an inexpensive way to send and receive QSL cards. Canadian amateur radio operators use the Radio Amateurs of Canada's incoming QSL bureau. QSL is a radiotelegraph Q-signal for "Can you acknowledge receipt?" Also known as bureau; burro; buro.
QSL card - A postcard, usually 3.5 inches by 5 inches, sent to a station confirming a radio contact.
QSL Manager (DX QSL manager) - A person (or organization), usually an amateur radio operator, who manages the receiving and sending of QSL reply cards for a managed station. A QSL Manager is needed because the managed station either has difficulty handling the volume of incoming QSL cards, or the station is geographically located such that it is difficult or impossible for that station to accept and/or send QSL cards. It is very common for rare distant stations (DX) and DXpeditions to have a QSL Manager.
QSLL - reply card - (Archaic) (CW term) A reply card to a received QSL card.
QSO - An amateur radio contact, more commonly referred to as simply a "contact," is an exchange of information between two amateur radio stations.
QSO party - An amateur radio contest relative to a particular state, province, region, or other grouping.
QST Magazine - A magazine for ham radio fans of the United States, it was first published in 1915 by the American Radio Relay League (ARRL).
QTH locator - (See grid locator)
quad antenna - A multi-element directional beam antenna with elements in the shape of a four-sided loop, approximately one wavelength in circumference. Also known as cubical quad antenna.
quad-band - (See multiband) Also known as quad band; quadband.
quadrature amplitude modulation (QAM) - In single-sideband, the special case where one of the baseband waveforms is derived from the other, instead of being independent messages.
quadrature phase - (See I/Q data)
quadrature phase-shift keying (QPSK) - A method of modulating a carrier in digital transmissions by changing its phase four times, with each change being represented by two binary digits. Also known as quadraphase phase shift keying.
quagi antenna - An antenna constructed with both quad and Yagi elements.
quality (Q) - A factor of a resonant circuit, it is the ratio of stored power to dissipated power in the reactance and resistance of the circuit. For antennas, the Q is inversely proportional to useable bandwidth, with reasonable standing-wave ratio (SWR). For example, an antenna with high Q will not provide a good SWR over a very wide range of frequencies.
quality factor (Q; Q factor) - A unitless circuit characteristic that quantifies its general performance such that the higher the Q of a resonant circuit, the lower its losses and bandwidth.
quarter-wave antenna - quarter-wavelength antenna - A ground plane quarter-λ antenna constructed of a quarter-wavelength long radiating element placed perpendicular to the earth. The λ is a Greek small lambda. Also called quarter-wave vertical antenna and quarter-wave monopole antenna.
Quarter Century Wireless Association (QCWA) - An amateur radio club with local chapters in which membership is offered solely to operators who were first licensed twenty-five or more years ago.
quartz crystal - A crystal of silicon dioxide cut to vibrate at a particular frequency when an electric current is applied to it. Used in high stability oscillators. Also known as crystal.
quasi-equiripple (QER) - A type of crystal ladder filter characterized by parallel crystal oscillators at each end of the crystal ladder, to reduce the passband ripple that normally plagues ladder filters.
Quebec - A North Atlantic Treaty Organization (NATO) phonetic alphabet code word representing the letter Q. Used in radio communication, particularly when spelling out a call sign. (Pronounced keh-BECK)
question pool - The set of questions from which an amateur license exam is constructed. There is one pool for each license class.
question set - A series of examination questions on a given examination selected from the question pool.
Quiet Channel (QC) - A Radio Corporation of America (RCA) trademarked name for continuous tone coded squelch system (CTCSS). General Electric called it CG (Channel Guard).
Quiet Zone - (See National Radio Quiet Zone)

To the top!   R

radar - (See radio detection and ranging)
radial - A horizontal counterpoise element of a vertically polarized antenna, sometimes buried to act as a low resistance path to ground, and running away from the antenna. (See counterpoise)
radian - The standard unit of angular measure or phase, used in many areas of mathematics. An angle's measurement in radians is numerically equal to the length of a corresponding arc of a unit circle and equals 360/2π or 57.3 degrees. The π is a Greek small pi.
radiate - To emit energy in the form of waves as from an antenna.
radiating element - The conductive, usually metallic, portion of an antenna intended to receive and/or transmit radio waves, also called the driven element in beams and other Yagi antennas. Also known as radiator.
radiation - The energy or particle (or both) given off (radiated, or emitted) from a source (such as ionizing, non-ionizing, electromagnetic, and solar radiation). (2) As it applies to ham radio, the emission or transmission of radio frequency (RF) energy as radio waves. Also known as RF radiation.
radiation angle - (See angle of radiation)
radiation pattern - A graph showing how an antenna radiates and receives in different directions. An azimuthal pattern shows radiation in horizontal directions. An elevation pattern shows radiation at different vertical angles. (See antenna pattern) (Also known as pattern; transmit pattern.
radiation resistance - That part of the total resistance of an antenna that results in radiation. The remainder generally results in loss of applied power as heat.
radiator - (See radiating element) Any component or object that emits electromagnetic radiation (radio waves), such as an antenna, wire, or any conductive material.
radio - An apparatus capable of receiving and transmitting messages between individuals, ships, planes, etc. over the airwaves. An Irish-Italian inventor, Guglielmo Marconi, is commonly credited for inventing radio in 1895. However, some eleven years earlier a dentist named Mahlon Loomis had actually gotten a patent for wireless telegraphy, and the electrical genius Nikola Tesla transmitted electrical energy though the electromagnetic spectrum before Marconi.
radio check - A test for (or report on) radio equipment functionality (workability), such as sufficient power level, ability to hit the repeater, clipping (on single sideband), frequency drift, or sufficient microphone gain. (See audio check; signal check)
Radio Amateur Civil Emergency Service (RACES) - A part of the amateur radio service that provides radio communication for civil preparedness organizations during local, regional, or national civil emergencies.
Radio Amateurs of Canada (RAC) - A national amateur radio organization in Canada.
Radio Craft Magazine - (Archaic) The first issue of Radio-Craft was published in 1929 and by late 1943 it had dropped the hyphen from the title. In 1948 the title changed to Radio-Electronics. It was published under that title until 1992, changing at that point to Electronics Now and surviving until 1999.
radio control (R/C) - The use of radio signals to remotely control a device.
Radio Corporation of America connector (RCA connector) - Model name for a type of audio and video connector (also called phono), once commonly used in amateur radio stations.
radio detection and ranging (radar) - An object detection system that uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio waves or microwaves which bounce off any object in their path. The object returns a tiny part of the wave's energy to a dish or antenna which is usually located at the same site as the transmitter.
radio direction finding (RDF) - The method of locating a transmitter by determining the bearings of received signals. This can refer to radio or other forms of wireless communication. By combining the direction information from two or more suitably spaced receivers or a single mobile receiver, the source of a transmission may be located in space by way of triangulation. (See amateur radio direction finding)
radio frequency (RF) - The rate of oscillation in the range of about 3 kilohertz (kHz) to 300 gigahertz (GHz), which corresponds to the frequency of radio waves, and the alternating currents which carry radio signals. RF usually refers to electrical rather than mechanical oscillations. Mechanical RF systems, however, do exist. Although radio frequency is a rate of oscillation, the term radio frequency or its acronym RF are also used as synonyms for radio, that is, to describe the use of wireless communication, as opposed to communication by way of electric wires. Radio frequency energy is measured in watts. Also known as radiofrequency.
radio frequency burn (RF burn) - A skin burn produced by coming in contact with exposed radio frequency (RF) voltages.
radio frequency carrier (RF carrier) - A steady radio frequency signal that is modulated to add an information signal to be transmitted. For example, a voice signal is added to the radio frequency (RF) carrier to produce a phone emission signal. Also known as carrier.
radio frequency choke (RF choke) - An inductor used to prevent or reduce the flow of radio frequency (RF) current. Also known as common-mode choke.
radio frequency combiner - (See combiner)
radio frequence exposure (RF exposure) - Federal Communications Commission (FCC) rules estblish maximum permissible exposure (MPE) values for humans to radio frequency (RF) radiation. (See maximum permissible exposure)
radio frequency feedback (RF feedback) - The distortion of transmitted speech caused by radio frequency (RF) signals being picked up by the microphone input circuits. Also known as RF in the shack; shack RF.
radio frequency front end - (See front end) Also known as RF front-end.
radio frequency gain (RF gain) - (See gain)
radio frequency ground (RF ground) - The connection of radio equipment to earth ground to eliminate hazards from radio frequency (RF) exposure and to reduce radio frequency radiation (RFI).
radio frequency hash - (Archaic) (See broadband noise)
radio frequency identification (RIFD) - (1) An identification and tracking method that uses radio waves to transmit and/or receive information stored in a electronic device embedded in, or deposited on, an object such as an animal, moving target, or person, for that purpose. (2) A passive device that contains electronically stored information that can be retrieved by another device by means of radio waves, to identify or track an object; or active device (powered by a battery or other electrical source) that can transmit stored information or real-time data from an object being identified or tracked.
radio frequency in the shack - (See radio frequency feedback)
radio frequency interference (RFI) - A situation in which an inadvertent radiator (computer, power line, appliance, etc.) produces radio frequency (RF) energy that interferes with a receiver intended to receive RF energy. (See electromagnetic interference)
radio frequency isolator - A device that allows transmission of RF energy in one direction, and effectively shields (isolates) a circuit from external sources of radio frequency (RF) energy, to prevent the de-tuning of a transmitter by a mis-matched load, for example. Also known as line isolator; RF isolator.
radio frequency overload (RF overload) (See receiver overload)
radio frequency power amplifier - (See power amplifier)
radio frequency protector - (See lightning arrester)
radio frequency radiation (RF radiation) - Waves of electric and magnetic energy. Such electromagnetic radiation with frequencies as low as 3 kilohertz (kHz) and as high as 300 gigahertz (GHz) are considered to be part of the radio frequency (RF) region.
radio frequency safety (RF safety) - Preventing injury or illness to humans from the effects of radio-frequency energy.
radio frequency signals (RF signals) - Any electrical signals with a frequency higher than 20,000 hertz (Hz), up to 300 gigahertz (GHz). Also known as radio signals.
radio frequency spectrum (RF spectrum) - The eight electromagnetic bands ranked according their frequency and wavelength.
radio frequency splitter - (See combiner)
radio frequency transformer - (See voltage balun)
radio group - A group of ham radio afficionados as opposed to an electrical group or a telephone group. (3) A term as in RG-8 Coax, a thick cable with a velocity factor of 75.
radio guide (RG) - The prefix and unit indicator for coaxial cable model names (formerly military radio equipment designations).
radio horizon - The most distant point to which radio signals can be sent by line-of-sight propagation. (See horizon; line-of-sight propagation)
Radio Inspector (RI) - (Archaic) A government district level official.
radio message servers (RMS) - Mailbox stations that receive email transmissions using amateur radio for the connection to individual amateur radio operators.
Radio News Magazine - (Archaic) An American monthly technology magazine published from 1919 to 1971. The magazine was started by Hugo Gernsback as a magazine for amateur radio enthusiasts, but it evolved to cover all the technical aspects to radio and electronics. In 1929 a bankruptcy forced the sale of Gernsback's publishing company.
radio orienteering - (See amateur radio direction finding)
Radio Regulations - The latest International Telecommunication Union (ITU) regulations to which the United States is a party. Covering both legal and technical issues, it serves as an instrument for the optimal international management of the radio spectrum.
radio relay - (See relay station)
radio shack - (See shack) Also known as radioshack.
radio signals - (See radio frequency signals)
Radio Society of Great Britain (RSGB) - The British equivalent of the United States' American Radio Relay League (ARRL).
radio station - (See station)
radio wave - An electromagnetic wave with a frequency greater than 20 kilohertz (kHz). Also known as radio waveform.
Radio-Television Manufacturers Association (RTMA) - A standards and trade organization for the consumer electronics industry in the United States. CEA works to influence public policy, hold events, conduct market research, and help its members and regulators to implement technical standards.
Radiocorp - (Archaic) Early shorthand for Radio Corporation of America (RCA).
radiogram - Formal written message traffic routed by a network of amateur radio operators through traffic nets.
radiolocation - The process of detecting and locating distant objects by using radio signals. Also known as radio location; radio-location.
radionavigation - A service that applies radio frequencies to determine a position on the earth. Also known as radio navigation; radio-navigation.
radiosport - (See amateur radio direction finding; contesting) Also known as radio sport.
radiotelephone - A communication system for transmission of speech over radio. (See phone)
radiotelephone distress frequency - An international distress and calling frequency for mobile radiotelephone stations, survival craft, and emergency position-indicating radio beacons. The radiotelephone distress frequencies are 2.182 megahertz (MHz) and 156.8 megahertz (MHz). The survival craft and maritime distress frequency is 243 megahertz (MHz) and the general aviation distress frequency is 121.5 megahertz (MHz).
radioteletype (RTTY) - (1) A telecommunications system consisting originally of two or more electromechanical teleprinters in different locations. (2) A mode that uses frequency-shift keying to form letters, numbers, and special characters for display on a printer or video monitor. (3) Keyboard-to-keyboard transmission mode originally conducted between special teletype machines. Now one of many modes that are frequently sent with a personal computer (PC) with a sound card.
Radiotron - (Archaic) A brand name for a Radio Corporation of America (RCA) vacuum tube. (See vacuum tube)
rag chew - Slang for chatting informally by amateur radio. Also known as ragchew; rag chewing.
Rag Chewers Club (RCC) - (Archaic) Traditionally an introductory amateur radio award, it was issued by the American Radio Relay League (ARRL) to the operators of thousands of amateur radio stations and many long-time operators who could proudly claim to have received it as their first award in the 1950s and 1960s. Originally available to ARRL members for the price of a confirmed half-hour QSO and a self-addressed stamped envelope, and later for a fee, the award was issued by ARRL headquarters until 2004 when interest waned. The award was discontinued by the ARRL in 2004 and is now being offered through the Society for the Preservation of Amateur Radio (SPAR) organization.
rain scatter - A type of microwave propagation in which signals are refracted by rain drops in a storm that is within radio range of both source and destination stations. Also known as rain-scatter.
random wire antenna - A multi-band antenna consisting of any convenient length of wire, connected directly to a transmitter or impedance matching network without the use of a feed line. Also known as random-length wire antenna; random-wire antenna.
random access memory (RAM) - A form of computer data storage. A random-access device allows stored data to be accessed quickly in any random order. In contrast, other data storage media such as hard disks, CDs, DVDs, and magnetic tape, as well as early primary memory types such as drum memory, read and write data only in a predetermined order, consecutively, because of mechanical design limitations.
random-wire antenna - A type of monopole antenna consisting of a reasonably long wire, whose (random or arbitrary) length is typically selected for convenience rather than wavelength, and so is not as efficient as one whose length is adjusted to resonate within a specific band. Also known as random wire antenna; long wire antenna; longwire antenna.
range - The longest distance over which radio communication can take place.
rat killing - Doing other things besides talking on the radio.
rat tail - (See tiger tail)
ray tracing - The modeling of a radio wave path through the ionosphere by calculating its behavior through a system with regions of varying propagation velocity. Also known as ray-tracing.
reactance - The opposition to current that a capacitor or inductor creates in an alternating current (AC) circuit. Capacitors exhibit capacitive reactance and inductors exhibit inductive reactance. Reactance is measured in ohms (Ω).
reactance amplifier - (See parametric amplifier)
reactance modulator - A device or circuit that controls modulation by varying the reactance of a transmitter circuit and altering its phase angle, often used in phase modulation and frequency modulation.
reactive power - (See power factor)
read-only memory (ROM) - A class of storage medium used in computers and other electronic devices that cannot be modified or only slowly or with difficulty.
readability, strength, tone (RST) - A system of numbers used for signal reports: Readability (1 to 5), Strength (1 to 9), Tone (1 to 9). On single-sideband phone, only R and S reports are used. The report is given as a series of three numbers, for example, 599, 579, 458. (See SINPO and S-meter)

Readability (Voice and CW)
2Barely readable, occasional words distiguishable
3Readable with considerable difficulty
4Readable with practically no difficulty
5Perfectly readable
Signal Strength (Voice and CW)
1Faint signals, barely perceptible
2Very weak signals
3Weak signals
4Fair signals
5Fairly good signals
6Good signals
7Moderately strong signals
8Strong signals
9Extremely strong signals
Tone (CW only)
1Sixty cycle AC or less; very rough and broad.
2Very rough AC; very harsh and broad
3Rough AC tone; rectified but not filtered
4Rough tone; some trace of filtering
5Filtered rectified AC; strongly ripple-modulated
6Filtered tone; definite trace of ripple modulation
7Near pure tone; trace of ripple modulation
8Near perfect tone; slight trace of ripple modulation
9Perfect tone; no trace of ripple modulation
If the signal has the characteristic steadiness of crystal control, add the letter X to the RST report.
If there is a chirp, add the letter C to the RST report.
If there is a click, add the letter K to the RST report.

read-only memory (ROM) - A non-volatile digital integrated circuit (IC) often used to store programs that run on microprocessors.
reading the mail - (CW term) To listen to a communication without participating.
real power - (See power factor)
real time - Communications that are taking place with no perceptible delay.
reboot - (See restart)
RCA connector - A model name (from Radio Corporation of America) for a type of audio and video connector (also called phono), once commonly used in amateur radio stations.
receive (RCV, RX) - To detect or pick up radio broadcast signals. (See receiver)
receiver (rcvr) - (1) A device that converts radio waves into signals that can be heard, seen or red by a computer. (2) (Archaic) When plural, an early synonym for headphones.
receiver incremental tuning (RIT) - A tranceiver control circuit that allows the receive frequency to be shifted from the transmit frequency by a small amount using frequency synthesis. On some radios it is called clarifier.
receiver overload - Interference to a receiver caused by a strong radio frequency (RF) signal that forces its way into the equipment. A signal that overloads the receiver RF amplifier (or front end) causes front-end overload. Also known as RF overload.
receiver passband - (See passband)
receiver voting system - (See voting repeater system)
receiving converter - A device that shifts the frequency of incoming signals so that a receiver can be used on another band.
receiving pattern - The relative field sensitivity of a receiving antenna in a set of applicable directions or in all directions. Also known as receive pattern.
reception report - A letter written to a radio station supplying details about a station's signal and the programming heard in order to solicit a QSL card from the station.
recharge - To restore an electric charge to a battery or a battery-operated device by connecting it to a device that draws power from another source of electricity.
reciprocal - (1) The mathematical inverse of a value, such that the value, if multiplied by its reciprocal, equals 1. (2) The mutually agreed upon, governed, or controlled by more than one body or set of rules; equally binding between, or bearing on, parties of an agreement.
reciprocal agreement - A set of rules between two parties equally bearing on an individual; in the case of amateur radio operation, by both countries on a person who is not a citizen of (alien to) one or both countries. Also known as rules of reciprocity.
reciprocal licensing - The amateur radio licensing that is governed by more than one set of rules; specifically, licensing of a person who is not a United States citizen (alien), for operating privileges that are governed by the Federal Communications Commission (FCC) and rules established by another country.
reciprocal mixing - The undesirable receiver response to a strong signal it's not tuned to (the strong signal is outside the passband) mixing with the phase noise of a local oscillator (usually originating from the frequency synthesizer), over-powering (hiding or masking) a weaker signal that it is tuned to, often if the strong signal and the tuned signal differ by the intermediate frequency, resulting in perceived reduction of the receiver signal-to-noise ratio.
reciprocal mixing dynamic range (RMDR) - A measurement of a receiver's dynamic range, based on reciprocal mixing, rather than its third-order intercept point, and expressed in decibles (dB).
reciprocal operating authority - Permission for amateur radio operators from another country to operate in the United States using their home license. This permission is based on various treaties between the United States government and the government of other nations.
reciprocal operation - Amateur radio station operation that is governed by more than one set of rules. Also known as reciprocity; alien reciprocal operation.
reciprocity - (See reciprocal operation) (1) The fundamental property of an antenna, which states that its receiving characteristics, such as sensitivity pattern, gain, impedance, resonant frequency, and bandwidth, are identical to its far-field transmit (radiation) characteristics. (2) The engagement between two parties (reciprocal operation) that operate under a mutually binding set of rules (reciprocal agreement).
rectangular coordinates - The two-dimensional coordinate system whose points are defined as ordered pairs of distances to its reference axes, often used to display the resistive, inductive, and/or capacitive components of impedance.
rectifier - A diode that allows current to pass through it in only one direction and is used in power supplies and power conversion circuits.
rectify - To convert alternating current (AC) to direct current (DC).
re-evaluation - (See compliance)
reflected path - The route that a transmitting antenna's signal takes to a receiving antenna when it is reflected by large objects such as buildings or terrain. (See direct path)
reflected power - Non-radiated power in a transmission line that is dissipated as heat when a transmitter is mismatched to the antenna or load.
reflection - (1) A change in signal direction as it encounters a surface or medium that returns the signal to the original medium, but at a different angle, such as light on a mirror or a radio wave on the ionosphere or a building. (2) The effect of some or all of a transmission line signal being returned to its source from its load due to an impedance mismatch between the source and the load. Also once known by the slang backlash current and incorrectly radio frequency (RF) feedback.
reflection coefficient - The ratio of the complex reflected signal voltage to the complex forward signal voltage, indicating how much of an electromagnetic wave is reflected due to a difference in impedance between the transmission line and its load, also indicating how closely they are matched, and also used to determine the standing-wave ratio (SWR) of an antenna system (symbol Γ, uppercase gamma).
reflector - (1) A parasitic element behind the driven element in a Yagi and some other directional antennas that focuses the radiated signal toward the forward direction. (See Yagi) (2) A server that allows multiple nodes or repeaters to be linked together at the same time. (3) A mail list that forwards news to the subscribers, for example, distant station (DX) Reflector or contest reflector.
refract - To bend. Electromagnetic energy is refracted or bent when it passes through a boundary between different types of material much as light is refracted as it travels from air into water or from water into air. Radio waves refract as they travel through the ionosphere.
region - An administrative area of the United States as defined by the International Telecommunications Union (ITU).
registered jack-11 (RJ-11) - The model name for a modular and keyed data communication connector, more properly called 6P2C (6-position, 2-contact), but often mis-named for 6P4C and 6P6C, and often used in a variety of amateur radio equipment, such as separated control heads, microphone cords, and computer interface cables. Also known as RJ11.
registered jack-45 (RJ-45) - The model name for a modular and keyed data communication connector, more properly called 8P8C (8-position, 8-contact), and often used in a variety of amateur radio equipment, such as microphone cords and computer interface cables. Also known as RJ45.
regulation - The ability of a power supply to control output volatage.
regulator - A device that maintains a constant output voltage over a range of load currents and input voltages.
relay - A switch operated by an electromagnet.
remote base - A high-frequency (HF) amateur station set up to operate by remote control, usually by connecting to the Internet through a computer.
remote control - The use of a control operator who indirectly manipulates the operating adjustments in the station through a control link to achieve compliance with the Federal Communications Commission (FCC) Rules.
remote receiver - (Repeater term) A receiver at a separate location from a repeater to extend the repeater's listening range.
relay station - Any radio station installed permanently (such as a repeater) or used temporarily (like during an incident) for receiving and re-transmitting (relaying) information between two or more other stations that might have difficulty communicating with each other, because of distance, terrain, conditions, obstructions, interference, or other causes. Also known as radio relay.
remote tuned antenna - Includes the Scorpion, all motorized screwdriver antennas, and some base-loaded antennas.
remotely controlled base station - A radio station that is either controlled through a radio link by an auxiliary station and that might be located apart from the auxiliary and regular stations during normal operation, or is itself a remotely located auxiliary station. Also known as remote base.
repeater - (Repeater term) A receiver/transmitter that listens for a transmission on one frequency, usually a weak one, and re-transmits it, usually at higher power, on another frequency for extended communication. Repeaters are usually placed at high geographical locations for access by very-high frequency (VHF) and ultra-high frequency (UHF) hand-held and mobile transceivers to extend the range of a transmission. The separation between these two frequencies is referred to as the offset. Also known as repeater station. (See offset)
Repeater Council - (Repeater term) A voluntary regional amateur organization coordinating repeater frequency pair assignments to minimize interference. As no individual amateur group owns any given radio frequency, a council does not exercise legal authority to force individual repeater operators onto a specific frequency, height, location, power, or directional pattern. Nonetheless, amateurs are obligated by national laws to avoid interference to other amateur stations and official regulatory agencies will resolve interference complaints between repeater operators by forcing uncoordinated repeaters to move off frequencies where their operation interferes with any coordinated repeater.
Repeater Directory - (Repeater term) An annual American Radio Relay League (ARRL) publication or software program that lists repeaters in the United States, Canada, and other areas.
repeater etiquette - (Repeater term) The customary code of polite behavior in society or among members of a particular profession or group. The following are a few repeater etiquette hints:


repeater offset - (Repeater term) The value difference between a repeater's input frequency and its output frequency (also known as its shift), with offset = finput − foutput determining both the repeater offset and offset direction, which is noted by the sign (plus or minus) of the offset. Also known as shift.
repeater operation - (Repeater term) Automatic amateur stations that retransmit the signals of other amateur stations.
repeater station - (Repeater term) An amateur station that automatically retransmits the signals of other stations.
repeater timer - (Repeater term) (See timeout timer)
repeater trustee - (Repeater term) A licensed amateur who is responsible for the maintenance of the repeater license (not the repeater equipment itself) and appropriate repeater operation.
reset - (1) The last-resort transceiver function that returns various settings to a default or original state (with a factory reset or hard reset or full reset often referring to one that clears channel memory as well), performed in the event of suspected transceiver malfunction or invalid setting states. (2) An action (either manually or automatically performed) by a repeater, in which its controller is restarted and its settings are returned to a default or original state. (3) An optional announcement made by a ham radio operator who has been transmitting continuously for a while, to indicate the need to release the press-to-talk (PTT) button long enough to reset the repeater timeout timer (to prevent the repeater's timer from expiring, thereby resulting in the repeater rebooting itself), and resume transmitting.
residual-current circuit breaker (RCCB) - (See residual-current device (RCD))
residual-current device (RCD) - A device that quickly breaks an electrical circuit to prevent serious harm from an ongoing electric shock. Also known as residual-current circuit breaker (RCCB); ground-fault circuit interrupter (GFCI).
resistance - The ability to oppose an electric current. Also known as direct current resistance (DC resistance).
resistive divider - A two-resistor circuit used to reduce an applied voltage.
resisitivity - The measure of how strongly a material, such as plastic, opposes the flow of electric current.
resistor - An electronic component with a specific value of resistance used to oppose or control current through a circuit.
resonance - In an electrical circuit or antenna, the frequency at which inductive reactance and capacitive reactance are absent or balanced such that their effects cancel. A resonant circuit will respond strongly to a particular frequency, and much less so to differing frequencies which allows the radio receiver to discriminate between multiple signals.
resonant circuit - A circuit in which the inductive and capacitive reactances are equal and cancel, leaving just the resistive part of the circuit, and that exhibits resonance at one or more frequencies.
resonant frequency - The desired operating frequency of a tuned circuit. In an antenna, the resonant frequency is one where the feed-point impedance contains only resistance.
resonator - A device or system that exhibits resonance or resonant behavior, that is, it naturally oscillates at some frequencies, called its resonant frequencies, with greater amplitude than at others.
restart - Applicable to most any computer-controlled device, and for amateur radio, more specifically to the action of a repeater, to (often shut it down, then) return its various settings to a preset state, in the event of suspected malfunction or the expiration of its timeout timer. Also known as restart.
rettysnitch - A fictional torture device for bad hams. (Also see Wouff Hong)
reverse - A transceiver configuration (also called reverse split) in which the input and output repeater frequency settings are swapped, allowing the operator to listen to the transmission of another station that is attempting to transmit to the repeater by simulating the repeater's frequency configuration (the operator acting as the repeater).
reverse biased - Not conducting.
reverse burst - (See squelch tail elimination)
reverse polarity SMA (RP-SMA) - A variation of subminiature version A (SMA) connector that presents a pin for the female interface and a receptacle for the male interface. Also known as RPSMA; RSMA.
reverse polarity TNC (RP-TNC) - A variation of threaded Niell-Concelman (TNC) connector that presents a pin for the female interface and a receptacle for the male interface. (Also known as RPTNC; RTNC.
reverse sideband - A single sideband operating mode opposite the convention of that of the band in consideration; USB for 40 meters, 80 meters, and 160 meters, but LSB for all other bands.
RG-8X - The model name for a common 50 Ω low-cost, low-power, fairly low-loss coaxial cable used as a feedline in high frequency (HF) and temporarily (testing, for example) in very-high frequency (VHF) applications. Also known as mini-RG-8; RG-8 mini; mini-8.
rhombic antenna - A directional, wide-band wire antenna formed by four equal-length sides in a rhombic (diamond) shape parallel to the ground and characterized by high gain.
ribbon line - (See window line)
rig - Slang for a wireless amateur-radio transmitter, receiver, or transceiver.
ringing - An undesirable oscillation added to a signal following a sudden change in the input (step response) due to resonance from parasitic capacitances and inductances in the circuit.
ripple - The residual alternating current (AC) left over after rectification and filtering when an AC supply has been converted to direct current (DC).
rock - (Archaic) Older slang for quartz crystal or crystal oscillator.
rock bound - A synonym for a crystal controlled oscillator used to stabilize frequencies in transmitters and receivers. Also known as rock-bound; rockbound.
rock crusher - (Archaic) A slang term for a spark transmitter.
rod - (See ground rod)
roger - (Archaic) The letter R has been used since the early days of continuous wave (CW) to indicate that "The message has been received." The voice code equivalent for R is Roger. Wilco is radio slang for "Will Comply." So, Roger Wilco means "The message has been received and I will comply."
roger beep - A tone that sounds when a radio operator un-keys a microphone. The tone can be short, long, or even a combination of multiple tones, such as, a dit-dah-dit sent at the end of a transmission. The intention of the roger beep is to let the other operator in the conversation and any other people on the radio know when the person talking has finished.
roll-call net - A type of net in which the net control station asks for check-ins by roll call; that is, by announcing the call signs listed on a roll.
rolloff - Steepness (sharpness) in the rate of change of filtering ability from one frequency to another, especially in the transition between the passband and the stopband (known as the transition band). Also known as roll-off.
Romeo - A North Atlantic Treaty Organization (NATO) phonetic alphabet code word representing the letter R. Used in radio communication, particularly when spelling out a call sign.
roof capacitor - (See capacitance hat)
roofing filter - A circuit that limits the passband of the first intermediate frequency stage of an RF receiver, reducing distortion and overloading from signals outside the intended frequency range, thereby improving its dynamic range.
rookie - (See novice) A contesting contact designation indicating that the operator has been licensed for (typically) less than three years.
root mean square (RMS) - A statistical measure of the magnitude of a varying quantity. It is especially useful when variates are positive and negative, for example, in sinusoids. RMS is used in various fields, including electrical engineering.
root mean square voltmeter (RMS voltmeter) - An alternating current (AC) voltmeter to read the root mean square voltage level.
rotary inductor - A variable inductor in which a sliding contact is moved along the coil as it is rotated.
rotate - To take batteries in and out of service, preventing continuous use.
rotator - (See antenna rotator) Years ago, this device was simply called a rotor. Also known as rotator unit.
rotator controller - (See antenna rotator controller) Also known as rotor controller; rotator control unit; rotor control unit.
rotor - (See antenna rotator)
roundtable - A contact in which several stations take turns transmitting in a rotating format. Also known as round table; round-table.
routine radio frequency radiation evaluation - The process of determining if the radio frequency (RF) energy from a transmitter exceeds the Maximum Permissible Exposure (MPE) limits in a controlled or uncontrolled environment.
rover - A type of mobile radio station that travels from one location to another, to make contacts with other stations from a variety of locations, often during contesting and often operated by a passenger, rather than the vehicle driver (also, a rover station is one that is typically designed with gear, such as laptop, power supply, transceiver, tuner, and antennas, that is appropriate for making occasional or even frequent contacts while traveling).
RS-232 - (Archaic) A standard that defined a serial computer connection arrangement. The standard specified pin-outs for a 25-pin (DB25) and 9-pin (DB9) subset, signal relations, voltage levels, and maximum cable lengths. RS-232 was renamed EIA232 in the 1990s.
RST Report - A telegraphy signal report system of Readability, Strength, and Tone. (See readability, strength, tone.)
rubber duck antenna - A shortened flexible rubber-coated antenna used with hand-held very-high frequency (VHF) and ultra-high frequency (UHF) scanners, transmitters, receivers, and transceivers. Also known as duck; rubber ducky antenna.
rubber stamp QSO - Slang for a quick, on-air, two-station trade of basic information, such as names, station locations, local outdoor termperatures, and other data, often patterned by the person who initiated the QSO or called CQ, similar to an exchange typically done during contesting.
rules of reciprocity - (See reciprocal agreement)
running - Slang for making one contact after another in rapid succession, while remaining on a particular frequency, unlike a sprint, in which the frequency is changed.
RW open protocol (RWOP) - (CW term) A system based on the electronic message unit (EMU) of the British tactical radio that used standard frequency-shift keying to protect against reception errors. It was created by Paul R. Signorelli WØRW. (See electronic message unit)

To the top!   S

S meter - (See signal-strength meter) Also known as S-meter.
S band - An alternate name for the 13-cm band.
S-line - (Archaic) A line of transmitters, receivers, amplifiers, and other accessories offered by the Collins Radio Company from 1958 to 1975.
SAE connector - The model name (from Society of Automotive Engineers) for a gender-neutral direct current (DC) power connector, once commonly used to supply power to amateur radio equipment. Also known as bullet connector; trailer plug.
safety - Radio frequency (RF) exposure limits, set by ANSI (American National Standards Institute), to minimize over exposure to RF signals from a nearby antenna.
safety ground - A ground connection intended to prevent shock hazards.
safety interlock - A switch that automatically turns off alternating current (AC) power to a piece of equipment when the cover is removed.
scan - To continually sweep and monitor frequencies or a set of memory channels looking for active signals.
satellite - (See amateur radio satellite)
satellite downlnk - A frequency or band and accompanying protocol by which an orbiting satellite transmits to an earth station.
satellite uplink - A frequency or band and accompanying protocol by which an earth station transmits to an orbiting satellite station.
saturation - (1) The quantity of amplifier input power for which an increase will not produce a discernible or significant increase (gain) in output power. (2) The state of a transistor in which its output voltage is at or near that of the supply voltage. (3) The state of an inductor whose ferrite core's ability to store magnetic energy has been exceeded.
sawtooth wave - A type of waveform that has a rise time significantly shorter than its fall time, or vice versa.
scan edge - The start or end frequencies for a scanning range.
scan line - A visible row of display monitor pixels produced by fast-scan TV or other video technology. Also known as scanning line.
scanner - A radio receiver that automatically tunes through a sequence of user-selected frequencies.
scanning - Rapidly switching between a list of frequencies to listen for an active channel. Tone scanning determines what sub-audible access tones are being used.
scatter propagation - (See high-frequency scatter).
scatter - Radio wave propagation by way of random scattering of a signal directly off the ionosphere overhead or off an obstruction. Scatter signals are usually weak.
scattering parameters - Elements of a scattering matrix that describe the electrical behavior of a linear two-port electrical network (port 1 — the input port which represents the point where the transmitter meets the feedline, and port 2 — the output port which represents the point where the feedline meets the antenna) with matched loads.
schedule 40 poly-vinyl chloride - A poly-vinal chloride plastic pipe with thicker walls than some other types and a popular material often used as antenna structural support or insulator.
schematic diagram - Semi-pictorial record of the circuits and electrical connections in a piece of electronic equipment by using symbols to repersent the electrical components.
schematic symbol - A standardized symbol used to represent an electrical or electronic component on a schematic diagram.
Schottky diode An electronic semiconductor component (formerly known as a hot-carrier diode, surface carrier diode, and hot electron diode) that performs the same function as a silicon diode, but has a very low forward voltage drop, lower capacitance, and very fast switching speed. Also known as Schottky barrier diode; surface-barrier diode..
scope - (See oscilloscope)
scratch-pad memory - Temporary frequency memories for quick access.
screen grid - (See grid)
screwdriver antenna - A motorized mobile multi-band high-frequency (HF) antenna invented by Don Johnson W6AAQ in 1991. A modified battery-powered screwdriver is used to move the loading coil in and out of the mast section. It is not as efficient as some claim because of the capacitive end affect caused by the requisite large diameter mast.
sealed lead-acid (SLA) - A type of lead-acid rechargeable battery whose contents are completely contained and isolated from external access (spillage) or exposure, and so can be placed in any orientation, and does not require constant maintenance, which provides an attractive and favorite emergency or standby power source for ham radio operators.
search - A feature in certain receivers that will scan a frequency range at certain increments (such as 1 kHz or 5 kHz) and pause on any frequency where a signal is present.
search and rescue (SAR, S&R) - The search for and provision of aid to people who are in distress or imminent danger. Amateur radio is used to communicate on a search and rescue.
secondary - (1) The output from a transformer, or its point of connection to a circuit, separating it from the power or signal source (the input typically called the primary). (2) A band or sub-band that is available (on a secondary basis) to a specific group of users or operators at a lower priority compared with that of a primary group. (3) A group of users or operators who has been granted a lower priority control (secondary control) of a band or sub-band compared with that of a primary group.
secondary allocation - The attribute of a range of frequencies over which a radio user (amateur or otherwise) shares the band with users of a different license type. Secondary users must not interfere with primary users and must accept interference from primary users.
secondary circuit - (Archaic) An early synonym for the grid circuit of a vacuum tube circuit design. (See vacuum tube)
secondary coupling - In a lightning environment, it is a transformer-like electro-magnetic coupling between powerful cloud-to-earth lightning strikes and nearby above ground wires and cables. A secondary coupling typically creates above-ground surges in those wires.
secondary-mode current - See common-mode current.
secondary service - (See primary service)
Section Emergency Coordinator (SEC) - An appointee of the American Radio Relay League (ARRL) who takes care of all matters pertaining to emergency communications and the Amateur Radio Emergency Service (ARES) on an ARRL sectionwide basis. The SEC is the assistant to the Section Manager (SM) for emergency preparedness.
Section Manager (SM) - An American Radio Relay League (ARRL) position, the Section Manager is accountable for carrying out the duties of the office in accordance with ARRL policies established by the board of directors who act in the best interests of amateur radio.
Section Traffic Manager (STM) - An appointee of the American Radio Relay League (ARRL) who coordinates all radio traffic efforts within a section so that routings within the section and connections with other networks and digital traffic nodes will result in orderly and efficient traffic flow.
segment - (See sub-band)
selectivity - The ability of a receiver to detect weak signals.
selective fading - The undesirable effect caused by partial cancellation of a radio wave within the received pass band due to the destructive interference resulting from the signal arriving at the same receiver but by multiple paths, while one or both of the paths is changing lengths.
self supporting - Not requiring guy wires to remain vertical.
self-addressed stamped envelope (SASE) - An unused envelope sent to another amateur radio operator with the sender's address and with return postage affixed.
self-controlled oscillator - (Archaic) An oscillator that is variable in frequency, as opposed to one that is crystal controlled.
self-discharge - The internal loss of energy without an external circuit. (See discharge)
self-spotting - Slang for the practice of advertising, promoting, or broadcasting your own ham radio station's frequency and location to aid other stations in making many contacts in a short period of time, which practice is usually prohibited during contesting, but encouraged for SOTA activities; see also spotting and cheerleading.
semi-break-in - (CW term) A Morse code (CW) station using voice-activated dialing (VOX) or other means to automatically switch from transmit to receive during sending pauses. Such stations generally cannot hear received signals between code characters or words needing a somewhat longer cessation in sending for automatic switch over from transmit to receive. The switch to transmit automatically occurs when the key is depressed. This is common in single-sideband (SSB) transceivers being used for CW. Also known as semi break-in.
semi-duplex - A mode of operation in which transmit and receive is accomplished on different frequencies alternatively. (Also known as semi duplex.
semiconductor - (1) An element that is normally an insulator but which can, under certain physical conditions, be made to conduct. (2) An electrical component constructed from semiconductor material.
semiconductor diode - A type of diode that is constructed with a metal-to-semiconductor junction, which can fail due to excessive temperature when excessive current passes through the diode. Also known as junction diode.
selectivity - The ability of a receiver to separate two closely spaced signals.
sense antenna - An omnidirectional antenna placed closely to a directional antenna or added to a DF antenna array to provide a null (very weak transmission/reception point) in one direction.
sensitivity - A receiver's ability to detect and receive weak signals. Also known as minimum discernible signal.
separation - To split the difference in kilohertz (kHz) between a repeater's transmitter and receiver frequencies. Repeaters that use unusual separations, such as 1 megahertz (MHz) on 2 meters (m), are sometimes said to have odd splits. (See split)
sequential - A type of call sign selected and issued by the FCC from an alphabetically ordered list appropriate for the applicant's license class and residence location.
sequential sampling - Digital signal processing (DSP) method used in analog-to-digital conversion, of sampling the analog signal at evenly spaced time intervals (sequences), whose rate is typically much greater than the frequency of the signal being sampled.
sequential system - One of three methods used to select a call sign for amateur station over-the-air identification purposes. (See call-sign system)
series circuit - An electrical circuit in which all the electrons must flow through every part of the circuit and there is only one path for the electrons to follow.
series inductance - An inductance used to cancel a residual capacitance.
service - (1) A set of regulations by the Federal Communications Commission (FCC) that defines a certain type of telecommunications activity. (2) A program or system that specifies the rules and operating principles for one or more radio frequency bands. (3) Slang or short for QSL service. (4) Slang or short for electrical service.
service entrance panel - A device generally located immediately behind the killowatt-hour meter that provides mains electricity fusing for the electric service wires. It then distributes the electrical load to a number of separately fused electrical circuits for customer equipment.
set mode - An operational mode used for radios to set less-frequently used control features.
shack - The room where an amateur radio operator keeps his or her wireless station equipment, such as a closet, or space in a basement, living room, or corner of a bedroom, and from which the radio station is operated. The term dates from the very early days of radio when those that could afford it built a small shack in the back yard to house their often large (many pieces of equipment), noisy (crackling spark gaps and sometimes whining motors and generators), smelly (ozone from the arcing spark gap and sparking motor/generator brushes), dangerous (very high voltages on fully exposed wiring and equipment), sloppy (chemical rectifiers that routinely boiled over and batteries containing spillable acid which generated explosive gases while being recharged) amateur station. Also known as radio shack; radioshack; static room. Also known as ham shack; hamshack.
shack-in-a-box - (1) A single transceiver unit that is capable of transmitting and receiving communication on HF (including 160 meters and World Administrative Radio Conference (WARC) bands), very-high frequency (VHF), and ultra-high frequency (UHF) amateur frequencies, typically up to, and including, the 70-centimeter (cm_ band). (2) A complete amateur station. Also known as shack-in-a-can.
shack radio frequency - (See radio frequency feedback)
shadow - (1) The intention to accompany (or remain in close proximity to) a particular leader during a drill or incident, to communicate information at the moment the leader needs the communication made. (2) Slang for a location where a radio frequency (RF) signal is degraded to the point that communication is difficult or impossible.
shadow net - A radio net, each of whose operators accompany (shadow), or at least remain in close proximity to, a particular leader during a drill or incident, to provide a network of radio communication between the leadership.
shadowing - Mounting an antenna too close to the body of a vehicle. Doing so increases shunt capacitance, thus lowering efficiency.
shape factor - A receiver's selectivity measured at the 6 and 60 decibels (dB) rejection points.
shared non-protected (SNP) - (Repeater term) In repeater coordination, an input/output (I/O) frequency pair on which no fixed or permanent repeater stations have been deployed. These frequencies remain available for temporary use only within a very limited coverage area by portable public service, emergency, search and rescue operations, or short experiments. Individual temporary repeaters on these frequencies are not regionally-coordinated, so are not protected from mutual interference with other temporary repeaters on the same frequency. Also known as shared non-protected frequency.
shared non-protected frequency (SNPF) - (See shared non-protected)
shield - The conductor in a cable that is designed to be at ground potential.
shielding - A coating surrounding an electronic circuit with conductive material to block radio frequency (RF) signals from being radiated or received.
shift - (See repeater offset)
shift direction - (See offset direction)
shift register - The clocked array of digital circuits that passes data in steps along the array.
shock - (See electrical shock)
shooting skip - (See working skip)
short circuit - An electrical circuit in which the current does not take the desired path, but finds a shortcut instead. Often the current goes directly from the negative power-supply terminal to the positive one, bypassing the rest of the circuit.
short skip - Propagation by way of the ionosphere over a distance of a few hundred miles or less.
short-time - (See early out) Also known as short time.
shortwave (SW) - Radio communication using the upper medium frequency (MF) and all of the high-frequency (HF) portion of the radio spectrum between 1,800 and 30,000 kilohertz (kHz). (See high frequency)
shortwave listener (SWL) - One who listens to shortwave.
shortwave listening (SWL) - The hobby of listening to shortwave radio broadcasts located on frequencies between 1700 kilohertz (kHz) and 30 megahertz (MHz).
shunt - (1) A component or conductor used to join two points in a circuit to provide an additional path for some of the current in the circuit. (2) The action of placing a component or conductor across two points in a circuit, to provide an additional path for some of the current in the circuit.
shunt capacitance - The effective capacitance in the parallel leg of the equivalent circit for a crystal oscillator.
side load - Also known as sidelobe. (See lobe)
Side Winders On Two (SWOT) - A radio club promoting single sideband (SSB) transmissions on the 2-meter (m) band.
sideband - A radio frequency (RF) signal that results from modulating the amplitude or frequency of a carrier. An amplitude modulation (AM) sideband can be either higher in frequency (upper sideband or USB) or lower in frequency (lower sideband or LSB) than the carrier. Frequency modulation (FM) sidebands are produced on both sides of the carrier frequency. (See single sideband and double sideband)
sideband line (SB line) - (Archaic) A line of transceivers (SB10x), transmitters (SB40x), receivers (SB30x), amplifiers (SB2xx) and other accessories (SB6xx) offered by the Heathkit Radio Company in the 1960s and 1970s. They were considered the poor man's Collins because of the similarities and much lower cost.
sideswiper - Slang for a sideways motion, manual, and non-electronic telegraph key (often cootie key or slap key) made for high-speed continuous wave (CW) transmissions.
sidewinder - A slang term for a single sideband (SSB) station.
siemens (S) - The derived unit of electric conductance, electric susceptance, and electric admittance.
Sierra - A North Atlantic Treaty Organization (NATO) phonetic alphabet code word representing the letter S. Used in radio communication, particularly when spelling out a call sign.
sign - (Archaic) An identifier for a specific operator at a station, usually two letters, used to distinguish one operator from another, and is a carry over from the days before government issued call signs when two-letter identifiers were used. Also archaically known as sine.
signal - A radio emission.
signal check - A test for (or report on) radio signal quality (integrity), such as picket-fencing, clipping (on single sideband), full-quieting (especially going into a repeater if using one), or choppy signal.
signal generator - A device that produces a low-level signal that can be set to a desired frequency.
signal ground - The reference point for which component or circuit voltages can be measured relative to this point, providing a local type of ground. Also known as circuit ground.
signal report - An evaluation of the transmitting station's signal and reception quality.
signal-strength meter (S-meter) - Originally used in the early 20th century as part of the readability, strength, tone (RST) reporting code, this was a subjective assessment of the received signal, based on a 9-point scale and reported in S-units. It is often provided on communication receivers, such as amateur radio receivers or shortwave broadcast receivers. The scale markings are derived from a subjective system of reporting signal strength from S1 (faint, barely perceptible signals) to S9 (very strong signals) as part of the RST code. There is often an additional scale above S-9 (S-9 + 10) calibrated in decibels (dB). (See readability, strength, tone)
signal-to-noise and distortion (SINAD) - A measure of the quality of a signal from a communication device. Also known as signal to noise and distortion.
signal-to-noise ratio (SNR; S/N) - (1) The amount of desired signal power with respect to the amount of noise power, expressed in decibles (dB). (2) (CW term) A measure used to compare the level of a desired signal to the level of background noise. The better the SNR ratio, the better the quality of the signal and the easier it is to decode. Also known as signal to noise ratio.
signing off - Ending the work with a particular station.
Silent Key (SK) - A deceased amateur radio operator.
silicone diode - (See diode)
silicone-controlled rectifier (SCR) - An electronic semiconductor component (also known as thyristor) that acts as a bistable switch, which allows current flow in one direction if voltage is applied to its gate terminal.
simpatch - (See autopatch)
simplex - A communication operational mode in which transmit and receive frequencies are the same. Most often used when communicating directly, in other words, not used when operating by way of voice repeaters. Also called talk around. (See duplex)
simplex autopatch - (See autopatch) Also known as simpatch.
simplex operation - Receiving and transmitting on the same frequency.
simplex repeater - (Repeater term) A radio that has a digital audio store-and-forward relay system that produces results similar to that of a conventional repeater. Also known as parrot repeater.
simplex teletype over radio (SITOR) - (See amateur teleprinting over radio)
Simulated Emergency Test (SET) - A nationwide exercise in emergency communication, administered by American Radio Relay League (ARRL) Emergency Coordinators and Net Managers. Both the Amateur Radio Emergency Service (ARES) and the National Traffic System (NTS) are involved. The SET weekend gives communicators the opportunity to focus on the emergency communication capability within their community while interacting with NTS nets.
simulated emergency training - A staged drill or mock scenario to train volunteers in emergency handling procedures and communication ability.
simulcasting - (See voting repeater system)
sine - A trigonometric function of an angle. The sine of an angle is defined in the context of a right triangle: it is the ratio of the length of the side opposite that angle to the length of the hypotenuse.
sine wave - A waveform with an amplitude equal to the sine of frequency times time.
single-pole, double-throw (SPDT) - A switch that connects one center contact to one of two other contacts. Also known as switch.
single-pole, single-throw (SPST) - A switch that only connects one center contact to another contact. Also known as switch.
single sideband (SSB) - A modulation mode of voice operation on the amateur radio bands in which one sideband and the carrier are removed. SSB is a form of amplitude modulation where the amplitude of the transmitted signal varies with the voice signal variations. SSB signals have a lower sideband (LSB), which is that part of the signal below the carrier, and an upper sideband (USB), which is that part of the signal above the carrier. SSB transceivers allow operation on either LSB or USB. Also known as single-sideband.
single-sideband suppressed-carrier (SSB-SC) - A refinement of amplitude modulation that more efficiently uses transmitter power and bandwidth.
single-signal receiver - (Archaic) A superheterodyne design in the 1930s using interstage filtering for added selectivity. Also known as S.S. receiver.
sinusoid - A mathematical curve that describes a smooth repetitive oscillation. It is named after the function sine, of which it is the graph. Also known as sinusoidal.
Six Meter International Radio Klub (SMIRK) - A club that promotes the use of the 6-meter (m) band, organized in 1973 by a group of San Antonio, Texas-area amateurs active on the 50 to 54 megahertz (MHz) amateur band.
sked - Slang or short for schedule, and indicates a pre-arranged contact between ham radio operators.
skin effect - The tendency of an AC signal within a conductor to become distributed with greater current density nearer to the surface of the conductor than to its center, such that the higher the frequency the greater the current density toward the surface.
skip - (1) A radio phenomenon in which signals are reflected or refracted by the atmosphere and return to earth in unexpected places, far away from the normal reception zones. In between transmitter and receiver there is a zone where no transmissions can be heard. (2) Slang for skywave propagation.
skip distance - The shortest distance, for a fixed frequency, between transmitter and receiver.
skip wave - (See skip zone)
skip zone - The distance between the point of no reception and the closest point of reception. It is an area of poor radio communication, too distant for ground waves and too close for sky waves. Also known as dead zone; zone of silence.
sky-wave propagation - The method by which radio waves travel through the ionosphere and back to Earth. Sky-wave propagation has a far greater range than line-of-sight and ground-wave propagation. Travel from the Earth's surface to the ionosphere and back is called a hop. Also known as skip. (See skip; blind zone)
skyhook - A slang word for an antenna. (See antenna)
SkyWarn - An organization of trained volunteer storm spotters for the National Weather Service (NWS). (See National Weather Service)
skywave - (See sky-wave propagation) Also known as sky wave.
skywire antenna - An adaptation of the rhombic antenna constructed with wires whose combined length totals greater than one full wavelength, and with all points of the wires installed at the same height off the ground. Also known as horizontal loop; loop skywire; skywire loop.
skywire loop - (See skywire antenna)
slanted dipole - (See sloper antenna)
slash - Slang for the fractional bar (/ or –), a part of a whole or, more generally, any number of equal parts. When spoken in everyday English, a fraction describes how many parts of a certain size there are, for example, one-half, eight-fifths, or three-quarters. It may be either an inclined bar from bottom left to upper right or a horizontal bar. It is differentiated from a stroke, such as found in the numeral Ø. Also known as stroke.
sled - Slang for removable battery case or battery holder capable of holding multiple batteries.
slim - A synonym for someone pretending to be a distant station (DX), usually rare, that is supposed to be on the air. For example, someone in southern Argentina pretending to be on Heard Island.
slop jar - (Archaic) A synonym for an electrolytic rectifier. Electrolytic rectifiers were common in the late 1920s and early 1930s. One cell consisted of two strips of dissimilar metals in a caustic potash, or lye solution. Many cells were needed for a high voltage supply.
sloper antenna - A type of dipole antenna whose radiating element section is installed at an angle to the ground. Also known as slanted dipole; sloper dipole.
sloping dipole antenna - Any kind of dipole antenna installed so the dipole wires slope from one end to the other. Often created when one end of the dipole is attached high on a tower and the other to some lower support.
slow-scan television (SSTV) - Graphic communication in the bandwidth required for a voice signal, usually still images by way of radio in monochrome or in color.
slow blow - (See fuse)
slug - A short, cylindrical unit that is inserted into a wattmeter that allows the unit to read power (watts) for a particular frequency range. A slug always has a finite frequency range and a maximum power rating. By swapping out different slugs, the wattmeter can be used for many different frequencies and power ranges. (See inductor core)
Smith chart - A graphical aid for displaying impedance components of electric circuits and transmission lines on the complex plane.
snap-on ferrite choke - (See ferrite choke)
snubber capacitor - An ordinary capacitor placed in a circuit to suppress (snub) or absorb transient voltage spikes and other rapid voltage changes.
socket-239 (SO-239) - Female antenna connector used on most high-frequency (HF) radios, it is a World War II threaded radio frequency (RF) connector design from an era when ultra-high frequency (UHF) referred to frequencies over 30 megahertz (MHz). Originally intended for use as a video connector in radar applications, the connector was later used for radio frequency (RF) applications. It mates the PL-259 plug.
Society for the Preservation of Amateur Radio (SPAR) - A non-partisan group of concerned amateur radio operators working together to ensure the vitality of the amateur radio service by promoting technical abilities among amateur radio operators.
software-defined radio (SDR) - Radio system in which the majority of processing is performed in a personal computer (PC) using special software that defines the radio's functionality.
solar cell - An electric device that converts light energy into electrical energy by means of the photovoltaic effect. Also known as photovoltaic cell.
solar coronal hole - (See coronal hole)
solar cycle - An 11 year cycle of intense sunspot activity. High activity equals good distant station (DX) propagation, low activity equals poor DX propagation. (See sunspots)
solar flare - A sudden burst of high energy observed over the surface of the sun, ejecting clouds of electrons, ions, and atoms into space, and often followed by a large coronal mass ejection.
solar flux - A solar emission at radio frequencies, the solar flux index (SFI) of which is a measure of solar radiation at 2800 megahertz (MHz) (or 10.7 cemtimeters (cm) – also known as the F10.7 Index – which has a major effect on long-distance 10-meter, 12-meter, and 15-meter propagation.
Solar Flux Index (SFI) - A measure of the radio noise on 2800 megahertz (MHz) (2.8 GHz), it is a gauge of solar particles and magnetic fields reaching our atmosphere. Higher numbers mean more solar wind is reaching the earth thus better propagation.
solar panel - An array or collection of solar cells arranged in a sheet or other surface.
solar particle event (SPE) - A highly disruptive solar storm that takes place when charged particles emitted by the sun become accelerated to very high energies, often associated with coronal mass ejections, and can be the source of disturbing or blocking all ionospheric radio communication.
solar power - A source of electrical power provided by a device such as a solar cell or solar panel, often used through a charge controller or whose energy is stored in a battery.
solar wind - A stream of charged particles released from the upper atmosphere of the sun, consisting mostly of electrons, protons, and alpha particles, which can interfere with radio transmission.
solenoid - A type of inductor formed by a coil of wire wound into a tightly packed helical shape. Also known as solenoid inductor.
solder lug - An electrical connector that has a toothed hole to fit under a machine screw or nut. It includes a protrusion with one or more holes designed as a place for wires to be soldered.
soldering copper - (Archaic) A soldering iron in the 1920s which were available electrically heated and stand-alone for heating over a flame.
solid state - A type of circuit or device, containing no vacuum tubes, in which all charge flows through solid material such as a semiconductor, an electrical component, a wire, or other metal, rather than a vacuum, the air, or other gas. Also known as solid state.
SOS or SOS - (CW term) A Morse code (CW) call for emergency assistance. In popular usage, SOS became associated with such phrases as save our ship, save our souls, and send out succour. These may be regarded as mnemonics, but SOS does not stand for anything and is not an abbreviation, acronym, or initialism. (See distress call)
source - (1) A circuit connected to the input of a load circuit to present a voltage to the load, such that typically the source circuit provides electric power to the load, and the load consumes the power from the source. (2) One of the electrodes on a field-effect transistor (FET). (See transistor) (3) The point where electromagnetic radiation is emitted, such as a radio transmitter antenna or noisy switch.
space - The lower frequency of a binary frequency-shift keying (BFSK) data signal, identifying the Ø bit.
Space Amateur Radio Experiment (SAREX) - (Archaic) SAREX has been superseded by the Amateur Radio on the International Space Station program. (See Amateur Radio on the International Space Station)
space frequency - In frequency-shift keying, the lower of the two frequencies used. (See mark frequency)
space station - An amateur radio station located more than 50 kilometers (km) above the Earth's surface. (See Amateur Radio on the International Space Station)
space telemetry - A one-way transmission from a space station of measurements made from the measuring instruments in a spacecraft, including those relating to the functioning of the spacecraft.
space weather - The general study of the time varying conditions within the solar system arising from the interaction of solar particles and radiation with the fields and atmosphere of the earth.
spark gap - (Archaic) An early transmitter design which used electrical sparks to generate radio frequency oscillations. Also known as sparkgap.
speaker (SP) - Short for loudspeaker, it is a device that converts electrical impulses into sound.
speaker microphone (speaker mic) - An optional accessory for a hand-held transceiver containing both a small speaker and a microphone.
special event - A radio operating event, usually on high-frequency (HF), in which a group or organization celebrates an event or holiday by making contacts and offering special QSL cards or certificates to confirm the contact. Ham radio magazines, such as QST, usually publish a monthly list of special events. Also known as special-event.
special event call sign - A type of call sign issued temporarily to an amateur radio station, to commemorate a special event, and is identified by a 1x1 format.
special-event system - One of three methods used to select a call sign for amateur station over-the-air identification purposes. (See call-sign system)
special license - (Archaic) A license granted for some stations to operate at wavelengths above 200 meters (m).
Special Temporary Authority (STA) - A temporary permit granted (typically no longer than six months) to an amateur station by the Federal Communications Commission (FCC) for communication outside the operating limits authorized for the station license, for emergency or experimental purposes.
specific absorption rate (SAR) - The rate at which radio frequency (RF) energy is absorbed into the human body. Maximum permissible exposure (MPE) limits are based on whole-body SAR values.
spectrum - The range of electromagnetic signals. The radio spectrum includes signals between audio frequencies (AF) and infrared (IR) light.
spectrum analyzer - An instrument that measures the range of power levels of an input signal among a frequency bandwidth of interest, known as its spectrum.
speech compression - Increasing the average power of a voice signal by amplifying low-level components of the signal more than high-level components. Also called compression and speech processing.
speech processor - A circuit that increases the average level of the modulating signal applied to a transmitter.
spike - A sudden but short-lived increase of voltage, current, power, or energy in a device or circuit or field. Also known as surge.
spin fading - The reduction in satellite communication signal strength due to the rotation of the satellite, such that its antenna becomes partially obstructed from the view of the receiver by the satellite body.
spin modulation - The rotation of a radio signal polarization brought about by the physical rotation of the signal source or by a reflection of the signal off a rotating object, such as a satellite.
splatter - Undesired emissions resulting from overdriving an amplifier or modulator, causing distortion.
split - (1) (Repeater term) An operational mode in which the transmit and receive frequencies are different. Repeaters that use unusual separations, such as 1 megahertz (MHz) on 2 meters (m), are sometimes said to have odd splits or separation. (See offset) (2) Distant stations (DX) often operate split, that is, transmitting on one frequency and listening at a different frequency or range of frequencies. This avoids congestion on the DX transmit frequency.
split channel - A frequency located between standard frequency allocations, such as the 10 kilohertz (kHz) spacing of amplitude modulation (AM) broadcast band frequencies or coordinated repeater frequencies.
split beads - (See electromagnetic interference sleeves)
splitter - (See multicoupler)
sporadic E (ES; Es; E-skip; E skip - (1) Layer of atmosphere (also designated ES) located within the ionosphere and made from clouds of intense ionization that allow reception of VHF signals from long distances at times. (2) Propagation mode using the E layer of the ionosphere and commonly associated with occasional, strong over-the-horizon signals on the 10-, 6-, and 2-meter bands.
sporadic E-layer skip - Unexpected and unpredictable propagation using refraction in the atmospheric E-layer. Also known as sporadic E-skip.
spot frequency net - (Archaic) A net where everyone is on the same frequency which was a novelty in the late 1920s and 1930s.
spotting - Slang for the practice of locating a ham radio station by use of online or local software, known as clustering software or spotters, in order to make many contacts in a short period of time, which practice is usually prohibited during contesting. Also known as cheerleading; clustering; spotter.
spread spectrum (SS) - A modulation method that spreads transmitter energy across a relatively wide frequency range according to a modulating code.
spread spectrum multiple access (SSMA) - A version of spread-spectrum in which the power density is limited by multiplying the signal with a spreading code sequence. Also known as code-division multiple access.
sprint - The practice of making a contact and changing frequency immediately afterwards, before making the next one, a requirement for some contests.
spurious emission - A signal from a transmitter on frequencies other than the operating frequency. Also known as spur.
spurs - (See spurious emissions)
squeak box - (Archaic) A spark coil, or spark coil-based transmitter.
squelch (SQL) - A circuit that mutes the receiver when no signal is present, thereby eliminating band noise.
squelch clamping - An undesirable operation of the squelch circuit in which it momentarily turns off the audio signal to mistakenly compensate for an increase in modulation level after confusing it with an increase of the noise level; the squelch circuit determines that no frequency modulation (FM) signal present when in fact an FM signal is present.
squelch tail - (Repeater term) A brief bit of noise heard between the end of a radio transmission and the reactivation of the receiver's squelch circuit. Also known as squelch crash.
squelch tail elimination - (Repeater term) A receiver feature that removes the squelch tail from your transceiver when a repeater switches from transmitter mode to receiver mode.
spread-spectrum emissions (SS) - Emissions using bandwidth-expansion modulation having designators with A, C, D, F, G, H, J, or R as the first symbol; <X> as the second symbol; and <X> as the third symbol.
stacked - The vertically collinear mounting or installation arrangement of two or more sets of (typically identical) antennas.
stage - (1) Transmitter or receiver circuitry or section that performs a specific function that's part of a collection of operations required by a device. (2) The act of performing some operation that simulates an incident or other situation.
stand by - Wait and listen, but do not change frequency.
standard-definition television (SD) - A television system that uses a resolution that is not considered to be high-definition television (HDTV).
standard frequency (SF) - (Archaic) An initialism for standard frequency, used in the 1930s.
standard phonetics - (See North Atlantic Treaty Organization phonetic alphabet)
standby - Something kept in reserve, or made readily available in case of an emergency.
standing wave - The vector sum of two waves, in ham radio this most usually refers to the forward and reflected waves in a feed line.
standing-wave bandwidth - The difference (bandwidth) between the highest and lowest frequencies at which the standing-wave ratio (SWR) for an antenna is 2.0:1 and less.
standing-wave ratio (SWR) - (1) The ratio of power sent down a feed line from the transmitter to the power reflected back through the feed line to the transmitter. A ratio of 1 to 1 is ideal; anything higher than 2 to 1 usually indicates a problem in the feed line or antenna. (2) A measure of how much radio energy sent into an antenna system is being reflected back to the transmitter.
standing-wave ratio meter (SWR meter) - A measuring instrument used to measure standing-wave ratio (SWR) that can indicate when an antenna system is working well. (See standing wave ratio)
State Government Liaison (SGL) - An appointee of the American Radio Relay League (ARRL) who collects and promulgates information on state legislation and regulation affecting amateur radio; and guides, encourages and supports individual radio amateurs and clubs in representing the interests of the amateur radio service at all levels, including the federal level.
static - A random signal with a constant power spectral density. In other words, a signal that contains equal power within any frequency band with a fixed width. Also known as white noise.
static crash - An undesirable radio receiver sound resulting from static electricity discharge, typically lightning or other type of electrostatic discharge.
static room - (Archaic) An early term for a ham shack.
station - (1) The physical equipment, apparatus, or software (including, but not limited to, power supply, transceiver, feedline, and antenna) that can transmit and receive information (a radio station is one that uses radio waves to communicate that information). (2) A unit made of a control operator and a radio frequency (RF) transceiver combined.
station grounding - An electrical connection of a circuit or conductor eventually to the earth. Connecting all of one's station equipment to a good earth ground improves both safety and station performance.
station identification - The transmission of a transmitter's identifying information (usually the call sign), required by law at least every ten minutes during and at the end of a contact.
station license - An amateur radio license. In some countries, an amateur radio license is necessary in order to purchase or possess amateur radio equipment. (See operator/primary station license)
steam - Slang for background hissing sound heard during a radio communication. Also sometimes referred to as bacon frying.
steep skirt - (See transition band)
step on - Slang for transmitting over somebody else's transmission or at the same time as another on the same frequency.
step-start - A circuit in a high-voltage power supply that limits the inrush current (step) on power-up by applying power at a reduced voltage, allowing the filter capacitors to charge gradually.
stinger antenna - (See whip antenna)
stopband - A band of frequencies, between specified limits, through which a circuit does not allow signals to pass, or the attenuation is above the required stopband attenuation level. Also known as stop band.
store-and-forward - A system for the receipt, storage, and later retransmission of packet radio messages. Also known as store and forward.
straight key (SK) - (CW term) A non-electronic Morse code (CW) key with one paddle. (See key)
Straight Key Century Club (SKCC) - A club promoting the use of hand keys for Morse code (CW) communication.
strap - (See ground strap)
strapping - (See bonding)
stray capacitance - An undesirable and unavoidable capacitance that exists between two conductors in a circuit because of proximity to each other, which can prevent an actual circuit from behaving like an ideal one. Also known as parasitic capacitance.
strays - (Archaic) Another word for static.
street power - (See household power)
strength, interference, noise, propogation, overall (SINPO) - A reporting system used by radio hobbyists to indicate how well a station was received: S equals Strength, I equals Interference, N equals Noise, P equals Propagation, O equals Overall. Reported as SINPO <4-digit number>. (See readability, strength, tone and strength unit (S-unit) - Unit of measure on S-meters (m). Each S-unit is intended to represent a factor of 2 in input voltage at the receiver antenna terminals. (See signal-strength meter)
stroke - (See slash)
stub - A length of transmission line that is open or shorted at one end. It is effectively a capacitor or inductor, depending on length, and can be used to achieve a match if connected at a selected point in the basic transmission line.
sub-band - A subset or portion of an amateur band 144.0 to 144.1 MHz is the continuous wave only (CW-only) sub-band of the 2-meter band. Also known as band segment; segment.
subaudible tone (SAT) - A tone that is used to trigger an automated event at a radio station. A subaudible tone is audible; however, it is usually at a low level that is not noticeable to the average listener at normal volumes.
subminiature version A (SMA) - A connector for an antenna, usually used on hand-held scanners, transmitters, receivers, and transceivers.
sudden ionospheric disturbance (SID) - An abnormally high ionization density in the D region of the ionosphere, caused by a solar flare, and resulting in daytime disruption of signals on lower high frequency (HF) frequencies more than those on higher frequencies.
suffix - In the United States, each call sign has a one-letter prefix (K, N, W), or a two-letter prefix (AA-AL, KA-KZ, NA-NZ, WA-WZ), and a one-, two-, or three-letter suffix separated by a numeral (0-9) indicating the geographic region. For example, WØ is a prefix for Colorado, while the call sign might have a suffix of ZYX for a call sign of WØZYX.
Summits On The Air (SOTA) - An amateur radio operating award program, it is an international event in which operators gain points from contacts to and from mountain summits over 500 meters (m).
sunspot cycle - The number of sunspots increases and decreases in a predictable cycle that lasts about 11 years. The broader sunspot cycle is 22 years because the polarity of the sunspots reverse every 11 years.
sunspot number (SSN) - A quantity that measures the number of sunspots and groups of sunspots present on the surface of the sun.
sunspots - (1) The sunspot cycle/solar cycle is an approximately 11-year period in which the number of sunspots varies from none to a high of between 100 and 200, and is perhaps the phenomenon that affects high frequency (HF) communication the most; see also solar cycle on American Radio Relay League (ARRL) and solar flux. (2) The sunspot number is the measure of solar activity based on counting sunspots and sunspot groups, with high sunspot numbers enhancing long-distance communication in the upper HF to lower VHF range of frequencies. (3) The solar rotation (sun's rotation on its axis) causes HF propagation conditions to vary periodically in a 28-day cycle with the number of sunspots facing the earth.
super turnstile antenna - A type of normal turnstile antenna constructed of a stacked array of batwing bays (sets), often used in broadcasting. Also known as superturnstile antenna.
super-high frequency (SHF) - The frequency range of 3 to 30 gigahertz (GHz). Also known as super high frequency.
superheterodyne - A classic receiver architecture in which an incoming signal is beat, or heterodyned, with a signal generated in the local oscillator (LO) to translate the incoming signal to an intermediate frequency for processing. The receive frequency is changed by moving the LO to shift a different incoming frequency to the same intermediate frequency (IF). This allows the same circuit elements to process signals of different frequencies providing consistency of operation and performance. (See heterodyne)
supersonic heterodyne - A receiver that uses frequency mixing to down-convert a received signal to a fixed intermediate frequency (IF) signal, which can be more conveniently processed than the original radio frequency (RF) carrier signal; the superheterodyne receiver being the most widely used application of heterodyning, and is made from a combination of high frequency (HF) oscillator, mixer, and detector in its simplest implementation. Also known as superhat; superheterodyne.
supressor grid - (See grid)
surface wave - (See ground wave)
surface-barrier diode - (See Schottky diode) Also known as surface barrier diode.
surface-mount technology (SMT) - A method of mounting minuscule components on circuit boards without leads.
surge - (See spike)
surge protector - (See lightning arrester) Also known as surge arrester; surge arrestor; surge suppressor.
susceptance - An imaginary component of admittance, or quantity of allowance for current flow in a circuit (symbol B), expressed in siemens (symbol S).
swamp - (Archaic) Older slang for drown out, overload, render helpless, or otherwise overwhelm a signal, a circuit, or the audio output of a system.
swap meet - An informal gathering (also called swapfest) of people who buy, sell, barter, display, or discuss ham radio gear or information or services, or simply observe their operation. Also known as hamfest.
swap net - A net whose primary purpose, or whose agenda includes as a major role, the announcing or advertising the availability of ham radio equipment for sale or trade.
swap-fest - (See swap meet) Also known as swapfest.
swing - (CB term) Slang for the largest difference in transmitter power between the output due to maximum modulation and that of a dead carrier (deadkey) from the same device, particularly in an amplitude modulation (AM) transmission.
swinging - (1) (Archaic) A synonym for fading. (2) (Archaic) The behavior of a signal having an unstable frequency.
swishing - (CW term) A synonym for changing the frequency of a transmitter while it is keyed.
switch - A device used to connect or disconnect electrical contacts. (See single-pole, double-throw; single-pole, single throw.
switched-mode power supply (SMPS) - A type of power supply that converts electrical alternating current (AC) power to direct current (DC) power by pulsing the energy during the conversion process, and is typically much lighter and more efficient than a linear power supply, but also typically (electrically) noisier.
switching power supply - A power supply that uses switching transistors (ON-OFF) to increase the efficiency of the power conversion, rather than the simple transformer/rectifier design of traditional power supplies. Also known as switcher; switched-mode power supply.
symbol rate - (See baud)
synchronous detection - An ingenious method of processing an amplitude modulation (AM) signal to improve audio quality and reduce interference from adjacent stations. It is similar to exalted carrier reception, but the replacement carrier tuning and tracking is done automatically by the receiver.
synchronous repeater - (Repeater term) (See voter repeater system)
synchronous transmission - (See voting repeater system)
synthesized frequency - (See frequency synthesis)
System Fusion - A system (created by Yaesu) of amateur radio repeaters and other stations that are interconnected by the C4FM digital protocol mode to transmit both voice and digital information over the air

To the top!   T

T connector - The model name for a direct current (DC) power connector that has two blade pins mounted perpendicular to each other on the radio-side (often jack) connector, plus an exterior tab on the power-side (often plug) connector to prevent accidental disconnection. Also known as T plug; T-style; T-shaped; Molex T; OEM-T, OEM connector; OEM-T connector.
T pad - One of the possible configurations used in attenuators. (See attenuator)
T-hunt - (See amateur radio direction finding) Also known as T-hunting.
T-match - A double-Gamma match that provides a balanced connection to an antenna. The circuit gets its name because it looks like the letter T. (See Gamma match)
T-network - A circuit made from series capacitors and a parallel shunt inductor, that serves as a high-pass filter capable of matching a large impedance range with relatively low-losses. Also known as T network.
table-top exercise (TTX) - An incident or emergency preparedness training exercise discussion, analysis, and possible walk-through, unlike a staged simulation or drill.
tactical call signs - Names used to identify a location or function during local emergency communication.
tactical communications - A first-response communication under emergency conditions that involves a few people in a small area.
talk-around - Two-way radio communication using a repeater output frequency for a simplex frequency (to talk around a repeater, or communicate by simplex on a duplex channel). Also known as direct radio; car-to-car in some commercial and official applications.
talk-in (TI) - A term for when a volunteer at a hamfest mans a radio and sets up on a repeater to provide general information and directions.
talk around - (See simplex)
Tango - A North Atlantic Treaty Organization (NATO) phonetic alphabet code word representing the letter T. Used in radio communication, particularly when spelling out a call sign.
tap - An electrical connection made to some point between the end terminals of a transformer coil or other component. Also known as center tap; inductor tap; tapping.
Technical Coordinator (TC) - An appointee of the American Radio Relay League (ARRL) who coordinates all technical activities within an ARRL section.
Technical Specialist (TS) - An appointee of the American Radio Relay League (ARRL) who supports the Technical Coordinator (TC) in two main areas of responsibility: radio-frequency interference and technical information.
Technician Class The current entry-level-2 license that garners all ham radio privileges above 30 megahertz (MHz), including the popular 2-meter (m) band. Many Technician Class licensees enjoy using small, 2-meter hand-held radios to stay in touch with other hams in their area. Technicians may operate frequency modulation (FM) voice, digital packet or computers, television, single-sideband voice, and several other interesting modes. You can even make international radio contacts by way of satellites, using relatively simple station equipment. Technician licensees now also have additional privileges on certain high-frequency (HF) frequencies and may also operate on the 80, 40- and 15-meter bands using Morse code (CW), and on the 10-meter band using CW, voice, and digital modes. It does not require familiarity with Morse code.
telecommand - A one-way transmission to initiate, modify, or terminate functions of a device at a distance.
telecommand station - An amateur station that transmits communications to initiate, modify, or terminate functions of a space station.
telecommunications - The electrical conversion, switching, transmission and control of audio, video and data signals by wire or radio.
telegraph - (CW term) The long-distance transmission of messages without the physical exchange of an object bearing the message. Thus beacons, flag semaphore, radiotelegraphy, reflected-light signals, and smoke signals are methods of telegraphy whereas pigeon post is not.
telegraph key - (See key.
telegraphy - (CW term) The transmission of information in Morse code (CW) and radioteletype (RTTY) format.
telemetry - A one-way radio transmission used for tracking and measurement data.
telephones - (Archaic) An early synonym for headphones in the early 1920s. Also known as receivers.
telephony - The transmission of information in voice format.
teleprinter - A machine that can convert keystrokes, or typing, into electrical impulses. The teleprinter can also convert the proper electrical impulses back into text. Computers have largely replaced teleprinters for amateur radioteletype work.
telescoping antenna - An antenna made of concentric tubular parts that slide into themselves so that the antenna becomes smaller. It may be motorized or unmotorized.
television (TV) - A system for transmitting visual images and sound that are reproduced on screens, chiefly used to broadcast programs for entertainment, information, and education.
television interference (TVI) - Interruption of television reception caused by another signal.
telex-over-radio (TOR) - (Archaic) A radio station in England provided worldwide maritime communication and long-range aeronautical communication beginning in 1928. During the 1950s and 1960s, there was a steady increase in traffic levels, and the TOR system started operations. The long-range services ceased at midnight on 31 August 1999.
Telnet - A remote terminal protocol that is fundamental to the operation of the Internet Protocol (IP).
temperature-compensated crystal oscillator (TCXO) - A heated crystal oscillator used for better frequency stability.
temperature coefficient - The amount a component value changes as a function of change in temperature.
temperature inversion - A condition in the atmosphere in which a region of cool air is trapped beneath warmer air.
temporary operating authority - Authority to operate an amateur radio station while awaiting arrival of an upgraded license.
temporary state of communication emergency - When a disaster disrupts normal communication in a particular area, the Federal Communications Commission (FCC) can declare this type of emergency. Certain rules may apply for the duration of the emergency.
ten-ten - A club promotion of the use of the 10-meter (m) band. Also known as 10-10; 10-X.
tera (T) - One trillion, or the metric prefix for 1012, or times 1,000,000,000,000.
terahertz radiation - (See tremendously-high frequency)
terminal - An inexpensive piece of equipment that can be used in place of a computer in a packet radio station.
terminal-node controller (TNC) - (1) A device used to convert digital signals from a personal computer (PC) into an analog form that can be transmitted by radio and to convert received analog signals into digital form for display on a personal computer (PC) monitor. It includes a modem and implements the rules of a protocol. (2) A device that groups characters into packets, generates modem tones, and implements the X.25 protocol used for various digital modes of transmission. Also known as terminal node controller.
terminated folded dipole antenna (TFD) - A type of once-popular horizontal folded dipole antenna (abbreviated T3FD for the three-wire version or T2FD / TTFD for the two-wire version), in which the elements are made of parallel wires that terminate at a non-inductive resistor, widely used at one time for HF and shortwave radio. Also known as tilted folded dipole antenna.
termination - A load or antenna connected to a transmission line.
terminator - The visible dividing line that separates daylight and darkness (night) on the earth.
terrestrial station location - Any location of a radio station on the surface of the earth including the sea.
test - (1) Emissions containing no information having the designators with N as the third symbol. Test does not include pulse emissions with no information or modulation unless pulse emissions are also authorized in the frequency band. (2) An announcement (typically testing) to the general public, that the current message is being transmitted as part of a verification or experiment, to determine equipment functionality, audio quality, or signal integrity, and to inform listeners that the operator is probably not requesting or expecting a contact or other reply. (3) Short for contest, and indicates, typically in continuous wave (CW), that the communication targets a particular contest.
test point (TP) - A location within an electronic circuit that is used to either monitor the state of the circuitry or to inject test signals.
that is (i.e.) - An abbreviation for the Latin phrase id est. It means that is and is usually followed by a comma. (See e.g.)
theoretical noise - (See noise floor)
thermal effects - Biological tissue damage resulting because of the body's inability to cope with or dissipate excessive heat (as applies to radio frequency (RF) radiation).
thermal runaway - The undesirable condition in an amplifier constructed from bipolar-junction transistors (BJTs), in which normal operation results in a rise in temperature, which causes a significant increase in leakage current, which in turn raises the temperature even more, eventually destroying the transistor or amplifier. Also known as thermal-runaway.
thermionic emission - The thermally (heat) induced flow of electrons or ions from a surface with one voltage potential to another surface of a lower potential (also known as the Edison effect), and forms the basis of vacuum tubes that use hot filaments.
thermionic valve - (See vacuum tube)
thermistor - An electrical component that exhibits a controlled changed in resistance with temperature variations.
thin-film transistor (TFT) - A special type of field-effect transistor used for displays in many transceivers, pan adapters, and other devices.
third party - An unlicensed person on whose behalf communication is passed by amateur radio.
third-order intercept point (TOI; IP3) - A calculated (indeed, unmeasurable) lowest receiver amplifier power level of nonlinear products that result from the third-order term of a Taylor polynomial modeling the amplifier nonlinearity, compared with the result of a perfectly linear amplifier for the same power level, and often expressed in decibels of the measured power (dBm); therefore, the higher the value, the more linear the receiver amplifier.
third-party communications - Messages passed from one amateur radio operator to another on behalf of a third person. Also known as third party communications.
third-party communications agreement - An official understanding between the United States and another country that allows amateur radio operators in both countries to participate in third-party communication.
third-party participation - The way an unlicensed person can participate in amateur radio communication. A control operator must ensure compliance with Federal Communications Commission (FCC) rules.
third-party traffic - Amateur communication by or under the supervision of the control operator at an amateur station to another amateur station on behalf of others.
third-order intercept point (3OIP) - The calculated (indeed, unmeasurable) lowest receiver amplifier power level of nonlinear products that result from the third-order term (often shortened intercept point or abbreviated TOI or IP3) of a Taylor polynomial modeling the amplifier nonlinearity, compared with the result of a perfectly linear amplifier for the same power level, and often expressed in decibels of the measured power (dBm) (therefore, the higher the value, the more linear the receiver amplifier).
third-order intermodulation product - An undesirable pair of amplifier output signals resulting from the mixing (due to amplifier nonlinearities) of two radio frequency (RF) signals presented to the amplifier input, such that twice the value of one input frequency (second order) minus the value of the other input frequency (first order) results in the undesirable frequency pair (first + second = third order), which is typically very close in vicinity to the input frequency components. Also known as odd-order intermodulation product.
threaded Niell-Concelman (TNC) - A standard connector type used on coaxial cable, named for its inventors, Paul Neill and Carl Concelman.
throb - An multi-frequency-shift keying (MFSK) digital mode based on tone pairs. (See frequency-shift keying)
through-hole mount - A type of common antenna mount, primarily for mobile applications.
throw - The number of alternative current paths for a controlled circuit in a switch.
throw out - Slang for transmit or announce over the air, without regard to mode (in other words, by voice or continuous wave (CW) or digital).
thyristor - (See silicon-controlled rectifier)
ticket - A slang word for an Federal Communications Commission (FCC) amateur radio license.
tie up - (Repeater term) Slang for excessively occupy a repeater, frequency, channel, or other communication medium or pathway, (typically temporarily) obstructing access to it.
tiger tail - Slang for a single-wire counterpoise that hangs from the point your antenna ground connects to your radio, typically an hand-held transceiver (HT). Also known as rat tail.
tilted terminated folded dipole antenna (TTFD) - A type of once-popular horizontal folded dipole antenna (abbreviated T3FD for the three-wire version or T2FD / TTFD for the two-wire version), in which the elements are made of parallel wires that terminate at a non-inductive resistor, widely used at one time for HF and shortwave radio. Also known as terminated folded dipole antenna; tilted folded dipole antenna.
time constant - An amount of time for the voltage across a capacitor or an inductor to decrease (fall) from an initial value (the voltage at the start) to 1/e (about 0.368 or 36.8%) times the initial voltage value, or increase (rise) from an initial value to 1 − 1/e (about 0.632 or 63.2%) times the difference between the applied voltage and the initial voltage values. The four specific cases are (1) The amount of time for the voltage across a capacitor in a series resistance-capacitor (RC) circuit to decrease 1/e times the initial voltage after the circuit voltage is removed, calculated as RC and expressed in seconds. (2) The amount of time for the voltage across an inductor in a series RL circuit to decrease 1/e times its initial value after the circuit voltage is applied, calculated as L/R and expressed in seconds. (3) The amount of time for the voltage across a capacitor in a series RC circuit to increase 1 − 1/e times the difference between the applied voltage and the initial voltage, calculated as RC and expressed in seconds. (4) The amount of time for the voltage across an inductor in a series RL circuit to decrease 1 − 1/e times the difference between the applied voltage and the final voltage, calculated as L/R and expressed in seconds.
time constant of an inductance - (Archaic) The old term for merit (Q) of an inductor. (Also known as capacitive time constant.
time division multiple access (TDM) - A method of transmitting and receiving different signals over a single path between a transmitter and a receiver by means of synchronized switches at each end of the transmission line, thereby giving the appearance of transmitting multiple signals simultaneously.
time division multiplexing (TDMA) - A type of time-division multiplexing that involves multiple transmitters targeting a single receiver.
time out - (Repeater term) Excessively long transmission on a repeater causing the repeater's timer circuit to stop further transmissions. (See alligator) Also known as time out; time-out.
time-out timer (TOT) - (Repeater term) A device that limits the amount of time any one person can talk through a repeater. Also known as dropout timer.
time averaging - The amount of electromagnetic radiation over a given time as applies to radio frequency (RF) safety. The premise of time averaging is that the human body can tolerate the thermal load caused by high, localized RF exposures for short periods of time. Also known as time-averaging.
timer - (Repeater term) A time limit of a single transmission from a user that is set by a repeater owner. Repeaters often incorporate a timer or transmit time limiter for this purpose.
tolerance - The amount the value of a component can be different than nominal value and still be considered good, usually expressed in percent or as a range of values.
tone - (See continuous tone-coded squelch system)
tone-burst - (1) A short signal which is used in acoustical measurements to make it possible to differentiate a desired signal from spurious reflections. (2) (Repeater term) A method of activating a repeater station that requires transmission of a brief tone before all transmissions can be relayed. Also known as tone access.
tone burst.
tone pad - An array of 12 or 16 numbered keys that generate the standard telephone dual-tone multi-frequency dialing signals. The device resembles a standard telephone keypad. (See autopatch)
tone scanning - (See scanning)
tone squelch (TSQL) - A function that mutes the speaker until the correct programmed subaudible tone is received.
top band - The 160-meter (m) amateur radio band which is the highest numbered meter band.
top-loading antenna - A shortening of the physical length of a vertical antenna by substituting an inductance at the top in place of additional height. Also known as top loading antenna; toploading antenna; top-loaded; top loaded; toploaded; capacitive top-loading; capacitance loading..
toroid - A donut-shaped solid, usually constructed of ferrite, used for transformers and inductors. Also known as toroidal inductor.
tower - (See antenna tower)
traffic - (1) A formal message relayed between amateur radio stations and others as part of the National Traffic System during an emergency or a drill. (2) An important message of instruction or other significance given by an Incident Commander or other leader to be conveyed in his or her behalf. (3) Any message, announcement, or other information conveyed on the air, but not necessarily directed to a specific station, typically coordinated by the net control station Also known as emergency traffic; formal traffic message.
traffic net - A scheduled meeting of amateur radio operators at particular time and frequency for the purpose of sending and receiving traffic. (See net)
trailer plug - (See SAE connector)
transceiver (TRX, XCVR) - A device comprising both a transmitter and a receiver that are combined and share common circuitry or a single housing. When no circuitry is common between transmit and receive functions, the device is a transmitter-receiver.
transcon - (Archaic) An abbreviation for a transcontinental message that was used in the early 1920s.
transequatorial propagation (TEP) - The radio wave propagation between two mid-latitude points at approximately the same distance north and south of the magnetic equator, most noticeable in the afternoon or early evening, and whose maximum range can reach 5000 miles.
transformer - An electrical component that transfers electrical energy from one circuit to another by means of a magnetic field shared by two or more inductors.
transient - A short pulse of energy on a power line, usually lasting for a few microseconds (μs).
transistor - A solid-state replacement for a vacuum tube that is made of three layers of semiconductor material. A bipolar junction transistor (BJT) has terminals labeled base, collector, and emitter. A small current at the base terminal (that is, flowing between the base and the emitter) can control or switch a much larger current between the collector and emitter terminals. For a field-effect transistor (FET), the terminals are labeled gate, source, and drain, and a voltage at the gate can control a current between source and drain. (See bipolar junction transistor; field-effect transistor; negative-positive-negative; positive-negative-positive).
transistor-transistor logic (TTL) - A class of digital circuits made primarily from bipolar-junction transistors (BJTs) and resistors, known for high switching speed and simple design.
transistor outline 220 (TO-220) - A type of electronic component package characterized by a relatively large tab that aids in dissipating a large amount of heat away from the component, and three or more electrical leads, often used for a discrete device, such as a transistor, regulator, or a semiconductor of some sort.
transition band - In the frequency domain during filtering, transition from the passband to the stopband or vice versa, the half-power bandwidth therefore referred to as the transition bandwidth. Also known as filter skirt; steep skirt.
transistor-transistor logic (TTL) - A family of logic gates found in many current lines of digital integrated circuits (ICs).
transition region - An area where power density decreases inversely with distance from the antenna.
translator - A device that receives multiple signals within a certain frequency range and simultaneously retransmits them in another frequency range. (See transverter)
transmatch - (See antenna tuner)
transmission-line loss - The fraction of power dissipated as heat as it travels through a feed line. Also known as feed-line loss.
Transmission Control Protocol (TCP) - One layer of the Internet protocol suite that deals with opening and maintaining connections between Internet hosts. (See Internet Protocol.
transmission control protocol/Internet protocol (TCP/IP) - The Internet protocol that is designed to be independent of the underlying hardware.
transmission line - The wires or cable used to connect a transmitter, receiver, or transceiver to an antenna. Also known as feed line.
transmit (TX) - To broadcast or send out a radio signal.
transmit pattern - (See radiation pattern)
transmit power switch (TXP) - A selector that allows switching between high, medium, or low transmitter power.
transmit-receive switch (TR switch) - A mechanical switch relay or electronic circuit used to switch and antenna between a receiver and transmitter. (Also known as T-R switch; T/R switch.
transmitter (XMTR) - A radio that produces radio-frequency signals with sufficient power to be useful for communication.
transmitter hunting - (See amateur radio direction finding) Also known as transmitter-hunting.
transmitter incremental tuning (XIT) - A transmitter circuit used for shifting the transmit frequency away from the receive frequency by a small amount, to compensate for frequency drift or related issues.
transmitter power - The average peak envelope power (PEP) (output) present at the antenna terminals of the transmitter.
transponder - A device usually used on satellites that emits a radio signal when it receives a radio signal on a certain frequency or that retransmits all signals in a range of frequencies. Also known as linear transponder.
transverter (XVTR) - A device that takes one signal in a specified frequency range and simultaneously retransmits it in another frequency range. This differs from a translator, which can handle more than one signal. (See translator)
trap - A device that allows a single antenna to resonate on two different bands by presenting a high impedance on one of the bands by means of a tank circuit that resonates on that band, thereby permitting multiband operation. Also known as antenna trap.
trap vertical antenna - A multiband vertical antenna that uses traps to allow radio transmission on multiple bands.
trap-dipole antenna - A dipole antenna with several coils, or traps, that allow the antenna to be used on several bands. Also known as trap vertical antenna.
travelling wave tube - A kind of tube found in microwave amplifiers.
tremendously-high frequency (THF) - The overall frequency range of 300 gigahertz (GHz) to 3000 GHz. Also known as terahertz radiation.
tri-state logic - The digital logic that allows an output to assume a high impedance state in addition to the Ø and 1 logic levels, effectively removing the device from the circuit and providing for the ability to connect many device outputs to a single bus. Also known as 3-state logic; three-state logic.
triangulation - A method of locating a signal source by using antenna headings from several different receiving locations.
triboelectric effect - The build-up of static electrical charge when two materials rub together, the most common source of static electricity build-up, of which P-static is one type.
trifecta - (Archaic) Slang for passing all three (Technician, General, and Amateur Extra) exams in a single exam session.
trimmer capacitor - A small adjustable capacitor, generally screwdriver adjustable, to set a calibration point as part of a system alignment.
trimmer potentiometer - Small adjustable resistor, generally screwdriver adjustable, to set a calibration point as part of a system alignment.
trip - (1) To activate when a threshold is exceeded or an event is detected. For example, a circuit breaker trips opening a circuit when excessive current flows. (2) Slang for the successfully completed communication path of a signal from a transmitter to a receiver, whether that path is direct (line-of-sight), by a hop, or through a repeater.
triplexer - A low-pass filter, a band-pass filter, and high-pass filter with their outputs connected.
tropo - (See tropospheric propagation)
troposphere - The region in Earth's atmosphere just above the Earth's surface and below the ionosphere.
tropospheric bending - A condition that happens when radio waves are bent in the troposphere and return to Earth farther away than the visible horizon.
tropospheric ducting - A type of very-high frequency (VHF) propagation that can occur when warm air overruns cold air—known as temperature inversion. Also known as tropo; ducting.
tropospheric propagation - Any method of radio wave propagation by means of atmospheric phenomena in the troposphere—abbreviated as tropo.
true horizon - (See horizon)
true power - (See power factor)
trunk-lip mount - (See lip mount)
trunked radio system (TRS) - A complex type of computer-controlled two-way radio system that allows sharing of relatively few radio frequency channels among a large group of users.
trunking - (Repeater term) A method of switching incoming signals between different repeater stations to prevent interference and ensure access to a repeater.
trustee - A licensed amateur who is a) entrusted with the maintenance of an amateur radio license other than his or her own, and responsible for the proper operation of a station that uses the call sign associated with the entrusted license.
tube - (See cathode ray tube; vacuum tube)
Tucson Amateur Packet Radio (TAPR) - An international amateur radio organization that researches, develops, and promotes packet radio and supporting software and hardware, such as terminal node controllers and high-performance software-defined radio (HPSDR).
tune - (1) To change or adjust the frequency of your transceiver for any reason (to talk with a person on another frequency, to more closely match the frequency of another transmission, to move your conversation away from a noisy frequency or one that has a lot of interference, etc.). (2) To alter or modify the impedance of a circuit to match that of another circuit, such as is done by a tuner. (3) To alter or modify the reactance of a circuit, often to change its resonant frequency.
tuned circuit - A circuit with a resonant frequency that can be adjusted, usually through the use of adjustable capacitors or inductors.
tuned plate, tuned grid (TPTG) - (Archaic) A style of transmitter circuit, used around 1930.
tuner - (See antenna tuner) (1) A circuit or device that filters out all but a narrow passband in a receiver prior to processing into an audio or data signal. (2) (Archaic) Often used as a synonym for receiver in the early 1920s, it referred mostly to a receiver's front end, particularly the grid and plate circuits of a regenerative detector.
tunes - (Archaic) A synonym for frequencies or wavelengths.
tuning - Adjusting the operating frequency of a radio or circuit.
tuning step (TS) - The frequency stop used when moving up or down channels. Also known as incremental tuning steps.
tunnel diode - An electronic semiconductor component that performs the same function as a silicon diode, but is capable of has very fast operation. Also known as Esaki diode.
turboscan - (See hyperscan)
turnstyle antenna - A crossed-dipole antenna made from two identical dipole antennas mounted at right angles to each other and wired 90° out-of-phase with each other, the two general types of which are called axial (because the direction of greatest gain is in the direction of the crossed axis) and normal (because the direction of greatest gain is in the direction broadside, or normal, to the crossed axis).
twin-lead - (See open-wire line)
twisted pair - An amateur radio nickname for telephone or telephone lines.
two-way radio - (1) A device (transceiver) that can both transmit and receive radio signals for communication purposes. (2) A type of radio service that permits both transmitting and receiving between two radio stations.
two-tone test - A method of testing a side-band transmitter by feeding two audio tones into the microphone input of the transmitter and observing the output on an oscilloscope.
type-acceptance - (See certified) Also known as type acceptance; type-accepted.

To the top!   U

Ufer ground - (Archaic) (See concrete-encased electrode).
ultra high frequency (UHF) - The frequency range of 300 to 3,000 megahertz (MHz).
ultra-high frequency connector (UHF connector) A coaxial cable connector commonly used to connect high-frequency (HF) antennas to radios with a PL-259 male plug and an SO-239 female receptacle and usually used below 300 megahertz (MHz). It was misnamed before World War II for frequencies over 30 megahertz (MHz).
ultra-high frequency mobile (UHF mobile) - The frequency range of 216 to 512 megahertz (MHz).
ultraviolet (UV) - Electromagnetic waves with frequencies grdater than visible light. Literally, above violet, which is the high-frequency end of the visible range.
ultraviolet protection (UV protection) - A coating placed on plastics or other materials to prevent degrading by exposure to ultra-violet light from the sun.
unattended operation - Operation of a radio station without a human operator at the control point.
unbalance-unbalance (unun) - A contraction for a device that couples an unbalanced antenna of one impedance to an unbalanced feed line of another impedance.
unbalanced antenna - An antenna that can be fed directly by coaxial cable without a balun needed.
unbalanced feedline - A pair of electrical transmission line conductors of consistently unequal size, shape, or material (and therefore the unequal impedance) their entire lengths, of which coaxial cable and microstrip are examples.
unbalanced line - A transmission line, primarily coaxial cable, in which one conductor, the shield, is designed to be at ground potential. Also know as an unbalanced feed line.
Uncle Charlie - The Federal Communications Commission (FCC).
uncontrolled environment - Any environment area in which a radio frequency (RF) signal may cause radiation exposure to people who may not be aware of the radiated electric and magnetic fields. The Federal Communications Commission (FCC) generally considers members of the general public and an amateur radio operator's neighbors to be in an uncontrolled RF radiation exposure environment to determine the maximum permissible exposure levels. (See controlled environment)
uncoordinated repeater - (Repeater term) A repeater station operating on frequencies not approved by the appropriate frequency coordinator.
undamped oscillations - (Archaic) A synonym for frequencies or wavelengths used prior to the 1920s. Also known as undamped waves.
unidentified communications - The signals or radio communication in which the transmitting station's call sign is not transmitted. Also known as unidentified signals.
Uniform - A North Atlantic Treaty Organization (NATO) phonetic alphabet code word representing the letter U. Used in radio communication, particularly when spelling out a call sign. (Pronounced OO-nee-form)
unintentional radiator - A device that radiates radio frequency (RF) signals not requred for its normal operation.
uninterruptable power supply (UPS) - A power system in which the alternating current (AC) input is used to charge batteries that in turn power an inverter to provide clean alternating current (AC) in case of a commercial AC power failure. Also known as uninterruptible power source.
United Nations (UN) - The world's largest, foremost, and most prominent international organization. The stated aims of the UN include promoting and facilitating cooperation in international law, international security, economic development, social progress, human rights, civil rights, civil liberties, political freedoms, democracy, and the achievement of lasting world peace. The UN was founded in 1945 after World War II to replace the League of Nations, to stop wars between countries, and to provide a platform for dialogue. It contains multiple subsidiary organizations to carry out its missions.
unity-gain antenna - An antenna that gives no gain or loss because its effective radiated power is equal to the transmitter power applied to it.
Universal Licensing System (ULS) - The Federal Communications Commission's (FCCs) consolidated database, application filing system, and processing system for all wireless telecommunications services.
universal resource locator (URL) - A specific character string that constitutes a reference to a resource. In most web browsers, the URL of a web page is displayed on top inside an address bar.
universal serial bus (USB) - A standard developed in the mid-1990s that defines the cables, connectors, and communication protocols used in a bus for connection, communication, and power supply between computers and electronic devices.
Universal Time Coordinate (UTC) - Also known as Greenwich Mean Time (GMT); Coordinated Universal Time; Zulu time.
unkey - The action of releasing the push-to-talk (PTT) button on your microphone (mic). Also known as un-key.
unmodulated carrier - A steady transmitted radio frequency (RF) signal carrying no information.
unnumbered information - A type of packet frame used to transmit Automatic Packet Reporting System (APRS) beacon data (location information), in which individual packet frames do not contain a sequence number to identify packet order, like an Information frame does. Also known as unnumbered frame; unnumbered packet.
unun - Device that matches the impedance of an unbalanced feedline (such as a coaxial cable) to that of another unbalanced one.
up - An announcement by a station that it is listening or receiving on a higher frequency (usually in kilohertz (kHz) than the one it is transmitting on.
up-conversion - (1) The process of modifying a signal by changing it to a higher frequency, allowing for convenient signal manipulation by analog circuitry, one step in the superheterodyne process, and integral to frequency-division multiplexing. (2) The process of modifying a signal by changing it to a higher frequency band, thereby extending the frequency spectrum available to a transceiver.
up-converter - A device or circuit that performs the up-conversion function by changing the frequency of an operating signal to one of a higher frequency, often part of a transverter. Also known as up converter; upconverter.
uplink - Transmitted signals or the range of frequencies on which a user transmits to a repeater or satellite. It is the opposite of downlink. (See downlink) Also known as up link; up-link.
upper sideband (USB) - The sideband higher in frequency than the transmitter's carrier. It is the common single-sideband operating mode on the 20-, 17-, 15-, 12-, and 10-meter (m) high-frequency (HF) amateur radio bands, and all the very-high frequency (VHF) and ultra-high frequency (UHF) bands. (See sideband) Also known as upper-sideband.
utility power - (See household power)
utility stations - Stations other than broadcast or amateur radio stations that are not intended to be heard by the public. They include aircraft communication, radiotelephone, marine, embassy, and military communication.

To the top!   V

vacation-style - Slang for a relatively relaxed station operating plan (typically in reference to a DXpedition or special event station), in which the station might not operate on a regular or preset schedule or set of frequencies; often synonymous with holiday-style.
vacuum relay - An electromechanical switching device in which the contacts are enclosed in an evacuated chamber, eliminating most contact oxidation, corrosion, burning, and pitting.
vacuum tube - (Archaic) An electronic component that creates or modifies electrical current in a vacuum or low pressure space between two electrodes. Also known as bulb; electron tube; fire bottle; grid current; jug; klystron; magnetron; Radiotron; thermionic valve; tube; valve. A three-element vacuum tube was called an audion.
vacuum tube era - The time period during which most amateur radio equipment was constructed around vacuum tubes, generally from the mid-1920s to the early 1980s.
vacuum tube voltmeter (VTVM) - (Archaic) A once-popular form of the voltmeter using a vacuum tube in the amplifier circuit. (See multimeter)
vacuum variable capacitor - A capacitor consisting of two electrodes, often concentric cylinders, in an evacuated glass envelope. One element is moved in and out with respect to the other.
valve - (Archaic) A synonym, still used in Europe, for vacuum tube. (See vacuum tube)
valve-regulated lead-acid (VRLA) - A type of sealed lead-acid (SLA) battery that includes formats such as absorbed glass mat (AGM) and Gel.
vanity call - A call sign selected by a licensed amateur radio operator instead of the one sequentially assigned by the Federal Communications Commission (FCC). A vanity call must be approved by the FCC.
vanity system - One of three methods used to select a call sign for amateur station over-the-air identification purposes. (See call-sign system)
varactor diode - A solid-state two-terminal device used in non-conducting mode. The capacitance between the terminals is changed by applying a different voltage between them resulting in a variable capacitor. (See variable capacitor) Also known as varicap diode.
variable-frequency oscillator (VFO) - An oscillator used in receivers and transmitters. The frequency is set by a tuned circuit using capacitors and inductors. The frequency can be changed by adjusting the components in the tuned circuit. (Also known as variable frequency oscillator.
variable capacitor - A capacitor that can have its value changed within a certain range.
variable crystal oscillator (VSO) - An oscillator with an oscillation frequency that is variable and can be electronically changed.
variable inductor - An inductor whose value can be changed or controlled, once used for tuning.
variable resistor - (See potentiometer)
variable-frequency oscillator - (1) An oscillator whose frequency can be tuned over a particular range. (2) A mode (setting or configuration) of your radio, in which you can manually or directly tune your radio to an arbitrary frequency within a particular range or band.
variometer - (Archaic) A transformer with variable coupling controlled by changing the angle of one winding with respect to the other, with one physically inside the other. It is used to get variable coupling between two inductors, or wherever a variable inductor is needed. One can connect the windings in series or parallel or have them independent.
varistor - Electronic component whose resistance varies with the applied voltage across it, of which the metal-oxide varistor (MOV) is the most common.
vector - (1) In rectangular coordinates, an expression that contains both magnitude and direction. (2) In polar coordinates, a quantity with both a magnitude and an angular component.
vector network analyzer (VNA) - A measuring instrument that characterizes network parameters of electrical networks, in particular scattering (S) parameters (and often impedance components) for radio frequency (RF) and microwave transmission lines.
velocity factor - The speed at which radio waves travel in a particular feed line, expressed as a percent of the speed of light.
velocity modulation - The process of varying (modulating) the velocity of a beam of electrons or ions by passing the beam through a high-frequency electric field.
vertical-interval signaling (VIS) - The digital encoding of the transmission mode in the vertical syncronization portion of an slow-scan television (SSTV) image.
vertical antenna - A common amateur radio antenna, often made of metal tubing, in which the radiating element is vertical. There are usually four or more radial elements parallel to the ground.
vertical metal-oxide semiconductor (VMOS) - A type of metal oxide semiconductor transistor.
vertical polarization - A transmission or antenna in which the electric field is propagated perpendicular to the surface of the Earth. Antennas intended for two-way radio communication with mobile stations, where vertical antennas are common, typically use vertical polarization, while broadcast television frequency modulation (FM) signals are most often horizontally polarized. (See circular polarization; elliptical polarization; vertical polarization)
vertically polarized wave - A radio wave that has its electric lines of force perpendicular to the surface of the earth.
very-high frequency high band (VHF high band) - The frequency range of 148 to 174 megahertz (MHz).
very-high frequency low band (VHF low bands - The frequency range of 30 to 50 megahertz (MHz) and 72 to 76 megahertz (MHz).
very high frequency (VHF) - The frequency range of 30 to 300 megahertz (MHz).
very low frequency (VLF) - The frequency range of 3 to 30 kilohertz (kHz) and wavelengths of 10 to 100 kilometers (km).
very limited coverage area (VLCA) - (Repeater term) Small portable repeaters deployed by emergency/disaster or public service groups to temporarily provide local communication within a relatively small area.
vestigial sideband (VSB) - A sideband modulation using a signal that has been partially suppressed (can be vestigial lower sideband or vestigial upper sideband), and used in television broadcasts if the video is transmitted in amplitude modulation (AM).
Victor - A North Atlantic Treaty Organization (NATO) phonetic alphabet code word representing the letter V. Used in radio communication, particularly when spelling out a call sign. (Pronounced VIK-tah)
video-display terminal (VDT) - A device using a video display such as a cathode-ray tube.
vintage - Slang reference to a piece of equipment, most notably a receiver, transmitter, or transceiver, that relies on vacuum tube technology to perform its primary functions, often synonymous with outdated, antique, and sometimes obsolete.
virtual ground - (See artificial ground)
visible horizon - (See horizon)
visual horizon - (See horizon)
visible horizon - The most distant point one can see by line of sight.
voice - Any of the several methods used by amateur radio operators to transmit speech.
voice communication - The communication by voice between amateur radio operators. Amateur radio operators may use several voice modes, including FM and single sideband (SSB).
voice keyer - A device that can transmit pre-recorded voice transmissions, useful for calling any amateur radio station (CQ) or during contest exchanges.
Voice of America (VOA) - The official external broadcast institution of the United States federal government.
Voice of America Coverage Analysis Program (VOACAP) - A high frequency (HF) propagation modeling software, useful for predicting band openings.
voice operated exchange - A voice-activated switch that turns on the transmitter without requiring the press of the push-to-talk (PTT) button. Also known as voice operated switch.
voice over Internet Protocol (VoIP) - The communication protocols, technologies, methodologies, and transmission techniques involved in the delivery of voice communication and multimedia sessions over Internet Protocol (IP) networks, such as the Internet. Also known as VOIP.
voice scan control (VSC) - A circuit that provides efficient scanning by skipping unmodulated signals so that the scan behavior can be customized to suit an amateur radio operator's needs.
voice squelch control (VSC) - A circuit that opens the squelch only when a modulated signal is detected and ignores unmodulated, beat noise signals, or heterodynes.
voice-activated dialing - (See voice-operated transmit)
voice-operated transmission (VOX) - Systems used to automate routine enquiries to switchboard operators, and are used in many hospitals and large businesses to reduce the caller waiting time. Also known as voice-activated dialing.
voice-operated transmit (VOX) - A function that automatically puts the transmitter in transmit when you talk into the microphone. Although commonly used for base station operation, its use for mobile operation is questionable because of the inherent high background noise level.
volt (V) - The basic unit of electrical pressure or electromotive force (EMF).
volt amperes (VA) - A measure of apparent power. Note that true power is I2 times R.
volt ohm meter (VOM) - An electronic measuring instrument that combines several measurement functions in one unit. A typical multimeter would include basic features such as the ability to measure voltage, current, and resistance.
voltage (ΔV) - The electromotive force (EMF) or difference in electrical potential that causes electrons to move through an electrical circuit. The Δ is the Greek capital delta.
voltage balun - A type of transformer inserted as a balun to match the antenna system impedance with the feedline impedance; so-called because it attempts to balance the output voltages (make them equal and opposite) regardless of the load impedances. Also known as RF transformer.
voltage-controlled oscillator (VCO) - A device used to produce video timing. Also known as voltage controlled oscillator.
voltage divider - A device that consists of two or more resistors connected in series across a source voltage. The source voltage must be as high or higher than any voltage developed by the voltage divider. As the source voltage is dropped in successive steps through the series resistors, any desired portion of the source voltage may be tapped to supply individual voltage requirements. The connection to the voltage divider is called a tap and such a circuit or component is said to be tapped. (See tap)
voltage doubler - A kind of power supply rectifier circuit in which a capacitor is charged during one part of the alternating current (AC) cycle and then placed in series with the input on another part to result in an output direct current (DC) voltage approaching twice the peak value of the input waveform.
voltage standing wave ratio (VSWR) - (See standing-wave ratio)
voltmeter - A test instrument used to measure voltage.
volts alternating current (VAC) - In the United States, current is controlled to run at 60 cycles per second.
volts direct current (VDC) - The unidirectional flow of electric charge (current) in a circuit.
volume - (See audio)
Volunteer Examiner (VE) - A person authorized by a Volunteer Examiner Coordinator (VEC) to administer examinations for amateur radio licenses.
Volunteer Examiner Coordinator (VEC) - An amateur radio organization empowered by the Federal Communications Commission (FCC) to recruit, organize, regulate, and coordinate Volunteer Examiners.
Volunteer Frequency Coordinator (VFC) - An amateur radio individual who maintains a database of repeater frequencies in active use (as well as new repeaters which are under construction but may not yet be in operation).
Volunteer Monitor Program - An organization instituted by agreement between the American Radio Relay League (ARRL) and the Federal Communications Commission (FCC), in which volunteers trained and accredited by the ARRL will monitor the air waves to collect reportable evidence of both rules violations and exemplary amateur operation, in an attempt to re-energize enforcement efforts.
voter - (See voting repeater system) Also known as voted receiver system.
voting repeater system - (Repeater term) A network of repeaters that re-transmits the strongest or cleanest of multiple signals received by all the repeaters in the system dictated by a device known as a comparator, which uses a policy known as voting and diversity combining (they all transmit the signal "voted" best-received, this simultaneous transmission. Also known as diversity operation; multiple receiver; multiple-receiver; synchronous repeater system; simulcasting; synchronous transmission; voting receiver; voting system.

To the top!   W

W - An abbreviation for the continental (lower 48) United States.
W/VE - An abbreviation for the continental (lower 48) United States and the provinces of Canada.
wabbulation - (Archaic) (See wobbulation)
walkie-talkie - A short-range, channelized, and low-power handheld two-way radio (HT) typically using the Family Radio Service (FRS) and General Mobile Radio Service GMRS) frequencies, but can be made for any frequency.
wall wart - A synonym for a small power-supply unit for low-power equipment with an integral plug for a standard alternating current (AC) wall outlet.
wallpaper - Wall decorations to an amateur radio station of QSL cards, award recognitions, special event certificates, and other items. (Also known as wall paper; wall-paper.
wall power - (See household power)
want to be (wannabe) - A synonym for a person with an ambition to be someone or something that he or she is not.
War Powers Act - An American law that provides the President of the United States enormous emergency authority to make strategic governmental changes and take control of communication, including conventional amateur radio service, by the activation of RACES and other communication services. Also known as Emergency War Powers Act; President's War Emergency Act.
waterfall display - A display used with digital modes of transmission that consists of horizontal lines showing signal strength as a change of brightness with frequency represented by position on the line. Older lines move down the display so that the history of the signal's strength and frequency form a waterfall-like picture.
watering hole - (Archaic) An older slang for frequency, band, or repeater on which (often a close-knit group of) hams tend meet consistently or frequently, typically for ragchewing or other casual QSOs.
watt (W) - A derived unit of power in the International System of Units (SI), named after the Scottish engineer James Watt. The unit, defined as one joule (J) per second, measures the rate of energy conversion or transfer. Also known as watts.
wattmeter A test instrument used to measure the power output in watts of a transmitter. A directional wattmeter measures both forward and reflected power in a feed line. Also known as power meter; watt meter.
waveband - (Archaic) An outdated term for band. Also known as wave band; wave-band.
waveform - The amplitude of an alternating current (AC) signal over time.
waveguide - A structure that guides electromagnetic waves. A fiber optic weveguide confines energy to travel in two dimensions. (See optical fiber)
wavelength (wave, λ) - The distance a radio wave travels during one radio frequency (RF) cycle. The wavelength relates to frequency in that higher frequencies have shorter wavelengths. The λ is a Greek small lambda. Also known as wave length.
weak signal - (1) The propagation mode using signals with radio frequency (RF) power levels of 5 watts or less, especially those used for earth-moon-earth (EME) or meteor scatter communication, often accompanied by software made for that purpose, such as weak-signal propagation reporter (WSPR) and weak-signal Joe Taylor (WSJT). (2) A signal whose strength is below the receiver noise level, such as with earth-moon-earth (EME) communication. Also known as weak-signal.
Weak Signal Joe Taylor (WSJT) - A suite of software programs for weak signal and meteor scatter communications. Initially written by Joseph Hooten Taylor, Jr., K1JT, the 1993 winner of the Nobel Prize in physics, it allows radio operators to communicate over long distances with other amateur radio operators. WSJT is now open source and is developed by a small team.
Weak Signal Joe Taylor - experimental (WSJT-X) - A ham radio software, allegedly 1.7 to 3 dB improvement in sensitivity over Weak Signal Joe Taylor (WSJT), used for weak-signal and low-power digital transmission modes using protocols for earth-moon-earth (EME) that includes JT65, JT9, JT4, QRA64), FT8, meteor scatter (MSK144), and ionospheric scatter (ISCAT) communication.
Weak Signal Propagation Reporter (WSPR) - A software program that enables you to participate in a world-wide network of low-power propagation beacons. It was written by Joe Taylor K1JT, the 1993 winner of the Nobel Prize in physics.
weak-signal mode - A single sideband (SSB) or Morse code (CW) mode used in relation to operating on the very-high frequency (VHF) and ultra-high frequency (UHF) bands, where many amateurs only operate frequency modulation (FM) phone.
Weak-signal Operation on Low Frequency (WOLF) - (CW term) A program written by Stewart Nelson KK7KA, it can operate over a wide range of signal levels. For example, a WOLF beacon transmits a 15-character message repeatedly. If the received signal would be adequate for conventional Morse code (CW), copy will be displayed in 24 seconds.
weather (WX) - An automatic position reporting system (APRS) for transmission of current meteorological readings by way of amateur radio. Many 2-meter (m) hand-held transceivers are also capable of extended tuning to permit reception of forecasts over very-high frequency (VHF) bands assigned to other services, such as marine radio.
weather alert - An alert that occurs when an National Oceanic and Atmospheric Administration (NOAA) or National Weather Service (NWS) weather station transmits alert signals.
weather facsimile (WEFAX) - Reconstructed satellite images and photographs.
web software-defined radio (web SDR) - A user-configurable or controllable software-defined radio (SDR) that is made available on the internet (website, app, etc.), typically to the general public. Also known as websdr.
whip antenna - An antenna with an element made of a single, flexible rod or tube. (Also known as stinger antenna)
Whiskey - A North Atlantic Treaty Organization (NATO) phonetic alphabet code word representing the letter W. Used in radio communication, particularly when spelling out a call sign. (Pronounced WIS-key)
whisper (WSPR) - white noise - (1) (Repeater term) A spectrum of broad band noise generated in a receiver's detector and sampled to control the receiver's squelch. This term is often incorrectly used in repeater work to describe the sounds heard when the received transmission is noisy and hard to understand, usually attributed to a weak signal and the repeater receiver limiters are not engaged. (2) White noise generated from a common commercial radio receiver tuned to an unused frequency is extremely vulnerable to being contaminated with spurious signals, such as adjacent radio stations, harmonics from non-adjacent radio stations, electrical equipment in the vicinity of the receiving antenna causing interference, or even atmospheric events such as solar flares and especially lightning. (See static)
Wide-coverage Internet Repeater Enhancement System (WIRES) - (Archaic) A standard created by Yaesu to link ham radio repeaters through the internet using voice over Internet Protocol (VoIP).
Wide-coverage Internet Repeater Enhancement System (Extended) (WIRES-X) - A standard created by Yaesu to link ham radio stations through the internet using VoIP over analog and C4FM, intended to replace WIRES wide-range antenna tuner - An antenna system matching device that can compensate for large impedance mismatches typically representing standing-wave ratio (SWR) of at least 10 to 1.
wide-range receiver - (See extended-coverage receiver)
wideband/narrow band switch - A selection that allows the operator to switch between wideband (25 kHz bandwidth) and narrowband (12.5 kHz bandwidth).
wideband frequency modulation (WFM). A modulation signal that requires a wider signal bandwidth than amplitude modulation. It also makes the signal more robust against noise and interference. Also known as W-FM; WBFM; wide band FM; wide-band FM; wide FM.
Wilderness Protocol - A recommendation by the American Radio Relay League (ARRL) to periodically announce your presence on any of a specific subset of the national calling frequencies while in a wilderness or back country location, with the intent to monitor the frequency and relay emergency information in case assistance is required.
Wilkinson divider - A circuit that distributes its input power equally among multiple output loads while maintaining electric isolation between the loads, preventing changes that might occur in one load from disturbing the power flow to the other output loads, and used mainly in microwave applications. Also known as Wilkinson power divider.
will comply (wilco) - (Archaic) Wilco is radio slang for "Will Comply." The letter R has been used since the early days of Morse code (CW) to indicate that "The message has been received." The voice code equivalent for R is Roger. So, Roger Wilco means "The message has been received and I will comply."
willful interference - (See harmful interference)
wind load - (1) The quantity of force applied by the wind to a structure, such as an antenna, tower, mast, guy-wires, or a combination of these, per unit wind speed. (2) A rating (more accurately, wind-speed rating) of an antenna, its mast, tower, guy-wires, or any combination of these, that indicates the amount of wind speed it can handle, such that the greater the wind load rating, the stronger (faster) a wind it can withstand. Also known as windload.
Windom antenna - An off-center-fed wire antenna (OCF). It is named after L.G. Windom W8GZ who described it in the September 1929 QST magazine.
window - A frequency range set aside for foreign amateur radio stations in which to transmit while stations in the United States and Canada do not. American and Canadian stations call foreign stations on frequencies outside the window.
window line - A type of transmission line that is similar to ladder line except the spacing is maintained by a plastic coating with cutouts that look like windows. (See ladder line; open-wire line) Also known as ribbon line.
wing circuit - (Archaic) A synonym for a vacuum tube plate circuit.
WinLink - A software-based system of electronic mail (email) transmission and distribution using amateur radio for the connection between individual amateurs and mailbox stations known as radio message servers (RMS). Also known as Winlink 2000 Network.
WINMOR - A sound card protocol specified for data message transmission and is a complement to the PACTOR modes in the high frequency (HF) portion of the WinLink system.
WINSystem - A community of amateur radio operators focused on educating all licensed radio operators so they can better serve their communities.
wireless - Without wires. Wireless radio as opposed to wired telegraph.
Wireless Institute of Australia (WIA) - The national organization for Australian amateur radio operators.
Wireless Telecommunications Services (WCS) - Cellular, personal communication services, specialized mobile radio, enhanced specialized mobile radio, paging, and similar services that currently exist or that may in the future be developed to provide wireless communications services. The term does not include services of any amateur radio facility owned and operated by a federally-licensed amateur radio station operator or used exclusively for receive-only antennas, nor does it include noncellular telephone service.
wobbulation - (Archaic) The modulation of a transmitter's frequency due to instability in its oscillator or amplifier while being keyed or modulated. Also known as wabbulation.
words per minute (wpm) - (CW term) Morse code (CW) speed is measured in words per minute (wpm) or characters per minute (cpm).
work - To communicate with another radio station or stations. Also known as working.
work first, worry later (WFWL) - A DXing term used when the validity of a distant station (DX) is in doubt.
Worked All Continents (WAC) - An award given to a ham who has made a contact with (worked) at least one other ham in each of the six continental areas of the world (Antarctica is excluded).
Worked All Britain (WAB) - An award from the Worked All Britain (WAB) website to any amateur radio operator who confirms two-way communication with all of Britain's grid system units.
Worked All Continents (WAC) - An award from the International Amateur Radio Union (IARU), to any amateur radio operator who confirms two-way communication with all continents. It is administered by the American Radio Relay League (ARRL).
Worked All States (WAS) - An award from the American Radio Relay League (ARRL) for to any amateur radio operator who confirms two-way communication with each of 50 United States.
Worked All Neighbors (WAN) - A station that continually gets complaints about signals showing up on the telephone or televisions at neighbor's houses. Not a desired situation. Polite conversation and changes in operation practices are a common solution. Another is providing simple and often inexpensive filters for the offended neighbor.
Worked All Prefixes (WPX) - An award given to hams who have made a contact with (worked) at least one other ham using each of the different call sign prefixes.
Worked All VE (WAVE) - An award from the Radio Amateurs of Canada (RAC) to any amateur radio operator who confirms two-way communication with an official RAC station using the suffix RAC in at least 10 of the 18 provinces with VE prefixes.
Worked All XE (WAXE) - An award from the Federación Mexicana de Radioexperimentadores, A.C. (FMRE) to any amateur radio operator who confirms two-way communication with operators in all the XE zones in Mexico.
Worked All Zones (WAZ) - An award from CQ magazine to any amateur radio operator who confirms two-way communication with each of 40 zones of the world.
working frequency - A frequency that two or more stations can use to communicate with each other.
working power - (See power factor)
working skip - Slang for the activity of making a contact with (working) a station by means of skywave propagation (also called shooting skip by Mores code (CB) radio enthusiasts).
World Administrative Radio Conference (WARC) - 1979 Geneva conference that established a set of radio bands allocated for amateur use.
World Administrative Radio Conference bands (WARC bands) - (Archaic) An expression to indicate the bands 17-, 12- and 30-meters (m) allocated in 1979 by the World Administrative Radio Conference (WARC), the predecessor of the World Radiocommunication Conference (WRC). (See World Radiocommunication Conference)
World Amateur Radio Day (WARD) - An annual event held on April 18 to commemorate the formation of the International Amateur Radio Union (IARU) in Paris and to celebrate amateur radio in general by making contacts with other hams world-wide in a non-competitive (non-contesting) approach.
World Radiocommunication Conference (WRC) - A technical conference of the International Telecommunications Union (ITU) where delegates from member nations of the ITU met to revise or amend the entire international Radio Regulations pertaining to all telecommunication services throughout the world.
World Radio Online Magazine - (Archaic) A monthly amateur radio enthusiast magazine published in the United States from July 1971 to November 2008. It was published in English and drew its subscription base primarily from the United States of America and Canada, although it had subscribers around the world.
worm burner - (Archaic) An older slang for very inefficient antenna (exhibits a lot of ground loss). Also known as worm-burner.
Wouff Hong - An instrument of sadistic torture for the punishment of amateurs who cultivate bad operating habits, who do not follow generally accepted rules of courtesy, and who nourish and culture their meaner instincts on the air. Discovered-by the Old Man, Hiram Percy Maxim W1AW, himself. The instrument looks something like a Saguaro cactus with one arm missing and is framed and hung in the office of the secretary of the American Radio Relay League (ARRL). Unfortunately, the Old Man never prescribed the exact manner in which the Wouff Hong was to be used. (See rettysnitch)
WWV - A radio station run by the United States National Institute of Standards and Technology (NIST) to provide accurate time and frequencies.
WWVH - A radio station run by the United States National Institute of Standards and Technology (NIST) to provide accurate time and frequencies.

To the top!   X

X-class - The largest of all classed solar flares (ten times the strength of an M-class flare and 100 times the strength of a C-class flare), whose relative strength is further designated by an appended decimal number representing a linear value for intensity, such as X5.2 and X3, making an X2 flare twice as great as an X1 flare, and an X3 flare three times as great as an X1 flare. Also known as X class.
X-ray - A North Atlantic Treaty Organization (NATO) phonetic alphabet code word representing the letter X. Used in radio communication, particularly when spelling out a call sign.
x-series, latch, resilient (XLR) - A standard for transferring balanced audio among professional audio equipment. An XLR connector is primarily found on professional audio, video, and stage lighting equipment. The connectors are circular in design and have between 3 and 7 pins.

To the top!   Y

Yagi antenna - Another name for a beam antenna array, the most popular type of directional antenna or beam antenna. It is a multi-element array in which one element, the driven element, is directly connected to the transmission line and others are coupled through radiation. Electromagnetic coupling between the elements focuses maximum power (or reception) in the direction of the director. Named after Hidetsugu Yagi who, along with Shintaro Uda, invented the array in 1926. Sometimes called the Yagi-Uda antenna, but most often shortened to Yagi.
Yankee - A North Atlantic Treaty Organization (NATO) phonetic alphabet code word representing the letter Y. Used in radio communication, particularly when spelling out a call sign.
Young Ham of the Year (YHOTY) - An annual award given to nominated hams age 18 or younger who have provided outstanding service to their nation, to their community, or to the betterment of the craft of amateur radio.
Youngsters on the Air (YOTA) - A social group of (mostly European) ham radio enthusiasts under 25 years old who plan and carry out activities centered around ham radio.

To the top!   Z

Z-signals - (CW term) Three-letter codes beginning with the letter Z and used only by MARS, in lieu of amateur Q-signals, to speed Morse code (CW) communication. Also known as Z-code. (See Q-signals)
zed - A phonetic for the letter Z and considered by many to be a more precise way of expressing that letter. It prevents one from confusing it with B, C, D, E, G, P, T, and V.
Zener diode - A two-terminal semiconductor that has a well defined reverse breakdown voltage. By conducting at that voltage, it can serve as a voltage regulating device.
Zepp antenna - Zeppelin antenna - (Archaic) The end-fed Zepp antenna was simply a weighted wire reeled down and up from early lighter-than-air ships.
zero beat - A circuit that adjusts the frequencies of two signals so that they are exactly equal and in phase. Also known as Ø beating; O beating; zero beating.
zero hour - Military terminology for the (planned or unplanned) time of occurrence of an event or the start of an operation, occasionally used by amateur radio operators. Also known as Ø hour; O hour.
ZS6BKW antenna - An adaptation of the G5RV antenna, but with somewhat improved matching characteristics on some high frequency (HF) amateur bands.
Zulu - (See Universal Time Coordinate)
Zulu Time (Z) - The military time designation for Greenwich Mean Time. (See Universal Time Coordinate)


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