Radio Terms and Abbreviations


Up Front





Glenn Hauser's SW/DX Report

Don Schimmel's Radio Intrigue

Joe Carr's Tech Notes

Radio Basics

Frequency vs. Wavelength

Modes and Modulation

Call Sign Prefixes

UTC/GMT Conversion

Radio Terms

Shortwave Radio

Introduction to Shortwave Listening

Tuning 150 kHz to 30 MHz

Selecting a Shortwave Radio

Reporting and QSLs

Receiver Reference

Modern Shortwave Receiver Survey

Favorite Tube-Type Shortwave Receivers

Scanner Monitoring

Introducing the "Action Bands"

The World Above 30 MHz

Selecting a Scanner

National Scanner Frequency Guide

Other Radio Hobbies

Ham Radio

AM Band DXing

Longwave DXing

Clandestine Radio

Pirate Radio

Numbers Stations


Radio Links

Shortwave Listening

Radio Clubs

International Broadcasters

Scanner Listening

Ham Radio

Web-Controlled Radios


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The nomenclature of the radio hobby can be bewildering! The following is a list of some of the more widely used (and confused!) terms and abbreviations found in ham radio, shortwave radio, and scanner monitoring.

Click below on the first letter in the term you wish to have defined, and you will go to the start of the terms beginning with that letter. The "digits" selection are terms that are numbers. You can return to the top of this page by clicking Top at the end of each section of definitions. If a definition contains an italicized phrase, that phrase is also defined on this page.

I J - L M N - O P Q R S
T U V W X - Z digits    

absorption: The reduction in strength of a radio signal due to refraction in the ionosphere.

active antenna: A physically short or small antenna with a high gain preamplifier; designed for use indoors or in limited space areas.

active filter: A circuit that eliminates unwanted audio frequencies from the audio output of a receiver.

address: The information in a packet specifying the intended receiving station.

aeronautical station: A radio station aboard an airplane or a ground station that communicates with aircraft.

AGC: Abbreviation for automatic gain control.

amplitude modulation: A modulation technique that varies the power output of a transmitter in accordance with the variations in the modulating audio signal.

AM: Abbreviation for amplitude modulation.

amplification: The process of increasing the strength of a radio signal.

AMTOR: Acronym for "amateur teleprinting over radio," a mode that uses FSK to send messages containing error detection capabilities and the ability request retransmission of missing or corrupted data.

ANARC: Acronym for "Association of North American Radio Clubs," an association of radio listener clubs in the United States and Canada.

antenna tuning unit: A device installed between a receiver or transmitter and the antenna to match the radio impedance to the antenna impedance for maximum power transfer.

ARQ: Abbreviation for automatic repeat request. In AMTOR, an ARQ is sent back to the transmitting station by the receiving station to request retransmission of missing or corrupted portions.

ARRL: Acronym for "American Radio Relay League," the national association for ham radio operators in the United States.

ASCII: Acronym for "American standard code for information interchange," a method of representing upper and lower letters in addition to numbers and special symbols.

attended operation: Operation of a radio station with a human operator at the control point.

attenuator: A circuit to reduce the sensitivity of a receiver in fixed steps measured in decibels.

ATU: Abbreviation for antenna tuning unit.

auroral propagation: Propagation of signals above 30 MHz via refraction by highly ionized regions around the Earth’s poles.

automatic gain control: A receiver circuit that adjust the amount of amplification given to a received signal so that the volume from the speaker stays relatively constant.


balun: A device used with to match an unbalanced feedline, like coaxial cable, to a balanced antenna, like a dipole.

bandpass: The frequency range that a receiver is currently tuning or that a filter permits to pass through it.

band pass filter: A filter that allows a certain range of frequencies to pass but which will reject frequencies below and above the desired range.

band plan: A plan to allocate different frequencies within a range for specific purposes and users.

bandspread: A form of electronic (not mechanical) fine tuning common on tube-era general coverage receivers. Usually the ham bands were "spread" to achieve better frequency display accuracy than the main tuning dial could provide. The proper setting of the main dial was critical.

bandwidth: The amount of frequency space occupied by a radio signal.

bank: A storage area for channels in a scanner radio.

base loading: Placing a loading coil at the base of an antenna in order to lower the antenna’s resonant frequency.

baud: The rate at which data is transmitted measured in bits per second.

BCB: Abbreviation for the AM "broadcast band" running from 540 to 1700 kHz.

BCL: Abbreviation for "broadcast listener," someone who listens to shortwave radio strictly for program content.

beacon: A station making one-way transmissions for navigation, homing, and propagation indication purposes.

beam antenna: An outdoor antenna, usually mounted on a rotor, that concentrates more transmitter power (or receives better) in a certain direction.

beat frequency oscillator: A receiver circuit that generates a replacement carrier to enable intelligible reception of CW, FSK, and SSB signals.

BFO: Abbreviation for beat frequency oscillator.

birdie: A false or spurious signal in a receiver inadvertently produced by the receiver’s circuitry.

bureau: A clearinghouse for QSL cards sent to and received from ham operators in other countries.

burst: Reception of a signal for a few seconds via meteor scatter.


calling frequency: An agreed-upon frequency where stations attempt to contact each other; once contact is made, stations move to a working frequency.

call sign: A group of letters and numbers used to identify a station and the country authorizing its operation.

carrier: The unmodulated output of a radio transmitter.

center frequency: The unmodulated carrier frequency of a FM transmitter.

center loading: Placing a loading coil at the center of an antenna in order to lower the antenna’s resonant frequency.

channel: The frequency on which a radio transmission takes place, or the input and output frequency pair used by a repeater station.

chief engineer: The person at a broadcasting station responsible for proper and legal operation of a station and maintenance of all required records.

chirp: Changes in the carrier frequency of a Morse code transmitter, usually due to power supply problems.

circular polarization: An antenna design where polarization switches rapidly between horizontal and vertical.

closed repeater: A repeater station that may be used only by stations belonging to a certain organization or group; access is usually restricted by tone access.

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.

co-channel interference: Interference from stations on frequencies adjacent to the desired signal.

coded access: A method of restricting access to a repeater station to stations that begin their transmission with a special sequence of tones.

collision: When two or more packet radio stations simultaneously attempt to transmit on the same frequency.

connected: Term used to describe a successful contact between two packet radio stations and exchange of packets between them.

continuous wave: The constant output of a radio transmitter that can be periodically interrupted to send messages by Morse code.

control operator: The person responsible for all functions and correct operation of a radio station.

control point: The physical location from which a radio station’s functions (setting frequency, turning the station off and on, etc.) are controlled.

coordinated universal time: An international time and date system derived from the 0 degree meridian at Greenwich.

coordinator: A non-governmental group that works to voluntarily assign frequencies to users in order to prevent interference, especially for repeater stations.

CQ: A general call sent by a station to any other station that may receive it. Hams and other stations "call CQ" to indicate they will answer any station replies to their call.

critical angle: An angle defined in reference to the Earth at which a radio signal is refracted in the ionosphere. The lower the angle, the greater distance the radio signal will travel through ionospheric refraction.

critical frequency: The frequency at or near the MUF at which the maximum sky wave propagation range is obtained.

crystal filter: A filter that uses a network of piezoelectric crystals to obtain high rejection of unwanted signals.

cut numbers: A system of sending numbers via Morse code by substituting shorter letter characters for the longer number characters.

cutoff frequency: The frequency at which a filter will begin to reject signals.

CW: Abbreviation for continuous wave.


D-layer: The lowest region of the ionosphere found approximately 25 to 55 miles above Earth; it fades away quickly after sunset and sometimes does not form at all on short winter days. The main impact of the D-layer on radio propagation is to absorb energy from signals passing through it.

dB: Abbreviation for decibel.

dead zone: A region where a radio signal cannot be received due to propagation difficulties.

decibel: The ratio between two power levels on a logarithmic scale. A 3 decibel increase is a doubling of power; a 20 decibel increase is a power increase of 100 times.

delay: How long a scanner radio pauses on a channel to await another transmission,

deviation: The change in the carrier frequency of a FM transmitter produced by the modulating signal.

digipeater: A packet radio station that receives and retransmits packets intended for other stations.

dipole: An antenna one half-wavelength long at the desired operation frequency that is divided into two quarter-wavelength sections; it transmits and receives in a figure-8 pattern.

direct: To communicate with another station without using a repeater.

direct wave: A radio signal propagated via line of sight.

drift: Slow, gradual change in the frequency of a transmitter or receiver.

dummy load: A device used in transmitter testing and adjustment that dissipates the transmitter’s energy without radiating it.

duplex: To transmit on one frequency while listening for replies on another.

DX: Any station that is hard to hear or contact on a particular frequency, or is rarely heard or contacted on a particular frequency. "DX" is the old telegraph abbreviation for "distant."

DXCC: Abbreviation for "DX Century Club," an award given by the ARRL to hams who contact other hams in at least 100 different countries.

DXpedition: An organized effort by ham radio operators to put a rare location on the air, or a trip by shortwave listeners to a site for favorable DX reception.

dynamic range: How well a receiver can handle strong signals with overloading; any measure of over 100 decibels is considered excellent.


E-layer: The region of the ionosphere found approximately 55 to 90 miles above Earth; it 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 communications on frequencies above 30 MHz.

effective radiated power: The output of a transmitter multiplied by the gain of an antenna.

Elmer: An experienced ham radio operator who mentors new hams and prospective hams.

EME: Abbreviation for "Earth-Moon-Earth," a method of communication on UHF frequencies by bouncing radio signals off the Moon.

ERP: Abbreviation for effective radiated power.

exalted carrier reception: A reception technique where the carrier produced by a receiver’s BFO circuit or product detector is used to replace the carrier of an AM signal for better reception.

exchange: The passing of all necessary information between two stations during a contact.

eyeball: Slang for a face-to-face meeting between two ham radio operators or radio hobbyists.


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 MHz. During the daytime (especially in summer), solar heating can cause the F-layer to split into two separate layers, the F1-layer and the F2-layer.

FEC: Abbreviation for forward error correction, a FSK mode that transmits each character twice to avoid errors. If the first character is received correctly, the retransmission of it is ignored.

feedline: The cable connecting a radio to an antenna.

filter: A circuit or device that will allow certain frequencies to pass while rejecting others.

final: The last transmission by a station during a contact, or the last amplifying stage of a radio transmitter.

fixed station: A station that always operates from a constant, specified land location.

flutter: The rapid variation in the signal strength of a station, usually due to propagation variations.

FM: Abbreviation for frequency modulation.

frequency modulation: A modulation technique that varies the carrier frequency of a transmitter in accordance with the variations in the strength of the modulating audio signal.

frequency shift keying: A mode that shifts the station’s carrier between two fixed frequencies to form characters.

frequency synthesis: A tuning method in transmitters and receivers which uses a few piezoelectric crystals to generate a wide range of frequencies.

FSK: Abbreviation for frequency shift keying.

full quieting: A FM radio signal strong enough to completely quiet the receiver background noise.


gain: The apparent increase in the strength of a signal radiated or received by an antenna caused by the antenna having better performance in some directions than others.

gallon: Slang for the maximum transmitter power authorized for ham radio operators.

gateway: A node that is a part of more than one network and can be used to pass messages between those networks.

general coverage: A term used to describe receivers and transmitters covering at least the frequency range of 500 kHz to 30 MHz and capable of operation in several different modes, including AM, CW, and SSB.

GHz: Abbreviation for gigahertz.

gigahertz: Unit equal to 1000 megahertz or 1,000,000 kilohertz

GMT: Abbreviation for Greenwich mean time.

great circle route: The shortest path by radio between any two points on Earth.

Greenwich mean time: An international time and date system derived from the 0 degree meridian at Greenwich; this has since been replaced by coordinated universal time.

ground: A connection to a point of zero voltage, like the Earth.

ground wave: A radio wave propagated along the surface of the Earth.


hamfest: A large gathering of ham radio operators and other radio hobbyists.

handle: A radio operator’s name.

harmonic: A frequency that is an integer multiple (two times, three times, etc.) of a lower frequency.

hertz: One complete cycle of a radio wave per second.

heterodyne: A high pitched "whistle" sound caused by two carriers interfering with each other. The pitch of the "whistle" depends on the frequency difference between the carriers.

HF: Abbreviation for high frequencies.

high frequencies: Frequencies from 3 to 30 MHz, although often used to refer to all frequencies from 1.7 to 30 MHz.

high pass filter: A filter that rejects all frequencies below a certain point but which allows all higher frequencies to pass.

hollow state: A slang term for equipment that uses vacuum tubes.

homebrew: Slang term for home-built, noncommercial radio equipment.

horizontal polarization: An antenna that radiates, or receives best, radio waves having their electric field parallel to the Earth’s surface.

hyperscan: A very high scanning rate in a scanner receiver; also called turboscan.

Hz: Abbreviation for Hz.


ID: Abbreviation for "identification."

image: A false signal produced in the receiver’s circuitry.

impedance: The opposition to the flow of electric current and radio energy; it is measured in ohms (W). For best performance, the impedance of an antenna, the feedline, and the antenna connector on a radio should be approximately equal.

increment steps: The discrete frequency steps (10 Hz, etc.) tuned by a receiver using frequency synthesis.

indirect FM: A term used to refer to phase modulation.

input frequency: The frequency on which a repeater station listens for signals to retransmit.

intermod: Short for "intermodulation," this means false or spurious signals produced by two or more signals mixing in a receiver or repeater station.

International Reply Coupon: A coupon that can be purchased at post offices which can be exchanged in foreign countries for return postage for a surface mail letter to the country that issued the coupon.

ionosphere: The electrically charged region of the Earth’s atmosphere located approximately 40 to 400 miles above the Earth’s surface that refracts radio signals.

ionospheric storm: A disturbed condition in the ionosphere caused by release of charged particles by the Sun which results in high absorption and poor radio propagation on most frequencies.

IRC: Abbreviation for International Reply Coupon.


junkbox: Slang for the collection of spare parts and miscellaneous items kept by a radio operator or hobbyist.

kerchunker: An operator that activates a repeater station by transmitting on its input frequency without speaking.

kHz: Abbreviation for kilohertz.

kilohertz: Unit equal to 1000 hertz.

kilowatt: Unit equal to 1000 watts of transmitter power.

K-index: A measure of the Earth’s magnetic field as measured at Boulder, Colorado. Propagation conditions improve with lower measurement numbers.

kW: Abbreviation for kilowatt.

landline: The telephone or a telephone call.

lid: Slang for an incompetent, unskilled radio operator.

line of sight: Communication between two radio stations that are in visual sight (even if telescopically) with each other.

lockout: To remove certain channels from the scanning sequence of a scanner.

longwave: Radio signals 300 kHz and lower in frequency, although this term is often used to mean any radio signal lower than 540 kHz.

loop antenna: A physically small receiving antenna usually designed for indoor use and tuning frequencies below 5 MHz; it receives in a figure-8 pattern.

lower sideband: The sideband lower in frequency than the transmitter’s carrier.

low pass filter: A filter that rejects all frequencies above a certain point but which allows all lower frequencies to pass.

LSB: Abbreviation for lower sideband.

LUF: Abbreviation for lowest usable frequency, the lowest frequency that can support propagation between two points.


machine: Slang for a repeater station.

major lobe: The direction of maximum radiation or received signal strength for a directional antenna.

maritime station: A two-way radio unit aboard a ship or a station on land that communicates with ships.

mark frequency: In FSK, the higher of the two frequencies used.

MCW: Abbreviation for modulated CW.

mechanical filter: A filter that uses a network of mechanical piezoelectric elements to obtain high rejection of unwanted signals.

medium wave: Radio signals from 300 to 3000 kHz, although this term is often used to mean any radio signal in the AM broadcast band (540 to 1700 kHz).

megahertz: Unit equal to 1,000,000 hertz or 1000 kilohertz.

megawatt: Unit equal to 1,000,000 watts of transmitter power.

meteor scatter: Propagation of signals on frequencies above 25 MHz via ionized trails left by meteors burning up in the ionosphere.

MHz: Abbreviation for megaHertz (1,000,000 Hz). In older publications it may show as Mc for megacycle or 1,000,000 cycles per second.

mobile station: A two-way radio unit installed in a car, boat, plane, etc., and used while in motion or at various stops.

modulated CW: Sending Morse code over an AM transmitter using an audio tone.

modulation: The process of altering the output carrier of a transmitter in some way in order to convey information.

moonbounce: Slang term for EME communication.

monoband antenna: An antenna suitable for operation on just one band of frequencies.

MUF: Abbreviation for maximum usable frequency, the highest frequency that can support propagation between two points.

multiband antenna: An antenna suitable for operation on several different bands of frequencies.

multihop: A radio signal refracted more than one time between the transmitting and receiving stations.

MW: Abbreviation for megawatt.


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, who calls the net to order, recognizes stations entering and leaving the net, and authorizes stations to transmit.

noise blanker: A receiver circuit that reduces electrical noise by quieting the receiver during noise pulses.

notch filter: A circuit that takes a small "slice" out of the bandpass tuned by a receiver; this is useful for reducing interference from narrow bandwidth signals.

OM: Abbreviation for "old man," an old radiotelegraph abbreviation for any radio operator (presumed to be male); now used to refer to any male radio operator or announcer.

omnidirectional antenna: An antenna that transmits and receives equally well in all directions.

open repeater: A repeater station that can be used by anybody; a carrier on its input frequency will automatically be retransmitted on its output frequency.

opening: When propagation is possible between two stations on the same frequency.

out: Spoken at the end of a transmission to indicate that you have made your last transmission and that you expect no response.

output frequency: The frequency on which a repeater station will retransmit signals its hears on its input frequency.

over: Spoken at the end of a transmission to indicate to the other station that it is their turn to transmit.

overloading: When strong signals in a frequency range interfere with proper operation of a receiver, creating false "ghost signals" on various frequencies in the frequency range.


parasitics: Oscillations in a transmitter on frequencies other than the desired one; these can produce spurious signals from the transmitter.

Part 15: The section of the FCC’s rules that permits operation of low power transmitting devices without a license.

pass: The period during which signals from an orbiting satellite can be heard at a ground location.

passband tuning: A receiver circuit that permits adjusting the bandpass for best reception under different interference conditions.

patch: A connection between a two-way radio unit and the public telephone system.

path: The route taken by a signal from the transmitting station to the receiving station.

phase locked loop: a circuit that can generate w wide range of frequencies in discrete steps such as 10 Hz.

phase modulation: Similar to FM, this modulation technique varies the carrier frequency of a transmitter in accordance with the strength and frequency of the modulating signal.

phone: Radiotelephone operation.

phonetic alphabet: A standard set of words used to represent letters of the alphabet.

picket fencing: A fluttering sound heard on a FM signal from a station on a moving vehicle, such as an automobile.

ping: Brief reception of a radio signal via meteor scatter propagation.

PLL: abbreviation for phase locked loop.

PM: Abbreviation for phase modulation.

polarization: Whether an antenna transmits or receives maximum radio energy in the horizontal or vertical plane.

preamp: A receiving circuit that gives extra amplification to weak signals but at the cost of additional background noise and possible distortion.

preselector: A circuit that tunes a receiver’s signal amplifying circuitry for maximum sensitivity on a desired frequency range.

priority channel: A channel a scanner will immediately switch to when a signal is present.

product detector: A receiver circuit consisting of a beat frequency oscillator and additional circuitry for enhanced reception of SSB signals.

propagation: The process of how a radio signal travels from a transmitting station to a receiving station.

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.


quad: A directional antenna consisting of two one-wavelength "squares" of wire placed a quarter-wavelength apart.

QRL: Radiotelegraph abbreviation meaning "this frequency is busy."

QRM: Radiotelegraph abbreviation meaning "interference."

QRN: Radiotelegraph abbreviation meaning "static."

QRO: Radiotelegraph abbreviation meaning "increase transmitter power."

QRP: Radiotelegraph abbreviation meaning "reduce transmitter power."

QRS: Radiotelegraph abbreviation meaning "send more slowly."

QRT: Radiotelegraph abbreviation meaning "stop transmitting."

QRU: Radiotelegraph abbreviation meaning "I have no messages for you."

QRV: Radiotelegraph abbreviation meaning "I am ready to communicate."

QRX: Radiotelegraph abbreviation meaning "wait."

QRZ: Radiotelegraph abbreviation meaning "who is calling me?" It is also used to solicit the next contact in a series of contacts.

QSL: Radiotelegraph abbreviation for "I confirm," it refers to a card or letter confirming that a contact did take place between two stations or that a listener did indeed hear a certain station.

QSO: Radiotelegraph abbreviation for a contact between two or more stations.

QSY: Radiotelegraph abbreviation for "change frequency."

QST: Radiotelegraph abbreviation for a transmission directed to all ham radio operators, it is also the name of the ARRL’s monthly magazine.

QTH: Radiotelegraph abbreviation for a station’s location.


radioteletype: A mode that uses FSK to form letters, numbers, and special characters for display on a printer or video monitor.

ragchew: Slang for an informal conversation via radio.

real time: Communications that are taking place with no perceptible delay.

receiver incremental tuning: A circuit that allows tuning between increment steps in a receiver using frequency synthesis.

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 from the station.

repeater: A radio station that receives stations on a certain frequency and simultaneously retransmits them on another frequency.

resonant frequency: The frequency at which an antenna radiates or receives with maximum efficiency.

rig: The main items of equipment used at a radio station.

RIT: Abbreviation for receiver incremental tuning.

RF gain: A control used to continuously vary the sensitivity of a receiver.

RST: A code used by ham radio operators to indicate a station’s readability, signal strength, and tone of its Morse code signals.

RTTY: Abbreviation for radioteletype.

rubber ducky: Slang for a shortened flexible antenna used with hand-held scanners and transceivers.


scanner: A radio receiver which automatically tunes through a sequence of user-selected frequencies.

scatter: Propagation via random "scattering" of a signal directly off the ionosphere overhead; scatter signals are usually weak.

search: A feature in certain receivers that will scan a frequency range at certain increments (such as 1 or 5 kHz) and pause on any frequency where a signal is present.

selectivity: How well a receiver can reject signals on frequencies adjacent to the one you want to tune. It is indicated by a number of decibels rejection at a frequency point away from the desired signal.

sensitivity: How well a receiver responds to weak signals, measured in microvolts (mV); the lower the number of microvolts indicated, the more sensitive the receiver.

shack: The room or other location where a radio station is operated from.

shape factor: A receiver’s selectivity measured at the 6 and 60 decibel rejection points.

SHF: Abbreviation for super high frequencies.

short skip: Propagation via the ionosphere over a distance of a few hundred miles or less.

shortwave: Frequencies in the high frequencies region of 3 to 30 MHz, but this term is often used to refer to frequencies from 1.7 to 30 MHz.

sideband: A signal equal to the bandwidth of the modulating frequency found above and below the carrier frequency in an AM signal.

sidewinder: Slang for a SSB station.

simplex: To transmit and receive on the same frequency.

single sideband: A modulation technique that suppresses one sideband and the carrier and transmits only the remaining sideband.

SINPO: A code used in reception reports to rate the signal strength, interference, propagation conditions, atmospheric noise, and overall quality of reception on a scale from 1 (lowest) to 5 (highest).

skip: Any type of sky wave propagation via ionospheric refraction.

skip zone: An area where a station being propagated via skywave cannot be heard because it is "skipping" off the ionosphere overhead.

skyhook: Slang for an antenna.

sky wave: Radio signals propagated by refraction in the ionosphere.

S-meter: A meter or bargraph that indicates the relative strength of a received signal.

solid state: A circuit that uses no vacuum tubes---only transistors, integrated circuits, etc.

space frequency: In FSK, the lower of the two frequencies used.

speech processing: A circuit that increases the average level of the modulating signal applied to a transmitter.

split channel: A frequency located between standard frequency allocations, such as the 10 kHz spacing of AM broadcast band frequencies or coordinated repeater frequencies.

sporadic-E: Random patches of intense ionization that form in the E-layer of the ionosphere and refract higher frequency signals that normally cannot be refracted by the ionosphere.

spread spectrum: A modulation method that spreads transmitter energy across a relatively wide frequency range according to a modulating code.

spurs: Undesired signals and frequencies in the output of a transmitter.

squelch: A circuit in a radio receiver that quiets the receiver until the strength of a received signal exceeds a specified level.

squelch tail: A brief bit of noise heard between the end of a radio transmission and the reactivation of the receiver’s squelch circuit.

SSB: Abbreviation for single sideband.

standing wave ratio: The ratio of power sent down a feedline from the transmitter to the power reflected back through the feedline to the transmitter. A ratio of 1:1 is ideal; anything higher than 2:1 usually indicates a problem in the feedline or antenna.

store and forward: A system for the receipt, storage, and later retransmission of packet radio messages.

super high frequencies: the frequency range above 3000 MHz.

surface wave: Another term for a ground wave.

SWL: Abbreviation for "shortwave listener."

SWLing: Abbreviation for "shortwave listening."

SWR: Abbreviation for standing wave ratio.

synchronous detection: Similar to exalted carrier reception, but the replacement carrier tuning and tracking is done automatically by the receiver.


telemetry: One-way radio transmissions used for tracking and measurement data.

terminal node controller: A device used to convert digital signals from a PC into an analog form that can be transmitted by radio and to convert received analog signals into digital form for display on the PC’s monitor.

ticket: The license or other operating credential for a radio station and its operator(s).

time-out: To transmit too long in a single transmission, causing a repeater’s timer circuit to stop further transmissions.

TNC: Abbreviation for terminal node controller.

tone access: A method of activating a repeater station that requires transmission of a brief tone before all transmissions to be relayed.

top loading: Placing a loading coil at the top of an antenna in order to lower the antenna’s resonant frequency.

traffic: Messages to and from third parties exchanged by radio stations.

transceiver: A combined transmitter and receiver sharing a common housing and many of the same components.

translator: A device that receives multiple signals within a certain frequency range and simultaneously retransmits them in another frequency range.

transponder: A device that will emit a radio signal when it receives a radio signal on a certain frequency.

transverter: 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.)

trap dipole: A dipole antenna with several coils, or "traps," that allow the antenna to be used on several bands.

tropo: Term referring to tropospheric ducting.

tropospheric ducting: Propagation of signals above 30 MHz via bending and ducting along weather fronts in the lowest layer of the Earth’s atmosphere, the troposphere.

trunking: A method of switching incoming signals between different repeater stations to prevent interference and ensure access to a repeater.

turboscan: A very high scanning rate in a scanner receiver; also called hyperscan.


UHF: Abbreviation for ultra high frequencies.

UHF low: The frequency range from 450 to 470 MHz.

UHF-T: The frequency range from 470 to 512 MHz.

ultra high frequencies: The frequency range from 300 to 3000 MHz.

unattended operation: Operation of a radio station without a human operator at the control point.

uncoordinated repeater: A repeater station operating on frequencies not approved by the appropriate frequency coordinator.

unity gain: An antenna that gives no gain or loss; its effective radiated power is equal to the transmitter power applied to it.

upper sideband: The sideband higher in frequency than the transmitter’s carrier.

USB: Abbreviation for upper sideband.

UTC: Abbreviation for coordinated universal time.


v: This is used after a frequency to indicate that it varies slightly.

variable frequency oscillator: A circuit used to set the frequency of a receiver or transmitter.

VEC: Abbreviation for "volunteer exam coordinator," a group of hams who give license exams to prospective hams under authorization from the FCC.

vertical polarization: An antenna that radiates, or receives best, radio waves having their electric field perpendicular to the Earth’s surface.

very high frequencies: The frequency range from 30 to 300 MHz.

VFO: Abbreviation for variable frequency oscillator.

VHF: Abbreviation for very high frequencies.

VHF high band: The frequency range from 150 to 175 MHz.

VHF low band: The frequency range from 30 to 50 MHz.

VOX: A circuit that can turn a transmitter on and off automatically whenever someone speaks into the microphone.


wallpaper: QSL cards, certificates, and other items decorating the walls of a radio station.

WAS: Abbreviation for "Worked All States," an award given by the ARRL to hams who contact other hams in all 50 states.

wavelength: The distance between the same points on two consecutive radio waves.

WAZ: Abbreviation for "Worked All Zones," an award given by CQ Magazine to hams who contact other hams in 40 different geographic zones dividing up the globe.

window: A frequency range set aside for foreign ham radio stations to transmit in while ham stations in the United States and Canada do not; American and Canadian stations call foreign stations on frequencies outside the window.

work: To communicate with another radio station or stations.

working frequency: A frequency that two or more stations can use to communicate with each other.


XYL: Radiotelegraph code for "ex-young lady," used to refer to the wife of a radio operator.

Yagi: A directional antenna consisting of a dipole connected to the receiver or transmitter and two additional elements, a slightly longer reflector and a slightly shorter director. Electromagnetic coupling between the elements focuses maximum power (or reception) in the direction of the director.

YL: Radiotelegraph abbreviation for "young lady," used to refer to a female radio operator or announcer.

zero beat: When the frequencies of two carriers are identical and there is no heterodyne heard between them.


73: Radiotelegraph abbreviation for "best regards."

88: Radiotelegraph abbreviation for "love and kisses."


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