Home » Glossary of Amateur Radio Terms

Glossary of Amateur Radio Terms

All0-9ABCDEFGHIJKLMNOPQRSTUVWXYZ
0-9
73
Best wishes (Intended for CW use but often used on voice)
88
Love and Kisses
A
Across the pond 
on the other side of the Atlantic Ocean
Again
Shortened version of “say again” which is often used to indicate that a repeat is required
Alternating current (ac)
Electrical current that flows first in one direction in a wire and then in the other. The applied voltage is also changing polarity. This direction reversal continues at a rate that depends on the frequency of the ac.
Amateur station
A station licensed in the amateur service, including necessary equipment, used for amateur communication.
Ammeter
A test instrument that measures current
Ampere (A)
The basic unit of electrical current. Current is a measure of the electron flow through a circuit. If we could count electrons, we would find that if there are 6.24 × 1018 electrons moving past a point in one second, we have a current of one ampere. We abbreviate amperes as amps. (Numbers written as a multiple of some power are expressed in exponential notation, as shown here.
Amplitude modulation (AM)
A method of combining an information signal and an RF (radio-frequency) carrier. In double-sideband voice AM transmission, we use the voice information to vary (modulate) the amplitude of an RF carrier. Shortwave broadcast stations use this type of AM, as do stations in the Standard Broadcast Band (535-1710 kHz). Few amateurs use double-sideband voice AM, but a variation, known as single sideband, is very popular.
AMSAT
Radio Amateur Satellite Corporation
AMU
Antenna matching unit
Ant
Abbreviation for Antenna
Antenna
A device that picks up or sends out radio frequency energy.
Antenna switch
 A switch used to connect one transmitter, receiver or transceiver to several different antennas.
Antenna tuner (ATU)
A device that matches the antenna system input impedance to the transmitter, receiver or transceiver output impedance. Also called an antenna-matching network, impedance-matching network or Transmatch.
ARRL
American Radio Relay League
Attenuate
To reduce the energy of a radio signal. As an example, heavy rain attenuates (reduces the strength of) radio signals at UHF and above
ATV
Amateur television (fast scan)
AVO
An electronic test instrument used to measure current, voltage and resistance in a circuit. Describes all meters capable of making these measurements, such as the volt-ohm-milliammeter (VOM), vacuum-tube voltmeter (VTVM) and field-effect transistor VOM (FET VOM).
B
Balun
Contraction for balanced to unbalanced. A device to couple a balanced load to an unbalanced source, or vice versa.
Band plan
An agreement to use certain modes on certain frequencies within a given band
Band police
A derogatory term for people who consider themselves to be better operators than everybody else and who do not hesitate to offer “advice” to other operators on what they are doing wrong
Band spread
A receiver quality used to describe how far apart stations on different nearby frequencies will seem to be. We usually express band spread as the number of kilohertz that the frequency changes per tuning-knob rotation. Band spread and frequency resolution are related. The amount of band spread determines how easily signals can be tuned.
Band-pass filter
A circuit that allows signals to go through it only if they are within a certain range of frequencies. It attenuates signals above and below this range.
Bands
The frequencies upon which radio amateurs are permitted to operate or the frequency ranges covered by equipment
Bandwidth
The width of a frequency band outside of which the mean power is attenuated at least 26 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.
Battery
A device that converts chemical energy into electrical energy.
Beam
Multi element directional antenna
Beat-frequency oscillator (BFO)
A receiver circuit that provides a signal to the detector. The BFO signal mixes with the incoming signal to produce an audio tone for CW reception. A BFO is needed to copy CW and SSB signals.
BNC
Type of connector used for connecting between radio equipment and an antenna (bayonet connector, twist-and-click)
Boafeng
A popular Chinese manufacturer of budget amateur radio equipment
Boots
A high powered amplifier
Break
An exclamation often used by operators wishing to draw attention to their presence on a frequency being used by an established QSO which they wish to join
Breaker
A station trying to join an established QSO
Broadcasting
Transmissions intended to be received by the general public, either direct or relayed.
BST
British Summer Time
Bug Key
Semi automatic Morse key (after the red beetle trade-mark of the Vibroplex Company)
C
Call Sign
A group of letters and figures, which is unique to each amateur radio operator. These callsigns are issued by the appropriate Government Department of the country in which the station is located. The callsign consists of a prefix, indicating the country, and a suffix, which is unique to each operator e.g. G3NPF and M1AIM where “G3” and “M1”, indicate England, and “NPF” and “AIM” are the letters unique to these operators
Capacitance
A measure of the ability of a capacitor to store energy in an electric field.
Capacitor
An electrical component usually formed by separating two conductive plates with an insulating material. A capacitor stores energy in an electric field.
Capacity Hat
A device mounted at the top of a vertical antenna to lower its natural resonant frequency
Carrier
Generally, the steady continuous RF component of an amplitude modulated signal, but commonly used to describe any, usually unwanted, steady signal on, or close to, the current operating frequency
CB
Citizens Band radio
Centre Fed Antenna
A wire antenna, where the transmitter/receiver/ATU is connected at the mid-point, via tuned feeders or coaxial cable
CEPT
European Conference of Postal and Telecommunications Administrations. Visit https://rsgb.org/main/operating/licensing-novs-visitors/operating-for-visitors/ to learn more
Channel
A specific frequency on a given band
Chassis ground
The common connection for all parts of a circuit that connect to the negative side of the power supply.
Chirp
A small, transient, change in frequency at the start of a transmission, most noticeable on CW.
Chirp can also relate to a software program used to program radios.
Closed, or complete circuit
An electrical circuit with an uninterrupted path for the current to follow. Turning a switch on, for example, closes or completes the circuit, allowing current to flow.
Co-Linear
An antenna in which resonant elements are connected end-to-end, with phasing circuits between them
Coaxial cable
Coax (pronounced kó-aks). A type of feed line with one conductor inside the other.
Conductor
A material that has a loose grip on its electrons, so an electrical current can pass through it.
Continuous wave (CW)
A communications mode transmitted by on/off keying of a radio-frequency signal. Another name for international Morse code.
Core
The material used in the center of an inductor coil, where the magnetic field is concentrated.
Counterpoise
A conductor located under a wire antenna, but positioned on, or very close to, the ground, which acts as an “artificial earth”,
CQ
“Calling any station”: the general call when requesting a conversation with anyone. Like many other telegraph terms which originated on the landlines, CQ was brought over into radio and used as a general call to all ships by the Marconi Company. Other companies used KA until the London Convention of 1912, which adopted CQ as the international general call or “attention” signal.
Crystal oscillator
A device that uses a quartz crystal to keep the frequency of a transmitter constant.
CTCSS
Continuous Tone Coded Squelch System in which very low frequency audio tones are used to access repeaters instead of the 1750Hz tone-burst.
Cubical quad antenna
An antenna built with its elements in the shape of four-sided loops. Current — A flow of electrons in an electrical circuit.
D
DARC
Dragon Amateur Radio Club
DARC
Dragon Amateur Radio Club
Data
Computer-based communications modes, such as packet radio, which can be used to transmit and receive computer files, or digital information.
dB (Decibels)
Unit associated with the measurement of gain (or loss). At Foundation, recall that Yagi (beam) antennas have a gain measured in dB, for example, a Yagi with a 3dB gain would double the radiated power
DE
The Morse code abbreviation for “from”
Delta loop antenna
A variation of the cubical quad with triangular elements.
Detector
The stage in a receiver in which the modulation (voice or other information) is recovered from the RF signal.
Digipeater
Simplex repeater for digital (packet) modes, where handshaking takes place between the two connected stations without involving the intermediate repeater, which only acts as a relay
Digital communications
Computer-based communications modes. This can include data modes like packet radio and text-only modes like radioteletype (RTTY)
Dipole antenn
A basic antenna used by radio amateurs. It consists of a length of wire or tubing, opened and fed at the center.
Direct current (dc)
Electrical current that flows in one direction only.
Director
An element in front of the driven element in a Yagi and some other directional antennas.
DMR
Digital Mobile Radio. A standard for two-way radios that allows different manufacturers’ equipment to work together. 
DPDT switch
A switch that has six contacts.
DPST Switch
A switch that connects two contacts to another set of contacts. A DPST switch turns two circuits on or off at the same time
Driven element 
The part of an antenna that connects directly to the feed line.
Dual-band antenna
An antenna designed for use on two different Amateur Radio bands.
Dummy load
A station accessory that allows you to test or adjust transmitting equipment without sending a signal out over the air.
Dummy Load
A device that plugs into a transmitter’s antenna socket to allow you to test a transmitter without radiating a signal into an antenna
Duplexer
A device that allows a dual-band radio to use a single dual-band antenna.
Duty cycle
A measure of the amount of time a transmitter is operating at full output power during a single transmission. A lower duty cycle means less RF radiation exposure for the same PEP output.
DX
Long distance communications to foreign countries
E
Earth ground 
A circuit connection to a ground rod driven into the Earth or to a cold-water pipe made of copper that goes into the ground.
Earth station
An amateur station located on, or within 50 km of, the Earth’s surface intended for communications 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.
EIRP
Effective Isotropic Radiated Power – How much power is being radiated by your antenna (compared to a theoretical “isotropic” antenna)
Elecraft
A popular manufacturer of amateur radio equipment
Electric field
An invisible force of nature. An electric field exists in a region of space if an electrically charged object placed in the region is subjected to an electrical force.
Electromotive force (EMF)
The force or pressure that pushes a current through a circuit.
Electron
A tiny, negatively charged particle, normally found in an area surrounding the nucleus of an atom. Moving electrons make up an electrical current.
EMC
Electro-Magnetic Compatibility. The avoidance of interference between various pieces of electronic equipment.
Emission
The transmitted signal from an amateur station
End fed wire
A wire antenna, usually tuned against ground, where one end is connected directly to the transmitter/receiver/ATU
eQSL
An electronic postcard that serves as a confirmation of communication between two hams
ERP
Effective Radiated Power – How much power your antenna is outputting (calculated by multiplying the power in watts, by the “gain” of the antenna when compared to a half-wave dipole antenna)
F
Feeder
transmission line connecting an antenna to a receiver or transmitter
Filter
A circuit that will allow some signals to pass through it but will greatly reduce the strength of others.
Final
The final tube(s) or transistors in an amplifier OR The last transmission in a contact before singing off
FM
Frequency Modulation. The type of signals used to communicate by voice (phone) over most repeaters. FM is a method of combining an RF carrier with an information signal, such as voice. The voice information (or data) changes the RF carrier frequency in the modulation process.
Frequency
The number of complete cycles of an alternating current that occur per second.
Frequency discriminator
A type of detector used in some FM receivers
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.
G
G5RV
A type of multiband wire dipole antenna designed by the late Louis Varney, G5RV
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 and the amateur bands from 160 to 10 meters.
Giga
The metric prefix for 109, or times 1,000,000,000.
Ground 
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 rod
A copper or copper-clad steel rod that is driven into the earth. A heavy copper wire from the ham shack connects all station equipment to the ground rod.
H
Half-wave dipole
A basic antenna used by radio amateurs. It consists of a length of wire or tubing, opened and fed at the center. The entire antenna is ½ wavelength long at the desired operating frequency.
Ham
An Amateur Radio operator licensed to operate amateur radio station. 
Harmonics
Signals from a transmitter or oscillator occurring on whole-number multiples (2×, 3×, 4×, etc) of the desired operating frequency.
Hertz (Hz) 
An alternating-current frequency of one cycle per second. The basic unit of frequency.
HF
High Frequency
High-pass filter
A filter designed to pass high-frequency signals, while blocking lower-frequency signals.
Homebrew
Antenna or other equipment made at home
I
Icom
A popular manufacturer of amateur radio equipment
Impedance
The opposition to electric current 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.
Inductance
A measure of the ability of a coil to store energy in a magnetic field.
Inductor
An electrical component usually composed of a coil of wire wound on a central core. An inductor stores energy in a magnetic field.
Insulator
A material that maintains a tight grip on its electrons, so that an electric current cannot pass through it (within voltage limits).
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.
Ionosphere
A region of electrically charged (ionized) gases high in the atmosphere. The ionosphere bends radio waves as they travel through it, returning them to Earth. Also see sky-wave propagation.
IOTA
Islands on the air
J
JT6M
A digital transmission system designed by K1JT, which is similar to FSK441 but optimised for meteor scatter use on 50MHz
Jumper
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.
K
K
When a CW operator ends their transmission with “K”, they are signaling that they are finished and are inviting the other station to respond or take their turn
Kenwood
A popular manufacturer of amateur radio equipment
Key
A Morse Key
Keying
Using a morse key to send morse code
L
Limiter
A stage of an FM receiver that makes the receiver less sensitive to amplitude variations and pulse noise.
Line-of-sight propagation
The term used to describe VHF and UHF propagation in a straight line directly from one station to another.
Long wire
A wire antenna, usually fed at one end and tuned against ground, where the length is equal to several wavelengths at the frequency being used, but often erroneously used to describe a wire antenna of any random length
Low-pass filter
A filter that allows signals below the cutoff frequency to pass through and attenuates signals above the cutoff frequency.
Lower sideband (LSB)
The common single-sideband operating mode on the 40, 80 and 160-meter amateur bands.
M
Mega
The metric prefix for 106, or times 1,000,000.
Metric
A system of measurement developed by scientists and used in most countries of the world. This system uses a set of prefixes that are multiples of 10 to indicate quantities larger or smaller than the basic unit.
Micro
The metric prefix for 10–6, or divide by 1,000,000
Microphone
A device that converts sound waves into electrical energy.
Milli
The metric prefix for 10–3, or divide by 1000
Mobile
A radio transmitting device designed to be mounted in a vehicle. A push-to-talk (PTT) switch activates the transmitter.
Modem
Short for modulator/demodulator. A modem modulates a radio signal to transmit data and demodulates a received signal to recover transmitted data.
Modulate
To vary the amplitude, frequency, or phase of a radio-frequency signal.
Modulation
The process of varying an RF carrier in some way (the amplitude or the frequency, for example) to add an information signal to be transmitted
Monitor mode
One type of packet radio receiving mode. In monitor mode, everything transmitted on a packet frequency is displayed by the monitoring TNC. This occurs whether or not the transmissions are addressed to the monitoring station.
Moonbounce
A method of communicating with other stations by reflecting radio signals off the Moon’s surface.
Morse Code
An alphabet or code in which letters are represented by combinations of long and short light or sound signals. “it transmits a signal of continuous dashes in Morse”
Multimeter
An electronic test instrument used to measure current, voltage and resistance in a circuit. Describes all meters capable of making these measurements, such as the volt-ohm-milliammeter (VOM), vacuum-tube voltmeter (VTVM) and field-effect transistor VOM (FET VOM).
Multimode transceiver
Transceiver capable of SSB, CW and FM operation
N
Network
A term used to describe several packet stations linked together to transmit data over long distances.
Node
A repeater for digital (packet) modes, where handshaking takes place between each of two connected stations and the intermediate repeater, with no direct handshaking between the two stations or any station on a digital network, whether linked by land-line or linked by radio
Nonionizing radiation 
Electromagnetic radiation that does not have sufficient energy to knock electrons free from their atoms. Radio frequency (RF) radiation is nonionizing.
NPN transistor
A transistor that has a layer of P-type semiconductor material sandwiched between layers of N-type semiconductor material.
O
Offset
The 300 to 1000-Hz difference in CW transmitting and receiving frequencies in a transceiver. For a repeater, offset refers to the difference between its transmitting and receiving frequencies.
Ohm
The basic unit of electrical resistance, used to describe the amount of opposition to current.
Ohm’s Law 
 A basic law of electronics. Ohm’s Law 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 = IR).
One-way communications
Transmissions that are not intended to be answered. The FCC strictly limits the types of one-way communications allowed on the amateur bands.
Open circuit
An electrical circuit that does not have a complete path, so current can’t flow through the circuit
Open repeater
A repeater that can be used by all hams who have a license that authorizes operation on the repeater frequencies.
Out of Band
Description of signals radiated on frequencies outside the permitted frequency bands
Output frequency
A repeater’s transmitting frequency. To use a repeater, transmit on the input frequency and receive on the output frequency.
P
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
Parasitic element
Part of a directive antenna that derives energy from mutual coupling with the driven element. Parasitic elements are not connected directly to the feed line.
Peak envelope power (PEP)
The average power of a signal at its largest amplitude peak.
Phone
Another name for voice communications
Phonetic alphabet
Standard words used on voice modes to make it easier to understand letters of the alphabet, such as those in call signs. https://en.wikipedia.org/wiki/NATO_phonetic_alphabet
Pico
The metric prefix for 10–12, or divide by 1,000,000,000,000. PL (see CTCSS)
Pile up
Being called by multiple callers at the same time.
PL
(Also known as CTCSS – Continuous Tone-Coded Squelch System) A sub-audible tone system used on some repeaters. When added to a carrier, a CTCSS tone allows a receiver to accept a signal.
PL258
Radio coax connector
PL259
Radio coax connector
PME
This stands for Protective Multiple Earthing, and relates to one of the ways that electricity companies connect houses to Earth. Special care is needed with RF earthing arrangements if your house has PME. More details can be found in the RSGB’s guide: RSGB UK Earthing Systems and RF Earthing
PNP transistor 
A transistor that has a layer of N-type semiconductor material sandwiched between layers of P-type semiconductor material
Polarisation
The electrical-field characteristic of a radio wave. 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, produces vertically polarized waves. An antenna that has both horizontal and vertical polarization is said to be circularly polarized.
Portable
A radio transmitting device designed to have a transmitting antenna that is generally within 20 centimeters of a human body.
Potentiometer
Another name for a variable resistor. The value of a potentiometer can be changed over a range of values without removing it from a circuit.
Power
The rate of energy consumption. We calculate power in an electrical circuit by multiplying the voltage applied to the circuit times the current through the circuit (P = IE).
Power supply (PSU)
A circuit that provides a direct-current output at some desired voltage from an ac input voltage.
Product detector
A device that allows a receiver to process CW and SSB signals. Propagation — The study of how radio waves travel.
PTT
push-to-talk button on radio or microphone
Q
Q code
Three-letter symbols beginning with Q. https://en.wikipedia.org/wiki/Q_code
QRL? 
Ham radio Q signal meaning “Is this frequency in use?”
QRM
Man made interference
QSB
Natural interference
QSL
Means all received OK (See Q-Code list for full meaning) also used as a short form of “qsl card”
QSL card
A postcard that serves as a confirmation of communication between two hams
QSO
A conversation between two radio amateurs.
Quarter-wavelength vertical antenna
An antenna constructed of a quarter-wavelength long radiating element placed perpendicular to the earth.
R
Radio-frequency interference (RFI) 
Disturbance to electronic equipment caused by radio-frequency signals.
Radioteletype (RTTY)
Radio signals sent from one teleprinter machine to another machine. Anything that one operator types on his teleprinter will be printed on the other machine. Also known as narrow-band direct-printing telegraphy.
Ragchew
Long discussion
Receiver
A device that converts radio waves into signals we can hear or see.
Reflection
Signals that travel by line-of-sight propagation are reflected by large objects like buildings.
Reflector
An element behind the driven element in a Yagi and some other directional antennas
Repeater
An amateur station that automatically retransmits the signals of other stations.
Resistance
he ability to oppose an electric current
Resistor
Any material that opposes a current in an electrical circuit. An electronic component specifically designed to oppose or control current through a circuit.
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.
Retavis
A popular manufacturer of amateur radio equipment
RF
Radio Frequency
RF burn
A burn produced by coming in contact with exposed RF voltages.
RF Radiation
Waves of electric and magnetic energy. Such electromagnetic radiation with frequencies as low as 3 kHz and as high as 300 GHz are considered to be part of the RF region.
Rig
The radio amateur’s term for a transmitter, receiver or transceiver.
Roger
A CB term meaning Yes, sometimes used by amateurs also.
RSGB
Radio Society of Great Britain
RST
A system of numbers used for signal reports: R is readability, S is strength and T is tone. (On single-sideband phone, only R and S reports are used.)
S
Selectivity
The ability of a receiver to separate two closely spaced signals
Sensitivity
The ability of a receiver to detect weak signals
Series circuit
An electrical circuit in which all the electrons must flow through every part of the circuit. There is only one path for the electrons to follow.
Shack
A room containing the amateur radio station
Short circuit
An electrical circuit in which the current does not take the desired path, but finds a shortcut instead.
Sidebands
The sum or difference frequencies generated when an RF carrier is mixed with an audio signal. Single-sideband phone (SSB) signals have an upper sideband (USB — that part of the signal above the carrier) and a lower sideband (LSB — the part of the signal below the carrier). SSB transceivers allow operation on either USB or LSB.
Silent Key (SK)
A deceased Amateur Radio operator
Simplex
Receiving and transmitting on the same frequency.
Single Sideband (SSB)
A common mode of voice operation on the amateur bands. SSB is a form of amplitude modulation.The amplitude of the transmitted signal varies with the voice signal variations.
Skip
In ham radio, “skip” refers to the phenomenon where radio signals, reflected or refracted by the ionosphere, can be received at long distances but not in a region closer to the transmitting station, creating a “skip zone”. 
Sky-wave propagation
The method by which radio waves travel through the ionosphere and back to Earth. Sometimes called skip, sky-wave propagation has a far greater range than line-of-sight and ground-wave propagation.
SO239
Radio Coax Connector
SOS
 A Morse code call for emergency assistance.
Splatter
A type of interference to stations on nearby frequencies. Splatter occurs when a transmitter is overmodulated
Split
Transmit on one frequency while listening on another, using VFO A and B. Routinely used on HF by DXpeditions with ‘pile ups’ of callers to keep their TX frequency clear and the callers slightly spread out. Usually they will listen for callers in a band slightly higher from their TX frequency and indicate by “UP” in CW and “Listening Up” on phone. Typically callers will be between 1-2kHz higher for CW and 5-10kHz for SSB.
Spurious emissions
Signals from a transmitter on frequencies other than the operating frequency.
Standing-wave ratio (SWR)
Sometimes called voltage standing-wave ratio (VSWR). A measure of the impedance match between the feed line and the antenna. Also, with a Transmatch in use, a measure of the match between the feed line from the transmitter and the antenna system. The system includes the Transmatch and the line to the antenna. VSWR is the ratio of maximum voltage to minimum voltage along the feed line. Also the ratio of antenna impedance to feed-line impedance when the antenna is a purely resistive load.
Sunspot cycle
The number of sunspots increases and decreases in a predictable cycle that lasts about 11 years
Sunspots
Dark spots on the surface of the sun. When there are few sunspots, long-distance radio propagation is poor on the higher-frequency bands. When there are many sunspots, long-distance HF propagation improves.
Switch
A device used to connect or disconnect electrical contacts
SWR meter
A measuring instrument that can indicate when an antenna system is working well. A device used to measure SWR
T
TCP/IP
Transport Control Protocol/Internet Protocol
Television interference (TVI)
Interruption of television reception caused by another signal.
Terminal
An inexpensive piece of equipment that can be used in place of a computer in a packet radio station.
Ticket
A common name for an Amateur Radio license.
Transceiver
 A radio transmitter and receiver combined in one unit.
Transistor
A solid-state device made of three layers of semiconductor material. See NPN transistor and PNP transistor
Transmission line 
The wires or cable used to connect a transmitter or receiver to an antenna. Also called feed line.
Transmitter
A device that produces radio-frequency signals
Troposphere
The region in Earth’s atmosphere just above the Earth’s surface and below the ionosphere.
Tropospheric bending
When radio waves are bent in the troposphere, they return to Earth farther away than the visible horizon.
Tropospheric ducting
A type of VHF propagation that can occur when warm air overruns cold air (a temperature inversion).
U
UHF
Ultra high frequency
Unbalanced line
Feed line with one conductor at ground potential, such as coaxial cable.
Upper sideband (USB)
The common single-sideband operating mode on the 20, 17, 15, 12 and 10-meter HF amateur bands, and all the VHF and UHF bands
V
Variable capacitor
A capacitor that can have its value changed within a certain range.
Variable resistor
A resistor whose value can be adjusted over a certain range, without removing it from a circuit.
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.
Vertical antenna
A common amateur antenna, often made of metal tubing. The radiating element is vertical. There are usually four or more radial elements parallel to or on the ground.
Visible horizon
The most distant point one can see by line of sight.
Voice
Any of the several methods used by amateurs to transmit speech.
VoiP
Voice over Internet Protocol
Volt (V)
The basic unit of electrical pressure or EMF
Voltage
The EMF or pressure that causes electrons to move through an electrical circuit.
Voltmeter
A test instrument used to measure voltage.
VSWR
Voltage Standing Wave Ratio. Often shortened to SWR.  An SWR of 1:1 would indicate that all of the power from the transmitter is being radiated by the antenna. An SWR reading of 2:1 or higher would indicate that a significant amount of power is reflected back to the transmitter from the antenna (indicating an antenna mismatch)
W
Watt (W)
The unit of power in the metric system. The watt describes how fast a circuit uses electrical energy.
Wattmeter
 Also called a power meter, a test instrument used to measure the power output (in watts) of a transmitter. A directional wattmeter measures both forward and reflected power.
Wavelength
Often abbreviated λ. The distance a radio wave travels in one RF cycle. The wavelength relates to frequency. Higher frequencies have shorter wavelengths.
Whisper (WSPR)
WSPR is an acronym for Weak Signal Propagation Reporter. It is a protocol, implemented in a computer program, used for weak-signal radio communication between amateur radio operators.
Wouxun
A popular manufacturer of amateur radio equipment
WSJT
Weak Signal Communication by K1JT. This is a computer programme written by K1JT, which decodes FSK441, JT44 and JT6M signals and generates appropriate replies. These types of transmissions are used for meteor scatter, tropospheric scatter, ionospheric scatter and eme communication, on the VHF and UHF bands
X
X
In electrical equations, this letter stands for “Reactance.”
Xiegu
A popular manufacturer of amateur radio equipment
XYL
Abbreviation for “Wife”
Y
Yaesu
A popular manufacturer of amateur radio equipment
Yagi
A multi-element directional antenna with one driven element and one or more additional elements.
Z
Z
In electrical equations, this is used to mean “Impedance.”
Zulu Time
Co-ordinated Universal Time (UTC) or Greenwich Mean Time (GMT)

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