Reference

Ham Radio Glossary

120 terms, jargon, and abbreviations — explained in plain English. New to the hobby? Start here.

#

73: Operating shorthand for "best regards," used to sign off.
88: Operating shorthand for "love and kisses," a warmer sign-off.

A

A-index: A daily index of geomagnetic activity (0–400); lower values mean better HF conditions.
AM (Amplitude Modulation): A voice mode in which the carrier amplitude varies; older and wider than SSB.
Amplifier (Linear): A device that boosts transmit power; a "linear" preserves the signal's shape.
Antenna: The conductor that radiates and receives RF energy — the most important part of any station.
APRS: Automatic Packet Reporting System — sends position and telemetry over VHF packet radio.
ARES: Amateur Radio Emergency Service — the ARRL's volunteer emergency-communications program.
Attenuation: Loss of signal strength — in feedline, components, or over distance.
ATU (Antenna Tuner): Matches the transmitter to the antenna system to minimize SWR; does not "tune" the antenna itself.

B

Balun: A "balanced-to-unbalanced" transformer that connects a balanced antenna (like a dipole) to coax.
Band: A range of frequencies allocated to a service, e.g., the 20-meter band (14.0–14.35 MHz).
Band plan: A voluntary convention dividing a band by mode and use to keep order.
Bandwidth: The range of frequencies a signal occupies.
Beacon: A station that transmits continuously or on a schedule to help operators gauge propagation.
Beam: A directional antenna (such as a Yagi) that concentrates energy in one direction.
Bug: A semi-automatic mechanical Morse key that makes dots automatically.

C

Callsign: Your unique, government-assigned station identifier (e.g., W1AW).
Carrier: The steady RF signal that is modulated to carry information.
Coax (Coaxial cable): Common shielded feedline such as RG-8, RG-58, or LMR-400.
Contest: An on-air competition to make the most contacts in a set period.
CQ: A general call inviting any station to answer ("seek you").
CTCSS (PL): A sub-audible tone that opens a repeater's squelch so it responds to you.
CW (Continuous Wave): Morse code, sent by keying a carrier on and off.

D

D-STAR: An Icom-led digital voice and data mode.
dB (Decibel): A logarithmic ratio of two power or voltage levels.
dBi / dBd: Antenna gain referenced to an isotropic radiator (dBi) or a dipole (dBd).
Desense: Receiver desensitization — loss of sensitivity caused by a strong nearby signal.
Dipole: A half-wave wire antenna fed in the center; the classic, simple HF antenna.
DMR: Digital Mobile Radio — a digital voice mode that uses talkgroups and networks.
Duplex: Transmitting and receiving on two different frequencies, as repeaters do.
DX: Distant stations or long-distance contacts.
DXCC: The ARRL "DX Century Club" award for confirming 100+ DXCC entities.
DXpedition: An expedition to activate a rare or uninhabited location for DX contacts.

E

Elmer: A mentor who helps newcomers learn amateur radio.
EmComm: Emergency communications.
EME (Moonbounce): Earth-Moon-Earth — communicating by bouncing signals off the Moon.
ERP / EIRP: Effective (Isotropic) Radiated Power — transmit power including antenna gain and losses.

F

Feedline: The cable connecting the radio to the antenna (coax, ladder line, etc.).
Field Day: The ARRL's big annual emergency-readiness operating event, held the fourth weekend of June.
FM (Frequency Modulation): The common VHF/UHF voice mode — clear audio but relatively wide.
FT8 / FT4: Popular weak-signal digital modes (in WSJT-X) that make quick, automated contacts.

G

Gain: How much an antenna or amplifier increases signal, often in a specific direction.
Grayline (Greyline): The twilight line between day and night, which often enhances low-band DX.
Grid square: A Maidenhead locator (e.g., FN31) that identifies your location for VHF and contests.
Ground: Connections to earth or a counterpoise for safety and RF performance.

H

Ham: An amateur radio operator.
Harmonics: Whole-number multiples of a frequency; unwanted harmonics cause interference.
HF (High Frequency): 3–30 MHz — the "shortwave" bands used for long-distance contacts.
HT (Handheld): A handheld VHF/UHF transceiver, also called a "handie-talkie."

I

Impedance: AC opposition to current (in ohms); antennas and feedlines target about 50 Ω.
Intermod (IMD): Spurious mixing products created when strong signals combine in a receiver or amplifier.
Ionosphere: The charged upper atmosphere that refracts HF signals, enabling skip propagation.
IOTA: Islands on the Air — an award program for contacting island groups.
ITU: International Telecommunication Union — sets worldwide frequency allocations and zones.

J

JS8 / JS8Call: A keyboard chat mode built on FT8 technology for weak-signal conversation.

K

K-index: A 3-hour geomagnetic activity index (0–9); low values favor good HF propagation.
Keyer: An electronic device that forms Morse dots and dashes from a paddle.

L

Ladder line: Low-loss balanced open-wire feedline.
License classes: In the US: Technician, General, and Amateur Extra — each with more privileges.
LoTW: Logbook of The World — the ARRL's electronic QSL and award-tracking system.
LSB / USB: Lower and Upper Sideband (SSB); convention is LSB below 10 MHz, USB above.

M

Maidenhead: The grid-square locator system that encodes location into letters and digits.
Mode: How information is carried — CW, SSB, FM, FT8, RTTY, etc.
MUF / LUF: Maximum and Lowest Usable Frequency for a given path and time.

N

Net: A scheduled on-air meeting run by a Net Control Station.
NVIS: Near Vertical Incidence Skywave — short-range HF using steep, near-vertical angles.

O

Offset: The transmit/receive frequency difference on a repeater (e.g., −600 kHz on 2 m).
OM: "Old Man" — any male operator, regardless of age.

P

Packet: A digital data mode (AX.25); the basis of APRS and older BBS networks.
Paddle: A lever key used with an electronic keyer to send Morse.
PEP: Peak Envelope Power — the standard measure of transmitter output power.
Pileup: Many stations calling one station (such as a DXpedition) at the same time.
POTA: Parks on the Air — a program for activating and "hunting" parks.
Propagation: How radio waves travel from transmitter to receiver.
PSK31: A narrow keyboard-to-keyboard digital text mode popular on HF.

Q

QRM: Man-made interference.
QRN: Natural noise or static.
QRO: High power operation.
QRP: Low-power operation — 5 watts output or less.
QRZ: "Who is calling me?"
QSB: Signal fading.
QSL: Confirmation of a contact — and the postcard ("QSL card") that confirms it.
QSO: A two-way contact or conversation.
QSY: To change frequency.
QTH: Your station location.

R

Ragchew: A long, relaxed on-air conversation.
Repeater: A station that receives and re-transmits signals to extend the range of mobiles and HTs.
RF: Radio Frequency — alternating electrical energy in the radio range.
Rig: A radio or transceiver.
Rotator: A motor that rotates a beam antenna to point it.
RST: A signal report: Readability (1–5), Strength (1–9), and Tone (1–9, CW) — e.g., "599."
RTTY: Radioteletype — a classic FSK digital text mode used in contests.

S

SDR: Software-Defined Radio — a radio whose functions are largely defined in software.
Shack: Your radio operating room or space.
Simplex: Transmitting and receiving on the same frequency, directly (no repeater).
SK: "Silent Key" — a deceased amateur; also the CW prosign that ends a contact.
Skip: HF signals refracted by the ionosphere to reach far beyond the horizon.
SOTA: Summits on the Air — a program for operating from mountain summits.
Split: Transmitting and receiving on different frequencies — common when working DX.
Sporadic E (Es): Patchy ionization in the E layer that enables surprise openings on 6 m and upper HF.
SSB (Single Sideband): The efficient HF voice mode; uses one sideband and suppresses the carrier.
SSTV: Slow-Scan Television — sending still images over the radio as audio tones.
SWL: Shortwave Listener — someone who listens but may not transmit.
SWR (VSWR): Standing Wave Ratio — how well the antenna system is matched; 1:1 is ideal.
System Fusion: Yaesu's C4FM digital voice and data system.

T

Transceiver: A combined transmitter and receiver in one unit.
Transverter: A converter that shifts a radio's band to another (e.g., an HF rig onto VHF).

U

UHF: Ultra High Frequency — 300 MHz to 3 GHz (e.g., the 70 cm band).
Unun: An "unbalanced-to-unbalanced" impedance transformer, common with end-fed antennas.
UTC (Zulu): Coordinated Universal Time — the standard time reference used in logging ("Z").

V

VE: Volunteer Examiner — a licensed ham accredited to administer license exams.
Velocity factor: How much slower RF travels in a cable compared with free space (e.g., 0.66 for RG-58).
VFO: Variable Frequency Oscillator — sets your operating frequency.
VHF: Very High Frequency — 30 to 300 MHz (e.g., the 2 m band).

W

WAS: Worked All States — an award for confirming contacts with all 50 US states.
Wavelength: The physical length of one RF cycle; λ (meters) ≈ 300 ÷ frequency (MHz).
WSPR: Weak Signal Propagation Reporter ("whisper") — beacon mode for studying propagation.
WWFF: World Wide Flora & Fauna — an award program for activating protected nature areas.

Y

Yagi: A directional beam antenna with a driven element plus parasitic reflectors and directors.

Frequently asked questions

What does SWR mean in ham radio?

SWR (standing wave ratio) measures how well your antenna is matched to your radio. 1:1 is perfect; under 1.5:1 is great; high SWR means power is being reflected back instead of radiated. See the full term list above.

What is a balun?

A balun (balanced-to-unbalanced) is a small transformer that connects an unbalanced feedline like coax to a balanced antenna like a dipole, keeping RF off the outside of your coax. It’s one of the most common ham radio accessories.

What does 73 mean?

“73” is ham shorthand for “best regards,” used to sign off. You’ll also see “88” (love and kisses) and Q-codes like QSL (I confirm) and QTH (location) — all defined in the glossary above.