Ham Radio Glossary: Every Term and Acronym Explained

Ham radio runs on jargon. Half the barrier to getting comfortable in this hobby is not the electronics, it is the alphabet soup that gets thrown around on every net, every forum thread, and every product listing. I built this page to be the one link I send someone when they ask what a term means, whether it is something they heard on a repeater or something they read on a spec sheet while shopping for a radio. It is organized by category so you can jump to the section you actually need, and I will keep adding to it as new terms come up.

Licensing, Organizations, and Regulation

FCC (Federal Communications Commission): The U.S. government agency that regulates radio spectrum, including amateur radio licensing and enforcement.
ARRL (American Radio Relay League): The largest U.S. amateur radio membership organization, publisher of study guides, QST magazine, and a major voice in FCC rulemaking.
VE (Volunteer Examiner): A licensed ham certified to administer amateur radio license exams.
VEC (Volunteer Examiner Coordinator): An organization, accredited by the FCC, that coordinates VE teams and processes exam paperwork.
Technician, General, Extra: The three U.S. amateur license classes, in order of increasing privileges and difficulty, with Extra granting the most operating privileges.
Callsign: The unique identifier assigned to every licensed station, required to be transmitted periodically during operation.
Vanity Callsign: A callsign specifically requested by a licensee rather than automatically assigned by the FCC’s sequential system.
Part 97: The section of FCC regulations that governs amateur radio specifically.
Part 90: The FCC regulations covering private land mobile radio, relevant to commercial radios sometimes cross-programmed for other uses.
Part 95: The FCC regulations covering personal radio services, including GMRS and FRS.
Elmer: Ham radio slang for a mentor, an experienced operator who helps a newer ham learn the hobby.

Bands, Frequencies, and Propagation

HF (High Frequency): The 3 to 30 MHz range, used for long-distance skywave propagation and most DX contacts.
VHF (Very High Frequency): The 30 to 300 MHz range, including the popular 2 meter (144 to 148 MHz) amateur band.
UHF (Ultra High Frequency): The 300 MHz to 3 GHz range, including the 70 cm (420 to 450 MHz) amateur band.
DX: Distance, generally referring to a long-distance or foreign contact.
Propagation: How radio waves travel from one point to another, affected by frequency, time of day, and atmospheric conditions.
Skip / Skywave: HF signal propagation that bounces off the ionosphere, allowing contacts far beyond line of sight.
Ground Wave: Signal propagation that follows the curvature of the earth near ground level, common at lower HF frequencies.
Sporadic E (Es): A propagation phenomenon on VHF caused by dense ionization in the E layer, occasionally opening up long-distance VHF contacts.
MUF (Maximum Usable Frequency): The highest frequency that will reliably propagate via skywave between two points at a given time.
Grid Square (Maidenhead Locator): A location encoding system used heavily in VHF/UHF and satellite work, dividing the globe into a grid identified by letter-number pairs like DM33.
Simplex: Direct radio-to-radio communication on a single frequency without a repeater in between.
Duplex / Split: Operating with different transmit and receive frequencies, as used through a repeater.
Offset: The difference between a repeater’s transmit and receive frequency.
Band Plan: A voluntary or regulatory allocation of specific frequency ranges within a band to specific uses or modes.

Transceivers and Radio Hardware

Transceiver: A radio that both transmits and receives, as opposed to a separate transmitter and receiver.
HT (Handheld Transceiver): A portable, handheld radio, sometimes still called a walkie-talkie.
Mobile Radio: A radio designed for vehicle installation, typically higher power than a handheld.
Base Station: A radio set up as a fixed home or shack installation rather than mobile or portable.
VFO (Variable Frequency Oscillator): The radio’s internal circuit that generates the tunable operating frequency, and colloquially the mode of tuning freely rather than using preprogrammed memory channels.
CAT (Computer Aided Transceiver): A control protocol that lets a computer remotely control a radio’s frequency, mode, and other settings.
RIT (Receiver Incremental Tuning): A control that shifts the receive frequency slightly without changing the transmit frequency.
AGC (Automatic Gain Control): A circuit that automatically adjusts receiver gain to keep audio output at a consistent level.
Squelch: A circuit that mutes receiver audio until a signal of sufficient strength is present, eliminating background noise.
PL Tone / CTCSS (Continuous Tone-Coded Squelch System): A sub-audible tone used to selectively open a receiver’s squelch, commonly required to access a repeater.
DCS (Digital-Coded Squelch): A digital alternative to CTCSS that performs the same selective squelch function using a coded data stream instead of a tone.
PTT (Push To Talk): The button or switch that keys a radio into transmit mode.
VOX (Voice Operated Transmit): A feature that automatically keys the transmitter when it detects voice audio, without needing to press PTT.
RF Gain: A receiver control that adjusts sensitivity to incoming signals, useful for managing strong nearby signals.
IF (Intermediate Frequency): An internal frequency a radio converts an incoming signal to during processing, used in superheterodyne receiver design.
SDR (Software Defined Radio): A radio architecture that performs signal processing in software rather than dedicated analog hardware, offering flexibility across modes and frequencies.
QRP: Low-power operation, generally defined as 5 watts or less on CW/digital and 10 watts or less on SSB.
QRO: High-power operation, the opposite of QRP.
Linear Amplifier: An external amplifier that boosts a transceiver’s output power.
Codeplug: The full configuration file loaded onto a digital radio (most commonly DMR), containing channels, contacts, and settings.
CPS (Customer Programming Software): Manufacturer software used to program a radio’s codeplug or channel memory.

Antennas

Dipole: A basic antenna consisting of two equal-length elements fed at the center, one of the simplest and most common HF antenna designs.
Vertical: An antenna oriented vertically, radiating omnidirectionally in the horizontal plane, popular for its compact footprint.
Yagi: A directional antenna with a driven element plus additional reflector and director elements, used to concentrate signal in one direction for added gain.
J-Pole: A vertical antenna design fed near the bottom using a matching section shaped like the letter J, popular for VHF/UHF because it can be built cheaply from tubing or wire.
EFHW (End-Fed Half-Wave): A popular portable HF antenna design fed at one end rather than the center, requiring an impedance-matching transformer.
Long Wire / Random Wire: A simple wire antenna of arbitrary length, typically requiring an antenna tuner to match impedance.
Loop Antenna: An antenna where the conductor forms a closed loop, available in both large full-size and small magnetic loop configurations.
Mag Loop (Magnetic Loop): A small, high-Q loop antenna popular for compact or stealth HF operation, tuned with a capacitor and generally narrowband.
Beam: General term for a directional antenna, most commonly referring to a Yagi.
Ground Plane: A set of radial elements or a conductive surface that serves as the electrical ground reference for a vertical antenna.
Radiation Pattern: The graphical representation of how an antenna radiates energy in different directions.
Gain: A measure of how effectively an antenna concentrates energy in a particular direction compared to a reference antenna, expressed in dBi or dBd.
Polarization: The orientation of an antenna’s radiated electric field, typically vertical or horizontal, with mismatched polarization between stations causing signal loss.
Take-Off Angle: The vertical angle at which an antenna radiates most of its energy, important for HF propagation over different distances.
NVIS (Near Vertical Incidence Skywave): A propagation technique using a low-mounted horizontal antenna to send signal nearly straight up, ideal for regional HF coverage without long-distance skip.
ATAS (Active Tuning Antenna System): Yaesu’s brand name for a motorized, self-tuning mobile HF whip antenna.
Whip Antenna: A flexible, single-element vertical antenna commonly used on handhelds and mobile installations.

Feedline, RF, and Impedance Matching

Coax (Coaxial Cable): The most common feedline type, consisting of a center conductor, insulating dielectric, and outer shield, characterized by its impedance (commonly 50 ohms in ham radio).
Impedance: The measure of opposition to alternating current flow in a circuit, which must be matched between radio, feedline, and antenna to transfer power efficiently.
SWR (Standing Wave Ratio): A measure of how well an antenna system is impedance-matched to the feedline and radio, with 1:1 being a perfect match and higher ratios indicating reflected power and potential damage risk.
Antenna Tuner (ATU): A device that matches an antenna’s impedance to a radio’s expected impedance, allowing operation even when the antenna itself is not a perfect match.
Balun (Balanced-Unbalanced): A transformer that converts between balanced and unbalanced feedlines, commonly used at the feedpoint of a dipole fed with coax.
Unun (Unbalanced-Unbalanced): A transformer that matches impedance between two unbalanced systems, commonly used on end-fed antennas.
Feedline Loss: Signal loss occurring within the feedline itself, which increases with cable length, frequency, and lower cable quality.
PL-259 / SO-239: The common UHF-series coax connector pair used throughout ham radio, PL-259 being the male plug and SO-239 the female jack.
BNC: A small, quick-connect coax connector commonly found on handheld radios and test equipment.
N Connector: A weatherproof, threaded coax connector rated for higher frequencies and power than PL-259, common on VHF/UHF and higher-end installations.
SMA: A small threaded connector common on handheld radio antennas, available in male and female, and normal and reverse-polarity variants.
Ladder Line / Open Wire Feedline: A balanced, low-loss feedline consisting of two parallel conductors, commonly used with high-impedance or multi-band antennas fed through a tuner.
Choke / Common Mode Choke: A device wound from feedline or a ferrite core, used to suppress unwanted RF current flowing on the outside of a coax shield.
Ground Loop: An unwanted current path caused by multiple ground connections at different potentials, a common source of RF interference.
RF Ground: A grounding system specifically intended to provide a low-impedance path for radio frequency energy, distinct from electrical safety grounding.

Modes and Digital Voice/Data Acronyms

SSB (Single Sideband): The standard analog voice mode on HF, more spectrum-efficient than AM.
FM (Frequency Modulation): The standard analog voice mode on VHF/UHF, including most repeater operation.
CW (Continuous Wave): Morse code operation, one of the oldest and most spectrum-efficient modes still in active use.
DMR (Digital Mobile Radio): A digital voice standard using TDMA to fit two conversations into one channel, widely adopted in ham radio through networks like BrandMeister.
D-STAR: Icom’s digital voice and data protocol, one of the earliest ham-focused digital modes, using its own network of reflectors.
System Fusion (C4FM): Yaesu’s digital voice mode and network, using the WIRES-X system for internet linking.
P25 (Project 25): A public safety-focused digital voice standard, primarily used by police, fire, and EMS agencies rather than hobbyist hams.
NXDN: A digital voice standard developed by Icom and Kenwood, common in commercial and some ham VHF/UHF use.
FT8: A weak-signal digital mode built for making quick, reliable HF contacts even under poor propagation, part of the WSJT-X software suite.
FT4: A faster variant of FT8, designed for contest-style operation.
PSK31: An early keyboard-to-keyboard digital text mode, still in occasional use on HF.
RTTY (Radioteletype): An older digital text mode using frequency-shift keying, still popular in HF contesting.
Winlink: An email-over-radio system used heavily in EmComm, allowing full email functionality without internet access.
VARA: A modern high-speed data mode, commonly used as the transport layer for Winlink.
APRS (Automatic Packet Reporting System): A packet-based system for real-time position tracking, messaging, and telemetry over ham radio.
Packet Radio: An older digital mode transmitting data in discrete packets, the technical foundation APRS was built on.
SSTV (Slow Scan Television): A mode for transmitting still images over radio, popular for its novelty and occasional use during ISS special events.
Meshtastic: An open-source LoRa-based mesh networking system, not amateur-radio-specific but frequently used alongside ham gear for off-grid messaging.

DMR-Specific Terms

Talkgroup: A virtual channel on a DMR network that a group of users can join, similar in concept to a repeater but existing purely in software.
Time Slot: One of the two TDMA divisions of a single DMR channel, allowing two separate conversations on the same frequency.
DMR ID: A unique numeric identifier, obtained through registration, required for any station transmitting on a DMR network.
BrandMeister: One of the largest global DMR networks connecting repeaters and hotspots.
Hotspot: A small personal device that connects a digital radio to the internet, letting an operator access DMR, D-STAR, or Fusion networks without a nearby repeater.
Zone: A grouping of channels within a DMR codeplug, used to organize large channel lists into manageable sets.
Color Code: DMR’s equivalent of a CTCSS tone, a value that must match between radio and repeater for the connection to work.

Operating Terms, Q-Codes, and Procedure

QSO: A conversation or contact between two stations.
QRZ: “Who is calling me?”, also the name of a popular callsign lookup website.
QTH: One’s location.
QSL: Confirmation of a contact, often exchanged as a physical or electronic QSL card.
QRM: Man-made interference.
QRN: Natural or atmospheric noise interference.
73: Best regards, a traditional sign-off.
Rag Chew: A long, casual conversation, as opposed to a quick contact.
Net: A scheduled, organized on-air gathering, often with a net control station managing check-ins and traffic.
Net Control: The station coordinating a net, managing who transmits and when.
Phonetic Alphabet: A standardized set of words (Alpha, Bravo, Charlie, and so on) used to clearly spell out callsigns and words over voice.
Break / Breaker: A call used to interrupt an ongoing conversation, typically for emergency or priority traffic.
Roger: Acknowledgment that a transmission was received and understood.
Over: Indicates the end of a transmission and invites a response.
Out: Indicates the end of a conversation, with no response expected.
DX Cluster: An online or radio-based system where operators report DX stations they have heard, helping others find rare contacts.
Contest / Contesting: Competitive operating events where stations try to make as many contacts as possible under specific rules within a time limit.
Fox Hunt / T-Hunting: An activity locating a hidden transmitter using direction-finding techniques.

Portable Operating, POTA, and SOTA

POTA (Parks on the Air): A program encouraging operation from designated parks, with activators setting up temporary stations and hunters contacting them from home.
SOTA (Summits on the Air): Similar to POTA but focused specifically on operating from qualifying mountain summits.
Activator: An operator setting up and transmitting from a POTA or SOTA location.
Hunter: An operator contacting activators from a home or other fixed station rather than activating themselves.
Field Day: ARRL’s annual nationwide operating event simulating emergency, off-grid operation.
Portable Operation: Any operation conducted away from a fixed home station, typically battery or generator powered.

Power, Batteries, and Field Electrical

LiFePO4 (Lithium Iron Phosphate): A lithium battery chemistry favored in ham radio for its safety, cycle life, and stable voltage under load compared to other lithium chemistries.
AGM (Absorbent Glass Mat): A sealed lead-acid battery type, heavier than lithium but historically common for backup power.
MPPT (Maximum Power Point Tracking): A solar charge controller technology that maximizes energy harvest from a solar panel under varying conditions.
DC-DC Charger: A charger that converts one DC voltage source to properly charge a battery of a different chemistry or voltage, commonly used to charge an auxiliary battery from a vehicle alternator.
Amp-Hour (Ah): A measure of battery capacity, indicating how many amps a battery can supply over one hour.
Anderson Powerpole: A widely standardized DC power connector in ham radio, allowing radios and power sources from different manufacturers to interconnect easily.

Emergency Communications and Preparedness

EmComm (Emergency Communications): The general practice of using amateur radio to support emergency response and served agencies.
ARES (Amateur Radio Emergency Service): An ARRL-sponsored volunteer organization providing emergency communications support.
RACES (Radio Amateur Civil Emergency Service): A government-sponsored emergency communications program, often working alongside or overlapping with ARES.
Served Agency: The organization, such as a Red Cross chapter or local emergency management office, that an EmComm group provides communications support to.
SHTF: Preparedness community shorthand for a major societal or infrastructure breakdown scenario.
PACE Plan: A communications planning method standing for Primary, Alternate, Contingency, and Emergency, used to build layered backup communication methods.
Traffic (as in “handling traffic”): Formal message handling, often following the National Traffic System format for relaying messages through a network of stations.
NTS (National Traffic System): A structured, ARRL-affiliated network for relaying formal written messages across the country by radio.

GMRS, FRS, and Non-Amateur Radio Services

GMRS (General Mobile Radio Service): A licensed (but no-test) UHF radio service allowing higher power and repeater use than FRS, popular for family and off-road communications.
FRS (Family Radio Service): An unlicensed, low-power UHF radio service intended for short-range personal use.
MURS (Multi-Use Radio Service): An unlicensed VHF radio service with a small set of designated frequencies, popular for low-power business and personal use.
CB (Citizens Band): An unlicensed HF radio service around 27 MHz, historically popular for trucking and casual short-range communication.

Software and Logging

Logging Software: Software used to record contact details for record-keeping, awards tracking, and QSL management.
ADIF (Amateur Data Interchange Format): A standardized file format for exchanging log data between different logging programs.
LoTW (Logbook of The World): ARRL’s electronic QSL confirmation system, used heavily for award verification like DXCC and WAS.
eQSL: A separate electronic QSL confirmation service, distinct from and not directly interoperable with LoTW.
TQSL: The ARRL certificate and signing software required to upload logs to LoTW.
GridTracker: Software that visualizes FT8 and other WSJT-X mode activity on a map in real time.

If a term you have run into is not covered here, drop it in the comments and I will add it. This page is meant to grow as the hobby’s vocabulary keeps expanding, which it never really stops doing.

The Complete Ham Radio Glossary: Definitions and Acronyms for Every Corner of the Hobby