Glossary
Radio and emergency prep run on jargon. Here's every term the rest of the site leans on, in plain English and in alphabetical order - jump to a letter or use your browser's find. Terms in a definition link to their own entry; where a term has a full guide, there's a link to it.
A
- AM - amplitude modulation; an older, simpler voice mode, what CB and AM broadcast radio use. Reliable, but uses more bandwidth than the alternatives.
- Amateur radio - the licensed radio hobby and service, informally "ham"; the only personal option with real power, HF access, repeaters, and legal room to experiment.
- ARES - the Amateur Radio Emergency Service: licensed volunteers who pass traffic when normal comms fail.
- ARL numbered messages - pre-agreed numbered phrases, so "ARL SIXTY" carries a whole sentence in two words. Reference →
- ARRL - the American Radio Relay League, the national association for amateur radio: study materials, band charts, advocacy.
B
- Band - a range of frequencies grouped together for a purpose. Hams name theirs by wavelength (the 2-meter band, the 80-meter band); the broad groupings are HF, VHF, and UHF. A radio only works the bands it's built for.
C
- CB - Citizens Band; license-free 27 MHz radio, 40 channels, the old trucker band. The services compared →
- Crystal set - a receiver so simple it needs no battery, running on the energy of the received signal itself; the classic "foxhole radio." More →
- CTCSS / DCS - see Privacy codes.
- CW - continuous wave; on-off keyed Morse code, the toughest-to-kill signal on the air. Learn it →
D
- Digital modes - computer-decoded modes (FT8 and its relatives) that pull tiny signals out of the noise for surprising distance on very low power.
E
- EAS - the Emergency Alert System; interrupts TV and radio with official alerts.
- Extra - the top of the three US ham license classes. See Technician.
F
- FCC - the Federal Communications Commission, which licenses and regulates US radio.
- FM - frequency modulation; the clean, static-resistant voice mode used on VHF/UHF and FM broadcast, short-range but quiet.
- Foxhole radio - see Crystal set.
- FRS - the Family Radio Service; license-free UHF bubble-pack walkie-talkies. Which to get →
- FT8 - see Digital modes.
G
- General - the middle of the three US ham license classes. See Technician.
- GMRS - the General Mobile Radio Service; a licensed UHF service ($35, no exam) with more power and repeaters.
H
- Ham - see Amateur radio.
- Handheld - a "handie-talkie" (HT), the walkie-talkie-style portable radio.
- HF - high frequency, 3-30 MHz: the low bands, where signals can bounce off the ionosphere and travel thousands of miles, unpredictably. CB and much of ham radio live here.
- HT - see Handheld.
I
- IPAWS - the Integrated Public Alert & Warning System; the federal backbone that feeds alerts to EAS, weather radios, and phones.
L
- Line of sight - at VHF and UHF, signals travel in nearly straight lines; put a hill or the horizon in the way and they generally don't get there.
M
N
- Net - a scheduled on-air gathering where operators check in by turn - where the skill actually gets built.
- NOAA / NWS - the National Oceanic and Atmospheric Administration and its National Weather Service, the source of official US weather warnings.
- NWR - NOAA Weather Radio; the nationwide network of VHF transmitters broadcasting weather 24/7 with automatic warning tones. Find your station →
- NTS - the National Traffic System; the volunteer network that relays written messages by radio. See Radiogram.
P
- Part 95 / Part 97 - the FCC rule sections: Part 95 covers the personal services (CB/FRS/GMRS/MURS), Part 97 covers amateur (ham) radio.
- Phonetic alphabet - Alpha-Bravo-Charlie letter spelling, so a word survives a noisy channel. More →
- Precedence - a message's priority (Routine / Priority / Emergency) so the system triages under load.
- Privacy codes - a sub-tone (CTCSS or DCS) that keeps your radio quiet unless someone uses the same code. It adds no real privacy - anyone can still hear you - so in an emergency, turn it off and hear everyone.
Q
- Q-codes - three-letter on-air shorthand inherited from the telegraph era (QSL, QRZ, QRN...). The ones worth knowing →
- QSO - a two-way radio contact or conversation.
R
- Radio horizon - how far a line-of-sight signal reaches before the curve of the earth cuts it off - a little farther than what your eye can see. Full explanation →
- Radiogram - the standard form for relaying a written message accurately by voice, carried through the NTS. How it works →
- Repeater - a community-run receiver-transmitter, usually high on a tower or hilltop and often on backup power, that rebroadcasts your signal to cover a whole county. GMRS and ham radio use them; FRS, MURS, and CB don't.
- RTL-SDR - the ~$40 USB dongle that kicked off cheap software-defined radio. See SDR.
S
- SAME - Specific Area Message Encoding: the digital county code a weather radio watches for so it only alarms for your area, not three counties over. The one feature worth paying for. More →
- SDR - software-defined radio; a USB dongle plus a phone or PC that receives across a huge span of frequencies, with the tuning done in software. More →
- Simplex - two radios talking directly to each other, no infrastructure in between.
- Skip - skywave; HF signals reflecting off the ionosphere to distant places and then fading, which is why CB range is a lottery.
- SKYWARN® - the National Weather Service's trained volunteer storm-spotter network. More →
- SOS - the international Morse distress signal (· · · – – – · · ·), chosen for being simple and unmistakable.
- SSB - single sideband; the efficient long-haul voice mode on HF, squeezing more range out of the same power than AM or FM.
T
- Technician / General / Extra - the three US ham license classes, in order; Technician is the entry exam. What it's like →
- Tropospheric ducting - a weather condition that bends VHF/UHF signals far past the normal horizon, occasionally hundreds of miles. More →
- Type-accepted - FCC-certified to operate legally on a given service. A radio meant for ham use (a Baofeng) generally is not type-accepted for FRS or GMRS.
U
- UHF - ultra high frequency, ~300 MHz-3 GHz: FRS, GMRS, and the 70-centimeter ham band. Shorter range in the open, but threads through buildings and cities better than VHF.
- UPS - an uninterruptible power supply; a battery box that keeps gear alive through outages and flickers, good household sense on its own. More →
V
- VHF - very high frequency, ~30-300 MHz: the 2-meter ham band, MURS, marine, and NOAA weather radio. Carries well over open ground, roughly line-of-sight.