APRSAutomatic Position Reporting System – provides position reporting using GPS and TNC
ARESAmateur Radio Emergency Service, sponsored by ARRL
ARRLAmerican Radio Relay League
channel The pair of input and output frequencies used by a repeater
closedA repeater with access limited to a select group (see open repeater)
coverageThe geographic area within which the repeater provides communications
CTCSS Continuous Tone-controlled Squelch System – a series of subaudible tones that some repeaters use to restrict access
digipeatera packet radio (digital) repeater
DTMF Dual-tone Multifrequency – a series of tones generated from a keypad on a ham radio transceiver
duplexAn operating mode where the transmit and receive frequencies are different
FMFrequency Modulation – Encoding information in a carrier wave by varying the instantaneous frequency of the wave
GPSGlobal Positioning System – a satellite network that provides precise location information
hamAn informal name for an amateur radio operator or enthusiast
hamfestA meeting often combining trade show, exhibits, forums, fleamarkets, and other activities of interest to amateur radio enthusiasts
hand-held A small, lightweight portable transceiver small enough to be carried easily
HFHigh Frequency – Radio signals between 3 and 30 MHz (1.9 MHz is normally also included)
HzHertz – a measure of cycles per second
NCSnet control station
netnetwork of stations
NWSNational Weather Service
offsetThe difference between transmit and receive frequencies (see split)
openA repeater with access that is not limited (see closed repeater)
PLPrivate Line – a tone used for filtering radio transmissions
simplexAn operating mode where the transmit and receive frequency is the same
SkywarnA network of NWS-trained volunteer storm spotters
split The difference (in kHz) between a repeater’s transmitter and receiver frequencies; also called separation
TNCTerminal Node Controller – a modem for data communication
VHFVery High Frequency – Radio signals between 30 and 300 MHz
UHFUltra High Frequency – Radio signals between 300 and 3,000 MHz
VARCVicksburg Amateur Radio Club
VEVolunteer Examiner – Licensed, accredited amateur radio volunteers who prepare and administer amateur service operator license examinations

For a comprehensive glossary of amateur radio terms see the ARRL Ham Radio Glossary.