Dictionary of Ham Radio Terms

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A
AC : Alternating Current

ADC : Analogue to Digital Converter. Also known as A/D and A-to-D. A device that samples an analogue wave and converts it into a digital signal, in which a series of numbers is used to represent the amplitude of the original wave.

ADIF : Amateur Data Interchange Format, a standard specification for format of exported logbook files.

Admittance : The reciprocal of impedance of a component in a series or parallel tuned circuit.

AF : Abbreviation for Audio Frequency. AF is in the range 20Hz to 20 000Hz

AFC : Automatic Frequency Control - used to prevent drift in FM receivers

AFSK : Audio Frequency Shift Keying.

AGC : Automatic Gain Control - a feedback system to reduce fading by automatically adjusting gain

AGL : (Height) Above Ground Level, for antenna installations.

ALC : Automatic Level Control - a feedback system in the transmitter output amplifier used to prevent overload.

 Ampere :(A) The unit used for measurement of current. Usually abbreviated to Amps

Amplitude : the height of a wave from the average or median position.

AMSAT : The name for amateur radio satellite organizations world-wide, but in particular the Radio Amateur Satellite Corporation.

AM : Amlpitude Modulation

Amplifier : A device that is used to increase voltage, current or power.

AMTOR : A specialised form of RTTY protocol. An acronym for AMateur Teleprinting Over Radio or AMateur Teletype over Radio.

Analog (also analogue): a continuously varying signal.

ANC, ANR : Active noise control, active noise reduction. Also referred to as automatic noise cancellation or antinoise on some transceivers.

 Antenna: a device to either radiate radio signals or to receive them from another station.

Antenna Switch " A switch used to change the output of a transceiver from one antenna to another.

 Antenna Tuner : A device used to match the output impedance of a transmitter to that of an antenna.

Anti-VOX : Transceiver circuitry used in voice-operated (VOX) stations to prevent audio from the receiver's speaker from actuating the voice-operated transmitter.

APRS : Automatic Position Reporting System, Automated Packet Reporting System.

ARC : Amateur Radio Club (also ARA, ARS - Amateur Radio Association, Amateur Radio Society) - usually prefixed by the name of the community or region served

ARDF : Amateur Radio Direction Finding

ARES : Amateur Radio Disaster Services, Amateur Radio Emergency Services

ARRL : The American Radio Relay League - the national ham radio association for the USA

ARISS : Amateur Radio on the International Space Station. A program that allows schools, with the help of an amateur club, to contact the amateur station on board the International space station.

ASL : Above Sea Level. Vertical height in metres or feet above sea level.

 Attenuator : A resistive device to reduce the amplitude or power of a signal.

ATS : Automatic Transfer Switch, switches equipment to a backup power supply in event of power failure.

ATV : Amateur Television - "moving picture" ham TV transmissions.

Az/El : used to describe an antenna rotator that can change both the Azimuth (horizontal) and the Elevation (vertical) direction of the antenna.

Azimuth : The horizontal direction (angle) measured clockwise from North.