Airband

From Wikipedia, the free encyclopedia

A Bendix/King KY197 Airband VHF communication radio mounted above a Cessna ARC RT-359A Transponder (the beige box) in a light airplane instrument panel. The VHF radio displays the active frequency of 122.8 MHz and a standby frequency of 121.5 MHz.

The airband or air band is the band of frequencies used for radio communication in aviation. Airband is used to mean the VHF band between 108 MHz and 137 MHz, which covers its use for commercial and general aviation, radionavigational aids, air traffic control and other uses. In common use among aviation professionals, the band of frequencies is sometimes referred to as VHF or Victor. Military aircraft also operate using additional frequencies (225 - 400 MHz) which are not part of the airband.

The lower part of the band, from 108 to 117.975 MHz, is reserved for navigational aids such as VOR beacons, ATIS and ASOS messages, and precision approach systems such as ILS or LAAS. Some types of aviation-related stations, such as NDBs and DMEs, do not operate on these frequencies; in the case of NDBs the longwave frequency band is used. The rest of the airband is allocated to voice communications using amplitude modulation.

Channel spacing on the airband has been 25 kHz, but increasing congestion has led to further subdivision into 8.33 kHz channels in some areas. A switch to digital radios has been contemplated, as this would greatly increase capacity by reducing bandwidth. However, this has yet to happen, partly because the mobility of aircraft necessitates complete international coordination.