The BC-639A is a ground based AM VHF receiver covering the nominal frequency range of 100 -156 m/cs. The set was built for the U.S. Army Air Force in WW2 as part of a communication system to communicate with aircraft. A system of similar intent was built in Australia during WW2 by Radio Corporation of Victoria (ASTOR), with the addition of FM facilities. This system used the ARl7 receiver and ATl7 transmitter. Many of the sets had been modified after the war by the then Dept of Civil Aviation for use as monitoring receivers.This type was used at the AeradioThe BC-639A is a ground based AM VHF receiver covering the nominal frequency range of 100 -156 m/cs. The set was built for the U.S. Army Air Force in WW2 as part of a communication system to communicate with aircraft. Dark grey US Military colourradio receiver, bc 639, bc 639a, 639, aeradio