This retired E.F. Johnson, VHF, half-duplex transceiver supported the 132-142,142-150, 150-162, 162-174 frequencies. The RF100 required an FCC frequency assignment and a frequency-matched antenna and cable. It was powered by the data logger or an external rechargeable 12 Vdc power supply (5 Ahr minimum capacity required). E.F. Johnson model 3420