VHF Era
The use of aircraft for search and rescue in World War II brought line-of-sight VHF radios into use. The much shorter wavelengths of VHF allowed a simple dipole or whip antenna to be effective. Early devices included the British Walter, a compact single vacuum tube oscillator design operating at 177 MHz (1.7 meter wavelength), and the German Jäger (NS-4), a two-tube master oscillator power amplifier design at 58.5 and, later, 42 MHz. These were small enough to include in life rafts used on single-seat fighter aircraft.
Post-war designs included the British Search And Rescue And Homing beacon (SARAH) beacon, the U.S. AN/URC-4 and the Soviet R 855U. These operated on the aircraft emergency frequencies of 121.5 and 243 MHz (2.5 and 1.2 meter wavelengths).
Read more about this topic: Survival Radio, History
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