automatic wellenbereichsumschalter for hochfrequenzempfangsgeraete

摘要

The waveband change-over switch, for HF or VHF receivers, has an oscillator with a varactor diode and tunable resonant circuit. A pre-tuning circuit contains another varactor and resonant circuit. The two resonant circuits are switched by diodes that receive their bias voltages depending on the result of a comparison between the selected tuning voltage and the voltage obtained by frequency/voltage converting the output of the oscillator circuit. A differential amplifier acts as comparator, and switches the waveband accordingly.