Tuning circuit for radio receiver - has correcting network deriving varactor tuning voltages from output of discriminator coupled to local oscillator5

摘要

The varactor antenna stage feeds the varactor-tuned RF stage whose output is mixed with the output of the mechanically tuned local oscillator (variable L or C) to give the IF signal. The tuning voltages for the varactors in the antenna and RF stages are derived from a discriminator coupled to the local oscillator's output. The output of the oscillator is coupled to a frequency-voltage converter that contains the discriminator. The discriminator is also varactor tuned and its output feeds a correcting network that produces the tuning voltages for all 3 varactor diodes.