Automatic circuit synchronisation in superheterodyne receiver - uses tuner voltage to balance deviation of difference frequency between main input and auxiliary oscillators

摘要

The input circuit with an electronic turner is synchronised with the oscillator circuit (main oscillator) oscillating at a higher frequency than the intermediate frequency. A second, auxiliary oscillator has a tuner identical with those of the input circuit. A difference frequency in the intermediate frequency range is produced from the main oscillator frequency and the auxiliary freqeuncy. Deviation of the difference frequency from the intermediate frequency is balanced outby a control voltage applied to the auxiliary oscillator. Its amplitude depends on the size of the diviations, and the same control voltage is also applied to the input circuit.