TV receiver preventing black and white impulse noise - controls centre frequency of bandpass filter by strength of received signal

摘要

The t.v. receiver has the centre frequency of the bandpass filter that selects the t.v. signal for passing to the FM detector lying between the frequency corresp. to the average level of the video signal and a frequency corresp. to the white signal level. The t.v. signal is produced by frequency modulation by the video signal. A frequency converter is connected to an oscillator whose frequency is set by the strength of the t.v. signal. Alternatively, the bandpass filter contains varactor diodes in its resonant circuits whose capacitance is set by a control voltage derived from the strength of the t.v. signal.