Noise suppression circuit for VHF stereo radio receiver - controls audio cross-talk attenuation according to amplitude of HF carrier and of LF signal

摘要

The noise suppression circuit has stages (8-11) to vary the crosstalk attenuation between the two sound channels in accordance with the magnitude of the LF signal taken from the FM demodulator (3). The crosstalk attenuation is reduced as the LF signal reduces in amplitude. The normal control signal for the cross talk attenuation is obtained from the HF carrier amplitude and passed to the stereo decoder (4) via an amplifier (8). The amplifier's gain is controlled by a voltage obtained from the FM demodulator (3) via a rectifier (9).