CIRCUIT DEVICE FOR INSPECTING RECEIVING QUALITY OF FM RECEIVER

摘要

The signal-quality monitor has a filter (7) connected to the output of the FM demodulator (4). The filter has a relatively narrow bandwidth above the stereo-multiplexed signal inside the IF band. The filter's output is passed to an integrator whose own output is connected to the input of a level comparator (10). The comparator's output is coupled to a control (2) that tunes the receiver or performs other functions. The FM demodulator's output also passes via a bandpass filter (11) and a rectifier (12) to give a dc control signal that operates a switch (8) between the output of the first filter (7) and the rectifier (9) at the comparator's input. The switch acts as a gate and is only active when an LF signal is present. It opens when noise is excessive.