Narrow band FM demodulator

  
For FM demodulation applications where the bandwidth is less than 10% of the carrier frequency, an XR-J567 can be used to detect the presence of the carrier signal. The output of the XR-567 is used to turn off the FM demodulator when no carrier is present, thus acting as a squelch. In the circuit shown, an XR-215 FM demodulator is used because of its wide dynamic range, high signal/noise ratio and low distortion.
Narrow band FM demodulator - schematic

The XR-567 will detect the presence of a carrier at frequencies up to 500 kHz.