Squelch Add-On

Recent feedback from our readers indicated that the VHF Airband Receiver described in our March 2002 issue has received a warm welcome. However, some of you have expressed some concern about the absence of noise suppression under no-signal conditions. Well, here is the circuit you need.Silence, please!Squelch is a system used to prevent weak, unintelligible signals and random noise (produced by the demodulator and receiver RF and IF amplifiers) from being heard by a radio operator while still allowing intelligible signals to be heard normally.