What is Squelch Circuit?
Good receiver design begins with the RF and IF filtering, but another important part of the receiver circuitry is the squelch system, or RF detection circuitry. This circuitry is the “gate” that allows the audio to turn on or off based on the RF signals entering the receiver. Simple gate squelch circuits that are commonly used in most competitive wireless receivers have a detector circuit that opens the audio path as soon as a preset level of RF energy is reached. When the signal is below the preset level, the audio path is “closed” or grounded to be very quiet. The obvious problem with a simple gate squelch is that any RF energy including distortion, hiss, harmonics from such sources as lighting dimmers, CD or DVD players, computers, digital effects and electric motors are indistinguishable from the desired signal. This extraneous RF energy will open the squelch gate just as easily as the intended transmitter. So, often times the user must “crank” up the squelch level all the way up t
