6 Squelch
David Wyatt, Mike Tooley · 2013
Figure 4.10 VHF radio adjustment points Aircraft VHF receivers invariably incorporate a system of muting the receiver audio stages in the absence of an incoming signal. This system is designed to eliminate the annoying and distracting background noise that is present when no signals are being received. Such systems are referred to as squelch and the threshold at which this operates is adjusted (see Figure 4.10) so that the squelch ‘opens’ for a weak signal but ‘closes’ when no signal is present.