What is the purpose of the squelch control on aviation radios?

it is a filter type thing that gets rid of a certain level of noise when no audio is being received.

presumably the purpose is to suppress noise

https://www.youtube.com/watch?v=AuoBQlSgNFA

Same as the squelch control on every other radio: if the received signal is below the level set by the squelch control, the radio doesn’t decode it.

diddly-squat said:

presumably the purpose is to suppress noise

Suppress…squelch

Squelch definition Wikipedia

pesce.del.giorno said:

What is the purpose of the squelch control on aviation radios?

Pretty much part of history now. the short-range VHF radios just don’t have it any more, only some of the old-ish HF long-range radio gear does.

you set it to a signal level (done from some stage in the radio) which is the mute threshold, with FM it’s generally set just above noise if wanting everything above noise. With UHF FM that might be same as ~ .3uV on the antenna, or higher if don’t want to hear very weak noisy signals.

depending on the frequency the noise might be atmospheric, electrical (including other radio transmissions), or they might be so low of a particular frequency/band the noise most important is generated in the front-end of the radio receiver.

If squelch function is switched off, is a transmission likely to be unreadable?

pesce.del.giorno said:

If squelch function is switched off, is a transmission likely to be unreadable?

you will just hear noise until a transmission is heard over it, when the transmission ends, its back to the noise

I remember the confusion when the society of short wave radio enthusiasts named Roger took place.

if the threshold is set too high a signal lower than the setting will not be heard, with FM.

with AM which is used in aviation some/still, because stronger signals tend not to completely queeze out weaker signals (like strong FM signals do – you can hear both/all with AM, though weaker signals have less volume), you will only hear a weaker signal (below the threshold) when a stronger one reaches the threshold and opens it up.

if the radios have tone squelch or selcall the situation is that if these are detected, given the radios are set to do so, then they’ll variously open/wake it up. Tone squelch is usually a subaudible tone transmitted which at the receiver is detected by a tone decoder(or whatever) that opens the radio up.