Squelch

On any given frequency, there’s always a certain amount of noise present. This is generated by a range of things that include other electronic devices and interactions between the sun and our atmosphere. However, when using radio, listening to a bunch of noise generally isn’t pleasant. As a result, radios typically have a squelch setting.

Quite simply, this is a minimum level that the received signal must achieve before it will be played on the speaker. This value is adjustable in most radios and allows one to turn off the noise. The downside of this is that if you have the squelch turned up too high, you’ll miss faint signals, etc. It’s a tradeoff between convenience and capability.

Generally, VHF and UHF frequencies are better for utilizing squelch. These bands are “cleaner” and have less noise. Additionally, with the FM modulation used, it’s generally easier to detect signals vs the noise. As a result, it’s normal on a VHF or UHF band to have complete silence until someone “breaks squelch” and begins transmitting.

On HF frequencies, you’ll generally have to put up with some amount of noise. These are inherently noisy bands, and you’re generally working with signals that may be very faint (coming from far away after bouncing off the ionosphere). As a result, use squelch carefully on these bands or you may risk missing many signals entirely.