I have a radio with a really horrible squelch. When the knob is all the way to most sensitive, the squelch has problems, the noise is not constant, the noise comes on and goes off.

When the antenna is disconnected, I hear the noise when the squelch is at the most sensitive point.

When I connect the antenna, this noise goes away, and the squelch has major problems, because I can not turn it to least sensitivity.

What is going on? Why would connecting an antenna make the squelch deactivate?

The squelch is for VHF, the Alinco DR-600 radio

  • $\begingroup$ How long is the cable between the antenna and the rig? It could be that the cable itself attenuates a bit of noise, so the noise floor goes below the minimum level required to turn the squelch off. $\endgroup$ – AndrejaKo Jul 21 '14 at 10:08
  • $\begingroup$ Huh? When you turn the squelch to most sensitive, you should expect noise. And when the antenna is connected, you "can not turn it to least sensitivity"? Why not? $\endgroup$ – Phil Frost - W8II Jul 21 '14 at 11:09
  • $\begingroup$ Something is wrong with the radio, when I turn the squelch knob down, it sometimes does not have noise. $\endgroup$ – Skyler 440 Jul 22 '14 at 17:28
  • $\begingroup$ It did it with an antenna with 6 ft and an antenna with 10 feet coax $\endgroup$ – Skyler 440 Jul 22 '14 at 17:30
  • $\begingroup$ I find your entire description ambiguous. Which way is turning the squelch "down"? Is that the same direction as "most sensitive", or the opposite direction? What's preventing you from turning it to least sensitivity, whichever way that is? Does "noise goes away" mean you hear a signal, or the audio is muted entirely? $\endgroup$ – Phil Frost - W8II Jul 25 '14 at 17:15

There seems to be quite a bit of confusion. First you should tell us if the squelch is for a VHF/UHF set, or some HF equipment. They are very different!

A VHF or UHF squelch works by detecting the disappearance (or at least lessening) of noise. That means you can't turn the knob clockwise for increasing sensitivity. The 'most sensitive' point is the point where the squelch is just on (below) the limit between letting the noise pass or not. If you connect an antenna, when the squelch is just open (i.e. lets the noise pass), it can happen that it then closes because of the extra noise coming in. It's just doing its job.

An HF squelch on the other hand, generally works by measuring the signal strength. Its most sensitive point is also between 0 and max, but increasing the noise with the connection of an antenna, generally tends to 'open' the squelch.

In both cases, the 'most sensitive' point is the limit between opening and closing the noise.

EDIT: As you update the question to specify it's a VHF radio, a 'de-activation' of the squelch (i.e. the passing of the noise), may indicate that some specific frequencies are absent from the antenna noise, which makes the squelch think that there is a valid signal on the input. This could be something like electric noise (possibly from fluorescent tubes), or some other source. Could be even some broadband signal such as an oscillation.

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  • $\begingroup$ I'm not even sure what the question means by "deactivate". Does that mean he's expecting audio to be muted but it isn't? Or expecting muting, but is hearing some audio? Or that the radio isn't sensitive to the presence or absence of signal, and the audio is either unconditionally muted or not muted? $\endgroup$ – Phil Frost - W8II Jul 25 '14 at 17:13
  • $\begingroup$ Exactly... I'm not quite sure either. $\endgroup$ – jcoppens Jul 26 '14 at 0:16

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