Squelch Control is found on the majority of CB and Amateur radios and is a noise limiter designed to reduce background noise levels.
When we switch on a radio, you hear a hissing noise along with local interference depending on where you live. Over a period of time, this noise can be very annoying. So to stop this, you can turn up the squelch knob until the noise has gone. If you where to turn the knob to the full position you would not be able to hear any noise or any stations, so it is important that you set the squelch to the weakest station on the channel otherwise you won’t be able to hear them.
Setting the Squelch control is great when you are talking to stations which are close to you, but if any weak stations come in, you will not be able to hear them as the squelch would be turned up to block out the hissing noise and weaker stations.
So bare this in mind when your setting your squelch control.