How often should you do this? It depends on the flow of traffic at
the time. If there was a constant flow of traffic and then all of a
sudden there is none, be suspicious. Turn the squelch off. However,
if traffic is infrequent and there is no traffic for a while, again,
be suspicious and turn the squelch off.
If you are being jammed,
don't forget to submit an interference report. One precaution should
be noted, however; the Russians have a jammer that transmits noise.
What to do? Change the MHz knob a megacycle up or down, then listen.
If there is noise you know you are not being jammed.
Move the MHz
knob back to correct MHz position.