Re: Why is aeronautical VHF AM?
Regarding squelch and sensitivity, the Pye Westminster radios had a variable gain control on the IF strip, this could be set so that with just enough gain that the squelch could be left open with just detectable noise, and that was how my base station operated for many years.
The only time we had any noise was in the sporadic 'E' season when we had eastern European radio stations breaking in, but they would have done that anyway even if the squelch was operative.
You can't possibly use all the gain that the receiver had, you could only hear signals above what would have been the squelch level anyway so I can't see why that system was not used universally - but I'm sure someone will tell me.
Peter
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