"Tauno Voipio" wrote:
...
If the sidetone is missing, either the audio path is
broken or the radio does not transmit properly. There
is a slight possibility that the sidetone receiving circuit is
the culprit, but it's so simple that the probability is tiny.

In the current Narco digital stuff, it isn't so simple at all. Can
be cantankerous.

Assuming that the radio behaves in another plane,

I wish I were clear on this, as I thought it works for a while then
doesn't. If heat is causing that, then no assumption can be made
that the stack gets as hot in the other plane. The probable
circuit fault if such the case draws zip, so it doesn't heat up.
It would be other heat, from within and/or external to the box.

Reg,
Fred F.