"scratchy" radio transmission

It is odd that he has a clear "sidetone", receives fine, and yet the
transmission is scratchy (apparently on both radios?). Also that both
radios apparently benchcheck fine.

Jim, do you have an audio mix panel, and if so does the mic input go
to it before splitting to the radios? Also, I read your original post
pretty quickly and didn't notice the part where you said you were
hearing the sidetone okay. That eliminates a lot of potential failure
points.

Another thought: Do you have an "intercom" that both mics and the PTTs
connect to before the mic audio gets to the radios? If so, the intercom
could be the culprit. There are so many ways that your aircraft could
be wired up that its hard for me to think of all of them. You could
probably get to the bottom of it all pretty quickly with an oscilloscope
if you have one and know how to use it.

RST, if both radios have the same static problem (with their different
RF XMIT sections, T/R switches, and antennas), it is not very likely an
RF problem.

OTOH, it could be a DC voltage problem, as in the DC voltage supply to
the radios is too low, causing the transmit power to be less than it
should.

Jim, have you tried both radios and verified that ATC hears them both as
scratchy?

Don W.

RST Engineering wrote:

If, as you have told us, the sidetone is clear and loud, then the odds of it
being in the microphone/jacks/PTT switch are nearly zero. My bet is an RF
problem of some sort.

And why would you consider some sort of "debounce" circuit? DO you have a
clue what a debounce circuit does?

Jim




wrote in message
oups.com...

If it was a broken/loose wire in the mic circuit I would think I would
not get a good sidetone in the headset. Have seriously cleaned both of
the mic jacks but now that you mention it I'll bet it could be the PTT
button (duh!). I probably need to make a debounce circuit or something
if possible. At least I could try taking a passenger to try the rear
xmit button. Thanks for the "wake up call".

Jim