I would start by disconnecting the antennas from ALL of the receivers
or if the antenna does not have a separate connector then removing the
receivers and using the hand held to detect the offending signal. If
you inject a strong enough signal into the antenna input you force the
receiver's RF amp into overload and it generates the intermod products
and sends them back OUT the same antenna to be picked up by the other
antenna's
There is one brand of ELT that is infamous for this type of problem
but I can not remember the model and brand.

On 4 Nov 2003 06:01:30 -0800, (Snowbird)
wrote:

wrote in message .. .

What you have here is a pretty classic case of intermodulation
interference.

Elliot, given what we did, is there a way to pinpoint what
signals might be the source of the problem?

Given the lat-long, is there a way to find out what antennas
are located there?

Is there something which might be a problem in our radios,
which could be fixed?

Yes, it is possible that the mixing
could be taking place in some corrosion of an antenna mounting or some such,
but that is, in my opinion, far less likely.

Well, one of the things which we did when the problem started
was take off all the easily-accessible antennae and clean the
connectors and check their ground. They all looked very good,
very well sealed and tight although the comm antennae didn't
have as strong ground as I'd like at first. The only antennae
we didn't check were the VOR/Glideslope because they're way
up at the top of the horizontal stab. and a b**ch to get at.

So unless it's the VOR antenna, I don't think corrosion in the
antenna mounting is likely, either.

At this point the question is whether the interference poses a threat to
safety or merely an annoyance. When the interference "breaks squelch while
you are tuned to the TRACON freq are you still able to hear the controller
when he/she transmits?

On one installed radio and the handheld, yes. On the other installed
radio, the controller becomes very faint against a background of
continued noise.

It may be a good idea for you to notify the FAA about the problem.

OK, I was thinking about this. Can you suggest which person in the
FSDO I'd ask for?

Thanks,
Sydney