On Mon, 03 Nov 2003 17:39:03 -0600, Jim Stockton
wrote:

It sounds like IMD in the receiver frontend.

It could also be passive intermodulation (PIM). If several high-power
transmitters are at the same location (as in an antenna farm), then
these signals can mix and reradiate. All that is necessary is
dissimilar or corroded metals in the radio towers.

After a Google search, I came up with this reference:

http://www.summitekinstruments.com/p...qcont.html#top

Notice the mention of "rusty bolt noise".

You say that your hand-held radio receives the same interference. Do
other pilots have the same issue? If so, this is a good indication of
PIM. Of course, it could also show that other receivers are similarly
overloaded with some strong out-of-band signals. But, once you have
some more evidence that it is PIM (i.e., others with the same issue),
then perhaps the FCC or the FAA might take an interest in doing an RF
site survey to isolate the cause of it.


Rob-
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Robert Cherney e-mail: rcherney(at)comcast(dot)net