On Mon, 23 Oct 2006 16:25:05 -0400, W9RE wrote:
>Any suggestions as far as isolating the problem?
Consider the possibility (even the liklihood) that the problem is
not in your system, and may even be miles away! All of the things
that could cause detection in your antenna could do the same at
the connection of any pieces of wire (or downspout, or building
cornice), with the same conductors that receive the signal then
re-radiating it. Perhaps when you thought you had gotten rid of
it, you were listening on some combo of antennas that killed it
with directivity.
I was bothered by exactly such a problem when I lived in Chicago,
and a few of the spurs were quite strong. They pulsed, varied in
strength, disappeared, and reappeared. I went nuts firming up
every electrical connection in my antenna farm, grounding, and
counterpoise, but never did kill it. Here in CA, I occasionally
hear signals just above the noise floor on 1810, 1820, and 1830.
Back in WV where I had my first ham ticket, I was about a mile
from 5kW on 930 and 5kW on 1470. That resulted in a VERY strong
spur on 3870 kHz. I got rid of it by moving to Chicago when I
graduated college. :)
Spurs like this CAN be generated in the output stages of
transmitters if they aren't well decoupled and filtered. VHF/UHF
sites require that every transmiter include a "circulator" that
prevents this. At least one mfr of professional wireless mics
includes a circulator in their higher priced transmitters. A year
to two ago, W8JI tracked down some products on 160 to a shortwave
broadcaster in the SE US and they were fixed.
Jim
_______________________________________________
RFI mailing list
RFI@contesting.com
http://lists.contesting.com/mailman/listinfo/rfi
|