If it was not snowing at the time then it was likely dirty or damaged
insulators on the primary power line. The noise could be conducted quite a
distance on the primary wire so would cover a big area. Noise like that may
sometimes only occur when things are damp because the small amount of
moisture will cause arcing through small cracks or across dirt on the
insulators, but when it is fully wet by rain it may stop... so try to check
in the morning if there is dew, or just as rain starts, or when snow or ice
is melting as you have seen. Be prepared to check a relatively large area,
a mile or two would not be surprising. Since you are looking for arcing the
higher you can go in frequency the closer you can define the source, vhf or
uhf AM or SSB receivers are good, especially with hand held yagis...
ultrasonic dishes are good for locating the source once you have it down to
a pole or two. Beware, there may be more than one source, especially if it
is a contamination problem... if you are downwind of plowed farmland or
industrial area contamination can be a real problem.
David Robbins K1TTT
e-mail: mailto:k1ttt@arrl.net
web: http://wiki.k1ttt.net
AR-Cluster node: 145.69MHz or telnet://k1ttt.net
-----Original Message-----
From: Matt [mailto:wedgef5@gmail.com]
Sent: Friday, March 15, 2013 20:22
To: rfi@contesting.com
Subject: [RFI] Strong, broadband noise during wet conditions
I'm having a problem with very strong, very broad noise that seems to be
associated with wet conditions. We recently had two significant snowfalls,
and of course everything was very wet as the snow melted.
The noise I have is just a constant grinding (I can't think of a better term
to describe it) that is virtually continuous from 40m up through 10m. It is
worst on 40-20m. The snow is all melted now and things have dried out a
bit, and my noise level is back down to normal. The connection to the
moisture is a subjective evaluation, but I've observed the high noise level
during wet conditions, which then abated upon drying, on at least two
occasions.
I had a friend come by with a mobile HF installation to see if he could hear
it in my driveway, and perhaps isolate it to something inside the house.
Not only could he hear it in the driveway, but he could also hear it 1.5
miles away as he drove home!
My initial thought is something power line related, but I thought I'd bounce
it off of the RFI experts on here. I'm not sure what else could produce
such strong noise over such a wide area.
Thoughts?
Matt, N0EYE
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