We had a similar problem here in Sacramento. Our power utility technician
used a vhf receiver and a 4 element yagi to spot which pole was the site of
the noise (or at least which group of poles) and then pinpointed the
offending phase conductor and its associated insulator with an ultrasonic
microphone (with parabolic reflector).
The noise went away when they fixed the physical problem.
I had run around with a $15,000 spectrum analyzer using a 19" external whip
without much success at locating the exact culprit. The mobile radio
interference test set (am radio mounted in ford van) gave a audible
indication as to the general location of the noise source. (radio got
louder when we got closer).
The offending pole and insulator were about 300 feet from where we heard the
loudest buzz on the am radio. What I'm trying to say is that it's very
difficult to locate the exact source with an omni antenna. It's difficult
with the proper test equipment if you're not experienced.
I've done this several times before in the area around W6GO's. I found the
trouble only once. It was a bird's nest built aroud a drop conductor fuse.
I was able to show him the cause of the rfi.
Other times I have only gotten close, except for once where the arc was so
pronounced that I could not only see it, but I heard it (which caused me to
look up to see it)
An experienced interference tech is a valuable commodity.
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