From: utzoo!decvax!harpo!eagle!karn
Newsgroups: net.ham-radio
Title: Interference
Article-I.D.: eagle.731
Posted: Mon Jan 17 23:55:57 1983
Received: Thu Jan 20 01:48:12 1983

Here's a book I can recommend to anyone interested in the details of
interference troubleshooting:

Interference Handbook, by William R. Nelson, WA6FQG, Former RFI
Investigator, Southern California Edison Company.

As you might expect from the author's former job, he is very thorough in
his discussion of the myriad ways power distribution networks can cause
RFI.  His method is very similar to the one Peter Hardie used to find his
noisy transformer.

I got interested in the problem of power line interference by
necessity (the usual route.)  When I lived in Illinois, a dual 138kv
transmission line passed my house 10 houses away.  As it turned out, the poles
near my house were not a problem, but the "corner towers" 1/2 mile away
where the line made a Z turn along a road toward a substation.  The symptoms
were somewhat strange: slowly rising horizontal static "bars" on the TV,
and intermittent broadband noise pulses ruining 2 meter SSB (especially
Oscar-7 mode B) reception. During heavy rainstorms, the noise would go
away instead of getting worse!

Although Oscar-7 failed in the summer of 1981, and I subsequently moved
to NJ without the problem never really being resolved, I was reasonably
certain I understood the problem.

Ground lines running across the top of high-voltage towers are there to
take lightning strikes, which could occur as often as every day or two
during the late summer in Illinois.  Although the ground lines were firmly
clamped to the towers on the straight runs, at the corners a double-loop
"dead-end" was used, with no hard connection between the ground line and
the tower.

Significant amounts of current were induced in the ground line from the
power conductors, and arcing occured at the dead-ends.  When it rained,
however, my theory is that it temporarily suppressed the arcing and
the interference.

Fighting power line interference can be an exhausting experience.  I
spent many hours on the phone, riding around with the Naperville
Electric Co maintenance men, and in desperation, writing letters to
the Mayor and the FCC, all with only partial success. 

The best medicine is preventative - don't live near a large power line!!

Phil Karn, KA9Q/2