---------- Forwarded message ----------
To: <towertalk@contesting.com>
Date: Tue, 13 May 1997 17:02:24 -0700 (PDT)
From: Pat Barthelow <aa6eg@tmx.com>
To: AA4NC@aol.com
Subject: Re: [TowerTalk] power line noise
Hi AA4NC (what's the name?)
Pat, AA6EG here from the NPS ARC. We have a guru that consults with the
Navy on noise amelioration for Navy HF receiving sites who gave a talk
about the art recently...at the K6LY club meeting. Yes! There are standing
waves of noise on
lines that can mislead you as to the source of the noise, due to their
spatial offsets from the noise source. There is a systematic way to go
after your noise, in fact our GURU, Professor Vincent, of ECE department, at
NPS Literally wrote the NAVY Reference (internal, unfortunately) book on
procedures to locate noise sources..., but look with an AM VHF receiver to
do the close in
work on locating the source.....Also, the noise going away when wet can
point to MANY different problems, probably NOT insulators. In fact
DIRTY INSULATORS DO NOT CAUSE HF noise interference, according to Prof
Vincent. Look for loose, rusty, or corroded metal fittings which develop
oxide coatings that are "puncutured" by the high voltage fields during
each swing of the AC waveform....Especially bad are Bell shaped insulator
stacks, especially those that are not under large mechanical strain. If
a noisy bell insulator is found, have the power company replace the bell
insulators with a newer type, called Epoxylator...worked wonders here.....
TOO MUCH TO GO INTO DETAIL HERE, but if you want to know more, get back
to me and I will refer you to the GURU, or one of his followers....
good luck....
73, de Pat, AA6EG/N6IJ; aa6eg@tmx.com
On Tue, 13 May 1997 AA4NC@aol.com wrote:
> I hope this subject is kosher for this reflector...
>
> I'm working on getting rid of a particularly nasty case of power line noise.
> I would appreciate any guidance that any of you folks could offer:
>
> Have any of you ever had a noise case that seemed to "propagate" down a line
> to show up at another spot? According to the technician that has been working
> with me, the noise source is showing up 65 degrees from the direction where
> my strongest interference is showing on 10 and 6 meters.
> My interference peaks at about a 45 degree heading (where two 13.2kV poles
> are located that have been noisy in the past). The tech. tells me that he
> sees nothing at those poles (with RF and ultrasonic testers), but has
> identified a large buzz about 300' down the same line (this pole is about 340
> degrees azimuth from my station).
> I hear almost no noise at this heading on several different frequency /
> antenna combinations.
>
> Is this one for the X Files, or is it common for noise to propagate down a
> line in a similar fashion to a transmission line and peak at a point that is
> some distance away from its source?
>
> Another very noticeable sysmptom - The noise almost goes away completely in
> high humidity / wet conditions, and is strong in dry conditions. I would
> think that this would suggest problems with insulators, but the tech. says
> it's not necessarily so.
> Their "fixes" so far have been to "tighten the hell out of everything" which
> seems to last anywhere from a couple days to a month. It is a major chore
> getting the interference tech. out here, and even harder to get the line crew
> scheduled. Keep in mind I work for the utility and I think I'm getting
> "preferential" treatment. I pity the service that outsiders probably get...
>
> Thanks - CU at Dayton,
>
> Will AA4NC
>
> --
> FAQ on WWW: http://www.contesting.com/towertalkfaq.html
> Submissions: towertalk@contesting.com
> Administrative requests: towertalk-REQUEST@contesting.com
> Problems: owner-towertalk@contesting.com
>
--
FAQ on WWW: http://www.contesting.com/towertalkfaq.html
Submissions: towertalk@contesting.com
Administrative requests: towertalk-REQUEST@contesting.com
Problems: owner-towertalk@contesting.com
|