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Pinpointing Powerline Radiation

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Subject: Pinpointing Powerline Radiation
From: (ken smith)
Date: Thu, 23 Jan 1997 23:01:10 -0500
At 12:00 PM 1/23/97 -0800, ve7av wrote:

>- At this point you should involve your power company.......

>At work I like using a spectrum analyzer in the vehicle. I usually look at 1
>to 200 MHz and can frequently drive up to the pole. An IFR 1200 and external
>attenuator box works great too!  Then I use an HP Ultra Sonic Detector which
>frequently points to the problem area on the power pole. (The detector is a
>small parabolic dish with ultra sonic microphone - very directional). Then I
>give the powerpole markings and any additional details to the power company.
>   Frank -

I find that there are two noise sources that can occurr. The ultra sonic
will pick up the type that occur when there is a physical arc or vibration ,
but misses a lot of the high frequency sources. Also if you use a spectrum
analyser be aware of the antenna being used as I find that there are some
false noise peaks that can occur due to the resonant frequencies of the
antenna. Also just because you find a noise peak at a pole doesn't always
mean that the source is there. I have found on a couple of occurences that
the actual noise source was located at a D.S. lightning arrestor more than
10 km away from the area where the noise was a problem, and I figures that
the noise was transmitted down the line( like a spark gap feeding a twin
lead) and the conditions were right at the offending pole to radiate the noise.

Also I would hope that any recent lines that have gone up are using clamp
top insulators, as the older tye wire types are very prone to loosening and
causing noise. A good starting point if you narrow the problem to a
pole.Cross arm hardware is also a frequent source.


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