[RFI] My power line noise problems, revisited (Warning, this islong!) No...

[Pete Smith]

At 11:33 PM 2/5/04 -0500, Tom Rauch wrote:
>I think when the smoke clears you'll find about 90% of the problems are
>slack spans allowing bell insulators to hang loosly and have pins corrode
>and arc, or other loose hardware or metal in the strong electric field area
>near the wires (like brackets) arcing. Sometimes the tie wires that secure
>the primary to knob insulators don't have a solid contact with the primary
>and arc. Sometimes they drill holes through poles and have two isolated
>pieces of metal near the primary in losses contact and arcing.


Amen.  I have had very good cooperation from my power company, as long as I 
can identify the pole or poles that were involved, because the local 
maintenance district does not have the equipment or knowledgeable people 
any more -- downsizing.  About 95 percent of the problems I've found and 
they have fixed were slack spans that were installed with taut span 
hardware -- in slack spans, this produces the exact problem Tom 
describes.  They have new hardware that involves a rigidly mounted 
insulator on each end and fixes the problem right.

The other noise-maker I found and they fixed was a lightning arrestor 
mounted with two lag screws through the bracket.  A woodpecker had 
undermined one of them so that the screw was loose, and it was so close to 
the 7500 volts that the field induced differing voltages on the bolt and 
bracket, producing mini-arcs.  Here, the lineman told me that the newer 
hardware has only one bolt; in effect, they would rather have the bracket 
come off the pole entirely than have hard-to-find loose hardware.

My noise-locating strategy involves the car radio, set to AM, followed by a 
portable SW radio, followed by a DFer built from the design in QST with a 
Moxon rectangle antenna at 136 MHz.  I listen threugh it with a 
shirt-pocket handi-talkie that has AM receive.  The Moxon has a nice deep 
null off the rear that makes it easy to first follow the maximum signal, 
then turn the antenna around to verify which pole it is.  If there's any 
doubt, rattling guy wires or thumping the pole will produce an easily 
identifiable change in the noise.


73, Pete N4ZR
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