Rain can also fill small gaps in hardware causing the arcing to become just
a steady current. It can also increase conductivity of dirty or damaged
insulator surfaces so again they pass a continuous current without arcing.
There are some other odd circumstances where even fiber optic cables and
dirty or salty insulators can arc or flashover when rain stops or very light
rain or even fog starts... look up terms like 'dry band arcing'.
David Robbins K1TTT
e-mail: mailto:k1ttt@arrl.net
web: http://wiki.k1ttt.net
AR-Cluster node: telnet://k1ttt.net:7373
-----Original Message-----
From: RFI <rfi-bounces+k1ttt=arrl.net@contesting.com> On Behalf Of Hare, Ed,
W1RFI
Sent: Sunday, August 8, 2021 12:47
To: qrv@kd4e.com; rfi@contesting.com
Subject: Re: [RFI] Line noise vs Frequency
The most common effect is that rain or high humidity swells wood structures,
tightening up hardware on the pole.
The cause is pretty much secondary, because you aren't going to be able to
fix it. Find the pole, learn what you can and the utility can usually take
it from there.
________________________________
From: RFI <rfi-bounces+w1rfi=arrl.org@contesting.com> on behalf of
qrv@kd4e.com <qrv@kd4e.com>
Sent: Sunday, August 8, 2021 11:40 AM
To: rfi@contesting.com <rfi@contesting.com>
Subject: Re: [RFI] Line noise vs Frequency
If the rain is stopping it - perhaps the conductivity of the soil is a
variable?
I seem to recall that they have a soil additive to improve grounding. (Salt
works, but eats the wire!)
Just a thought ...
kd4e
> Interesting you would bring this up. My current 120hz target peaks at
> roughly 19.5mhz. Falling off below roughly 10mhz to where its almost
> insignificant and goes up to about the 2 meter band where its very
> weak with directional antennas. I started hunting it after the power
> co fixed my primary source back in the spring. I had isolated to a ~3'
> area of ground wire stapled to the pole, I think. 7.2kv 3 phase pole
> with lots of hardware so not easy to tell with ultrasonic dish. I
> wanted to do some more investigating but then came the high Tennessee
> humidity for the summer and the target has been >98% absent.
>
> I greatly suspect it will return more frequently with the lower
> humidity in late Sept/Oct forward. A few days ago the humidity got
> down to close to 60% and it returned for a few hours.
>
> Its on a pole in my back yard thus very close in proximity to my
> antennas. As to why the peak, I would be interested to know also. Some
> of the utility hardware of such a length it resonates on a certain
> frequency? Just a guess.
>
> One thing is for sure, an open mind is essential to hunting this
> stuff, lol. My biggest surprise is finding 3 sources on 2 poles so far
> related to the stapled ground wire. The one they fixed I actually saw
> it arcing with binoculars. Another due to a crepe myrtle growing
> around the pole (and stapled ground wire). Cut the limbs off it and it
> was gone. And this third one that appears right now to be related to
> the stapled ground but that has yet to be resolved.
>
> Chuck
>
> W4NBO
>
>
>
> On 8/8/21 7:24 AM, Pete Smith N4ZR wrote:
>> A (probably) dumb question: I have a severe line noise to my west.
>> For some reason it is manageable on 20, much worse on 15 and
>> crippling on 10. These subjective descriptions are confirmed on my
>> S-meter. Why would this be happening, and does it offer any helpful
>> clues to finding the source?
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