in my experience (and I just concluded finding another one a few weeks ago,
the power company finally isolated it and confirmed it) when the noise
remains in the rain it is a transformer issue - micro arc inside or
something in the bushings internal where weather doesn't affect it. I
realize there can be other noise sources that continue in wet weather but I
haven't seen that, not on local distribution at 14kv. Internal arcs do not
seem to have much VHF energy (not that gets out of the can anyway) but they
are wicked at lower HF frequencies like 40m and down.
73 Don
VE6JY
On Mon, Oct 11, 2010 at 7:37 PM, Hare, Ed W1RFI <w1rfi@arrl.org> wrote:
> Maybe, but not necessarily. Some power-line noises can continue in the
> rain. Anecdotally, it has been reported to me that insulators that
> develop noise tend to not have that noise diminish in the rain. Of
> course, noisy devices in neighbors' homes also don't diminish in the
> rain, either. If I had 120-Hz noise that didn't change when it got
> really wet, I'd not rule out power-line noise, but would give a bit more
> thought to what man-made source it could be.
>
> If noise does go away when it gets wet, that usually tells you that it
> is outside. Mosture can short out a weak spark or tracking source. More
> likely, it tends to make wood increase in size, so old wooden structures
> can have loose things tightened up by the rain.
>
> Mike Martin is smarter than I am, so he may have some addition (better)
> words of wisdom.
>
> Ed Hare, W1RFI
> ARRL - The national association for Amateur Radio
> ARRL Laboratory Manager
> 225 Main St
> Newington, CT 06111
> Tel: 860-594-0318
> Internet: W1RFI@arrl.org
> Web: http://www.arrl.org/
> Member: IEEE, Standards Association, Electromagnetic Compatibility
> Society
> Secretary: IEEE, Connecticut Chapter
> Secretary: IEEE EMC Society Standards Development Committee
> Member: ASC C63 EMC Committee, Chairman: Subcommittee 5, Immunity
> Vice Chair: IEEE P1775 BPL EMC Committee
> Member: ICES SCC-28 RF Safety
> Member: Society of Automotive Engineers EMC/EMR Committee
> Board of Directors: QRP Amateur Radio Club International
>
> >-----Original Message-----
> >From: Kim Elmore [mailto:cw_de_n5op@sbcglobal.net]
> >Sent: Monday, October 11, 2010 8:20 AM
> >To: rfi@contesting.com
> >Subject: [RFI] POwer line noise (cont)
> >
> >After a night of rain, we have a foggy morning. I was
> >expecting quiet on the bands. but absolutely NOTHING has
> >changed! I still have 120 Hz power line noise of S9 + 20 dB on
> >40 M in AM mode with 6 kHz bandwidth.
> >
> >Is this telling me something significant?
> >
> >73,
> >
> >Kim Elmore, N5OP
> >
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> >RFI@contesting.com
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> >
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