Re: [RFI] Power Line Noise Specific to 15 meters

[Michael Carter <Mike.Carter@unh.edu>]

Pete,

Does your noise remain constant in intensity/signal strength
across the 15 meter band?  If not, you may have a non-power
line source to hunt.

If you have an oscilloscope, place its probe across the
speaker/headphone output and set the scope trigger
source to LINE.  If you see a stable waveform (and you
don't have an AC hum source in the receiver/transceiver
you're using), then the RFI is likely synchronized with
the power line.

There isn't really a "fundamental" for power line
arc noise - the arcing creates a very wideband
(up into the upper UHF range) excitation for the
distribution wiring.  The length of the conductor
that is excited does affect the relative intensity
of the received arc noise as does the frequency
selectivity of your antenna.

Others on this forum have pointed out that
a band-specific, arc noise-like source may be
due to the arc exciting a piece of hardware
(e.g. pole guy)  with length close to a resonant
length for the band on which you find the
RFI to be strongest.

I'd check first to be sure that your received
noise (absent any real signals in the passband,
of course) is synchronized with the AC power line
before hunting the source.

One more tip: if the RFI doesn't abate when
it's raining, it is likely not an external power line
arc source.  My local power line RFI goes away
whenever we have a damp morning or a good
steady rain.

73,
Mike, K8CN
________________________________
From: RFI <rfi-bounces+mike.carter=unh.edu@contesting.com> on behalf of Pete 
Smith N4ZR <pete.n4zr@gmail.com>
Sent: Sunday, October 3, 2021 4:01 PM
To: RFI List <rfi@contesting.com>
Subject: [RFI] Power Line Noise Specific to 15 meters

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This is a bit of a puzzle, to me anyway.  With my tribander pointed in
one direction (west), I have extremely bad what sounds like line noise.
This noise is not audible on 20 meters, on 10 meters, or on lower bands
using my Carolina Windom.  I won't be able to get out and try to DF it
for 10 days or so, but I always thought line noise got progressively
worse as you went down in frequency toward its fundamental.  What am I
missing, or what should I be looking for?

--
73, Pete N4ZR
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