Don,
Great story! Thanks for sharing.
We had a very similar experience near my QTH several years ago affecting my
home location and also another ham on about a mile north of me. Only
difference was it was strong on low bands, and it was strongest on 80 meters at
S9+, and probably on 160meters too but neither of us had antennas for 160 meter
back then. The other ham is a mile north of me and we are both in nearly a
north-south line perpendicular to a 161 KV transmission line.
Also, I should mention that I work in the utility department that is
responsible for tracking power-line noise although it's our technicians that do
these RFI cases regularly. I only get involve in problem case, or in this case
when I am affected at my home shack.
It appeared to be coming from the direction of the161KV line that runs
East-West; however, when the tech was using our new HF loops we had the same
perpendicular indications no matter which direction we traveled. It was
staying strong for 1 to 2 miles in each direction before beginning to fade.
Our mistake was to stay too focused on using HF freqs for tracking that day,
but we were also initially confused by the southwest direction we got at the
ham's QTH 1.5 miles north of the 161KV line. We only switched to VHF/UHF in
the area to the southwest finding nothing there.
We unknowingly drove past the actual source directly south of both ham's QTHes
a few times not realizing this before ending our search at the end of the work
day (techs are union, no OT on RFI cases).
The actual source turned out to be a distribution pole on a 13.8KV line that
ran parallel with the 161KV line for a short distance as it crossed over the
main street perpendicular to both lines to reach a couple houses on that
street. The RFI source was apparently causing induction into the 161KV line
from the shorter 13.8KV line.
We never had to track the source down to fix it. On my way home from the
office that same day, as I drove toward the 161KV line while listening to a
blank spot on my AM radio, it appeared the noise was already gone! As I
approached the 161KV line I see a couple of our utility trucks working to
install a new pole replacing one of the old poles on the line that ran parallel
under the 161KV line. Since the noise never returned, I assume the old pole
that was replaced was our source pole.
Some days you just get lucky!
73, de ed -K0iL
-----Original Message-----
From: RFI <rfi-bounces+eedwards=oppd.com@contesting.com> On Behalf Of Don Kirk
Sent: Tuesday, March 9, 2021 6:27 PM
To: RFI <rfi@contesting.com>
Subject: [RFI] Difficult power line RFI find.
Just thought I should share something that was a first for me when tracking
down power line RFI and man it was frustrating, and I have tracked down a lot
of powerline RFI.
I noticed some weak RFI at Dans (KB9AX) on 160 meters earlier this year but did
not have time to track it down. Dan also complained about the RFI and he
mentioned this week that it was not strong but had become very consistent. It
definitely looked and sounded like powerline noise (120 Hz spikes observed on
audio scope and SDR receiver, etc.) ---snip---
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