Similar story here, but never had much doubt about
presence of multiple arc sources at different poles,
all within about 1/2 mile or less from my house, based
on my own DF'ing efforts.
Bottom line: local electrical utility sent out very
competent RFI DF personnel, they independently confirmed
all of my offending arc source locations (more than 20!).
Although I certainly didn't request it, their report led to
replacement of 13 poles and all new hardware and transformers
on those poles.
The unfortunate part: I still hear power line arc noise across
the HF range. The search for more distant arc sources
continues.
Mike, K8CN
Durham NH
________________________________
From: RFI <rfi-bounces+mike.carter=unh.edu@contesting.com> on behalf
of Alan Higbie <alan.higbie@gmail.com>
Sent: Thursday, September 23, 2021 12:06 PM
To: Rfi List <rfi@contesting.com>
Subject: [RFI] CASE HISTORY - Powerline - Multiple Sources
CAUTION: This email originated from outside of the University System.
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Amongst the usual residential area microprocessor RFI trash, I have
also
endured powerline RFI at my station for years. I only operate on 160
to 6
meters. Sometimes it gets worse - sometimes it subsides somewhat. Wind,
moisture, and frequency dependent.
I have kept an RFI log for at least the past 3 years.
Despite my best efforts, finding the location of the source has been
difficult. I didn't want to squander any goodwill with the power
company
by having them come out before I had actually located the offending
pole(s).
I had always assumed I had one RFI source.
I have been using the National Radio HFDF loop with a Tecsun PL660
receiver. And, also I use an SDR (and the Tecsun) with a WD8DSB portable
flag. Also an FT817 on 440 MHz with 7 element yagi.
Eventually, I noted very strong RFI that appeared to be coming from
an area
of a chain-link fence that runs below and parallel to the powerline.
I was
perplexed.
Using my station's SteppIR I finally figured out that on 21 MHz the RFI
peaked in one direction (240 deg.) and on 28 MHz the RFI peaked in
another
(105 deg.).
So, that indicated at least 2 separate sources. There is a power
pole (with a transformer) along each of those headings.
But, I still wondered if this distinction was a result of
re-radiation or
induced RFI.
Eventually, I was awakened in the middle of the night by high winds.
So I
came into the station, flipped on the receiver to note how the suspected
sources were acting. At one point, the 21 MHz predominant source
sputtered
off and the other (28 MHz) kept going. Then I knew for sure I had 2
separate sources!
The next day I emailed our utility RFI guy. I sent pole numbers,
photos of
the hardware on the poles, an aerial map showing my beam headings to
their poles. I asked him to come out. Within a few days he and another
engineer (who is a ham!) showed up with a troubleshooter-lineman and
bucket
truck.
I demonstrated the DF steps I had gone through (station receiver, beam
headings, how the RFI drops dramatically when the SteppIR is put into
the
180 reverse mode).
We DF'ed again outside with the Tecsun and the VHF gear. We walked
to the
1st pole (21 MHz source) and the lineman went up. He inspected and
reported seeing significant deterioration on top of the transformer and
also track marks from arcing. As he poked around with the fiberglass hot
stick - the RFI sputtered and he eventually got it to stop (at least
temporarily).
The utility guys had a Radar Engineers M 331 - but didn't use it today -
relying on my 440 MHz set-up instead.
We repeated the process on the next pole down the line and then the
next.
During the visit, there was much discussion about the age of the
poles/hardware. The subdivision dates to the late 1940's - so the
equipment might be 75 years old. There has been at least one lightning
strike to one of the poles within the past 2 years.
Well, after these sources were calmed down - listened some more - and
still
had RFI coming from close to the same beam heading as one source we had
located. I went hunting with the VHF gear. I was able to confirm
that the
next pole down the line was also generating significant RFI (which I was
still hearing on HF). We had figured this was re-radiated or induced
RFI -
- but it now turns out to be an independent source all on its own. I
have
supplemented my trouble ticket request and am told they will confirm
it, etc.
Note: After the two sources on the poles were quieted down - the
chain-link
fence RFI also went quiet.
The good news: The utility advised yesterday that it will "replace 3 of
those poles and associated equipment" within the next 2 to 5 months.
The bad news: Yesterday I saw my neighbor getting an estimate for a
solar
system.
73, Alan K0AV
Colorado Springs
and honing my DF skills - I finally determined that I actually have 3
separate sources of powerline RFI - on 3 separate poles in the alley
up and
down behind my house.
2 days after we were poking around at your place - I was with Colo.
Spgs.
electric utility guys last Friday doing precisely the same thing we
did at
your place: engineer (also a ham!) + troubleshooter/lineman with a
bucket
truck. And, just like at your place, the lineman poked around the
hardware
with a long fiberglass pole. He located several particular places where
there was active arcing and which had track marks and deteriorated
insulation. It was agreed that the RFI problems resulted from the
age of
their equipment (60 years old) and perhaps lightning strikes.
Bottom line: they emailed yesterday saying they will be completely
replacing 3 poles and their hardware in the next 2 to 4 months!
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