[RFI] CASE HISTORY - Powerline - Multiple Sources (re-post w/o errata)

[Mike Martin]

That's all good stuff Eddie

⁣Be safe,
Mike Martin
RFI Services
51 W Bay Front Rd
Lothian, MD 20711
240-508-3760​

On Sep 29, 2021, 11:50 AM, at 11:50 AM, "EDWARDS, EDDIE J via RFI" <rfi at contesting.com> wrote:
>Alan, 
>
>Sorry for my delayed post on this subject.  Some things previously
>mentioned on this group by the professional RFI investigators who have
>posted in the past but I wasn't sure if you were aware of in your post:
>
>1. In older neighborhoods with older power lines, you should be able to
>find dozens and maybe over 100 RFI sources within a short distance to
>your station.  Not all of them are creating RFI being picked up at the
>location of you antenna(s).  And the utility is not required to fix all
>of them if they are not causing harmful interference to anyone.  
>
>2. Best way to verify that a source in the field is your RFI source on
>your radio is to get a noise signature on a scope, save it on the
>scope, then go into the field and find a matching noise signature in
>the field.  One ham on the list has done this using his ears, but most
>of us with tinnitus need visual scope readings.  LOL
>
>3. If you let multiple sources ramp up, you will be "pealing the onion"
>as you remove the loud sources first only to find less strong ones
>below that layer.  You may have found this to be the situation in your
>case.  
>
>4. Back in the pre-cable, pre-streaming TV days, it was the utilities
>responsibility to find and repair RFI sources causing interference to
>TV or radios.  It is to their benefit to perform their work tasks in
>the most efficient way possible.  So it is to their benefit to have
>trained and well equipped RFI investigators.  Not all utilities will be
>this efficient as you have found.  Utility's budgets and internal
>politics can interfere with these tasks.  But the FCC's viewpoint is
>that it is the utilities responsibility to find and eliminate harmful
>interference from their equipment and only their equipment. The ham
>should only verify that it is from the utility's equipment and not his
>own or his neighbors'. 
>
>5. Always continue to listen at higher and higher frequencies when
>searching for RFI sources on powerlines.  You should be able to confirm
>a source by finding it at 300Mhz or higher.  If you cannot hear it that
>high, keep moving down the line until it gets stronger or fades away. 
>And it is possible it is not from the utility equipment at all if it is
>not broadband noise.  
>
>
>73, de ed -K0iL
>
>
>-----Original Message-----
>From: RFI <rfi-bounces+eedwards=oppd.com at contesting.com> On Behalf Of
>Alan Higbie
>Sent: Thursday, September 23, 2021 11:21 AM
>To: Rfi List <rfi at contesting.com>
>Subject: [RFI] CASE HISTORY - Powerline - Multiple Sources (re-post w/o
>errata)
>
>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
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