Hi Scott,
Great point and I normally try and match up fluctuations when possible but
I can’t be certain on this one as it did not fluctuate (it was on constant
versus the easy find I had 2 days earlier). I will know pretty soon as the
utility company in this area usually responds to our reported cases within
a few days time (usually next day). The reason I actually wanted to track
it down yesterday was because it had become so constantly on but that
prevented matching up fluctuations. The only thing I can go on in this
case is that we did wind up with final heading matching up closely with his
4 element HF beam at 112 feet heading and also very little alternative
sources between Dan’s house and the pole in question (lots of open farm
land and only one other string of poles between Dan’s and the suspect pole
which where on Dan’s road running North/South which were clean up on VHF).
So you are absolutely correct that I’m jumping to conclusions about this
one, and I will report back as soon as the utility company responds.
But the real purpose of my posting was that this was the first case of
power line RFI hunting I have done in which case ground based tracking on
HF made absolutely no sense as the direction finding gear always appeared
to point perpendicular to these specific lines regardless how much I walked
the lines even though I made sure I was back away from the lines a great
distance (typically 300 to 500 feet away from the lines) and this situation
existed on 1.8 MHz as well as 24.9 MHz. If I went far enough North of
these East/West lines I could hear and see on my SDR display similar noise
coming from the NW direction but that did not match what Dan’s 4 element
beam yielded which was NNE, and definitely no longer A North direction
which is what the portable HF gear indicated when South of these lines
(very confusing situation to say the least). It appeared if I was South of
the lines I would always point North which was perpendicular to the lines
and if I got a reasonable distance North of the lines I would point NW
which definitely did not agree with Dans HF beam at 112 feet.
Keeping my fingers crossed and getting the suspect pole fixed will
hopefully clear up my direction finding confusion even if it’s not the
source of Dan’s problem as it’s definitely polluting the East/West string
of poles I mentioned.
Thanks again for the comment and I was kind of expecting it from someone
(including myself). I will provide update as soon as the utility company
responds.
73,
Don (wd8dsb)
On Wed, Mar 10, 2021 at 12:07 AM K9MA <k9ma@sdellington.us> wrote:
> I presume that you know that was the right source because the problem
> went away after it was fixed. However, you don't say how you knew you
> were tracking the right source earlier. I've also tracked a lot of power
> line RFI, and have found that this is a huge issue. You will hear many
> noise sources while walking or driving around, most of which are NOT the
> one causing you the problem. My solution is to simultaneously listen to
> the noise relayed from the receiver at home and the tracking receiver.
> There are almost always fluctuations in the noise. When they match, I
> know I have the right source.
>
> 73,
> Scott K9MA
>
>
>
> On 3/9/2021 6:27 PM, Don Kirk wrote:
> > 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.) Today I decided
> to
> > follow up on this RFI and using both my portable flag as well as a tuned
> > loop the direction indicated the noise was North from Dans QTH. I did
> some
> > tracking and both antennas kept pointing perpendicular to some power
> lines
> > a long distance North from Dans that were running East/West along a major
> > road and I was standing a good distance from the lines out in farm
> fields.
> > No matter where I walked my antennas kept indicating the signal was
> coming
> > from the lines with my antennas always pointing perpendicular to the
> lines
> > for peak signal even when I was hundreds of feet away from the lines
> (like
> > 500 feet or more away from the lines). Dans 4 square receive antenna
> > system (DX Engineering 4 square receive array) indicated the signal was
> > about equal when pointing NE and NW which pretty much agreed with the
> North
> > direction my portable flag and tuned loop indicated and the East/West
> power
> > lines are 0.75 miles North of his receive array. I started to get the
> > feeling that the ground wave signal from the pole generating the signal
> was
> > weaker than the signal propagating down the line in our direction, and
> > therefore I could not detect the RFI directly from the faulty pole with
> my
> > ground based antennas.
> >
> > We therefore looked for another frequency where the powerline RFI might
> be
> > heard from Dans, and using his horizontal HF beam (4 element beam up at
> 112
> > feet) we found the signal up on 24.9 MHz and it was strongest when
> pointing
> > NNE. Again my portable flag and tuned loop used on 24.9 MHz indicated
> the
> > signal was coming from the North (antennas perpendicular to the power
> > lines) when standing at Dans house very far from these lines (0.75 miles
> > from the lines). I then decided traditional direction finding was not
> > going to work. I then used my tuned loop adjusted for 24.9 MHz and with
> > receiver gain backed way down I drove the East/West lines with my small
> > tuned loop sticking out the window until I could hear the signal on 24.9
> > MHz. I then got out of my car and used my portable 4 element beam on 135
> > MHz and quickly found the faulty pole but the faulty pole was different
> > than all other poles I have located in the past from an RFI level
> > standpoint. I normally have to use 20 to 30 dB of attenuation with my
> 135
> > MHz receiver and 4 element portable beam to isolate a faulty pole, but I
> > actually was able to isolate the pole from nearby poles using no
> > attenuation at all but 10 dB of attenuation was ideal. This pole was
> > definitely generating RFI and I could even see low level of RFI coming
> from
> > it up on 437 MHz with a portable 4 element beam with SDR receiver, but it
> > was generating the weakest amount of RFI than I have ever encountered
> with
> > a power pole and I believe this is what caused traditional radio
> direction
> > finding to be useless (propagated signal along the lines was stronger
> than
> > the ground wave signal when viewed from Dans house). The faulty pole
> > turned out to be located 0.84 miles from Dan at a heading of 44 degrees
> > which really is not very far compared with other faulty poles we have
> > encountered at his QTH and some have been double that distance while
> > generating much stronger RFI. When close to the pole (few hundred feet
> > away as an example) my traditional HF direction finding techniques using
> > both my portable flag as well as tuned loop worked great and pointed
> > directly at the faulty pole which I was happy to see but this sure had me
> > scratching my head as I spent many hours tracking down this faulty pole.
> >
> > I just wanted to share this experience as it was definitely frustrating,
> > but I'm glad I didn't give up. I suspect others may unknowingly run
> into a
> > similar situation but hopefully it will be few and far between.
> >
> > P.S. I had my easiest powerline RFI find just a few days ago at Kens
> (KJ9B)
> > and the utility company responded today and said the problem was a bad
> > insulator. You can see my youtube video of this find at
> > https://youtu.be/X_5h-gSc6Ns
> >
> > 73,
> > Don (wd8dsb)
> > _______________________________________________
> > RFI mailing list
> > RFI@contesting.com
> > http://lists.contesting.com/mailman/listinfo/rfi
>
>
> --
> Scott K9MA
>
> k9ma@sdellington.us
>
> _______________________________________________
> RFI mailing list
> RFI@contesting.com
> http://lists.contesting.com/mailman/listinfo/rfi
>
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