Hi Don,
I've had some of those very constant sources, which makes tracking
harder. Usually, they eventually go into some kind of fluctuations,
often subtle ones. In my case, identifying the right source is
particularly critical, as I live in an urban area surrounded by overhead
power lines, with thousands of potential noise sources nearby. I can
only hope to track down the very worst of them, but many weaker ones
always show up when I'm out tracking. That's less likely to happen in an
area with fewer potential sources.
73,
Scott K9MA
On 3/10/2021 2:19 AM, Don Kirk wrote:
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
<mailto: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 <https://youtu.be/X_5h-gSc6Ns>
>
> 73,
> Don (wd8dsb)
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Scott K9MA
k9ma@sdellington.us <mailto:k9ma@sdellington.us>
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