This past week I spent a considerable amount of time out in the brutal cold
and snow tracking down RFI at Mike's (W9RE) QTH.
On the first day I had limited time and Mike and I tracked the RFI down to
an area 2.6 miles away from Mike's house where we could also hear it on VHF
but we had a hard time believing this was correct as this was almost a mile
more than anything I had previously tracked down.
I then came back down a second time to Mike's and everything pointed me
right back to the general area we wound up at on the 1st day's attempt but
at this new location (0.3 miles from the 1st days location) we did not hear
the signal on VHF. All of the tracking to get us close was done on 160
meters as the RFI was not detected at Mike's on 80 meters or higher and due
to the brutal cold I had to skip some steps that I would normally take
looking at higher bands on my SDR receiver when getting closer to the
source.
I then went back a 3rd day and did direction finding but from a totally
different direction (angle) than Mike's house (and starting from 2.8 miles
away from the eventual source) and everything led me right back down to the
same general area but a lot of times the 160 meter DFing headings did not
converge upon each other and at times I felt like I was just pointing
perpendicular to high voltage transmission lines versus right at the source
regardless if using my portable flag or tuned loop (I had witnessed this
situation a long time ago on another case).
It turns out the first location on day 1 where we heard the RFI on VHF was
indeed legit and I went back to that location and my 4 element VHF yagi
pointed me right at a group of poles which were 0.2 miles away. I then
switched to UHF with a 4 element yagi and isolated the RFI to a 138 kV
transmission line structure that was running parallel to a distribution
line as well as a much higher transmission line. I documented this case
the best I could considering the brutal conditions and here is a link to a
youtube video I just uploaded that documents this case.
https://youtu.be/jeBNCAFmoiE
Mike and I fortunately have a great working relationship with the "Radio
Group" at AES who respond to RFI complaints (I even trained this group late
in 2025 on the use of the portable flag they purchased for use with their
Radar Engineers model 243 receiver). We called AES and told them of our
finding and using their model 243 receiver as well as Radar Engineers
parabolic ultrasonic dish they confirmed the structure we identified as the
problem was indeed generating the RFI and they have written a work order to
get it repaired/overhauled.
This case was made more difficult because the RFI goes away when
temperatures get much above the mid to upper 20's.
Just FYI for those interested in this kind of stuff.
73,
Don (wd8dsb)
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