Hi Scott,
I can guarantee you that in 1 previous case I had where the MF/HF antennas
pointed perpendicular to the transmission line instead of the pole
generating the RFI was due to the signal we were chasing and not another
RFI source and I was not standing near the transmission line (I always
stand as far from power lines as possible and in this previous case I stood
in the middle of farm fields). I eventually found the source of RFI, and
in that case I was able to turn on and off the RFI at the pole (I will not
divulge online how I was able to do that in order to avoid stirring up a
rats nest but please trust me when I say it was a complete fluke/accident
in an attempt to view the wooden power poles pole identification number).
When I turned the RFI off at the pole the signal along the lines that
caused my DF antennas to point perpendicular to the lines was gone and the
DF antennas no longer could detect any RFI regardless of what direction
they pointed but when I turned the RFI back on the DF antennas (portable
flag as well as tuned loop) pointed perpendicular to the lines versus back
at the faulty pole when located about a half mile down the line from the
pole as an example (and I was standing out in the middle of farm fields
versus next to the power lines).
In numerous power line cases I've been involved with including this one
there was no noticeable change in the pattern as the arcing was
occurring 100% of the time (but yes if you listen very closely you can
sometimes hear variation which can be helpful). The noise to the NE at
Mike's house which we were not chasing definitely had an irregular pattern
and it was very easy to differentiate it from what we were chasing and we
totally ignored that signal which actually went away after our 1st day of
tracking.
Also on 160 meters the near field extends out at least 0.2 miles which
likely comes into play and that's why I prefer moving up in frequency as I
approach the source when conditions permit but I was often suffering near
frostbite conditions on my fingers during this recent case so I had to take
lots of short cuts.
73,
Don (wd8dsb)
On Tue, Feb 10, 2026 at 1:52 PM K9MA <k9ma@sdellington.us> wrote:
> On 2/9/2026 4:31 PM, Don Kirk wrote:
> > 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
> This issue can often be avoided by relaying the RFI heard on the station
> receiver, so you can hear it while you are tracking. There is almost
> always a pattern of fluctuations in the noise. When they match, you know
> you are hearing the correct source. This is the same principle as
> "signature analysis", but you don't need an extremely expensive piece of
> equipment, just a couple 2 meter radios. (Cell phone latency is too high.)
>
> The station receiver should be in the AM mode, AGC off, and RF gain
> reduced to avoid overload, if necessary.
>
> 73,
> Scott K9MA
>
> --
> Scott K9MA
>
> k9ma@sdellington.us
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