Looking for some help with the following problem, if possible, (I'm going
to 'throw a handful of rice at the side of the barn and see if any sticks'
wrt to background information - just in case some of the ancillary info is
actually more useful than I might have thought.
Every year I seem to need to track down some sort of new RFI here at the Ti5W
station in northern Costa Rica. Two years ago it was a faulty sensor for a
sodium streetlight and last year it was a sodium streetlight itself.
This year's nut has been a bit harder to crack. The RFI peaks in a
particular direction (about 335 degrees) and is s9 at some spots on the 15m
band. It is broadband, and can be heard on all the bands, but is worst on
15m, noticeable on 10m and less so on 20m. (Presently I don't have WARC
band antennas, but I'm guessing 17m and 12m pick it up also.) It can be
heard on the low bands, but is in the noise floor. This noise started
intermittently about three months ago and gradually became more frequent
until it's now on 24/7. Rain doesn't seem to affect it these days (I don't
really recall if rain affected it at all.) One interesting thing is that
the noise has gone from something that the noise blanker on my FT5000 would
easily kill to one that the NB seems to have minimal effect on (I'm assuming
it is the same noise - but that's not a 100% given.)
I have an AM mode recording WAV file of the noise that I'm happy to share if
anyone cares to listen.
Although the noise is broadband, there are a couple of frequencies where it
is highly attenuated. For example 21.260Mhz seems to be a null. But there
are not many nulls. That's the only one on 15m.
My attempts so far at tracking it down have been somewhat successful - today
there was a serendipitous power outage only in my immediate neighborhood.
The noise did not go away, which led me to believe it was farther away than
I thought. It is also loudest on the highest antenna - another vote for not
being in close proximity.
So, I flew my camera drone in a line with the peak RFI heading on my yagi to
see what may be out there farther away. At about 2.7km away, the pastures
gave way to a road with several businesses and homes in the 'target zone.'
I built up a loop antenna, fixed it in the bed of my pickup truck, put a
K3 in the passenger seat and listened as I drove to the area.
The noise seemed to peak when I got very close to a particular utility pole
in the target zone. I still need to figure out how to be 100% sure that the
pole is the culprit, since the interference is worst on 15m, and it seems
like the RFI may be radiating on some of the power lines around that area.
I was wondering if anyone could take a listen to the recording I made of
the noise, and possibly identify it, or have any other suggestions on how to
approach this. I've tracked down a reasonable number of RFI issues in
Maryland, and also a couple down here, but none has involved a utility pole
potentially being the culprit. I tried comparing the noise to the ARRL RFI
noise database, but am not confident I can say it matches anything. The
main reason I'd like to have as much/overkill information as possible is
that down here in Costa Rica, it is harder for me to communicate effectively
in order to explain an issue like this and also it's difficult to get the
utility company to act, or to ask entry into someone's home. So I guess I'm
trying to be as sure as I can be about what is going on before I try to pull
any action triggers.
Thanks for reading and please feel free to reply in the group or directly to
me.
73,
Kam
N3KS
Ti5W
..
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