Massive overkill IMO to stress the need for an SDR to accomplish this task.
Find or buy a little battery powered Degen 1103 receiver and equip it
with a small tuned loop for the band of interest.
I will try and post a video of this scheme later on. I was DFing noise
near the 20m band.
de Jim WB5WPA
------------------------------------------------------------------------
*From:* Dave Cole (NK7Z) <dave@nk7z.net>
*To:* rfi@contesting.com
*Sent:* Monday, September 25, 2017 6:04 AM
*Subject:* Re: [RFI] Help Identifying RFI
If you can get a portable SDR, say an RSP-1 using an Raspberry Pi, then
you can use your loop to track down very selected RFI sources by
watching the spectrogram of that RFI as you turn the loop.
A small subset of signals will fade in and out as you rotate the loop,
this will help you separate out which are the really offending ones...
I use the process described at:
http://nk7z.net/sdr-rfi-survey-p1/
to initially locate what RFI I want to track, then I zoom in time wise,
and use a loop to follow just that source by looking at the nulls as I
turn the loop. This way I see only a few signals fade, out of the many
RFI signals... This allows me to select what signals I want to track.
Takes a bit of practice, but once I got the hang of it, it shortened the
locate time down to minutes in most cases...
73s and thanks,
Dave
NK7Z
http://www.nk7z.net <http://www.nk7z.net/>
On 09/24/2017 08:32 PM, Kam Sirag (Yahoo) via RFI wrote:
> 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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> RFI@contesting.com <mailto:RFI@contesting.com>
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>
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