[RFI] Help Identifying RFI

Mon Sep 25 11:32:16 EDT 2017

Hi,

Setting up a SDR is mindlessly simple, the resultant setup is about the 
size of a pack of smokes, including display, and battery...

In fact, the display looks almost exactly like the photo you show on 
your web page of the radio with the plus/minus 100 KHz display.

Remember I framed the comment in the vain of being able to discriminate 
between sources simply, as one turned the loop.  I was not implying that 
this is the only way to track RFI, so not overkill IMHO, just a 
different way of discriminating between signals.

Try it sometime if you have not.  It really makes the task of finding a 
bearing on one signal simple, when it is mixed with a large number of 
others..

73s and thanks,
Dave
NK7Z
http://www.nk7z.net

On 09/25/2017 06:56 AM, JW wrote:
> 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 at nk7z.net>
> *To:* rfi at 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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> 
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