[RFI] carried powerline noise on 15m and 20m

[Hare, Ed, W1RFI]

This is critical!  If you have a noise and 6 sources around you, you may hear only one of them. Some propagate down the lines for a long distance, while others are strong locally, but drop off rapidly with distance. If you make the utility fix 5 noises you are not hearing, they may stop working on your case altogether, leaving you with the noise and a much harder time to get them moving.

There are two ways to correlate your noise with noises in the field.  The first and best is getting a time-domain signature with Radar Engineers or similar equipment.  The second is less reliable, but if you can hear your noise from your driveway with an HF mobile receiver and you can follow it to a source, getting louder and louder (standing waves notwithstanding) as you approach a source, this is also a reasonable correlation. If you can't do either, you have no guarantee that you have found the right source.

Ed, W1RFI



________________________________
From: RFI <rfi-bounces+w1rfi=arrl.org at contesting.com> on behalf of AA5CT via RFI <rfi at contesting.com>
Sent: Wednesday, February 16, 2022 8:32 AM
To: Rfi List <rfi at contesting.com>; Charles Plunk <af4o at twc.com>
Subject: Re: [RFI] carried powerline noise on 15m and 20m

I want to "second" what Charles wrote! Always make sure the
'rabbit' you're after with VHF/UHF is the one bothering you on HF!!

I have chased down 160m and 80m noise sources that were miles
away and, of course, there were many low-level 'sources' between
my place and the *real* source that I did not hear on 80 or 160m
bands at my QTH/place.

de Jim AA5CT

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    On Wednesday, February 16, 2022, 2:24:55 AM GMT-6, Charles Plunk <af4o at twc.com> wrote:

 Ignacy,

I sent you a more detailed message direct.

Have you got a VHF yagi you could more accurately pinpoint its
direction? If so, does the VHF noise match the HF noise? Helps a lot if
the noise goes intermittent (has a distinctive pattern) to match. I no
longer use 2m at all, but have left my 2m horizontal up for just this
reason.

Have you tried to see the 120hz spikes somehow?

Are the private property poles drops 120/240 or higher voltages (mine
are 7.2kv for example)?

A strategy may be to try triangulating on 2m then 70cm.

And most important, make sure you are triangulating the source you are
hearing at your station. From my experience, there is lots of near field
noise when out using a loop/2m yagi etc to easily throw you off your
intended target. Those sources may not even be heard at your station.
This maybe why you are getting confusing directions with the loop. I
retransmit my noise to an ht to match the noise audibly with my tracking
receiver. Again, helps a lot if the target source is intermittent to
more easily match. Not easy to do, I have ran out at a moments notice
when the target went intermittent, lol. Not any single technique has
helped me as much as this. Ignoring all the other noise. Seems every
pole has some noise when near it that will throw you off track.

73

Chuck
W4NBO

On 2/15/22 20:43, Ignacy Misztal wrote:
> My radio shows about S4 noise on15m when the beam is oriented towards the
> nearest power pole. There is S3 noise on 10m and almost none on 20m and
> below. The noise is canceled completely with NB so I assume it must be from
> a single source.
>
> My MFJ VHF sniffer detects just a trace or nothing. A DX engineering loop
> has weak readings, similar in strength to the nearest pole and to the next
> few poles.
>
> The QTH is in a rural area. I walked along power lines for a mile and
> could not find anything strong. There are some poles deep on private
> properties.
>
> My first question is whether the power lines are somewhat resonant on 15m
> and carry the signal for a long distance. My second question is about a
> strategy to find the RFI when teh culprit is far away and directions from
> loops change every 50 ft.
>
> Aside from the MFJ 3 el sniffer, I have their ultrasonic dish, a tuned loop
> for HF and a DX engineering directional loop. Also a Yagi for 70cm.
>
> Ignacy NO9E
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> RFI at contesting.com
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