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

To: Rfi List <rfi@contesting.com>
Subject: Re: [RFI] carried powerline noise on 15m and 20m
From: Charles Plunk <af4o@twc.com>
Date: Wed, 16 Feb 2022 02:24:36 -0600
List-post: <mailto:rfi@contesting.com>
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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