[RFI] Power Line Noise Conundrum

[Paul Christensen]

Chas,

Your detection method closely mirrors my own.  The key to quick detection as 
you have indicated is to have a highly directional HF loop antenna.  With a 
loop, triangulating common switch-mode and broadbanded arcing noise is a 
relatively easy task.  However, noise that propagates down a power line can 
often give misleading results.  Sometimes it takes multiple triangulation 
points in order to find power line arcs.

For the receiver, I use a combination of two devices while I am on foot: 
The first is an SDR-IQ and netbook PC.  Noise values can be seen over a 
spectrum area up 190 kHz wide.  Seeing the noise signature on a panoramic 
display often gives clues as to the type of source.  I save images and 
document the noise levels as I am walking.

The second receiver is an old Panasonic RF-B65.  However, any portable SWBC 
receiver in AM mode like that used in your set-up will work very well for 
folks not wanting the added complexity and cost of an SDR receiver and 
netbook PC.

I have never been very successful in finding power line noise using portable 
VHF receivers in AM mode.  It could be because almost all the noise sources 
that aggravate me are very low level, typically -110 to -120 dBm at the 
receiver.   Common household appliances can generate a ton of low-level 
noise, especially on 160m, and 80m.  By the time you're up into the VHF 
region with these low-level sources, amplitude often falls to the point 
where there's no detection of the noise.  There's nothing like trying to 
localize noise on the very band of operation that's giving trouble.

Paul, W9AC

----- Original Message ----- 
From: "chuck shinn" <chuck.shinn at verizon.net>
To: <rfi at contesting.com>
Sent: Saturday, October 09, 2010 2:56 PM
Subject: Re: [RFI] Power Line Noise Conundrum


> I have been successful in remedying my local noise with the help of a
> small, easily built, B Field Loop and a cheap short wave receiver with
> an external antenna jack. With this setup I can locate a direction, a
> wire or a pole very easily. You can see what I am talking about here:
> http://w5pg.wordpress.com/2009/10/17/noise/   or closer up view at:
> http://w5pg.wordpress.com/2010/04/22/serendipity-marconi-day-and-some-noise-help/sniffing_loop_dwg-3/
> Simply listen in AM mode and wand your home/area at the frequency that
> is of interest and rotate the wand to null and insure you are at the
> correct wire/conduit/pole etc.
> Chuck W1HIS shared this with me and has been a very large help over the
> years. My short wave receiver is a simple Yachtboy I picked up at Fry's
> as an open box special for about 25 dollars. Recently this helped me
> locate noise on AC Air handler plumbing and Natty Gas pipe that were
> killing me on 30M. It is essentially a free construction project and
> works wonderfully, far better than any yagi or quagi I have tried at
> higher frequencies. Best, Chas
>
>
> On 10/9/2010 1:39 PM, Kim Elmore wrote:
>> I have a recurring power line RFI issue. At one point, it seemed to
>> have been remedied, but has returned. It sounds similar to what I had
>> earlier in the spring. That was repaired by the power company along
>> with the help of a tornado (really!).
>>
>> Now, though, I hear it again.
>>
>> Trying to be helpful, I'm trying to track it down and have had
>> confusing results.  First, I've tried chasing it with my rotatable
>> antennas as home. I have K9AY loops that have a good null off the
>> back. I laso have a 2 el 40 beam, along with a 20 m-10 m tribander
>> and a dipole for 30 m-12 m. Depending on the time of day, I hear it
>> pretty much everywhere relatively well, save for 20 m, which seems to
>> be the quietest.
>>
>> On 80 m with the K9AY loops, I have minimum noise when the null is
>> either SW or NE; which strikes me as inconsistent.
>>
>> On the 2 el 40 m bean, I get deep, narrow nulls off of what i believe
>> to be the sides when it is oriented either N or S. I also get a
>> weaker null when it's pointed roughly W, indicating the source is to my 
>> East.
>>
>> I don't hear much noise on 20 m. On 15 m I get a null to the N, but
>> on 10 m I get a null to the S! the antennas work as they should (CW
>> signals are peaked when the antenna is pointed at their source).
>>
>> Using the dipole, I get weak nulls when it's pointed N or S.
>>
>> I have a corner reflector for 2 m and 70 cm but cannot hear anything
>> on either band when I use AM detection regardless of where it's pointed.
>>
>> I drove around the area in my car, using my dual-band rig set for AM
>> detection. Using 2 m, I tended to hear it over a broad stretch along
>> a road that is about 1/2 mi to my east. I found a localized source to
>> my ENE when I went up to 70 cm. I suspect that is the source, as it's
>> very near a pole that carries quite a bit of hardware (lots off bell
>> insulators and lighting arrestors) and what appears to be a 25 kV line.
>>
>> But I'm perplexed about the inconsistency I hear using my HF
>> antennas. Is this because of standing waves along the lines, or am I
>> hearing different sources? And, how can I use this to be most helpful
>> to the power company? They were very helpful the last time and I
>> don't want to send them on any wild goose chases.
>>
>> 73,
>>
>> Kim Elmore N5OP
>>
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