[RFI] Power Line Noise

Hare, Ed W1RFI w1rfi at arrl.org
Fri Apr 17 01:07:46 EDT 2020

This is a key point, Mike.  Many noise sources that might be very strong when you are right on top of them are not heard at all at the amateur station.  This is why the signature method is the only really efficient way to identify the actual soure of an interference problem.

Some hams get in their cars, drive around and find noise sources and assume that they are all causing them part of their inferference.  This is not usually the case.  Others truly do go on a crusade, feeling that if they force the utility to fix all the noise on their system, their noise environment will be quieter.  Some mistakenly think that any noise source they can hear 3 feet away under a pole is breaking FCC rules and so must be fixed.  All of these premises are flawed.

There is one very big risk in finding dozens of noise sources and demanding that the utility fix them all.  The utlity may fix a few of them, if they aren't the one(s) you are hearing, they will often conclude that you are never going to be satisfied, so they may stop working on your case.  If your case then gets to the FCC, the utility will defend itself and say that it fixed noise sources, but you still have interference, so it must be from a non-utility source (and, if you don't have signature confirmation, that could very well be the case.)

FCC rules do not require them to fix every noise source.  The rules set NO specific limits on indidential emitters, but only require that noise sources be corrected if they are causing harmful interference to licensed radio users.

The bottom line is that it is important that the correct source(s) be identified and that you only ask the utlity to fix noises that are actually the one(s) causing interference.  Any other approach runs the risk of getting your case into an attorney letter-writing campaign that the FCC may well accept, making it all the harder for you to re-prove your case again and again.


From: RFI <rfi-bounces+w1rfi=arrl.org at contesting.com> on behalf of Michael Martin, RFI Services <mike at rfiservices.com>
Sent: Thursday, April 16, 2020 6:25 PM
To: K9MA <k9ma at sdellington.us>
Cc: AA5CT via RFI <rfi at contesting.com>
Subject: Re: [RFI] Power Line Noise

Another observation I'd like to share.
I commonly find powerline noise sources on poles in front of ham's homes that are very high in level but have no effect on their HF reception.
Often I find from the ham to the source as many as 10 to 15 power line noise sources before I get to the one that's affecting the ham.

⁣RFI Services
Michael Martin

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On Apr 16, 2020, 6:16 PM, at 6:16 PM, K9MA <k9ma at sdellington.us> wrote:
>On 4/16/2020 17:02, AA5CT wrote:
>> re: "I went out today to track down a noise source, which on the
>> HF bands appears to be coming from the east. "
>> Scott, I give you even money odds that you found ANOTHER noise
>> source on VHF, and not the one that was affecting you on HF (unless
>> you already got it fixed, and that was it, in which case I lose hi
>I doubt it. This source is just too incredibly loud at 135 MHz and
>(maybe 300 feet from the antenna) that it can't possibly NOT be causing
>HF interference. I agree with your point, though. When tracking at VHF,
>I always hear lots of sources that are not the one causing the HF
>problem. I deal with that by relaying the noise from the HF receiver at
>home so that I can hear it while I'm out tracking. There is always a
>pattern to the fluctuations. When I find that they match, I know I've
>got the right source. This is the same principle as taking the "noise
>signature", without the expensive equipment. It has served me well.
>I didn't bother this time because the source is so ridiculously strong
>on VHF right out my front door.
>Scott K9MA
>Scott  K9MA
>k9ma at sdellington.us
>RFI mailing list
>RFI at contesting.com
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