[RFI] Power line noise

W6YN Don Milbury w6yn at juno.com
Mon Feb 8 11:18:16 PST 2010

Using a higher frequency is helpful in pinpointing the problem. This noise is very wide spectrum.
I use 33cm am equipment for this purpose as HF signals travel well along power lines.

The possibility of a ground wire on the  transformer pole will make the RFI appear louder when sampled at ground level near the pole.

Transformers are rarely the cause of RFI. An internal arcing may not be detected with an ultrasound detector.
Transformers are often suspected because it's "the biggest thing up there."

Any loose connection in close field proximity to the HV circuits can cause sparking between the metal parts.
Wooden construction may shrink over time and just tightening the hardware can solve this problem.

Sometimes striking the affected pole (Watch your head! Junk may fall.) with a large hammer or mallet can change or even temporarily stop the noise.

Good Luck!

73,  Don,  W6YN

---------- Original Message ----------
From: Ash Thornton <thorntonash at comcast.net>
To: rfi at contesting.com
Subject: [RFI] Power line noise
Date: Mon, 8 Feb 2010 13:36:08 -0500


I found the posting from Corn country interesting.

I have a situation that also seems to appear with the cold weather,  
appears to be limited to a stretch of poles that dead end near my  
QTH. I found it with a loop cut for 7Mhz and a K3. Several other hams  
in the local neighborhood have the same noise problem I am seeing,  
160-40. I see S9 +20-30 noise under several poles and then drops off  
rapidly as I move along the line.

NStar the utility her near Boston has been checking this problem for  
several weeks. They use a ultra sound detector which has shown  
nothing. Several of there grounds are suspect and they will add  
additional grounds. A question, anyone know how to recognize a pole  
transformer failing?The noise seemed to peak on an AM radio just  
under one of them. NStar is coming back tomorrow to look again before  
they send out a maintenance crew for the grounds. I am getting a  
little worried because if it is not a ground problem they are saying  
nothing they can do as they see no arcing.

Any ideas?



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