[RFI] 200 khz AC line noise

[Aaron Kreider]

I've got constant hum/buzz that is strongest in the 150 khz - 250 khz 
area and is coming from the power lines. It is around S7 on my Drake R8 
(with a low noise Wellbrook 1530+).  On my noise antenna (a 6 foot 
horizontal wire) it was S9+10db (when using a triplite powerbar that 
isolated me from the AC noise) or S8 (when using a regular power bar 
that didn't isolate the radio from the AC and thus cancelled out the noise).

I went around my neighborhood testing 50+ power poles using a Tecsun 
PL-380 and holding it up to the ground line on the power pole. This is a 
portable shortwave radio with a digital dbu meter.  The noise floor on 
the dbu meter is 15.  About 20% of the poles showed no noise - possibly 
due to faulty grounds which meant I was too far from the noise to hear 
it.  The rest of the poles ranged from around 30 dbu to 50 dbu.   I was 
hoping to find a single pole or two that I could blame, so I could work 
with the utility to fix it.  But I didn't detect any major patterns.

I'm wondering if my noise could be coming from multiple power poles?

Unfortunately the PECO power lines run through my property and thus it 
is very hard to get away from them, and they are impossible to null with 
full effectiveness (as they are on multiple sides).  Even if I go up 
10-20 feet over my roof line, I'll probably still hear the noise.  The 
other downside of going up is that Wellbrook loop antenna's ability to 
receive low angle signals degrades when you go high.


Any advice?

Aaron