Guess I should've sent this to the whole list. Better late than never.
de ed -K0iL
> -----Original Message-----
> From: EDWARDS, EDDIE J
> Sent: Monday, 30 April, 2001 2:50 PM
> To: 'John Pelham'
> Subject: RE: [RFI] A description of my RFI problem - help solicited
> From: John Pelham
> Actually there are (at least) two noise sources. But they have similar
> characteristics. They sound, on AM, just like an electrical arc.
> with an ac-hum component plus higher harmonics. With a product detector,
> they sound more like higher pitched buzzing or hissing.
> One of the noises affects primarily 6M, but is audible on 10 and 15. The
> other affects primarily 10M and 15M. The noises come and go
> but are most often present on dry days. They were a real problem during
> dry winter, and are present less often now that the summer humidity has
> kicked in here in Georgia. They are never present when it's raining,
> although they can be present (very seldom) when it's drizzling. They are
> never present late at night, dry or wet, but they can be present in early
> evening when it hasn't been dark for too long.
> Your description is "Classic" powerline noise caused by loose hardware on
> the pole. When wood gets humid or wet, it expands, and the hardware is no
> longer loose. The noise is then gone! And don't overlook the squirrel
> Also, the noises seem to be more prevalent when the band conditions are
> good, but that's gotta be my imagination!
> Blame Murphy! ;^)
> I would think that the above paragraph would indicate that the source is
> outside, and I would think probably it's power line noise, but my reading
> indicates that power line noise gets stronger at lower frequencies. These
> noises are not audible below 20M.
> How have you checked this? From one location or multiple? Using only one
> polarization (horizontal yagi) or both? Are you using a different antenna
> with different electrical characteristics on bands below 20 meter compared
> to 20 meters & up?
> The noise may just not be as readily picked up by your low band antenna(s)
> compared to the high band antenna(s). Or it's possible you're in a
> standing wave null for the lower frequencies. Or the higher band
> antenna(s) used has more gain?
> Does anyone have any ideas? I've done some limited investigating, but I
> thought I'd keep this first e-mail short. I'd be glad to go into more
> detail about my noise problem; just ask me!
> What reading have you done so far? The "Interference Handbook" by William
> Nelson, WA6FQG, and edited by the late Bill Orr, W6SAI, is the "Bible" on
> power line noise. There's also a chapter in the ARRL's new "RFI Book"
> that looks pretty good, but I've only had time to skim it.
> I don't know how close your station is to the power lines, but keep in
> mind Electro-Static Discharge (ESD) as a possible cause. (Ch 3 of
> "Interference Handbook") This is also a "Dry & Windy Day" type of noise
> de ed -K0iL
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