At 07:39 AM 10/11/2008, G. White wrote:
>Hope you can help:
>
>In trying to resolve several different interfering sources, I am wondering
>about how to best identify powerline noise vs other types.
>
>I always believed Powerline noise to be be very wide band, sounding
>similar throughout most of the HF band. Or at least, several bands. Is
>this correct?
>
>I seem to get confused when I hear powerline type noise, but only
>at certain frequencies- and at differnt bandwidths... anywhere from a 5
>-100KHz bandwidth, for example. So is it possible that the nature of the
>arcing, flashover or corona is resonating within specific bands and/or at
>specific frequencies - or is that highly unlikely?
>
>I have often re-evaluated my long time belief that :"if its powerline
>noise, its has to cover the entire HF band"
>
>thanks and looking forward to your repy
I hope Mike will respond, but in the meantime..
Real "powerline" noise is broadband, but that isn't necessarily to say that
noise with significant 60/120 Hz components can't be narrow-band. As an
anecdotal example, when I was trying to finish up my 80M DXCC from a
townhouse, I was frustrated by a noise generator operating in the vicinity
of 3505 KHz, repeating around 3700 KHz. In each instance the noise began
abruptly on the high end and gradually tapered off over ~ 15 KHz. It was
there sometimes, others not.
Finally, I took a portable shortwave RX and was able to track it down to a
neighbor's house. With some trepidation, I knocked on the door and
explained what I was looking for. Kindly, he let me sniff around in his
house with the receiver. No joy, until we were almost ready to give
up. He switched off a bathroom light, and there the noise was, very
strong. Switched it on, and the noise went away. The light was an
ordinary incandescent.
With his permission, I replaced the light switch - it was an ordinary
72-cent "silent" type, but it made noise, and the replacement (same kind)
did not.
Later I tracked down another one in a house across the street. Same
thing. Nobody has ever explained what physical mechanism might have been
generating the relatively narrow-band RF, but there you are.
I think this validates the view that the important thing is to figure out
where the noise is coming from; you don't necessarily have to know what it
is, before you get there.
73, Pete N4ZR
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