Other things that may help identify sources... if the bars in waterfall
shift when the line voltage changes it is likely a poorly regulated device
like a charger, wall wart, pc power supply, motor controller, or lamp
ballast. If they are rock solid it is more likely to be a tv, monitor,
modem, or other computerized device that has a good clock. In my experience
the poorly regulated devices also make wider bars and mix with the 60/120hz
more since they are switching it directly, the well regulated ones have
narrower lines in the waterfall and don't radiate as far since they are not
directly on the power line.
David Robbins K1TTT
e-mail: mailto:k1ttt@arrl.net
web: http://wiki.k1ttt.net
AR-Cluster node: 145.69MHz or telnet://k1ttt.net:7373
-----Original Message-----
From: RFI [mailto:rfi-bounces@contesting.com] On Behalf Of Pete Smith N4ZR
Sent: Wednesday, March 29, 2017 22:29
To: RFI List
Subject: [RFI] More on 160 M RFI - significance of hum bands
I'm having more trouble than I expected localizing my power-line
interference. In particular, one component of the interference varies from
almost negligible to whopping big, as visualized on HDSDR, and often appears
in wide bands 22 KHz apart.. See the Dropbox link
<https://www.dropbox.com/s/qaxt7qnyl51hnp3/hum%20bars.png?dl=0> for a
visual. You can see the hum every 120 Hz on the audio display - when I move
the AM passband away from the hum bands, the 120-Hx multiplesessentially
disappear. The bands themself vary, without apparent pattern, from very
strong - as seen in the illustration- to invisblle/inaudible. Just now, they
stuttered a few times and then disappeared from the waterfall (and the
audio) entirely, in the course of a few seconds. With the AM passband in
one of the hum bands, the base noise level is about S9; without them, it is
S7, which still isn't great, but worst things first.
Really puzzling - any advice on what I'm seeing and how to track it down
will be much appreciated.
--
73, Pete N4ZR
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at <http://reversebeacon.net>, now
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