LF: Re: QRM analysis

To:	"RSGB LF Gp" <[email protected]>
Subject:	LF: Re: QRM analysis
From:	"Alan Melia" <[email protected]>
Date:	Sat, 13 Nov 2010 23:45:10 -0000
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Hi John what does it sound like?? I have seen pics similar to that on my
waterfal by the audio load FMing the psu is a flatscreen TV. Becuae the mod
you would decome is x 4 or so, you wont resognise it. What  did was flip
round the channels and correate the cadence of the noise with the TV sound.
This is best dont with speech. I also found the pattern jumped usually at
"half hours" I took this to indicate a channel change. It also drifted
around as TV PSUs will.

One noise source turned out to be self inflicted as a normally quiet PC
drifted into the band.....it turned out the PSU fan had failed, the extra
heat causing the switching frequency to drift up.

Seeing Marco's message ....mmmmm yes my sidebands were 100Hz from those
sources.

Alan G3NYK



----- Original Message ----- 
From: "John RABSON" <[email protected]>
To: <[email protected]>
Sent: Saturday, November 13, 2010 7:53 PM
Subject: LF: QRM analysis


Please see attached screen print taken with Argo at 2010 Nov 13 1941z.  The
frequency marks across the top are relative to 136.0 kHz approx.  The
vertical bar is an artefact of the RX.

The signal can occur at any time and drifts across the RX passband, with
occasional jumps of a few hundred Hz.

What software would people suggest for analysing it with a view to determing
its cause and perhaps locating it?

F5VLF

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