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Message-ID: <18AC751DD96A43A3B3B271967EDDF8C2@JimPC>
From: "James Moritz" <james.moritz@btopenworld.com>
To: <rsgb_lf_group@blacksheep.org>
References: <1285607600.1755.7.camel@gerhard-desktop>
In-Reply-To: <1285607600.1755.7.camel@gerhard-desktop>
Date: Mon, 27 Sep 2010 21:00:10 +0100
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Subject: LF: Re: Aliens on LF !
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Dear Gerhard, LF Group,

>
> Has anybody an explanation for the kind of signals displayed on my
> grabber sometimes?
>

I think quite a few people have seen signals like this - one possibility is 
switch-mode variable speed drives for AC 3-phase induction motors. The RF is 
centred on some harmonic of the switching frequency, the spacing of the 
sidebands depends on the motor speed (i.e. the output frequency of the 
inverter) ... it would seem quite low in your case.

Cheers, Jim Moritz
73 de M0BMU