Dear Jim !
Thank you for the tip. I really have no idea where it could come from
but a motor is a possible source. Until now, I just have seen this
signals during the day but that could have to do with the fact that I
usually have my grabber running in the TA-window during the night.
73 es gl
OE3GHB
Gerhard
Am Montag, den 27.09.2010, 21:00 +0100 schrieb James Moritz:
> 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
>
>
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