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 
> 
>