On 7 Apr 2011, at 17:24, qrss wrote:
>  Considering they 
> originate from a 50Hz source they are strongest at lower frequencies, 
> rarely climbing above 6kHz but peaks sometimes get to 8.971kHz not much 
> higher..

Yes, but they disappear between 8970.03 Hz and 9876.57 Hz - that's a very small 
band for anything to knock them out. It's 0.00105 of an octave. If something is 
acting like a low-pass filter, at 6dB/octave/order, it'd have to be something 
like a 500th order filter to drop the signal by 3dB.

I agree, it does look strange. 


73,
Chris G4OKW
 
-----------------------
Dr Chris Trayner
School of Electronic & Electrical Engineering,
The University of Leeds,
Leeds LS2 9JT, United Kingdom
Tel: +44 113 34 32053
Fax: +44 113 34 32032