Re: LF: VLF QRM puzzle - why not the same in a split screen on SL?

["qrss@talktalk.net" <qrss@talktalk.net>]

Hi Chris

Coincidentally, yesterday I watched the peaks of dirty sine waves 
climbing up in frequency and for the first time I have observed them 
reaching above 8.971kHz, causing problems for me recieving Ossi 
on8.9697kHz. The peaks need no filter to knock them out, they go no 
farther (turn round and come back down again:-) ) so producing 2 
vertical lines for each sine wave peak if you look below nothing above.
73 Eddie G3ZJO

On 07/04/2011 17:45, Chris Trayner wrote:
> 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
>
>
>
>
>
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