Hi Jim,

you asked:
For this reason, the filter was added to
> 
> reduce the level of the powerful VLF utilities, and the lower frequency 
> mains noise, and TV line timebases etc., in the sound card input signal. I 
> think it should be possible to configure Spectrum Lab to do the necessary 
> filtering, along with limiting and FFT, but I have not yet been able to get
> 
> it to do all this at the same time as a high resolution complex FFT centered
> 
> on 9kHz - perhaps Wolf could comment?
> 

Yes, that's possible. There are various noiseblankers which can be included in 
the signal path before the analyser. 
The most simple one is in each "DSP blackbox" (the square objects labelled with 
a question mark). 
I think Markus has already used them to defeat QRN with some success.

BTW The "soundcard sampling rate calibrator" has been modified in SL V2.75 b6 . 
 It has an immediate effect now, after entering a reference frequency, and the 
measured frequency. For the next release, the 'continuous' sample rate 
calibrator will support synchronizing to the ALPHA beeps; I am still working on 
that (either with a boxcar integrator, or with a sufficiently narrow-band 
detector).


Cheers,
  Wolf .





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