Re: [Discuss-gnuradio] Bins smaller than pixels. was: WX GUI FFT Sink Performance

[Marcus D. Leech]

On 05/28/2013 01:28 PM, Simon IJskes wrote:
> On 17-05-13 02:22, Marcus D. Leech wrote:
> > Again, given the fact that your display geometry is likely less than
> > 1280 wide, you'll simply lose information for FFTs larger than that.
>
> I one is looking for weak CW signals, in a waterfall, wouldn't a wide 
> bin, make this signal invisible in among the noise? If more bins fit 
> in one pixel, there could be a mode where the bin with the most power 
> is displayed. If this is complete non-sense, how would you implement 
> looking for faint cw carriers, in like EME applications?
>
> Gr. Simon
There are a number of ways to do this.  One can make a scrollable FFT 
window -- either waterfall or plot.

One can use various "compression" techniques to reduce the much-wider 
FFT data to the number of displayable bins you have. There are three
  in common use:

     o strictly decimate the bins -- keep-one-in-N bins
     o average input bins together to make a display bin
     o pick the highest power in a given bin set to make a display bin

I believe that the wxGUI widgets in Gnu Radio do the first 
one--keep-one-in-N

I agree it would be useful for the FFT display widgets to have more 
options for processing FFTs that are wider than the display.


--
Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org