[Linrad] Re: system gain

[Leif Asbrink <sm5bsz.com; leif@xxxxxxxxxxxxxxxx>]

Hi Dave,

> What parameter do I use to set the bin bandwidth at 5 hz?  I know where 
> the waterfall average adjustment is on the screen, but the bin BW is a 
> mystery to me.  I think most of my confusion is not understanding terms. 
> I have spent hours reading the material, but just don't seem to get 
> it--sorry.
OK. When you start Linrad the first time you are prompted to the
parameter selection screens. Once for every receive mode.

The bin bandwidth is set with the parameter "First FFT bandwidth"
in case you do not select to use the second FFT. With the second
FFT enabled, your bin bandwidth will be as set by "First FFT bandwidth"
multiplied by the factor derived from "Second FFT bandwidth
factor in powers of two." If you make it 3 the bin bandwidth
of the second FFT will be 2 to power 3 (=8 times) narrower
than the first FFT bandwidth.

> >>> It occurs to me that the band width of the filter in LINRAD's 
> >>> demodulation window (sorry I know I am probably not using correct 
> >>> terminology here) is affecting the signal to noise of the audio output. 
> >>> I have fiddled with the little green ellipses, but can't get them to go 
> >>> any narrower and really don't understand how this all works.
> > Little green ellipses?
> 
> Tee Hee!  Since wrote that I have figured out that they are probably 
> yellow arcs in the baseband window that show the filter width and 
> offset. You can grab them with the mouse and make them wider and 
> narrower to a certain extent...again my problem with proper terminology.
OK. Yellow lines:-)

Place the mouse inside the window (e.g. on the yellow line) and press F1.

Good Luck:-)

73

leif / SM5BSZ


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