Re: Waterfall Rate and FFT2 Size

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

Hi Guy,
 
> > Win   time factor
> >  0       1.0
> >  1       0.666
> >  2       0.5
> >  3       0.416
> >  4       0.364
> >
> Right, I had figured out the factors, which are mostly obvious anyway
> (except the last 2).
> Should that be -6dB for the overlap point?
Oooh! YES!!

> From the numbers we are obviously talking about the half height,
> and this is a voltage scale, isn't it?
Yes. (Sometimes I write what I seem to remember without thinking.
To the extent I have done so on my homepage I am grateful for
E-mails about it)

The exact overlap is near the -6dB point, but since back transforms
are done in fewer points (in case fft2 is not enabled) the overlap
must go even in the smaller transforms. "First mixer bandwidth
reduction factor" is the parameter that controls the finer details
of the time factors when fft2 is not enabled.

When fft2 is enabled, the above factors are accurate.

73

Leif / SM5BSZ

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