the spectrum looks as I would expect.
are your random numbers uniformly distributed ?
I dont know how the spectrum display is generated in the freeDV IE if it
is just taking slabs of samples with some arbritrary FFT boundary, or it
is aligned to the symbol clocks etc. or how many grabs are used to
generate the display, or if they are time averaged, and if they are
voltage or power averaged or log averaged etc etc
looks fine to me- the OUT OF BAND is still clean.
that's what you need to look for for this case, rubbish more than a
couple of tone steps away from the end tones.
Run it through SPECTRAN or SPECTRUM LAB. see how it looks
there are various averaging/ analysis options
glen
On 14/06/2018 6:44 AM, Steve wrote:
Thanks Glen,
By the way those views are via the freedv spectrum display.
What I was thinking was the random numbers are of course hitting all
the tones equally, whereas the vocoder bits are not as pure, and may
in fact favor bit combinations over another. Maybe a sequence of the
same bit patterns.
I'm wondering if I need to create a transmit filter before the D/A. It
being a lot less sophisticated than a sound card.
Steve
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