Thanks Steve and Glen,
I'll do a SVN get and compile up my "parrot" repeater, right now.
And, put it on-air.
It'd be nice if somebody actually used it.
14.153MHz USB, put my callsign in the text to trigger repeat.
The codec2-dev build just finished on the Banana Pi M2 Berry here.
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
2314 alanb 20 0 21744 3304 2312 S 27.7 0.3 0:08.57 parrot
That's 27% of ONE cpu on a quad core box.
BTW: Looks like I'll have a Codan available for 20m to deploy
at Ian's place in Wellington NSW.
Guys, If you want a login to it, just ask.
Alan VK2ZIW
On Tue, 18 Dec 2018 18:20:14 +1030, David Rowe wrote
> Thanks Steve and Glen,
>
> IIRC James' use case was a home brew SDR with complex baseband inout,
> rather than a traditional SSB Tx. Interesting points about modulator
> distortion Glen.
>
> Another approach might be some optimisation of the code, SIMD
> vectorisation, gcc tricks etc.
>
> Cheers,
>
> David
>
> On 18/12/18 07:54, glen english wrote:
> > Hi STeve
> >
> > I would think a 40dB stopband would be sufficient.
> >
> > bear in mind the modulator distortion in the rig will probably be about
> > no better than 3% at best.
> >
> > IE put a 600Hz tone in your sideband radio and at various drive levels,
> > have a look at the harmonics...
> >
> > there will be harmonics from ahead of the sideband filter, (whatever the
> > implementation) .
> >
> > then have a look at IMD products with say 1000Hz and 500Hz. probably at
> > best -25 down.
> >
> >
> >
> > On 18/12/2018 8:14 AM, Steve wrote:
> >> I have played around by using a smaller number of coefficients.
> >> Currently the filter uses 160 and I created a filter that uses 63
> >> instead.
> >> The current filter is very sophisticated (designed by James Ahlstrom),
> >> as it uses complex coefficients (essentially doubling the numbers I
> >> listed above, one for the I and one for the Q sides. This filter can
> >> be tuned to other center frequencies.
> >>
> >> It's kind of neat how it works, but you need about 2 GHz CPU. It
> >> provides 100 dB attenuation for a @1100 Hz BW and looks great on the
> >> SDR spectrum view :-)
> >>
> >> My change to 63 filters cut the time in half, but I only used a 40 dB
> >> attenuation. This left some higher amplitudes on the ends, but
> >> probably acceptable. I didn't transmit the signal, just looked at it
> >> from a saved file in Audacity and using FreeDV spectrum view.
> >>
> >> I also tried an 81 coefficient filter with 55 dB attenuation, and to
> >> tell the truth I didn't see much change.
> >>
> >> Be a good area to experiment on the air. I believe the filter was
> >> implemented early on because there was kind of a step in the spectrum,
> >> so it cleaned that up, but I don't think the step would be a killer,
> >> and leaving the filter off if you are out of CPU ought to be fair game.
> >>
> >> 73, Steve
> >>
> >>
> >>
> >>
> >> _______________________________________________
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> >> Freetel-codec2@lists.sourceforge.net
> >> https://lists.sourceforge.net/lists/listinfo/freetel-codec2
> >
> >
> >
> >
> > _______________________________________________
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>
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Alan
Evil flourishes when good men do nothing.
Consider the Christmas child.
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