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Re: Digital Voice on AO-40?



I'm thinking that dedicated hardware is at this point not the best way 
to attack this problem. After hearing some LPC-10 (the source for LPC-10 
is also freely available) compressed audio (its good, especially for 
2400bps) and reading about the algorithm and its complexity you'd need 
some pretty nice DSP's to do it in hardware boxes. However we all have 
some pretty sophisticated Intel DSP's on our hands that will do what we 
want for nothing for than the cost of a few ham-hours coding. One could 
argue that always having to have a PC around is a major detriment but 
then PC hardware is getting pretty tiny (physically). One could imagine 
an embedded linux based ham DSP solution that was essentially a 6" cube 
with cheap pentium class hardware that could run some pretty advanced 
and free software.

This is a really good discussion---I'm much enjoying everyone's comments.
-David Carr
KD5QGR
[currently studying up on IQ signal representation and QPSK modulation]

Emily Clarke wrote:

> The specs seem impressive, but if it was perfect for AO-40 I would 
> think they would have put it in the brochure. One issue may be:
> "Header: 1 Sec. 3 tones + BPSK training pattern for synchronization "
>
> I wonder what effect doppler would have on that? Also, with 36 carrier 
> tones poured into 2,5K, that's ~69 hz of separation per carrier center 
> frequency. Assuming a guard frequency of 25 percent on each side of 
> each carrier, that would mean it would be out of it's detection range 
> at ~35 hz. The question would be - does it send the header to re-sync 
> periodically or only at the beginning of a transmission.
>
> It doesn't mention it being full duplex, so I would assume you would 
> need two? At ~$550 each this seems pretty expensive for very little gain.
>
> - Emily
>
>
>
> At 12:18 AM 10/24/2003 +0000, Alan P. Biddle wrote:
>
>> AOR has a new plug and play digital voice unit shown in the latest QST.
>> http://aorusa.com/ard9800.html I wonder who will do the first tests on
>> AO-40?
>
>
>
> W0EEC - CM87tm
> ARRL - AMSAT - MSARC - ARCA - Project OSCAR
> http://www.projectoscar.net
> http://www.emilyshouse.com/W0EEC
> http://www.experthams.net/ao7
>
>
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