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Re: Digital Voice



I've used digital modes on HF but not satellites. WinDRM uses a 47 Hz
subcarrier spacing and most other high speed digital modes use a 62.5 Hz
subcarrier spacing. Since tuning must be accurate to 1% of the subcarrier
spacing, I don't believe that anyone has been successful on satellites.
DIGTRX nwould be the best PC software to try. Subcarrier spacing is 230 Hz
so it will be less susceptible to doppler shift. A better bet would be
Icom's D-STAR which is GMSK (a form of FSK) and should be fairly insensitive
to doppler shift.

The digital modes designed for HF usually run at 50 baud or less to combat
multipath propogation and must use multiple subcarriers (OFDM). Since this
is not a problem with satellite communication, a single carrier system
designed for VHF amd UHF, like D-STAR, is better than those designed for HF.

73,

John
KD6OZH

----- Original Message -----
From: "Eric Christensen" <kf4otn@ericsatcom.net>
To: "'AMSAT BBS'" <amsat-bb@AMSAT.ORG>
Sent: Saturday, June 11, 2005 02:58 UTC
Subject: RE: [amsat-bb] Digital Voice


> Well, I haven't tried digital voice in the ham bands...  I'm sitting
> here at Radio NAM working on the big birds and realized that I've
> been doing digital voice and data, both at various speeds, and
> wondered if anyone was doing something similar to this.
>
> Doppler shift is easily controllable with software and radio control.
> If you are using your computer for your voice compression then you
> can also have it control the Doppler on your radio.  The HEOs would
> be easier but it would be nice to still have software to control the
> radio to keep your radios set to the same frequency as seen at the
> sat (The One True Rule).
>
> I'm just thinking about how much stuff we could put into one pass
> band if we used digital versus analog...
>
> Just thinking out loud...
>
> Eric KF4OTN
>
> -----Original Message-----
> From: Walter Holmes [mailto:walterh@k5wh.net]
> Sent: Friday, June 10, 2005 11:02
> To: 'Eric Christensen, KF4OTN'
> Subject: RE: [amsat-bb] Digital Voice
>
> Hey Eric,
>
>  I just installed the Windrm software last weekend, and have been
> trying to find stations on HF, with no luck so far. But I would like
> to understand if you have been using something like that so far. Or
> perhaps a different program. Guess I'm too cheap to try a hardware
> solution. :)
>
> I haven't considered using it on the birds, because of the extreme
> Doppler shift on the leos. Perhaps when the HEOs get up there that
> might be a lot different.
>
> Take care,
> Thanks,
> Walter/K5WH
>
>
> -----Original Message-----
> From: owner-AMSAT-BB@amsat.org [mailto:owner-AMSAT-BB@amsat.org] On
> Behalf Of Eric Christensen, KF4OTN
> Sent: Friday, June 10, 2005 7:59 AM
> To: amsat-bb@amsat.org
> Subject: [amsat-bb] Digital Voice
>
> Has anyone tried digital voice on any of the birds, yet?  If so, what
> protocol are you using and what are your results?
>
> 73s,
> Eric KF4OTN
> kf4otn@amsat.org
> http://www.ericsatcom.net
>
> Project OSCAR Member
> AMSAT-NA Member: 35360
> AMSAT Eastern North Carolina Area Coordinator
> ----
> Sent via amsat-bb@amsat.org. Opinions expressed are those of the
> author.
> Not an AMSAT member? Join now to support the amateur satellite
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> ----
> Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
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----
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