[amsat-bb] Re: Can D-Star work on VO-52?

[joseph Murray]

Dear Trevor ( M5AKA )

I continue to ask one question about digital voice on HF.

When will Hams see a digital voice system that will be able
to Handle a 20 meter pile up.

So far , the answers have been negative.

Would Trevor know of any system that could accomplish that feat.

My best 

Joe  K0VTY
===============================
On Sun, 25 Feb 2007 21:15:13 +0000 (GMT) Trevor <m5aka at yahoo.co.uk>
writes:
> In the next 10 years or so we can expect All Amateur voice 
> communications to
> switch to Digital in preference to SSB or FM. It will be as 
> traumatic a shift
> as the move from AM to SSB was back in the early 60's.
> 
> I don't expect that any of the different Digital Voice systems 
> currently in
> iuse will be the ones eventually adopted for HF and VHF/UHF - rate 
> of
> techonological progress can be rapid in this field.  But whichever 
> format
> eventually dominates there will be significant challenges for 
> satellite
> operation.
> 
> When newcomers try out the satellites for the first time they don't 
> use fully
> computerised doppler correcting set-ups, they compensate for doppler 
> by hand.
> 
> Now the existing satellites modes - CW, SSB, FM are all relatively 
> "frequency
> insensitive" - you can be offtuned by 300 Hz on a CW signal and a 
> human
> operator will still be able to copy it just fine. SSB is the most 
> critical of
> the three, but even that can still produce understandable audio even 
> with a 150
> Hz+ frequency offset. 
> 
> All existing Amateur Digital Voice modes are very frequency 
> sensitive, you need
> to stay within 50 Hz of the correct frequency to decode them and 
> this would be
> problematic for a LEO sat where the operator is tuning manually. 
> 
> What we need is a Digital Voice mode that occupies a bandwidth of 
> less than 2.5
> kHz, can be decoded with very low S/N ratios (<15 dB) and can 
> tolerate tuning
> offsets of at least 150 Hz - a tall order but not impossible.
> 
> Satellite users need to give some thought to this because unless 
> there is
> Amateur Satellite Community input to the development of Amateur 
> Digital Voice
> we could end up with the situation where none of the commercially 
> available
> Amateur Digital rigs (that's all they'll be in 10 years time) can 
> use LEO
> Amateur Satellites ! 
> 
> 73 Trevor M5AKA
> 
> --- Dave hartzell <hartzell at gmail.com> wrote:
> 
> > Interesting idea...
> > 
> > Doppler tracking might also be an issue....do these radios 
> support
> > incremental VFO adjustment via computer control?
> > 
> > 73,
> > 
> > Dave
> > NøTGD
> > 
> > On 2/23/07, Patrick Green <pagreen at gmail.com> wrote:
> > > Hi All,
> > >
> > >   I'm wondering if the GMSK modulation scheme in D-Star can be 
> inverted and
> > > whether the Icom 91AD dualband HT can work full duplex for 
> satellite work.
> > > D-Star uses a 6.25kc channel which is way better than the 15kc 
> needed for
> > > standard FM but not as friendly as SSB and CW.  Let me know.  I 
> haven't
> > > purchased this equipment but it's worth at least a debate.
> > >
> > > 73 de Pat --- KA9SCF.
> > > _______________________________________________
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> > 
> > 
> > -- 
> > "It is far better to grasp the Universe as it really is than to
> > persist in delusion, however satisfying and reassuring." - Carl 
> Sagan.
> > 
> > _______________________________________________
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> 
> 
> 
>                 
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