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

[Robert Bruninga]

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

Or the uplink to a LEO bird.  It seems I LEO-digital will only
probably work in a closed system, where a protocol allows
checkins and assigned slots.  Then the hardware/software manages
the TX times for each station...

Bob

> 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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> > author.
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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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