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
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@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@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.
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