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Phase 4 satellite(s)?



In looking at all the mail passing through this reflector recently it is
obvious that the only type of satellite project for the future that will
satisfy everyone is one that doesn't cost much, allows world-wide
communication and is usable from a portable station with a fixed antenna.

This isn't technically feasible with one satellite. However, it is feasible
with a network of satellites that are interconnected. The number of
satellites must be limited in order to fit AMSAT's budget. I read through
some old AMSAT-NA Proceedings and see one possible solution.

Perhaps AMSAT should be considering a marriage of satellite and Internet
technology for voice communications similar to what is happening with APRS.
Two articles in the 1997 Proceedings of the AMSAT-NA 15th space symposium
provide some interesting information.

Martin Davidoff, K2UBC, "Selecting Orbits for LEO Constellations: SSB/CW
Communications"

Daniel Schultz, N8FGV, "Digital Voice Modulation for a Future Generation of
Ham Satellites"

K2UBC proposes multiple satellites in RS-15-like 2000 km polar orbits. One
satellite provides coverage of an entire continent wile it is overhead and
does not require the use of directional antennas.  It also provides fairly
long passes of 30 minutes or more and 4 satellites can provide as much
access time per day as AO-13 did. More will provide even better access.  The
cost of the project is also spread out over time as all satellites don't
have to be launched at once.

To provide long distance communication, these satellites must be linked even
if they are not visible to each other. 20 ground stations, interconnected
via the Internet, can provide this linking. Initially, coverage will not be
continuous but intercontinental communication is provided in long enough
intervals to permit a normal QSO.  Each satellite must have the capacity to
support at least 10 simultaneous conversations so we don't have the problems
associated with existing single-channel LEOs. The capacity and coverage can
be improved over time as there are more users of the satellite network.

Since communications will be relayed through 2 satellites and the Internet,
it makes sense to use digital modulation for the uplinks from and downlinks
to the Internet. These would probably be TDMA links to minimize complexity,
power requirements and signal degradation while relaying. User uplinks and
downlinks could support both analog FM and digital modes. N8FGV indicates
that digital voice requires 2.4-13 KBPS or 5-25 kHz of spectrum per
conversation so the Intenet bandwidth is not that expensive and we have
enough spectrum available in the V, U, L and S bands for many of these
satellites.

Does this sound like a useful project?

73 and Merry Christmas,

John
KD6OZH


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