> I got to thinking
> how nice it would be to be able to use my earth station not
> JUST as a receiver, but be able to uplink as well.
>    I'm an Amateur Op, so I've had a chance to experiment
> with the use of ax.25 packet protocols and TCP/IP comms,
Me too, WA5VNV
> and I can't think of a reason that it SHOULDN'T be poss-
> ible (with the proper hardware) to use a satellite in the
> same way as one would use a mountain top digipeater.
Almost anything is possible.  The question is; why hasn't
it happened yet?  Of course you could not use any existing
geo satellite with Amateur Radio because none of them have
Amateur frequency transponders.  The phase 3 satellite
will be almost as good as a geosynchronous sat because
of its highly eliptical orbit that will park it over
North American for many hours at a time.  You are probably
just using Amateur Radio as an example, right?
>    With the advent of DBS/DSS Ku-Band satellites there has
> been room created on C-Band.  It seems a shame to let this
> resource go to waste.
Actually the surplus of C-band space is due to;
- users converting to digital which allows many channels per
transponder, and
- C-band being only useful for large dishes since the FCC /
sat-industry goof of converting to 2 degree spacing.
> What would be involved in building
> a microwave transmitter (or better yet, a tranceiver) that
> would be 'rockbound' on maybe one or two frequency pairs
> so the average public earth station could have uplink
> capability as well ?
There are already systems similar to what you describe
that have been operating on Ku-band for many years.
They are not crystal controlled one-frequency transmitters
though.  They are synthesized "network controlled" similar
to cell phones.  The network instructs each transmitter
to switch to a certain frequency (channel).  The transmitter
is disabled when not receiving the control signal so that it
cannot transmit on the wrong satellite.
Most of these systems use a 5 to 10 watt solid state amplifier.
Examples of these systems include the credit card authorization
network used by gas stations -- especially rural ones.  Another
example is Wal-Mart which is in constant 2-way communications
with each store and distribution center from their Bentonville,
AR headquarters.
>  With the speed of 19200kbps digital
> (which I understand is actually becoming comparativly slow)
> and the packetizing protocol that would allow many connects
> on one frequency via rotational sharing, I would think that
> quite a large number of stations could be served from one
> transponder on the audio frequencies.
Many of the radio networks use satellites
for transmitting their signals to local broadcast
stations.  The uplinks require larger
dishes than 10 feet on C-band.  What you are talking
about would have to be done on Ku-band or higher.
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