[Date Prev][Date Next][Thread Prev][Thread Next] - [Date Index][Thread Index][Author Index]

Re: FM satellites (Millennium Project)

Quoting KF4FDJ (Mike in Ft. Myers, FL) (seven77@gate.net) [990726 18:05]:
> The reason SSB birds like FO20/29 are so efficient is SSB.  The
> transponders are linear, in that whatever they receive on the uplink,
> they retransmit on the downlink.  SSB is efficient because it
> concentrates energy into a narrow slice of spectrum.  FM on the other
> hand uses a very large slice of spectrum to carry any intelligence.  The
> larger the slice, the more power it takes.

SSB transponder or digital are really the right way to go (until we come up with
something better) but there is the paradox; SSB/digital requires more of
a groundstation investment and that limits the number of stations who
will use it which results in less crowding by default.

The idea behind the FM LEOs has been to get more interest by making them
available to hams who only own a handheld. It is an interesting yet
problematic challenge and I'm certain there is a good solution that the
worldwide amateur sat community will solve; it is a little like the
early days of pacsats where a broadcast protocol had to be developed to
allow multiple stations to receive files at the same time...

Jeff Davis, N9AVG
Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org