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Re: P3D information



>With the light weight of antennas (meaning easier to aim :) ) for the higher
>bands, 1.2 and 2.4 GHz should be practical for portable use.  I can't see

Yes. Globalstar phones operate on L and S band with nondirectional
user antennas. So there's an existence proof, albeit a non-amateur
one that uses LEO satellites.

When designing a downlink, there's always a tradeoff between satellite
power, satellite antenna gain and earth station antenna gain. Omni
ground antennas are quite workable if the satellite runs high power,
has a big antenna or is at low altitude. The key is to use the most
efficient modulation and coding available, which mandates digital.

As I pointed out in my original note, you can use an omni antenna on
70cm to receive the RUDAK high speed link (67 kb/s) from
apogee. That's a link that just won't work with analog. Of course, we
could support even higher data rates with directional antennas and
higher frequencies, but I'll be the first to agree that our prime
concern must be to reduce the size, cost and hassle factor of the
minimum usable amateur satellite ground antenna. That's *the* key to
growing AMSAT beyond its present small niche.

Phil

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