[amsat-bb] ISS First IMpressions..

[Bob Bruninga <bruninga@xxxxxxxx>]

ISS is on the air and giving everyone a great time!

As you may know, my particular interest is in mobile and handheld
satellite operations, so I think I might make a pre-mature assessment in
comparing it to the last 2m 1200 baud digi in space which was SUNSAT... as
received on a stock mobile with a NON-OPTIMUM 5/8 wave antenna. (My van
roof is mostly plastic!)  But it is the same set-up I used the last year
on SUNSAT...  A good mobile installation will probably do a dB or so
better...

Compared to the SUNSAT downlink, it appears to me that ISS signals peak to
about the same level, but there seems to be a lot more variability.  Of
course this is expected with the multifaceted geometry of the ISS compared
to an attitude controlled SUNSAT with no blockages.

Oh yes, and the passes are a lot shorter due to the lower altitude...

So, although I can get in with the Mobile's uplink power, I do not reveive
a solid downlink from horizon to horizon like I did with SUNSAT.  It
appears to me that some antenna gain is going to be needed for consistent
performance in the downlink for low passes.  Of course a Handheld beam
antenna will be just the trick for the handheld operator...

Many of you may recall that we did an HT-to-HT stock-rubber-duck
digipeating test via MIR in June of 99 and demonstrated that 55 stations
exchanged packets during that week.  Fortunately we were able to do that
test without a lot of higher power QRM... 

It is human nature that as more people jump on the ISS uplink there will
be a power escallation in the short term, but we are in this for the long
haul.  And after a few months and the initial excitement flattens out, I
suspect we will begin to see many HT demonstration's via ISS!  That is my
dream, for handheld school, studnet and scout demos...

For details on the HT<->MIR<->HT tests see the 1200 baud ASTARS link on:

  http://web.usna.navy.mil/~bruninga/astars.html

So if you havent gotten in yet, just hang in there.  I'm going to drop
back now to a 5W uplink only (in the middle of the night) and see when it
gets through.

de WB4APR, Bob


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