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PCSAT-1 Mobile Communications Test



> ... approved the following Eagle communications payloads:
> c.  A low rate text message system, like SMS. It will 
> operate on U/V-bands and be usable over 75% of the orbit 
> by a small terminal on the ground.

Sounds just like APRS... <grin>

Of course, I know that they are not talking about APRS, but then
when one considers the ten thousand or so D7 and D700 radios
with APRS messaging built into the front panel, one wonders why
we don't have more APRS satellites to use for this purpose.
These days, PCSAT-1 is doing great links to mobiles...

In my mind, one of the best applications of any Amateur
Satellite is to serve the mobile operator, since the fixed
operator in most cases has access to many other communicaitons
paths already, such as the internet and satellites that need
beams.  But the mobile ham operator could really use a satellite
link!

Again, the point of this post is not at all to suggest a change
to the Eagle plans, not in any way, but to remind future
satellite builders that there is this vast mobile Ham radio
community that already has a built-in 1200 and 9600 baud front
panel radio message and tiny-web-page display capability out
there fully fielded by thousands of operators that could benefit
from PCSAT type uplinks and downlinks.

See the Tiny-Web-Page applications of the D7 and D700 radios
presented at the TAPR/ARRL DCC 2000:
http://www.ew.usna.edu/~bruninga/aprs/TWP.html

We tried to extend the mission of PCSAT-1 with PCSAT2, ANDE and
RAFT, but all of those have limited lifetimes.  If you have a
mobile D7 or D700 and haven't tried PCSAT-1 during this current
recovery period, you should try it.  On any good pass, I see as
many as a dozen stations and messages on my mobile.  Simply tune
your D7 or D700 mobile to 145.825 and leave it overnight.  Next
morning, look to see who all you see on the front panel of the
radio.  Also check the MSG list.

Here are some hints on the best way to do that experiment:

1) Observe call of the last normal APRS station heard (so you
can tell what is new and what is old in the morning).
2) Be sure your RANGE LIMIT is set to 0, and not 50 miles or so,
because the radio will filter out all satellite packets since
they come from 500 to 1500 miles away unless it is set to 0.
3) Check that your radio CLOCK is set so that you can see the
packet times of arrival
4) Clear out any old incoming messages to make room for
Satellite messages.
5) Park your car to see the sky above about 15 degrees especialy
from the Southwest through North East.  
6) Please, only do unattended at night so that you do not
conflict with command stations during the day.  

Next morning, check the station list and message list on the
radio and see what you got!

Oh, for unattended operation like that, be sure your TX rate is
only one packet per 5 minutes so you will equitably share the
channel with dozens of others...  If we overload PCSAT-1 in the
dark we will kill it. We won't see a positive power budget until
March for only a week.

To see everyone live, who is playing on PCSAT-1, see
http://pcsat.aprs.org

Good luck!

Bob Bruninga, WB4APR
Naval Academy Satellite Lab

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