[OZAPRS] PCSAT Nearly QRT

[Richard Hoskin]

Subject: PCSAT Nearly QRT
From: Bob Bruninga <bruninga at usna.edu>
Date: Tue, 29 Apr 2003 12:55:12 -0400 (EDT)
X-Message-Number: 1

PCsat is back in eclipses and its batteries are practically shot.  On
saturday it went back to negative power budget and so it can now barely
even work in the sun due to the peak power needed for each packet burst.
The only packets that can possibly get through even while PCsat is in the
sun are VERY SHORT.

The best very short packets are Mic-E formatted packets or Kenwoods which
can contain a callsign, position, course and speed with only 9 bytes in
the payload. Thats about a 0.2 second data burst.  Unfortunately the TXD
on PCsat defaults to 300 ms and so it is sending 0.3 seconds of overhead
to send just 0.2s of data.  But that 1/2 second packet is about all you
can get through now.

Also since the UHF receivers default to ON, and they listen for 9600 baud
packets, you can really get some short packets through that way too.
Just set your D7 or D700 to 9600 baud and split band operation.  Ah!  You
can also transmit up on 1200 baud and use the DIGI path of VIA XBAUD and
your 1200 baud packet will come back down at 9600 baud, also making a very
short packet.

For all practical purposes except for experimenting with these short
packets, I'd say PCsat's mission for providing a continuous availability
of an AX.25 digipeater for UI packets on 145.825 is over.  The next full
sun isn't till July 12th and thats another 1000 deep cycles on the
batteries.

I hope other satellite designers are considering adding such transponders
in the future to continue this "easy-sat" technology.

WB4APR at amsat.org, Bob

PCsat WEB  page     http://www.ew.usna.edu/~bruninga/pcsat.html


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