[aprssig] PCSAT2 Packet experiments
bruninga at usna.edu
Thu Sep 15 16:52:37 CDT 2005
PCSAT2 Ops notes:
The PCSAT2 packet system is enabled for
both 1200 and 9600 baud digipeating, and
it can also do cross-BAUD digipeating. That
is 1200 up and 9600 down or 9600 up and
1200 down. We had no specific application
in mind, but it is there for experimentation.
For 1200 or 9600 use the path VIA ARISS.
For cross-BAUD operation go VIA XBAUD
The easiest way to experiment is to use either
the Kantronics KPC-9612+ TNC or the Kenwood
D7 or D700 that can both easily switch between
1200 and 9600 baud.
1200 baud has a 7 dB advantage over 9600
so typically you might want 1200 on the
2 Watt downlink. But on the 50W uplink from
your mobile you have 13 dB more power to
make up for the 7 dB worse performance.
The advantage comes in because the 9600
baud packet is shorter, your probabily of a
collision on the uplink is reduced.
Therefore there is an advantage under high
loading to experiment with setting your UPLINK
Kenwood mobile to 9600 baud and using the
path VIA XBAUD. Most of the satgates are
listening at 1200 baud so that is why you want
to cross BAUD. The down side is that you will
be listening at 9600 and probably wont hear
Experiment with the shortest TXD delay you can
get by with at 9600 baud. Typically for one-at-
a-time packets like APRS, there is not much
advantage for operating at 9600 baud, because
the TXD delay is often as long or longer than the
data, so the actual throughput advantage of
9600 is more like a factor of 2 than 8.
Maybe the value of operating at 9600 baud would
be in downloading Mail from the PCSAT2 PBBS.
That is the only time when all the delays will be
amortized and 9600 baud woiuld give you a
significant throughput advantage.
SO anyway, Users are welcome to use the
PCSAT2 digipeater for experimentation.
Uplink is 145.825
Downlink 435.275 +/- 10 KHz Doppler
DIGIpeater call is ARISS for 1200 or 9600
DIGIpeater call is XBAUD for cross-baud
PBBS callsign is MAIL-1
P.S. The D7 and D700 can do either 1200 or
9600 and on either band, but not both baud
rates at the same time. The KPC-9612+ can
transmit either 1200 or 9600, but because it
is dual port, it can receive both at the same
Bob Bruninga, WB4APR
US Naval Academy Satellite Lab
Sent via amsat-bb at amsat.org. Opinions expressed are those of the author.
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