PCSAT2 9600 Buad Data Challenge                       28 July 2005
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Updated 26 Sept 2005

PCSAT2 carries a solar cell experiment to measure cell degradation 
over time.  Having many ground stations capturing the data will 
help assure a complete initial data set.

A data set consists of 54 lines of 9600 baud data transmitted as a 
beacon group once every 3 minutes 20 seconds consisting of 11 one-
sec data bursts of 5 lines spaced every 2 secs.  The 7th byte of 
each line is human readable as a serial number starting with "A" 
through "Z", then "a" through "z" and then "0", and "1".  Here is 
an example 128 byte line (truncated to fit this document):

ISSTLM>APRS,SGATE,WIDE:{TPrVQEAwEAAwEAAwEAAwEAAHoAAwEAAwEAAwEAAH...

Notice the 7th byte is an "E" meaning this is the 5th line of the
data dump.  For a complete file, see:

http://www.ew.usna.edu/~bruninga/pec/PC2oct14FTSCE.TXT

The "challenge" to receive this data is due to the high +/- 9 KHz 
UHF Doppler during the pass and the fact that the data is in bursts.  
You have to anticipate the Doppler to get a complete set since 
there is nothing to tune in until it has begun.  Consider:

1) Please be sure to set your TNC and PC clock to UTC within a 
second or so.  Be sure time-stamping of your TNC or software is ON.
ALOGGER is an ideal logging tool.  http://www.billdiaz.dynip.com/

2) Use this file name convention with time stamp and your call, to
save the data to file and also use the same format for the subject 
line of the Email. 

    PC2_YYMMDD_HHMM_CALL.txt

3) Email to PC2@grc.nasa.gov  (this is no longer needed since we
are now getting sufficient data via the APRS internet system).

4) If you can simultaneously feed your live 9600 baud RX data
via IGate software, then feed to port 20150 on satgate.aprsca.net.

5) If you are a 1200 baud only station, then feed to ANY APRS
server on the global APRS-IS system.

TUNING DOPPLER:  Remember that at AOS the UHF signal will be as 
much as 9 KHz high and at LOS will be as much as 9 KHz low.  But 
at these times the doppler is *changing* the least and this is
probably the best time to catch a complete file without any tuning 
glitches.

In the middle of the pass, the Doppler rate of change is the 
highest and although the signal will be strongest, over the center 
2 minutes the doppler will shift as much as 8 KHz!  This is why 
we expect to have to combine files from multiple users to get a 
complete set.

Computer tuning may not help, since the step-transition during a 
tuning step may garble a packet?


Bob Bruninga, WB4APR
USNA Satellite Lab