PCSAT2 Downlink Challenge

When PCSAT2 is enabled on Monday or Wednesday, (1,3 Aug) we'd like to capture as much of the 1200 baud and 9600 baud telemetry on 437.975 MHz as possible. See the plan on: http://www.ew.usna.edu/~bruninga/pec/pc2ops.html

1200 baud telemetry is just an occasional packet every 10 or 60 seconds just like PCsat. 1200 baud stations can simply feed their downlinks directly into the global APRS system like normal. These will help update the LIVE PCSAT2 telemetry page by G4DPZ at:
http://www.pcsat2.info/PCSat2Web/RealTime.jsp

1200 baud capture files will not be requested to be emailed unless there is an anomoly and we need some missing data.

9600 baud stations will see the special solar cell experiment data which is used to measure cell degradation over time. We need the first data sets as a benchmark for future comparisons. Having many ground stations capturing the data will help assure a complete initial data set.

54 lines of 9600 bd data are 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 5th 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".

The "challenge" is due to the high UHF Doppler and the burst nature. You have to anticipate the Doppler to get a complete set since there is nothing to tune in until it has begun.

Volunteers who want to take on this challenge:

1) Please be sure to set your TNC and PC clock to UTC within a second or so. Be sure time-stamping is ON. Use Hyperterm or ALOGGER or any other capture tool (ALOGGER format is preferred).

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

PC2_YYMMDD_HHMM_CALL.txt

3) Email to PC2@grc.usna.gov

Soon we will have a separate SATGATE server just for collecting this data and a specialized version of ALOGGER which can not only log, but also serve as a simple IGate for feeding your serial port TNC into the SATGATE server.

ALOGGER is available from: http://www.billdiaz.dynip.com/

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?

Also, all of our web pages will be down during this critical time since our entire building will be shut down for long planned electrical power work. Our command station will be operted via an emergency generator and a single long
extension cord offering 15 amps. So read these web pages well prior to the event.

Good luck.
Bob Bruninga, WB4APR
USNA Satellite Lab

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