this pass at 12:19 UTC shows a nearly linear frequency drift till 12:23:20 UTC (COMM A) –
no beacon at 12:24:20 UTC – next beacon was 600 Hz lower and COMM B.


Sequence Number: 13854   Timestamp: 2009-Jun-06 20:32:33   COMM A    1040 Hz
Sequence Number: 13856   Timestamp: 2009-Jun-06 20:33:32   COMM A    1160 Hz
Sequence Number: 13858   Timestamp: 2009-Jun-06 20:34:30   COMM A    1260 Hz
Sequence Number: 13860   Timestamp: 2009-Jun-06 20:35:29   COMM A    1320 Hz
Sequence Number: 13862   Timestamp: 2009-Jun-06 20:36:27   COMM B    650 Hz *** -> adjust
Sequence Number: 13864   Timestamp: 2009-Jun-06 20:37:26   COMM B    1150 Hz
Sequence Number: 13866   Timestamp: 2009-Jun-06 20:38:25   COMM B    1210 Hz
Sequence Number: 13868   Timestamp: 2009-Jun-06 20:39:24   COMM B    1280 Hz
Sequence Number: 13868   Timestamp: 2009-Jun-06 20:40:23   COMM B    1350 Hz

The first packet after the CW beacon says which comm system is being used (A or B).
The two COMM systems are using the exact same parts, but due to tolerances, layout differences, etc, the two COMM systems are always just a little different in frequency. Once launched, they can’t change the frequency, and the differences you see are probably due to the cheap computer crystals that we use as reference. Possibly temperature differences across the board change things as well.

Thanks, Bryan!

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