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.