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09/28/2004 Entry: "WWVB morning phase jump"

Boy, it's been a while since there've been any updates here. Been busy on other stuff for the last few months...

Anyway, I have been using my Spectracom 8164 WWVB clock and two Z3801A GPSDOs as NTP reference clocks and logging the data. I generate graphs every 15 minutes showing the offset and jitter values for all three devices -- see www.febo.com/stats/ntp.

For the last few days, the WWVB clock has shown a regular spike of -100uS every morning at around 0712 local time. This has to be a momentary loss of lock at local sunrise; we've already seen that there's a very short, very deep fade in signal strength that occurs at local sunrise -- see www.febo.com/time-freq/wwvb/sig-strength, and in particular www.febo.com/time-freq/wwvb/sig-strength/wwvb-spectracom.html.

What's surprising is that I didn't notice this pattern before today. I should put together a composite log of the WWVB data to see whether it truly is an every-day occurrence.