My collection recently rolled over the year boundary: http://www.megapathdsl.net/~hmurray/time-nuts/line/Calif-60Hz-2014-2015.png
The grid is 4 weeks in the X direction. The start of the Y offset is arbitrary. I picked the start of the data. The pairs of colors are a month. Within a month, days alternate colors. Here is May 2015: http://www.megapathdsl.net/~hmurray/time-nuts/line/Calif-60Hz-2015-May.png There were a few interruptions. I lined things up by eye. They are probably off by a few cycles. I don't think they are off by a second. There are also occasional extra cycles. I assume they are caused by noise. One of these days, I'll catch one. They add up to ballpark of a second. Here is an old example: http://www.megapathdsl.net/~hmurray/time-nuts/line/2012-Aug-10-a-pick.png Here are the days before and after the leap second: http://www.megapathdsl.net/~hmurray/time-nuts/line/Calif-60Hz-2015-Jun-30-le ap.png Here is the same data zoomed in to 1 hour each side: http://www.megapathdsl.net/~hmurray/time-nuts/line/Calif-60Hz-2015-Jun-30-le ap2.png There is one frequency point way up high. (1 second out of 10 is huge on that scale.) I set the Y2 scale manually in order to make the main section interesting. As you can see, I screwed up the leap second processing. I sure knew the leap second was coming, but I don't remember considering what that program (or any others I'm running) would do when one happened. I can't see a simple way to fix it. I think I'd have to convert the program to use TAI, and then find or write a package to convert normal/UTC time to TAI. That needs a table lookup. Google's smearing inserts a second over 20 hours: 1/72000 or 13.8 PPM. If my collection system was playing the smear game, I think a 60 cycle shift would be visible if you had a reference to compare to, but not significant relative to all the other changes. (That pair of days has 500 cycles peak-peak, so 60 is only 10%.) On the frequency scale, it's probably lost in the noise. -- These are my opinions. I hate spam. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
