[time-nuts] 60Hz line data

[Hal Murray]

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.



-- 
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