[time-nuts] 60 Hz line quirks, anybody recognize this stuff?

[Hal Murray]

The context is using the 60 Hz line for timing.

I'm feeding 60 Hz from a wall wart transformer into a modem control signal 
that the kernel PPS stuff watches.  Mostly, it works as expected, but 
occasionally, it picks or drops a cycle.

In order to understand what was going on, I fed the same signal into the 
audio input and setup a job to capture the audio.  Here is an example of a 
pick:
http://www.megapathdsl.net/~hmurray/time-nuts/line/2012-Aug-09-a-pick.png
http://www.megapathdsl.net/~hmurray/time-nuts/line/2012-Aug-09-a0.png
http://www.megapathdsl.net/~hmurray/time-nuts/line/2012-Aug-09-a1.png

OK, that somewhat makes sense.


Something happened several days ago.  I used to get picks/drops rarely, say 
ballpark of 1 a month.  Now I'm getting 10 or 20 per day.  So I started 
looking closer.

I'm now seeing stuff like this.  I've got lots and lots of examples.  I added 
a second PC with different hardware.  It sees the same stuff.

Does anybody recognize this?

http://www.megapathdsl.net/~hmurray/time-nuts/line/2012-Sep-01-a0.png
http://www.megapathdsl.net/~hmurray/time-nuts/line/2012-Sep-01-b0.png
http://www.megapathdsl.net/~hmurray/time-nuts/line/2012-Sep-01-c0.png
http://www.megapathdsl.net/~hmurray/time-nuts/line/2012-Sep-01-d0.png
http://www.megapathdsl.net/~hmurray/time-nuts/line/2012-Sep-01-e0.png


-- 
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