Hal, where are you taking off the signal to the audio line? At the low voltage wall wart or at the modem pin? - assuming there's an isolation or dropping resistor.
I agree with others that the power company isn't doing this. There would be inductive ringing. Can you confirm with another wall wart going right to another audio channel? Or maybe a real filament transformer instead of a wart. Who knew you could find so much interesting stuff on the power line . . . Bill Hawkins P.S. I think the mild flattening of the sinusoid peaks is caused by saturation of the barely-enough-iron in the wart. -----Original Message----- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Hal Murray Sent: Saturday, September 01, 2012 1:35 AM To: time-nuts@febo.com Subject: [time-nuts] 60 Hz line quirks, anybody recognize this stuff? 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 -- These are my opinions. I hate spam. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.