Hal, do you have a resonant 60 Hz filter in the pickoff? The waveform in Aug-09-a1 certainly had multiple zero crossings.
Remote-controlled tap changers can do things like that. If I got the UTC offset right, that happened at about 2 PM local time, when a big transformer tap could have been changed for more A/C load. I expect you'd rather do things in software, but the mechanical solution is to couple a synchronous motor to a flywheel marked with 60 Hz lines for photocell pickup. A precision 33 1/3 rpm turntable with strobe markings would work very well. Bill Hawkins -----Original Message----- From: Hal Murray Sent: Friday, August 10, 2012 3:51 AM Actually, there were 2 extra pulses. Here is the PPS view: http://www.megapathdsl.net/~hmurray/time-nuts/line/2012-Aug-09-a-pick.png (Samples every 10 seconds.) Here is the audio view: 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 (16 bit audio, 8 KHz) I noticed a couple of other fishy areas: http://www.megapathdsl.net/~hmurray/time-nuts/line/2012-Aug-09-b0.png http://www.megapathdsl.net/~hmurray/time-nuts/line/2012-Aug-09-b1.png They didn't confuse the PPS collector. I'm probably overlooking lots of similar glitches. I only noticed that pair because the first one happened at the bottom of a cycle and that was big enough to stand out. I noticed the second one because it was close enough to the first one. Anybody got software to emulate a PLL? I'm looking for something that will track a sine wave and tell me when it finds noise. I haven't seen any of the ground problems in the last day or so. I don't know if that is just luck or if upgrading to Fedora 17 fixed something. (Or maybe I accidentally fixed something.) -- 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. _______________________________________________ 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.
