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

David McGaw n1hac at Alum.Dartmouth.ORG
Sat Sep 1 19:57:55 UTC 2012


In the second set it looks like the wrong input is being sampled at 
times.  Notice the offset is always the same.  I have seen this happen a 
lot with simple sampling programs.  Even if this were real I doubt it 
would cause false triggering of the clock.  The pulse shown in the first 
set would.  When digital clocks are run off the power line they need 
very good 60 Hz filtering as even a refrigerator coming on will cause 
trouble.

David


On 9/1/12 3:31 PM, tcurlee at sbcglobal.net wrote:
> Perhaps a dumb question, but the wall wart is plugged into the wall, connected directly to the grid?  You aren't powering the wall wart through a UPS or some type of inverter?
>
> Tom
>
> Sent from my HTC Inspire™ 4G on AT&T
>
> ----- Reply message -----
> From: "Bill Hawkins" <bill at iaxs.net>
> To: "'Discussion of precise time and frequency measurement'" <time-nuts at febo.com>
> Subject: [time-nuts] 60 Hz line quirks, anybody recognize this stuff?
> Date: Sat, Sep 1, 2012 11:42 am
>
>
> 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-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
> Behalf Of Hal Murray
> Sent: Saturday, September 01, 2012 1:35 AM
> To: time-nuts at 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
>
>




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