[time-nuts] PPS sync

Jerry Hancock jerry at hanler.com
Mon Jun 5 00:36:06 EDT 2017

1) I have my TAPR M12 Kit working now next to my lucent RFTG-U REF0/1 pair.  I was comparing the PPS outputs triggering on the Lucent as channel 1 and the M12 as channel 2.  I can’t tell which is moving around but the symptoms are that at T0 (not the top of the minute or hour) they are in sync within a nanosecond.  From T1 to T20 they move progressively out of sync until hitting around 100ns and then snapping back to being in sync. I would think that if both were moving that it wouldn’t be that consistent, no?

Since I can’t tell which is moving, most likely both,  I plan to take the disciplined 10Mhz out of the Lucent and divide it down with my TAPR TADD-2 to 1PPS.  I would think that would be more stable on a PPS by PPS basis and compare again. 

Any other ideas?

2)  When I first fired up the M12 and let it do a survey, it was off for some reason by 7KM.  I then set the M12 reference location to the Lucent location as I know it to be correct.  I was thinking though, would the PPS phase comparison in 1, above, be impacted by the reference locations being off?  Both GPS cables are the same length.  The only thing I don’t know is the internal processing delay of the units.  The SynTac software allows you to take this into consideration for PPS timing when using the M12.  Interesting unit by the way.  Lots of configuration options exposed with the Syntac software.  Not that I would replace Lady Heather or anything, I’m just using it while I get some of these issues figured out.


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