[time-nuts] Sawtooth correction: next or previous PPS

Poul-Henning Kamp phk at phk.freebsd.dk
Tue May 22 02:39:02 EDT 2018

In message <20180522011345.4DB43406060 at ip-64-139-1-69.sjc.megapath.net>, Hal Mu
rray writes:
>holrum at hotmail.com said:
>> One thing to look out for when messing with sawtooth messages is the
>> question of does the message come out before or after the PPS pulse...  good
>> look finding the answer in the receiver documentation... 
>Has anybody asked the manufacturers?

It is trivial to measure with a HP5370: Capture a series where you
measure the 1PPS against a good 10MHz and record the serial datastream.

Then offline apply the negative sawtooth and plot the result.

If you get ugly spikes at the turning points of the "hanging bridges"
you're doing it wrong.

For the UT Oncore etc. it is predictive of the next 1PPS flank.

Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.

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