ntpsec is ignoring PPS
halmurray at sonic.net
Wed Dec 1 23:26:32 UTC 2021
> PPS(0) is a regular garmin lvc18, while PPS(1) is a GPS disciplined
> oscillator, this one: http://www.leobodnar.com/shop/index.php?main_page=produc
> t_info&cPath=107&products_id=234 The GPSDO emits a 10MHz signal that is
> divided to 1PPS using a "picdiv" (http://www.leapsecond.com/pic/picdiv.htm ).
> As suggested by the website, a 100nF capacitor has been connected.
I think you are missing the key step.
The PPS from a GPS unit is carefully setup (by the GPS box) to start at the
start of a UTC second.
The picdev doesn't know anything about UTC. Its pulses will be 1 second apart
(if your 10 MHz is accurate), but they will start at an arbitary time relative
to the start of a UTC second.
> So that works but PPS(1) shows an 'x' before it. I see a rather
> (surprisingly) large offset but jitter is always low (less than 0.02).
Basically, that GPSDO and a picdev isn't the right tool for what you are
trying to do.
If you power cycle your picdev you will get a new offset.
Does the picdev have a way to move the PPS around so you can adjust the
PPS-UTC offset? That would need a good PPS to compare it to If nothing else,
you can short out the clock input.
Plan B is to fudge the offset in the config file.
How good is your antenna? The picdev output will probably drift a bit when
the GPSDO looses contact with GPS.
These are my opinions. I hate spam.
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