Gary E. Miller writes:
> Poll=2s is still the bast for this hardware, but there is a little
> tradeoff between offset and jitter.  Since NTP is about time, not
> frequency, we go with the best time.

You 've made this argument before, but I think it's circular reasoning.
You make the local clock follow external jitter faster.  Whether or not
that gets you closer to true time isn't something you can decide from
your data, since the NTP offset value only tells you how close the PLL
controller thinks it is to the external source.

> Now the good news.  On a quad XEON, with an MR-350P serial GPS:

I think as that example amply shows (I think you are using serial line
discipline for PPS here), having the obviously better (than the rasPi)
local clock follow a noisy reference (likely more jittery than the one
on the rasPi) isn't helping the precision.

BTW, both your plots showed relatively large swings in frequency offset
in a short period of time.  Do you have an A/C that is producing larger
temperature swings?


Regards,
Achim.
-- 
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