Best practices question

Paul Theodoropoulos paul at
Wed Jun 26 20:14:36 UTC 2019

On 6/26/19 11:22, Paul Theodoropoulos wrote:
> wow, fascinating - I set my c-ntpsec PPS min/maxpoll to 2. The RMS 
> time jitter rose a fairly significant amount, from hovering around 
> 0.6µs  to now 1.0µs  -- while the RMS frequency jitter plummeted from 
> hovering around 4ppb down to, well, barely discernably above 0ppb on 
> the graph.
> eh, saying it just doesn't tell the story -
> Time jitter:
> Frequency jitter:
I think maybe I'm  hitting a bug or I'm just not understanding (usually 
the latter), as it doesn't seem possible:

jitter fluctuating between 400 parts per trillion and 800 ppt?? From a 
Raspberry Pi running at 1.4Ghz?

That said, I switched to min/maxpoll 1 for PPS, and saw a corresponding 
change - so Time jitter appears to be inversely correlated to Frequency 
jitter - less frequency jitter, more time jitter, and vice-versa. This 
is all fascinating.

Paul Theodoropoulos

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