[time-nuts] Raspberry Pi TCXO Hat

[Richard Laager]

On 11/2/19 1:15 AM, Hal Murray wrote:
> 
> rlaager at wiktel.com said:
>> I'm curious if this would provide any meaningful improvement in system clock
>> accuracy, for NTP, if I'm already a GPS PPS hat. If there's a reasonable
>> chance this could be interesting, I'm thinking about ordering a couple and
>> "sacrificing" a Pi 3 and/or Pi 4. 
> 
> What are your goals?  NTP server?  Neat graphs?

Closer to the latter.

> The Pi 3 has Ethernet on USB.  That adds a layer of jitter to packet timings 
> so a Pi 3 even with GPS will never make a great NTP server.

Right, though a Pi 4 may be better.

> How stable is your temperature?  Self heating as the CPU load changes is 
> important even if the room temperature is stable.  A TCXO won't help if the 
> temperature is already stable.

The graph in ntpviz shows the jitter and temp almost perfectly correlated.

> If you have 2 identical Pi-s, you could put the TCXO on one and run a 
> side-by-side comparison and tell us what happens.

Right, that's the sort of test I had in mind.

-- 
Richard