[time-nuts] Re: Suggestions solicited for Pi/GPSDO ntp server

[David Taylor]

On 26/05/2022 17:44, Lee Reynolds via time-nuts wrote:
> Hi, Lords of Time!
> 
> (Been a lurker for many years, just know too little to add but am always
> fascinated by your discussions. It almost reads like theological
> discursions at some points, it gets into such fine and abstruse points!)
> 
> I think it's about time to retire my old former cell site GPSDO.
> 
> Technology has improved and I'm thinking of setting up a Raspberry Pi
> based ntp server for the local devices. (I also have some spare Pi's, so...)
> 
> Does anyone have any suggestions for a good solid Pi/GPSDO setup and
> code for such a purpose? Something like Leo's device but, of course,
> much cheaper?
> 
> Any suggestions would be greatly appreciated.
> 
> TIA,
> 
>   Â Â Â Â Â  Lee

Lee,

What accuracy are you wanting for your "local devices"?  A Windows box NTP 
server could give you hundreds of microseconds, a Raspberry Pi tens of 
microseconds.  With the RPi you could have several local GPS/PPS/NTP servers 
perhaps located in different parts of the building.

Hal has given some good advice.  I particularly sympathise with the "out of 
date" part, where Linux OS changes almost on the basis of (it sometime seems) 
"if it works, break it!".  I've built a few of the Raspberry Pi NTP servers, 
and in practice the Ethernet being over USB isn't an issue, but if you can get 
a Pi 4 that would reduce that problem.

But the Pi4 isn't so easily obtainable right now, and it generates rather more 
heat, so the stability of the CPU clock isn't as good as on earlier RPi models. 
  Ambient temperature can be a problem, so try to keep the RPi out of direct 
sunshine, preferably in a cupboard away from any heating.  All to keep the CPU 
clock stable!  No need for a display, it can all be built from the command line 
over SSH.

Ask if you have further questions.

David
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