NIST NTP servers

[laszlo at heliacal.net (Laszlo Hanyecz)]

On 2016-05-13 14:12, Lamar Owen wrote:
> On 05/11/2016 09:46 PM, Josh Reynolds wrote:
>> maybe try [setting up an NTP server] with an odroid?
>>
> ...
>
>
> You really have to have at least a temperature compensated quartz 
> crystal oscillator (TCXO) to even begin to think about an NTP server, 
> for anything but the most rudimentary of timing.
>

There are WWVB clocks that try to sync nightly.  Many of them don't even 
have a second indicator, but they give reliable time to the minute.  NTP 
is a lot better than this as it continuously disciplines the clock 
instead of just lining it up once a day, but we're talking about doing 
this over the internet where we measure latency in milliseconds.  If 
you're working down at the picosecond level you will probably not be 
using NTP to distribute your clock signal.  Running an NTP client 
against pool servers is a lot better than not running it at all, but 
running it against a fancy local server with a GPSDO hooked up to it is 
only marginally better than the pool servers.

It all depends on what you want to do but a cheap ARM or Intel Atom 
computer works well for an NTP server (remember millisecond level 
accuracy).  If you can afford to build a secure bunker with armed guards 
and redundant everything for your time server that's good, but a few RPi 
style computers with GPS hats are almost as good, and you can buy a lot 
of them for very little money..

-Laszlo