[time-nuts] Advice on NTP server needed

[Chris Albertson]

On Mon, Jun 13, 2011 at 1:37 PM, Per Molund <pmolund at gmail.com> wrote:
> Hello,
>
> I have an upcoming need for a GPS disciplined NTP server in a low cost
> project. Checking price
> on commercial units shows that these are out of reach so I have been looking
> into the possibility
> of building an NTP server.

Almost any PC hardware will work.  If cost is an issue find a used
computer.  Even an old Pentium II is fast enough.  Also NTP does not
need it's own dedicated hardware,  run NTP on any sever you happen to
already have.  NTp has very minimal hardware requirements.  What you
will need is a real hardware serial port, not a USB serial converter.
So older computers really are good in that way.

The ideal operating system is any recent Linux or even better BSD. But
it can be made to work on most any OS.

The GPS will cost more than the computer.  You will need to give the
antenna a clear view of the sky in all directions and then lead the
cable inside to the GPS receiver.  You should think about lightening
protection and grounding.  At some locations snow and ice on the
antenna is a concern.   If you need to have this work professionally
done for you the cost will be more than a small computer.

Next thing is to think about your requirements for reliability.  If
this is more than a hobby then you will likely need multiple NTP
servers.  How many more is an on-going debate.  The answer depends if
you have Internet connection and your requirement for accuracy and
tolerance to down time.

Even if you buy a commercial server you might think "How do I know if
it is serving correct time?"  This can be a hard problem or not
depending on the details of your setup.

The least expensive option is to simply run NTP on any computer you already have
-- 

Chris Albertson
Redondo Beach, California