[ntp:questions] Trying to use Dimension 4 time keeper

David Taylor david-taylor at blueyonder.co.uk.invalid
Sat Sep 14 09:45:45 UTC 2013


On 14/09/2013 05:48, W. eWatson wrote:
> What have I gained?  What does the data mean from ntpq -n -clpe -clas?

Please see:

   http://www.satsignal.eu/ntp/setup.html#check

for a brief guide to checking that NTP is working.

The command "ntpq -p" or "ntpq -pn" will show the delay between the 
servers and your PC (in milliseconds, expect 20-30 ms for network-locale 
servers 100+ ms for servers on an inappropriate continent), and the 
offset column shows how well NTP is doing, the lower the offset the 
nearer to UTC is your PC running.  The offset value will be highly 
dependant on the OS (i.e. Windows of Linux/FreeBSD), the servers you are 
using (i.e. Internet or local), and whether or not you have a PPS (pulse 
per second) feed to your PC.

In general, you will see offsets in the tens of milliseconds range for a 
purely Internet-synced Windows PC (but may be better with some versions 
of Windows), and sub-millisecond for FreeBSD/Linux PCs.  For best 
performance, you may want a local Linux PC synced to the Internet (or 
with a GPS/PPS source), and sync the Windows PCs to that server (but 
sync them more tightly than you would to the Internet).  I don't think 
you're at that stage yet, but it's worth bearing in mind.  The Linux box 
could be as simple as the Raspberry Pi card PC, and even adding a GPS to 
that only adds ~US $35 to the cost.
-- 
Cheers,
David
Web: http://www.satsignal.eu



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