[ntp:questions] NTP server with no network, no GPS signal

David J Taylor david-taylor at blueyonder.co.uk.invalid
Fri Apr 29 15:09:13 UTC 2011

> Hi!
> I am looking for a solution to install an NTP server in a very 
> restricted network which can not be connected to other networks even 
> through a firewall because of strict security policy. RS232 and usb are 
> ok. Using GPS or DCF77 reference clocks would require a long antenna 
> wire to get signal. Installing the antenna cable would be expensive, but 
> there is good LAN cabling between a space with good GPS signal and the 
> room with high security.
> What kind of cheap solutions would you think of? For instance, is it 
> possible to feed time signal from one NTP server to another via 
> RS232/usb? Or is there an affordable usb/rs232 reference clock which has 
> an IP based separate antenna unit?
> With best regards,
> -- 
> Cristian Seres


I would consider installing a GPS puck (such as the GPS 18x LVC or Sure 
Electronics board) in the antenna space, and use the LAN cabling to 
distribute the RS-232 signal with PPS from the GPS to your NTP server PC 
(or multiple PCs).  If needed, you could use line drivers and receivers to 
improve the signal integrity on a long cable run, and to distribute the 
PPS component of the signal to multiple server PCs.


Example of use:

Once you have one or two stratum-1 servers, the rest can be synced over 
the LAN to within a few milliseconds, if that's good enough.


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