[ntp:questions] Re: Using a Rubidium clock with NTP

Geoff Horner geoffh at bigfoot.com.au
Thu Oct 7 11:18:10 UTC 2004


Paul,

I do have a GPS time server on the same network and had considered this, but was worried about the long term drift of the Rb ticks. I image I could easily monitor the difference between the two and edit the fudge factor on the Rb machine's ntp.conf every day or so, but restarting ntpd daily would be very detrimental. I think ntpdc can alter the fudge factor on the fly, but haven't checked it out and am not sure if that's the best idea. Since posting my question, I have found (with TVB and friend's help - many thanks) how to program the DDS in the Rb oscillator. I was thinking it might be best to set the Rb osc internal freq to 14.31818 MHz and substitute the GPS PC xtal for this. 

With all this effort,  I'm starting to think the easiest way to get a good stratum 1 server is to use one of the  miniature OCXO that I've seen, and substitute the 14.31818 MHZ PC xtal.and with one of them and a Motorola M12+ GPS timing receiver, producing good results for little outlay. Maybe next clock....
Can't wait for the miniature rice grain size Rb clocks to be available. An atomic wristwatch would be nice.

Geoff



"Paul Croome" <Paul.Croome at softwareag.com> wrote in message news:ea26a3f3.0410062328.6f76f168 at posting.google.com...
> "Geoff Horner" <geoffh at bigfoot.com.au> wrote in message news:<mailman.31.1095599860.26599.questions at ntp.org>...
> > Hi all; My first post.
> > 
> > What is the best way to use a Rubidium oscillator with a PPS output as a st
> > ratum 1 server?
> ...
> 
> Geoff,
> 
> I suggest using your Rb PPS with the NTP PPS driver (type 22).
> Your Rb oscillator probably doesn't tick synchronously with the TIA/UTC/GPS
> second, so observe the offset between the Rb ticks and GPS time, then
> set the time1 fudge factor to compensate.
> 
> The NTP server that is running the PPS driver also needs another source of time,
> so that it can number the ticks. Any clock that is within +/- 0.5 second
> should do.
> 
> Paul
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