Hallo, Alby, > My NTP server is running with a Sure GPS as my Stratum-0 device and I'm > able to get microsecond level of accuracy. Averaging an offset of +/- 10µs.
I understand any GPS device needs to know the time down to a precision of some 20..50 nanoseconds or so. It simply takes that kind of precision clock internally to display the position as accurate as these gadgets do. Now, some GPS devices may take more care to export the time with good precision to the outside than others. Personally, I never had a GPS hooked up as a clock source. My ntpd are always stratum 2 or more. But I am surprised that you get only +/- 10µs. This is some 200x worse than I would have speculated. Are you sure your clock isn't actually much, much better than that? How do know it isn't? Just comparing with other ntpd out in netland doesn't count. Ntpd will allow you to see clock imprecision up to somewhere in the single-digit µs range, if you are careful and a bit lucky. Below that, with today's typical network package delays, ntp is blind. So you'd need something else, something better than plain ntp, to compare your clock to. Mildly related to your original question: I find http://www.leapsecond.com/ amusing and enlightening reading. Among other things, http://www.leapsecond.com/ten/ has a list of increasingly precise clocks and what they can achieve. Regards, Andreas Am 13.08.2012 20:52, schrieb AlbyVA: > > > > My NTP server is running with a Sure GPS as my Stratum-0 device and I'm > able to get microsecond level of accuracy. Averaging an offset of +/- 10µs. > > So I'm wondering, what device out there (that is "reasonably priced") will > provide nanosecond level accuracy? > > -Alby > > > _______________________________________________ > pool mailing list > [email protected] > http://lists.ntp.org/listinfo/pool _______________________________________________ pool mailing list [email protected] http://lists.ntp.org/listinfo/pool
