[ntp:questions] Installing more stable oscillator?

Hal Murray hal-usenet at ip-64-139-1-69.sjc.megapath.net
Mon Jul 16 05:29:50 UTC 2007


In article <f7bcdq$fq3$1 at scrotar.nss.udel.edu>,
 "David L. Mills" <mills at udel.edu> writes:

>My own rubidium oscillator and, I suspect, P-H's do not have a PPS
>output, just a raw 10-MHz signal. However, there is a provision via an
>external DC signal to vary the frequency over a small range. So, find a
>cheap counter/timer on eBay to divide that signal to 1 PPS. Use a
>ADC/DAC add-in card on your computer to drive the rubidium frequency
>control. Modify the kernel ntp_adjime() routine to send offsets to the
>DAC. Use a poll interval on the high side to match the Allan intercept.

I've been thinking of a FPGA on a PCI card with an input connector
for an external clock.  Then patch the kernel to use it for
timekeeping.

I was expecting it to work without any PPS or tweaking of the
external oscillator.  Won't the normal drift mechanism correct
for any (minor) frequency inaccuracies in the external clock?

Suppose I build something like that.  Is there anything I should
tinker with to tell ntpd that it has a (very) stable local clock?


-- 
These are my opinions, not necessarily my employer's.  I hate spam.




More information about the questions mailing list