[time-nuts] Choosing an Oscillator...
phk at phk.freebsd.dk
Sat Jul 28 13:16:21 EDT 2007
In message <46AB6C13.1070708 at kudra.com>, Robert Sexton writes:
>I'm still headed towards getting a Stratum 1 NTP server up and going.
> From what I've learned so far, higher quality PPS signals aren't going
>to do a lot for me if my server has a wiggy clock. That makes perfect
>sense. Now I just have to figure out how to get a good clock into my
>server a la the soekris clock-block approach.
>So what do people recommend for somebody working on a small budget?
Get yourself one of the TAPR.org clock-blocks as the first thing, because
that will free you to use any clock source you come across, no matter
what frequency it has, thus making upgrades easier.
Almost anything is better than a regular uncompensated quartz X-tal.
TCXO's are usually a few dollars each on eBay, a TCXO is temperature
compensated quarzt osc.) and they can get down to total tolerances
in the +/- 5 PPM range.
Almost any OCXO (even much simpler ones than the HP '811 or '544)
will get you microsecond stability on your NTP server.
Rubidium and Cesium is only really relevant if it is important for
you to have long hold-over (how long your server stays precise
after your GPS antenna gets hit by lightning).
Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG | TCP/IP since RFC 956
FreeBSD committer | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
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