Frequency Reference for NTP Use?

[Brad Hards]

On Fri, 12 Jul 2002 17:47, Alex Satrapa wrote:
> Ideally, I'm looking for a 1PPS source with an RS-232 or Parallel port
> interface, that has accuracy as low as a few seconds a month (which
> means I'd be happy with a Quartz oscillator).  I would love to have a
> Caesium clock, but I just can't scrape up the $1M odd that I'd need ;)
Note that a lot of these devices are also sensitive to motion and gravitational
effects - you can't move them without needing to recalibarate.

> My biggest reasons for avoiding GPS-based external clocks is that:
> 1) I already have a GPS
> 2) I don't want to rely on the GPS network for my time (I may not be
> able to receive the signal)
A few seconds a month is probably going to require some kind of temperature
stabilisation. There is an IEEE Spectrum (March 1998) article "Fine tuning
time in the space age" that explains this.

You've probably come across a lot of these already, but:
http://www.eecis.udel.edu/~ntp/hardware.html
http://www.eecis.udel.edu/~ntp/ntpfaq/NTP-s-refclk.htm
http://www.ieee-uffc.org/freqcontrol/piezo.html
http://www.boulder.nist.gov/timefreq/general/receiverlist.htm

Unless you are really concerned with GPS availability, I'd look for
a GPS with a 1PPS output.

Brad
-- 
http://conf.linux.org.au. 22-25Jan2003. Perth, Australia. Birds in Black.