Frequency Reference for NTP Use?
grail at goldweb.com.au
Sun Jul 14 00:27:20 EST 2002
On Saturday, July 13, 2002, at 10:06 , Brad Hards wrote:
> A few seconds a month is probably going to require some kind of
When you move from temperature compensated oscillators to ovenised*
oscillators, you move from 1 second/week to about 1 second/year
stability. You also move from the order of $x00 to $x000.
> Unless you are really concerned with GPS availability, I'd look for
> a GPS with a 1PPS output.
The catch is that such units are usually designed to be rack mounted,
and they're usually in the order of $1500. My budget is significantly
less than that.
I'll probably try to read through the NMEA driver to figure out where it
gets the second-edge from, and find some way of reducing the jitter -
such as the first character in the stream, rather than the first
character of the time stamp.
The least expensive ovenised oscillator with 1PPS output I could find is
According to the NTP server, the jitter on the processor clocks of my
Pentiums is about 0.008ms. That may actually do for the meantime.
* When I first read through the xntpd documentation, I read this as
oven-sized. Which isn't that far off, when you see the setups that some
places have for their Campus' Master Clock.
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