[ntp:questions] Slow convergence of NTP with GPS/PPS

Hal Murray hal-usenet at ip-64-139-1-69.sjc.megapath.net
Tue Oct 21 19:47:00 UTC 2008

>We target for millisecond accuracy. As I understand, the oscillators on 
>standard PCs are mostly cheapest crap and there are way better 
>oscillators I could use to replace the original. Is that correct?

There are two parts to that "crap".

One is that the actual frequency doesn't match the number printed
on the can.  That's not a problem because the drift file corrects
for that type of error.

The other is that it may be highly temperature sensitive while
a more expensive crystal may be less so.  You can probably measure
that be heating up the box, perhaps by just running soem compute
intensive task rather than letting it sit mostly idle.

The suggestion for an external ovenized (OCXO) crystal/oscillator
was a way to avoid  the temperature shifts.  The basic idea
is that you run the crystal in an oven and have a mechanism to
keep it at a constant temperature.  (Warmer than normal is
easier to implement than keeping it at room temperature.  All
you need is a heater, no refrigerator.)

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

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