[time-nuts] Re: Do crystals still jump?

[ed breya]

Rick wrote:

"I just wanted to clarify that crystals are quite capable of
jumping without any help from temperature shifts.  The E1938A
proved this.  With a thermal gain in the hundreds of thousands,
the crystal temperature never budged.  Yet the crystals (which
were essentially the same as what was in the 10811) did jump;
every one of them from time to time.  There were no crystals
that "never" jumped, depending on how you define "jump".
A crystal might appear not to jump for while, but if observed
long enough you would always see a jump sooner or later.
It wasn't like you could sort them for "non-jumping" units.

The situation reminded me of the so called "smart clock"
concept, where the clock would "learn" what its aging was
and then compensate it out during hold over.  The trouble
with this was that the aging curves have "knees" in them
and you are hoping that a knee doesn't occur during holdover.

With the advent of small, low power, affordable atomic frequency
sources, we now have a way to get rid of jumps."

But don't all these atomic frequency sources ultimately (in practice) 
depend on crystal oscillators anyway, making them subject to the same 
jump issues?


Ed