I am curious: is the quartz in a high quality quartz crystal perfect?
That is; is the
crystalline lattice perfect, without flaws or impurities? I assume
that the quartz is
grown in a furnace, can we grow perfect quartz crystals?
Pete.
On 2/5/2017 6:31 PM, Bob Camp wrote:
Hi
Aging can be caused by many things. Stress on the blank (and can and leads and
plating and …) is one
source. There are good reasons to believe that quartz vs metal stress can take
> 1 month to settle out
to the 90% level. Particle (think borders down to atoms) equilibrium inside the
can is another source.
Adsorption / desorption rates on many of the likely candidates also run out into
the > 1 month range.
More or less — you can adsorb stuff in a few seconds that takes many weeks to
desorb. Yes this is
only the start of a very long list ….
How long an interruption to stir things up? Does the oven go to full power
after your interruption? If it
does, things are likely to get tossed around and aging (or retrace or warmup or
whatever you want to
call it) is going to get going.
Pile on top of this the fact that crystals are not the only thing that does
aging like things. Capacitors
have a fun characteristic known as dielectric absorption. Some (tantalums) have
leakage that drops
a LOT with time spent at temperature and voltage. Either way, bump the voltage
and things move around
for a while. Use the wrong caps and it can be quite a while.
Next layer is keeping the OCXO at the same temperature. When a “normal” OCXO is
sitting there on
the bench, it’s in it’s own very specific temperate zone. Convection (and maybe
other things) have acted
over quite a while to set up that zone. Touch it / bump it / move it / blow on
it …. you will change the
temperature. Most likely you will change the gradient across the package. Rick
wrote some papers
back in the 90’s about why this really messes things up…. ( Again this is the
start of a very long list …).
It’s even longer if you have DAC’s and voltage references external to the OCXO.
So yes, you can get aging a lot of ways. Knowing what is and what is not aging
can get a bit complicated.
Bob
On Feb 5, 2017, at 3:11 PM, John Ackermann N8UR <j...@febo.com> wrote:
We know of OCXO that have been continuously running for years and have
exceptional aging, supposedly as a result.
What does it take to interrupt that? A momentary loss of power? The oven
cooling down? Some long period of off-time? Or, once the oscillator has baked
in will it return to that low aging once it has been powered up and thermally
stabilized?
John
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