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

[Bob kb8tq]

Hi

Crystals most certainly do still jump. Like a lot of “features” of 
crystals this does not get a lot of attention in the form of published
data. Manufacturers are not very excited to talk about problems.
Doubly so if they happen to have an in house solution for this or 
that issue :).

Academics are mostly interested if they can propose a new solution 
(or at least a new source for the problem ). Most theories relate to
mechanical stress in the part. Micro fractures in the blank are a 
classic “answer”. 

Either way, you don’t get a lot of papers or published data. That 
said, there are tons and tons of data out there. It simply is not
in the public domain. Manufacturers test thousands of parts a week
for this sort of thing ….What they do next is very much in the 
“we don’t talk about that” category. 

Yes it does depend a bit on just what you call a jump. Steps in
the ppb range were pretty typical on AT OCXO crystals back in 
the 80’s. Steps in the < 1 to 0.1 ppb range showed up on SC cuts in
the 90’s. As the decades ticked off, the typical magnitude dropped. 

If you drill down to parts in 10^-11, you will see steps. Are they the
same thing? How sure are you when you measure a 5x10^-12 “step”
in an OCXO aging curve? If a crystal is aging at +3x10^10 per day 
for a couple days and switches to -1x10^-10 per day. Is that
a step? ( even if there is no abrupt change ). At some point things 
become more than a bit unclear.

Data wise a classical frequency jump ( or phase hit ) looks really boring. 
The crystal is moving along on some curve due to aging or whatever. 
On the next reading, it has taken a step up or down in frequency. It then 
continues on the same curve as before. 

Time wise, the classical steps tend to show up on new crystals. The 
spacing between steps might be days, weeks, or months. They tend 
to space out more and more as the crystal ages. ( making them tough 
to see on older parts ). 

These are not the same as temperature perturbations. Those happen
at very specific temperatures ( typically in TCXO’s ). They are related
to pretty well known physics. They repeat again and again as the
temperature is changed. 

Bob

> On Sep 2, 2022, at 6:25 AM, iovane--- via time-nuts <time-nuts at lists.febo.com> wrote:
> 
> 
> Some time ago there have been some discussions here on crystal jumps. Do crystals still jump? If anybody out there has data (only date and time) of old crystal jumps (first decade of this century) I would be pleased to receive some, thanks.
> 
> I8IOV Antonio
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