[time-nuts] HP 5345A

[Brooke Clarke]

Hi Rick:

Is there a way to know about the type of aging up front.  For example 
what crystal makers have only micro cracks as the aging mechanism?  For 
what starting date?  My guess is that there are plenty of crystals that 
have aging that's mainly due to contamination or other causes that the 
better makers have eliminated.

Have Fun,

Brooke Clarke

w/Java http://www.PRC68.com
w/o Java http://www.pacificsites.com/~brooke/PRC68COM.shtml
http://www.precisionclock.com



Rick Karlquist wrote:

>Hal Murray wrote:
>  
>
>>I thought aging was generally uni-directional and reasonably predictable
>>if
>>you had enough data.
>>
>>Does it wander in both directions?
>>    
>>
>
>This is probably on the list of the "10 greatest myths about
>crystal oscillators".  Many decades ago, there were systematic
>aging effects such as you speak of.  I remember learning as
>a youth that glass crystals age up and metal crystals age down.
>Over the years, any such systematic effects have been analyzed
>one by one to understand the root cause, and then the process
>has been fixed to get rid of that aging effect.  What we are
>now left with are tiny cracks and crevasses that grow sporadically
>like a crack in an auto windshield.  At least that is what we
>think is going on.  The process people, like my friends Charles
>Adams and Jack Kusters, have worked themselves out of a job
>had taken retirement, because, like the "efficient stock market"
>theory, there is no predictability to the aging data.  It is truly
>a "random walk down Wall Street" or in this case a random walk
>in time.  Oscillators will age in one direction for a while but
>may then age in the opposite direction for while for no particular
>reason.  Not only that, but crystals will jump a part in 1E^9
>or so every so often.  I've never seen a 10811 crystal without
>jumps if you wait long enough.  I don't know of any other crystal
>makers who claim to not have jumps.
>
>Rick Karlquist N6RK
>
>
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