[time-nuts] AN/URQ13 reference AT cut crystal? ==> Crystal Robot

[Bob kb8tq]

> On Feb 18, 2021, at 9:57 AM, Poul-Henning Kamp <phk at phk.freebsd.dk> wrote:
> 
> --------
> Bob kb8tq writes:
> 
>>> What properties would you program a quartz-crystal-prototyping robot
>>> to search for ?
>> 
>> You very much want to (eventually) know about perturbations over 
>> temperature for a given resonator design at a specific frequency. That 
>> tends to be the 'gotcha' on a new cut. Running 100% of the production
>> through a 150C sweep at 1C per minute is *not* going to make the
>> production people (or the customer) happy. 
> 
> Yes, but that's once you have found a promising cut.

Mathematical modeling lets you make some pretty good guesses about 
where you might want to look to get this or that basic result. The 
gotcha is always in the grubby details.

> 
> I was asking:  What would a promising cut be in the first place ?
> 
> What properties could it have or be free from, that would make it
> relevant, as opposed to join the the hundreds of already "parked"
> cuts you mention ?

In order to put numbers on most of the stuff on the list below, you need to 
get them well into the “production design” phase. We know a few
things about them, but not a lot. 

> 
>> More Q is always nice.
>> Better ADEV never hurts
>> Lower aging is popular
>> Flat(er) temperature curves are attractive to an OCXO or TCXO designer
> 
> So you only see incremental improvements, there are no unfound
> "philosophers stone" properties we think are there but havn't been
> able to locate yet ?

Quartz has been looked at since at least the 1920’s. It is unlikely there 
is anything in there that is “magic”. 

The SC is simply an incremental step over what came before it …. It involves 
degradation of some specs (over prior art) and improvement of others. One 
would guess that would be true of any “new” cut as well. 

Even if you went with a different material, moving any of the specs listed
above by 10X would be pretty amazing. Indeed folks have looked at 
different materials, Quartz still dominates. We have high Q sapphire resonators, 
so quartz is not the only possible way to make a production part. 

Bob

> 
> -- 
> Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
> phk at FreeBSD.ORG         | TCP/IP since RFC 956
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