[time-nuts] What’s the BEST crystal?

[Bob kb8tq]

Hi

> On Feb 29, 2020, at 2:44 PM, Poul-Henning Kamp <phk at phk.freebsd.dk> wrote:
> 
> --------
> In message <2E09A559-B476-45C0-A476-7D5808A93428 at n1k.org>, Bob kb8tq writes:
> 
>> One wonders what the result would be of doing a large blank (> 50mm) 2.5 MHz 5th OT using modern 
>> design, packaging and mounting techniques. Given that it would take a rather large pile of nickels to 
>> find out (like > $50M worth), I very much doubt we ever will know the answer. 
> 
> Why would it be so expensive ?

You would have to do a *lot* of things from scratch. First up, there is no “modern” cold weld package
big enough to put the beast into. You would have to tool that right up front. Same issue ripples into the
processing gear. A typical modern setup for normal packages is around $3M to develop and about $1.5M
to duplicate. Best guess is that you would at least double (and more likely triple)  those numbers for the 
much larger package. 

The blank, being larger than anything anybody uses today would need custom gear to cut / round / polish
the part. Again, a lot of work from scratch. Probably not as exciting as the final plate / seal end, but still
something that needs money and attention. 

It is unclear if anybody grows (or has the ability to grow) high quality quartz bars big enough to cut the 
blanks from. One would *guess* not since there is no demand for them. At the very least there would 
be some tooling and a custom run involved in sourcing the synthetic quartz. Sourcing seeds that are 
significantly larger than normal might be interesting as well. 

Simply doing the design of the resonator and proving that out is a multi pass process. Based on the
way it typically seems to be done, you would run a couple hundred trials to get the right design worked
out. Each of those would involve many dozens of finished crystals and some fairly involved analysis of 
those crystals. 

On top of all that, you have the inevitable management costs, overhead, and other nonsense that are
all part of any modern undertaking. All that said, it’s just a guess. 

Bob

> 
> -- 
> Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
> phk at FreeBSD.ORG         | TCP/IP since RFC 956
> FreeBSD committer       | BSD since 4.3-tahoe    
> Never attribute to malice what can adequately be explained by incompetence.