[Milsurplus] TBS Crystal Question

[Bob Camp]

Hi

I *think* you will find that the magic hole is there for pressure  
compensation. The idea was to keep the part sealed and not have it  
"breathe" as the outside pressure changed.

Bob


On Jul 31, 2007, at 11:48 AM, J Forster wrote:

> Here's a question for crystal gurus. Two examples of the crystals  
> for a
> TBS (Talk Between Ships) WW II radio have putty like seals over
> something in the center. See:
>
>  http://www.jproc.ca/rrp/tbs_crystals.html
>
> Does anyone know what the material is covering? Perhaps a set screw  
> for
> adjusting the pressure on the quartz slab?
>
> Thanks,
> -John
>
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