[time-nuts] optically excite a quartz crystal?

Bob Camp lists at rtty.us
Mon Apr 21 10:40:48 EDT 2014


Hi

Early in the WWII era, quartz blanks were not commonly etched after begin ground / polished to frequency. This left debris on the surface of the blank. The net result was that the resonators failed after a period of time in the field, especially under damp conditions. The problem got so bad that it actually threatened the ability to communicate in 1942. A fairly high level team looked into the issue and etching of blanks (and a few other mods) were made a mandatory part of all crystals suppled to the government. Ammonium bi-flouride and water was the most common etchant in that era. There are a number of papers about the whole deal in the FCS, and many stories told by those who were part of the changes. 

Bob


On Apr 21, 2014, at 10:10 AM, J. Forster <jfor at quikus.com> wrote:

> No. There is just a little rectangular quartz wafer. No plating.
> 
> In fact, post WWII, when many ham transmitters were 'rock bound' (ie:
> crystal conteolled) it was common pratice to regrind mil surplus rystals
> to move them into the ham banda.
> 
> Apparently, some were also etched using a cleanser called Whink, which
> contains a flourine compound.
> 
> Also, some advocated applying graphite from a pencil lead was used to
> decrease the frequency.
> 
> If the crystal ativity was low, they were taken appart and cleaned.
> 
> 
> 
> -John
> 
> ==============
> 
> 
> 
> 
>> I'm puzzling over this statement.  The FT-243's I have seen have a spring
>> that squishes the quartz blank between the electrodes.  They aren't plated
>> onto the quartz, but they are still in intimate mechanical and electrical
>> contact.
>> 
>> -Chuck Harris
>> 
>> Bob Camp wrote:
>>> Hi
>>> 
>>> The WWII era FT-243 is one example of a crystal that has the active
>>> portion of the
>>> electrodes separated from the resonator by an air gap. There are lots of
>>> similar
>>> holders from that era that do pretty much the same thing. Non-contacting
>>> electrodes are not very new.
>>> 
>>> Bob
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> 
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