[time-nuts] optically excite a quartz crystal?

[Bob Camp]

Hi

Well I can name at least one post war ham (me at age 14) who did not understand the need for etch after grinding…

Bob

On Apr 21, 2014, at 11:21 AM, J. Forster <jfor at quikus.com> wrote:

> The etching referred to was by post-war hams,
> 
> -John
> 
> ===============
> 
> 
> 
>> 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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> 
> 
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