[time-nuts] optically excite a quartz crystal?
jfor at quikus.com
Mon Apr 21 15:21:36 UTC 2014
The etching referred to was by post-war hams,
> 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.
> 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.
>>> I'm puzzling over this statement. The FT-243's I have seen have a
>>> that squishes the quartz blank between the electrodes. They aren't
>>> onto the quartz, but they are still in intimate mechanical and
>>> -Chuck Harris
>>> Bob Camp wrote:
>>>> 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
>>>> holders from that era that do pretty much the same thing.
>>>> electrodes are not very new.
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