[time-nuts] optically excite a quartz crystal?
Bob Camp
lists at rtty.us
Mon Apr 21 15:26:16 UTC 2014
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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