[time-nuts] Grinding crystals...

[Bob Camp]

Hi

For a period of time, the USAAF was essentially shut down due to people grinding crystals and not etching them afterwords. The particles you inevitably leave behind are the issue. Etch is the only practical cure. It's also a quite effective way to move the crystal frequency small amounts. The etchants are all "will dissolve glass or your hand" sort of things, so maybe not for the average kitchen experiment. Ammonium bifluoride and water is one common etchant. 

Bob

On Jun 20, 2013, at 11:21 PM, Ed Palmer <ed_palmer at sasktel.net> wrote:

> I have a copy of  " Understanding Amateur Radio" published by the ARRL in 1963.  One of the appendixes is titled "Changing Crystal Frequencies" and talks about grinding crystals from FT-243 holders.
> 
> Just google on < "ft-243" crystal grinding > and you'll find lots of web pages and at least one YouTube hit.
> 
> Ed
> 
> On 6/20/2013 8:06 PM, Hal Murray wrote:
>> nuts at lazygranch.com said:
>>> A common scheme in metal deposition measurement is to measure the frequency
>>> of a crystal prior to starting the deposition process, then monitoring the
>>> frequency shift of the crystal as the metal is sputtered.
>>> I was told crystals are tuned this way at the factory, but don't know this
>>> for a fact.
>> I don't have any good references, but I've seen that story several times, and
>> at least some of them were credible enough so that my opinion changed from
>> sounds-good to really-works.
>> 
>> -------
>> 
>> Many years ago (50+), I remember stories of grinding or leading crystals.  I
>> remember taking one apart.  It was only a few screws.  Does anybody have an
>> ARRL handbook from that era?
>> 
>> Does anybody have any estimates on what the performance of a hermetically
>> sealed crystal is compared to an old non-sealed mounting?  (Do they still
>> make the old non-sealed mounting?)
>> 
>> I also remember getting several crystals cut to order, one each for me and a
>> few friends.  That was through the local radio/TV fixit parts store, a block
>> or two from the high school.
>> 
>> 
> 
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