[time-nuts] Grinding crystals...

[Gary]

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.

"Burt I. Weiner" <biwa at att.net> wrote:

>Brian,
>
>I remember grinding FT-243 crystals.  I had a TV set safety glass 
>about 18" square and about 1/4" thick.  That and some Comet type 
>cleanser mixed with water to make a thin paste would work wonders.  I 
>was taught to put my finger on the corners and grind an equal amount 
>on the 8 corners (4 on each side) so as not to remove the bevel of 
>the quartz.  Once I applied this lesson I was able to grind crystals 
>that were more stable and more active.  When I over-leaded them I was 
>generally able to remove the lead using alcohol.  I've still got the 
>old TV safety glass although it has an area near one corner that is 
>very opaque do to all the grinding that was done in that area.  Those 
>were fun days!
>
>Burt, K6OQK
>
>
>>From: Brian Alsop <alsopb at nc.rr.com>
>>
>>Reminds me of the FT-243 xtal controlled transmitter Novice days. 
>Xtals
>>of the frequency you wanted were hard to come by.  We would grind
>xtals
>>a bit on a bed of very fine abrasive to raise their frequency.
>>
>>The other trick was taking a pencil and adding graphite to the xtal
>>faces to lower it's frequency.  You couldn't add too much or it would
>>stop oscillating-- forever.  Never did understand the forever part.
>>Removing the graphite didn't bring it back to life.
>>
>>Brian
>>K3KO
>
>Burt I. Weiner Associates
>Broadcast Technical Services
>Glendale, California  U.S.A.
>biwa at att.net
>www.biwa.cc
>K6OQK 
>
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