[ARC5] Crystals and WWII

[Richard Knoppow]

----- Original Message ----- 
From: "Dennis Monticelli" <dennis.monticelli at gmail.com>
To: <wrcromwell at gmail.com>
Cc: <arc5 at mailman.qth.net>
Sent: Sunday, March 17, 2013 9:04 AM
Subject: Re: [ARC5] Crystals and WWII


> Twinning of crystals is just when separate crystals share 
> some of the same
> crystal lattice.  In other words, when two crystals 
> inter-grow    You've
> all seen photos of inter-grown crystals of quartz or other 
> minerals.   But
> sometimes the twinning is not visually obvious so it gets 
> sliced across the
> shared region and that rock won't do its piezo thing. 
> There are more
> sophisticated optical and radiation tests that can be 
> performed to weed out
> the twinned material so later in the war effort, that's 
> what they did.  The
> equipment for doing this was shipped to Brazil so only 
> good stuff would
> take up precious plane weight.  Yes, they had to fly it to 
> the US because
> earlier in the war a U-boat sank a freighter that happened 
> to be carrying a
> large shipment.  That sinking caused such a severe 
> shortage that US makers
> had to reclaim crystal stock from their scrap pile.
>
> Dennis AE6C
>
     Those interested in the electronic use of crystals 
might want to read about Walter Cady, who invented the 
piezoelectric oscillator.  See for instance
http://en.wikipedia.org/wiki/Walter_Guyton_Cady

Cady's classic text _Piezoelectricity_ is available as a 
free (but very large) download  at: 
http://archive.org/details/piezoelectricity031514mbp



--
Richard Knoppow
Los Angeles
WB6KBL
dickburk at ix.netcom.com