[ARC5] Crystal Question

[Brian Clarke]

Hello Wayne,

The word 'crystal' has many meanings. In physical chemistry it usually 
refers to the solidus phase of an element or a compound. This can be the 
result of drying out a saturated solution of a compound - such as table salt 
or copper sulphate - or the temperature-related structures we find in cast 
iron and solder, to name a couple. The main characteristics of crystals are 
the regularly repeated structures that resolve inter-molecular and 
intra-molecular forces.  The different shapes and colours we see in some of 
the more common crystals can often be traced to the number of water 
molecules attached to each 'parent' molecule.
* The crystal glassware that women like to display [produced by usually male 
glassware artists] is based on silicon, oxygen, boron, lead and a few other 
elements - but none is conductive or even semi-conductive.
* The work of Watson and Crick in determining the structure of DNA was the 
result of painstaking analysis of X-ray crystallography images.
* The frequency determining crystals we radio-oriented people use are made 
from quartz, a form of silicon dioxide which is a very good insulator, but 
can be made to act like a big capacitor with a small inductor. The crystal 
lattice structure is what determines the frequency stability. Silicon 
dioxide is not a semi-conductor. Some sands are also forms of silicon 
dioxide - but great heat is required to convert sand into quartz.
* Doped silicon in contact with doped germanium can be a semi-conductor. 
These can be crystalline structures.
* Galena is a crystalline form of lead sulphide; it does make a good 
semiconductor.
* The crystals that greenie tree-huggers collect are not rare, not 
semi-conductors, nor very valuable. And they have no known magical or 
medicinal properties - except to scribblers / journalists for whom a science 
education would be a luxury. Some gemstones are crystals, eg, ruby and the 
various '-ites'.

So, the word 'crystal' has become morphed and its meaning hijacked by the 
ignorant [in the Latin sense]. But this is a characteristic of all living 
languages - so, we need to have our 'shock-proof crap detector' [Ernest 
Hemingway] working properly.

How about suggesting to your foxhole constructor to use a 1N34 or a 1N21 - 
both readily available, cheap, reliable and will work straight off the 
shelf. He could have such a device hidden and put a piece of galena or a 
razor blade with its scratchy wire up front for cosmetic, suck-in purposes 
for those yet to get their Ernest Hemingway moment.

Hope that helps.
73 de Brian, VK2GCE.

----- Original Message ----- 
From: "Robert Eleazer" <releazer at earthlink.net>
To: <arc5 at mailman.qth.net>
Sent: Friday, November 12, 2010 4:08 AM
Subject: [ARC5] Crystal Question


>I did some looking on that website where the B-26 radio compartment 
>pictures are and found that someone has asked an interesting question.
>
> It seems they salvaged some parts from some warbird crash sites in Florida 
> and found some radio crystals. The one he shows looks like it is out of an 
> SCR-522 . The guy who found them wants to use these to make a WWII style 
> "foxhole radio" crystal radio receiver and is asking for help on how to do 
> that.
>
> It never occurred to me that a radio crystal might work as a detector in a 
> crystal set. Is this possible? And did the improvised crystal sets in WWII 
> use radio crystals? I guess that crystals from downed aircraft and wrecked 
> tanks were probably available on the battlefield in WWII.
>
> Thanks
>
> Wayne
>
> WB5WSV