[ARC5] SCR-274 calibration Xtals

[Richard Knoppow]

     There is a good history of quartz crystal manufacture and its 
expansion during WW-2 at:

http://ihanatech.com/technical_notice/a%20histrory%20of%20the%20quartz%20crystal%20industry%20in%20usa.pdf
    A google search for "virgil bottom" will find much more.

On 8/19/2016 1:47 PM, Dennis Monticelli wrote:
> FYI.  I have worked with surplus WW2 crystals a lot and can say that it
> was relatively common for the upward drift to occur.
>
>  It was not until approximately late 1943 or well into 1944 that ground
> crystals were put through the proprietary Bliley final etch process.
> This process was developed to improve frequency accuracy but
> incidentally cured serious drift problems with early rocks put in
> service in the ET.  The Signal Corps eventually forced Bliley to pass
> that secretive process to other suppliers, though I don't think all
> makers applied it.
>
> How it works:
> Grinding produces lots of fine grit, some of which lodges in the
> roughened surface of the blank and does not wash out.  As the crystal
> vibrates in operation it works loose some of the grit, which reduces
> loading and moves the crystal freq upward.  The final short HF bath
> easily removes the embedded grit along with molecules that are weakly
> chemically attached to the surface.  What is left behind is a well
> ordered stable crystal surface.
>
> An experiment you can do:
> Take a rock from 1943 or earlier and give it a dip in a weak acid for a
> minute, wash thoroughly with distilled water and alcohol, and then
> remeasure freq.  It will move upward.  Do this again for an additional
> minute, then a minute more, etc.  You will observe a curve of freq
> change vs time that drops sharply at first and then settles into a
> linear relationship of slow change vs time.  You are observing the acid
> attacking the "low hanging fruit" and then hitting the well ordered
> crystal.  Usually, activity will improve as well.
>
> Maybe more than you wanted to know :-)
>
     Its never too much:-)
> Dennis AE6C
>


-- 
Richard Knoppow
1oldlens1 at ix.netcom.com
WB6KBL