[ARC5] Crystals in WWII

[Kenneth G. Gordon]

On 15 Mar 2013 at 8:10, Dennis Monticelli wrote:

> Ken,
> 
> Thanks for your comments.
> 
> I have learned through much experience that if you take a typical
> FT-243 or CR-1/A WW2 era crystal that is kind of sluggish and give it
> a brief dip in a weak HF bath (less than 1 min) at room temp and then
> follow that with a 3 step rinsing process involving both DI water and
> alcohol, the freq will jump up nearly a KHz and the activity comes
> back.

Ah HA! Thanks very much for that info, Dennis! I'll add it to my "bag-o-tricks" 
for crystals.

>  All that "loading" on the surface has been removed.  If you
> return the blank to the weak HF bath for further etching it will
> experience a very slow increase in freq proportional to the minutes in
> the solution because by this time the acid is working on a native
> tightly-bonded crystal surface.  I did a time graph once and found
> that most of the cleaning took place in the first 15 sec.

To me, that is very valuable information: I have bought a hundred or more 
FT-243s in frequencies capable of being moved up into a ham band with the 
idea of obtaining crystals on frequencies every few Khz from the bottom to at 
least the middle of a band.

All of the above will be a big help.

Thanks again for passing on your experience, and especially for your insight.

Ken W7EKB