[ARC5] Crystals in WWII

[Geoff]

----- Original Message ----- 
From: "Kenneth G. Gordon" <kgordon2006 at frontier.com>
To: "Dennis Monticelli" <dennis.monticelli at gmail.com>; "Arc5 mail list" 
<arc5 at mailman.qth.net>
Sent: Friday, March 15, 2013 11:46 AM
Subject: Re: [ARC5] Crystals in WWII


> 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

I have done similar with the various crystal filter ones also. A good 
cleaning with 90-95% Isopropyl can raise some well low off frequency and 
sluggish crystals almost 2 kc from a 455-465 kc base, and then etching to 
bring them right on the nose. Also clean the holder.

Carl


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