[ARC5] SCR-274 calibration Xtals

[Leslie Smith]

  Hello Richard,
  About 3 months ago I got the  1.000MHz calibration crystal from a
  BC-221.
  You'll remember these crystals - they have the same form as the ARC-5
  crystals 
  - octal socket and their own "hound-house".

  Apart from use in a BC-221, my intent is to build a solid state
  oscillator and see what I can 
  discover about "decades-long drift" in a good quality crystal.  I plan
  to use the Butler circuit.
  I've already had the circuit working with HC-49 crystals.

  Having measured the signal from my all-singing, all-dancing 
  "standard" crystal, I will compare the "drift" figure I infer with the
  specs given in my (very ordinary) Fluke digital counter and infer
  something about the reliability of the spec in the Fluke.

  The topic of standards (even "toy" standards, such as I have in my own
  home) is interesting.
  For example - this 1.000MHz, completely unchecked crystal gives me the
  ability to measure frequency more precisely than the best equipped
  laboratory of 100 years ago.    My (very ordinary) Fluke and
  multimeter aren't too bad by the standards of the 50s and 60s.  We
  live in a golden age!


  73 de Les Smith
   vk2bcu at operamail.com

  P.S.  With my luck, I imagine the 1.000 MHz crystal will fail, and
  I'll throw it in the bin!!  HA!

On Sat, Aug 20, 2016, at 06:30, Richard Knoppow wrote:
>     I was thinking the same thing. By now the crystal is probably 
> perfectly stable.
> 
> On 8/19/2016 12:37 PM, Bill Cromwell wrote:
> > Maybe the crystal started out 70 years ago at 10 kc low <evil grin>.
> >
> > 73,
> >
> > Bill  KU8H
> >
> > On 08/19/2016 01:31 PM, Kenneth G. Gordon wrote:
> >> On 18 Aug 2016 at 14:57, J Mcvey via ARC5 wrote:
> >>
> >>> Just for fun, I decided to see how the magic eye transmitter
> >>> calibration system
> >>> worked in practice. It actually worked pretty well, but the
> >>> resonance  was at
> >>> 3502 khz instead of 3500 khz ( marked on xtal) .
> >> Gee!! That close? That is amazing for a crystal which is over 70 years
> >> old...not to mention the other components in the circuit which could
> >> effect the
> >> resonance frequency,
> >>
> >>> Is this typical?
> >> No. It is far too good. Typically, crystals drift upwards a certain
> >> amount per
> >> year. By now, it should have been a lot further off.
> >>
> >> As others have mentioned here, you can tweak it exactly on to frequency
> >> with external components. Parallel capacitance will lower the frequency.
> >>
> >> Ken W7EKB
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> 
> -- 
> Richard Knoppow
> 1oldlens1 at ix.netcom.com
> WB6KBL
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