[ARC5] SCR-274 calibration Xtals

[Kenneth G. Gordon]

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