[time-nuts] Ancient OCXO in scope calibrator.

[Bruce Griffiths]

Magnus Danielson wrote:
> Dave, Bruce,
>
>   
>> Need a few more circuit details.
>> The crystal current wont be very high unless their are other components 
>> connected to G1.
>>     
>
> As expected, BAMA can assist:
> http://bama.edebris.com/manuals/tek/184/
>
> I am thinking about undamped overtones/other modes of the crystal and 
> similar.
>
> Cheers,
> Magnus
>   
The crystal oscillator is in effect a miller oscillator using the screen 
grid as the oscillator anode/plate see:
http://www.ieee-uffc.org/freqcontrol/tutorials/s6310508.pdf

The oscillator plate/anode (screen grid is grounded) in this circuit.
The tube plate/anode forms a well isolated auxiliary output tuned to the 
5th harmonic of the crystal.

If the tube emission has dropped the gm may have fallen rather too close 
to the critical value required for oscillation making the circuit 
sensitive to loading at the grid.
Both the trimmer and the cathode tank slug affect the frequency.


Bruce