[time-nuts] Another "atomic" clock question

Charles Steinmetz csteinmetz at yandex.com
Mon Mar 3 19:51:54 EST 2014

Chris wrote:

>If do have an external frequency reference then the crystal itself 
>makes a good thermometer.  So why not use THAT thermometer to 
>control the heat added by the resister.  Such a system would respond 
>to changes in ambient temperature by adjusting the power in the 
>resister.  We don't even have to care if the crystal's temp-co is 
>nonlinear because we are using a very small temperature range, so 
>small it looks linear.
>I'll build it.  Can you or anyone else subject a simple XCO 
>schematic?  Hopefully SIMPLE.   What I need is a design that can be 
>pulled down a few PPM so that I can raise it back with a bit of 
>heat.  I will have to be kept at a temperer above the hottest it 
>will ever get inside the house, maybe 100F.

See below or attached (hopefully).  L and C are chosen to resonate at 
the crystal frequency with XC and XL in the general vicinity of 100 
ohms to 1k ohms.

What you are proposing is a disciplined oscillator using the oven 
setpoint as the control input.

Best regards,


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