[time-nuts] Fury Interface Board: 5MHz needed?

Peter Schmelcher nebula at telus.net
Thu Nov 8 19:27:01 EST 2007


>How do you distinguish this effect from oven temperature variations due
>to finite thermal gain, particularly with a single oven OCXO?
>For small changes the effects are both linear.

Bruce many OXCO have an internal voltage reference that is brought out to a 
pin and I would guess the reference voltage would track the ground bounce. 
The catch is how stable is the internal voltage reference. If stable the 
difference between the reference voltage pin and EFC pin should cancel the 
ground bounce and expose the oven temperature error. A rather drastic 
alternative is to open the oven and solder a thin wire to a ground point 
close to the tuning diode. Then solder the other end of the thin wire to 
the main board DAC voltage reference ground. Lastly unsolder the OXCO +12V 
and ground pins from the main board and connect them to a separate isolated 
12V supply. The thin wire has no heater current in it so all heater current 
drives the OXCO ground pin a fraction of a mV below the main board ground 
eliminating any EFC interaction. With great care I implemented the second 
approach.

Peter 




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