[time-nuts] Centering ocxo

Hal Murray hmurray at megapathdsl.net
Wed Oct 3 00:54:41 EDT 2012


docdailey at gmail.com said:
> I am ok for awhile but how do you center the efc of an ocxo?  I understand
> there is something (screw) to adjust the ocxo so it is approximately on freq
> with 2.5v efc.

> Specific oscillator datum-1111c. I have he datasheet but doesn't say "coarse
> frequency adjust this screw" or some such. 

There may not be a coarse adjustment.  If the tuning range is big enough to 
cover the aging over your design life, you don't need one.


There is a tradeoff between adjustment range and the number of bits you need 
in a DAC to get a required accuracy.

Suppose I have an adjustment range of 1 Hz (peak to peak) on a 10 MHz 
oscillator.  That's 1 part is 10^7.  If I have a 10 bit DAC, I can adjust to 
1 part is 10^10.  A 20 bit DAC can get to 1 part is 10^13.

But if the tuning range is 10 Hz, the same 20 bit DAC setup only gets you to 
1 part is 10^12.



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