[time-nuts] FE-5680A Mechanical Question

EWKehren at aol.com EWKehren at aol.com
Fri Jan 13 15:41:36 EST 2012


wrong there is no DAC involved, it is a DDS
 
 
In a message dated 1/13/2012 3:36:33 P.M. Eastern Standard Time,  
charles_steinmetz at lavabit.com writes:

Bert  wrote:

>we would be talking +- one step and using different rate but  reading the
>frequency over 1000 seconds would be my  answer.

Rather than dithering the existing 7e-13 steps, perhaps it  would be 
simpler to adjust the 5680A step size?  Presumably, the  C-field is 
being controlled by the current or voltage output of a DAC, and  the 
7e-13 steps represent the LSB of the DAC.  From the reports so  far on 
the list, the DAC output range is much larger than necessary (I  think 
someone said ~ +/- 2 Hz ??).  If you attenuate the DAC output  by 10x 
in the analog domain, you would have a +/- 0.2 Hz range with 7e-14  
steps (or, if you like, attenuate by 7 for 1e-13 steps, or by 14 for  
5e-14 steps).  You would have to be a little careful about the tempco  
of the implementation (particularly, you may need to add some  
low-tempco bias to get the range centered on 10.000000000 MHz again),  
but I wouldn't think it would be so critical as to be beyond the  
ability of the home time nut.

Best  regards,

Charles







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