[time-nuts] DMTD phase shifter

EWKehren at aol.com EWKehren at aol.com
Sat Jul 25 02:37:09 UTC 2009


On the chance that I may be totally wrong let me suggest the following. In  
my opinion you are looking at the wrong information. When you mix a 10 MHz  
signal with a signal offset by 1 Hz you are subtracting from a 10 E 7 
signal 10  E 7 and as a result get 1 Hz representing 10 E 7. Counting it with a 
counter  with 1 ns resolution, you in effect get at the last digit 10 E 16. 
Obviously  some of the last digits are irrelevant due to noise and trigger 
error. Using two  mixers with the common offset oscillator you want the two 
phases to be as close  as possible to reduce the noise contribution of the 
offset oscillator. That is  why you want the phase shift. Measuring the time 
difference between the zero  crossings in my opinion is not the way to go.
I am inspired by the simplicity of the NBS unit (thank you Corby for the  
info) to lay out a PC Board; reading some of the comments I would appreciate 
any  links to more info on that subject that may make the design more 
effective. Any  help would be greatly appreciate. 
Bert Kehren  WB5MZJ
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