[time-nuts] Fury Realhamradio listing

Dr Bruce Griffiths bruce.griffiths at xtra.co.nz
Sun Apr 29 21:25:47 EDT 2007


SAIDJACK at aol.com wrote:
> C) I don't believe the Z3801A has 100ps single shot resolution and accuracy  
> (for resolution doesn't do anything without accuracy) until someone will  
> prove it to me. And even then it would be wasted resolution since the GPS 1PPS  
> source noise will totally swamp out any benefit a 100ps resolution would  give.
>   
Said

The timestamp resolution may well be much greater than needed 
particularly if they leveraged an existing well characterised and 
debugged design from another product.
This can save time and money over the alternative of developing a time 
stamp circuit with just the appropriate resolution.

You have to be more precise in your definition of accuracy.  An unknown 
but very stable time offset is of little consequence when disciplining 
an OCXO, however a scale error is another matter. Thus an interpolator 
with an unkown offset of a few nanoseconds which is stable to within a 
few tens of picoseconds allows an interpolator with a resolution of say 
100ps sec to be useful if its gain is known sufficiently accurately and 
the signal being timestamped has sufficient stability.

Bruce




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