[time-nuts] Z3816a and newbie questions

[Tom Van Baak]

> Tom already posted an excellent answer to your question, but I'll add a 
> bit more.  The GPSCon software generates a lot of information and some 
> really pretty pictures, but as Tom said, you need to compare against an 
> external reference to see what the unit is really doing.  I'm currently 
> measuring two Z3801As against each other, and there is a plot (updated 
> automagically every 15 minutes) of the results at 
> http://www.febo.com/time-freq/plots/z3801a.html.

Very nice plots.

> Anyway, as I write this I have about 5.75 days worth of data, and during 
> that time the maximum difference between the two units was about 58 
> nanoseconds.  The frequency offset between the two is about 1x10e-14.  
> Over time, of course, that offset should reduce to zero as both units 

Nope, it won't ever get to zero. Both of your Z3801A
are already tracking GPS just fine so there is no
long-term drift of one against the other. What you see
in your plot, then, are the residuals, the noise floor,
and that will continue to have particular random look
of 50+ ns peak-to-peak noise over every day, forever.

/tvb