[time-nuts] ADEV - my GPSDO vs KS-24361

Bob Stewart bob at evoria.net
Tue Nov 4 09:02:18 EST 2014

Here is a plot of the overnight ADEV I just ran comparing my GSPDO to my KS-24361/Z381x.  The red line is the ADEV which seems to cross at 200 and 2000 tau.  The green is the output of my board's TIC in ns.  It measures the phase of my OCXO against the sawtooth-corrected PPS from the LEA-6T.  The blue is the time interval between the 10MHz from my GPSDO and the 10MHz from the KS-24361 in ns as measured by my 5335A.

As you can see, the phase of the KS-24361 seems to wander around from time to time as compared to the relatively straight line plotted by my TIC.  The divergences seem to match what I can see happening on the Satstat screen in the "1PPS TI xx ns relative to GPS" field.  Eventually I will get that in real time and see if correcting for that flattens the plot and changes the ADEV.

I should point out that there are some thermal drift problems that aren't very apparent on this plot.  I ramped up the differential gain, and combined with the relatively stable temperature overnight, the effects are fairly muted.  Hopefully a new regulator design will resolve the temperature problems.

Could someone tell me if there's any significance to the fact that the ADEV crosses (or whatever the proper term is) at about 200 and 2000 tau rather than the usual 100 and 1000?

Bob - AE6RV

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