[time-nuts] Datum FTS 4065B Plot

Tom Van Baak tvb at LeapSecond.com
Wed May 14 17:49:46 EDT 2008

> If you look at the plot I attached as a .pdf you can see that the current slope 
> looks like a nice straight line covering almost 4 days so temperature is not a 
> factor.  The only factor I can think of is magnetic field.  I guess the next 
> step is to rotate the box 90 degrees and see what happens unless there's some 
> other suggestions.

Since you are plotting phase (not frequency) the nice straight
line you see simply means you have a frequency offset. This
is normal and expected with any standard compared to GPS.

What may be temperature effects are the little wiggles above and
below the line. You can almost see they form a diurnal pattern.

If you subtract the frequency offset before you plot, you'll get
phase residuals, which will reveal patterns in greater detail.
There are Excel functions that will help you fit lines to the data
and remove trends, etc. Email me your XLS file offline and I'll
show you.


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