[time-nuts] Datum FTS 4065B Plot

Brooke Clarke brooke at pacific.net
Wed May 14 18:39:40 EDT 2008

Hi Tom:

On 8 May I had been plotting for a number of days and saw a similar line 
indicating a frequency offset of 472E-15.  So on that date I dialed in an 
offset of +472E-15.

For a couple of days the frequency didn't change more than +/- 10ns.

Then on the third day it started the plot you see AND the new slope is about 
the same as the old slope i.e. 470E-15.  BUT, the frequency offset display 
reads 472 (E-15 units).  Do you see my dilemma?

See Attached display photo.

Have Fun,

Brooke Clarke
http://www.prc68.com/P/Prod.html  Products I make and sell
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Tom Van Baak wrote:
>> 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.
> /tvb
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