[time-nuts] Datum FTS 4065B Plot

Tom Van Baak tvb at LeapSecond.com
Wed May 14 15:01:36 EDT 2008

> Hi:
> I've been looking at the 4065B Cesium standard vs. GPS this month.  After the 
> plot showed a slope of 472E-15 the frequency offset was changed from zero to 
> 472 on 8 May (gambling on the sign).  For the next couple of days the points 
> all were in a box 20 ns high.  BUT then the slope changed.  It's now got a 
> positive slope that's very close to 472E-15 and the frequency offset is at 472 
> not zero.  See attached plot.
> What might be causing this?  For example the 4065B is just sitting on a chest 
> of drawers and might be moved or rotated a little from time to time.  Is there 
> a requirement that it be in a temperature controlled room on a concrete pillar 
> to get into the E-14 area?
> It just turns on better than 5E-13 and the attached plot seems to indicate that 
> it and be manually adjusted to parts in E-14 but so far I've not been able to 
> do that.


At the level of e-14 and e-15 you might need weeks of data to
separate the normal flicker noise from any clear frequency
offset or drift trends. Yes, it's quite possible that environmental
effects are also polluting your data. You can either control
temperature, or just collect temperature data and see if there
is a correlation with your standard.

Do you have a continuous set raw GPS-Cs 1PPS data that I
can look at to see if I can help you?


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