[time-nuts] Temperature stability for Thunderbolt: results

Magnus Danielson magnus at rubidium.dyndns.org
Fri Jan 28 00:36:21 UTC 2011

On 27/01/11 22:37, Tom Van Baak wrote:
>>> By this (quite possibly imperfect) measure: When the EFC goes down
>>> 3:1, you have improved the thermals by 3X. If you started at 1 C
>>> swings, the OCXO is now seeing 1/3 C swings.
>> Agreed (re: the EFC component that correlates to changes in Tbolt
>> ambient temperature).
> A number of posts have mentioned LH measurements and
> variations in DAC voltage or TI or OSC values. I'm curious
> how close to the truth this is.

There are three observables to use:

time measurements (GPS t measurement)
frequency measurements (GPS f measurement)
DAC control values (PLL PI-loop output)

The last one is scaled by the EFC sensitivity which is uncalibrated and 

The time and frequency measures is the observables towards GPS, for the 
car analogy precision measurements against reference points along the road.


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