[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 
non-linear.

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

Cheers,
Magnus



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