[time-nuts] Achievable temperature stability for Thunderbolt

WarrenS warrensjmail-one at yahoo.com
Sat Jan 15 19:44:12 UTC 2011

As long as the Tbolt's Osc is being disciplined, I have found:

Most Tbolt's with factory default settings (i.e TC = 100) will show minimum 
effects with standard room temperature changes. No special protection 
A unit that is tuned a bit better (in a box and TC of 300 to 500), then 
temperature changes of less than 1 deg / hr will be OK.
A better optimized setup with TC settings in the 500 to 1000 sec range, a 
max temperature rate of change  of up to 0.1 deg C per hr will have minimum 
If you want to go all out time nuts, (with "Special" TC setting above 1000) 
then best to hold the sensor temperature to within 0.02 deg total change, 
which can be done using Lady Heather's Temperature controller.

How high you can go with the TC setting, depends on many things, such as how 
stable the Tbolt's Oscillator is. Each setup is different.
A TC setting of 1000 sec is generally the max you should go. With this 
Tbolt, the best results can be obtained with a 'special' TC setting to 2000 
to 3000.

Attached is the last 2 weeks of a Lady Heather plot, showing a temperature 
tracking test I did to see how long it takes a Tbolt to learn a new 
This unit has a Poor antenna, 1 sec ADEV of 1e-12, Aging of 4 e-12 / day, 
Temp coeff  of 2.5e-10 / deg.

Have fun

[time-nuts] Achievable temperature stability for Thunderbolt environment?
Achim Vollhardt avollhar at physik.uzh.ch
Sat Jan 15 16:36:56 UTC 2011
> Hi list,
> as my Thunderbolt is now nicely cooking for a few weeks now, I am
> wondering what a typically achievable ambient temperature
> stability/variation is in your setups.
> Of course, a more stable environment is better, but currently I am
> struggling to achieve more than +-0.5 K variation on the temperature
> reading on a weekend.. during working days (when I am around in the
> lab), the variations are as much as 3 times higher.
> I am just wondering, if I should rather worry more about high
> temperature gradients rather than excursions from a mean value, as slow
> variation can be compensated by the control loop while for quick
> changes, the loop is just too slow :)
> 73s Achim, DH2VA 
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