[time-nuts] Thunderbolt oven / non-stable operating temperature

Charles P. Steinmetz charles_steinmetz at lavabit.com
Fri Dec 14 10:36:11 UTC 2012

tvb wrote:

>do either of you have actual tempco numbers?

I checked my notes and found that I did not record any free-running 
tempco values.  My observations were based on the scale factors I had 
to use to get the temperature and DAC graphs in Lady Heather to 
overlay each other.  I initially noticed it because there was a very 
pronounced tracking of the two graphs for one Tbolt and for the other 
two there was not (the temperature-compensating component of the DAC 
voltage is mostly lost in the noise).  I had checked the actual EFC 
sensitivity of each oscillator in the vicinity of the operating 
point, so all relevant variables were more or less controlled.

My impression is that the better ones are comparable to a single-oven 
10811, maybe even a bit better.  LH typically reports tempcos of 
1e-12/C to 1e-11/C.  My worse unit (and, from what I can infer from 
LH plots posted to the list and on-line, it appears many others as 
well) typically reports a tempco of 1e-10/C to 1e-9/C.  Of course, 
the LH numbers are all to be taken with some caution since LH does 
not have any a priori means to separate tempco and drift.

Best regards,


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