[time-nuts] Thermal insulation choice?

Magnus Danielson magnus at rubidium.dyndns.org
Fri Jan 6 23:10:03 UTC 2012


Rick,

On 01/06/2012 10:14 PM, Rick Karlquist wrote:
> John Ackermann N8UR wrote:
>> I am looking for a readily available (from Home Depot or other local
>> source) insulating material to use in a chassis that's housing a
>> sensitive OCXO.  My goal is just to slow down any external thermal
>> transients so the oven loop has time to react gracefully.
>
> Before making this into a science project, consider this data
> point:  We converted the oscillator in a 10811 to run in mode
> B at 10.95 MHz.  The tempco in mode B is about 30 ppm per degree
> C.  Needless to say, the converted 10811 was extremely sensitive
> to crystal temperature.  I could wave my hands around it and notice
> the temperature change from the air currents.  However, simply
> putting the 10811 into a small empty cardboard box completely
> solved this problem.  No rocket science necessary.  So in the
> short term, this simple box was like a double oven.  Of course,
> in the long run, the 10811 thermal gain is only 1000 or so and
> you can see the effect of the HVAC shutting down at 7PM, etc.

This is essentially what I've found quite useful at many times, quick 
air fluctuations affects crystals pretty good but just blocking the air 
helps to slow down things. Long-term creeps through but is not on the 
same scale.

A large enough cardboard box will leak over-temperature such that the 
oven keeps working.

Cheers,
Magnus



More information about the time-nuts mailing list