[time-nuts] Thermal insulation choice?

Rick Karlquist richard at karlquist.com
Fri Jan 6 21:14:53 UTC 2012


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.

Rick Karlquist
N6RK




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