[time-nuts] Thermal insulation choice

[EWKehren at aol.com]

Rick
I see this even with double oven units with much smaller changes but I run  
tests with the unit sitting on a foam base and as a second test slide a 
card  box, just a box, over it with the foam cut in such a way that it seals 
the unit.  Big difference.That is how I plan to do all my D/M tests with that 
unit again in  a metal enclosure.
A picture is attached.
Bert Kehren
 
In a message dated 1/6/2012 4:15:12 P.M. Eastern Standard Time,  
richard at karlquist.com writes:

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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