[time-nuts] Thermal insulation choice?

[Bob Camp]

Hi

A metal shell inside a metal shell pretty well takes care of everything.
Gradients, transients, drafts, what ever. You don't need super thick stuff.
Bud chassis, Hammond boxes, copper pipe, PC board material, or soldered
brass flashing all will do the trick.

Simply tossing a fluffy towel over the unit works amazingly well if drafts
are the only real concern. 

Bob

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Rick Karlquist
Sent: Friday, January 06, 2012 4:15 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Thermal insulation choice?

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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