On 12/20/2012 01:34 PM, Bob Camp wrote:
Hi
Temperature transients are not a good thing for an OCXO. If you deliberately
use the fan to create a transient, then yes the OCXO will not be happy. The
question it - what happens after the transient has settled out? The plot you
have still looks a lot like a step function.
I agree. Temperature steps stresses the OCXO oven loop and easily
creates a gradient over the crystal. As the oven loop tracks in, the
frequency returns to around normal. The trouble with forced air over a
crystal is that the metal shield couples very well and acts like a heat
sink. A think plastic cover over it and forced convection doesn't have
the same effect. There is even being used by at least one vendor. Works
very well for the extra cents of manufacturing cost.
The HP10811 is recommended to be put in a airflow-quiet corner of the
world. Look at it's mounting in the HP5370A/B for instance.
Cheers,
Magnus
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