[time-nuts] 10811 Extra Lagging etc

[Brooke Clarke]

HI Rick:

For humidity control in other applications I have used Zip-Lok bags.  
How about putting the 10811 in a Zip-Lok bag and run the wires through a 
hole that gets epoxy sealed?  Some desiccant would lower the humidity if 
that is an advantage.

Have Fun,

Brooke Clarke

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Richard (Rick) Karlquist wrote:

>>Given that HP's engineers have done such a good job with
>>the oven and oscillator design, is there anything to be gained
>>by adding extra thermal insulation (lagging)?  How much
>>    
>>
>
>Not a good idea.  The best thing you could do to improve
>temp stability of a 10811 is to tweak the resistors that
>proportion the power between the two heater transistors.
>At some ratio, the thermal gain will peak at over 1000
>typically.  If you just take pot luck, you would be lucky
>to do 100.  You are still limited by the tempco of the 
>electronics, no matter what thermal gain you achieve at
>the crystal. 
>
>You should also be aware that the 10811 is fairly humidity
>sensitive, which can seem like temperature sensitivity
>if the humidity and temperature change together.
>
>The HP E1938 was a much better design in terms of environmental
>insensitivity, but that didn't help much because the 
>ultimate stability was limited by crystal frequency jumps,
>which didn't seem so bad with the 10811 due to the large
>environment errors in it.  In the E1938 they stuck out like
>a sore thumb.
>
>Rick Karlquist N6RK
> 
>
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