[time-nuts] 10811 Extra Lagging etc

Rick Karlquist richard at karlquist.com
Tue Jun 20 20:54:46 EDT 2006


You must be kidding.  No way are Zip Lok bags hermetic.
Water vapor will diffuse right through.  (Note that waterproof
does not equal hermetic).

Rick N6RK


Brooke Clarke wrote:
> 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
>
> --
> w/Java http://www.PRC68.com
> w/o Java http://www.pacificsites.com/~brooke/PRC68COM.shtml
> http://www.precisionclock.com
>
>
>
> 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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>
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