[time-nuts] 10811 Extra Lagging etc

[Brooke Clarke]

Hi Rick:

Thanks for pointing that out.  Maybe the factor is air density.  I know 
air density was the thing we used to monitor to jet the carbs in racing 
cars.
It was better than using a barometer and/or thermometer.

Have Fun,

Brooke Clarke

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



Rick Karlquist wrote:

>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
>>>
>>>
>>>      
>>>