I have not tried the Dewar or mineral oil, but I have tried putting it
inside a second oven that is set just above ambient, both a very simple home
built one using a box and a light bulb and a HP built double oven.
Both can be made to work great.
ws
***************
Don Latham djl at montana.com
Thanks, Warren. I simply cannot remember, 'cause this is a long on-going
thread. Has anyone tried a dewar device in which the 10811 or similar is
suspended in mineral oil?
Don
WarrenS
The test took a while, but I finally got around to testing the effect of
setting a HP10811's inner oven to the xtral's EXACT turn over
temperature.
Short answer is NO Help.
I did not see any improvement in freq stability with environmental
temperature changes.
It did help in reducing the small but temporary freq step caused when
the oven PS voltage was changed.
The reason why changing the oven to the Exact turnover temp does not
help is because there are many other things that are still temperature
sensitive that far exceeded the freq change due to xtral temperature
changes when it is at it's Turnover point, such as mechanical stress
on the case and changes of the internal buffer loading.
My method was much more accurate and repeatable than the way it was done
in the existing "somewhere report".
The test consisted of bringing out the temperature bridge voltage of a
sealed 10811 Oscillator thru a high value resistor so that a large
external voltage could be used to make very small changes in the Oven
temperature set point.
Next I adjusted the Oven temp by way of the attenuated external voltage
to the bridge resistors to find the exact turn-over temperature.
Freq resolution, repeatable and turn over was within a couple parts in
e-12
Frequency TC after setting the oven was still a couple parts in e-11 /
deg C.
Just to be sure, I rechecked the xtral's turn-over temperature at
different room temperatures.
The turn over temperature still happen at exactly the same external
voltage. That did not change, although the Freq was different, any
temperature change in the oven setpoint still caused the Freq to change
in the same direction, by the same amount when the oven temperature
setpoint was raised OR lowered by the same amount.
ws
****************************
from
http://www.mail-archive.com/time-nuts@febo.com/msg27938.html
Warren,
there is a report somewhere of resetting the oven temp in a HP 10811
to exactly find the turnover temperature.
How high is this on your list of things to do to improve a HP 10811?
Does it make the double oven unnecessary?
cheers, Neville Michie
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--
"Neither the voice of authority nor the weight of reason and argument
are as significant as experiment, for thence comes quiet to the mind."
R. Bacon
"If you don't know what it is, don't poke it."
Ghost in the Shell
Dr. Don Latham AJ7LL
Six Mile Systems LLP
17850 Six Mile Road
POB 134
Huson, MT, 59846
VOX 406-626-4304
www.lightningforensics.com
www.sixmilesystems.com
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