[time-nuts] Making a HP 10811 better

WarrenS warrensjmail-one at yahoo.com
Mon Sep 19 06:45:29 UTC 2011

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.


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?

> 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

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