[time-nuts] Making a HP 10811 better
djl at montana.com
Mon Sep 19 06:31:25 UTC 2011
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
> 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
> 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.
> 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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