[time-nuts] HP10544A Confusion

Richard (Rick) Karlquist richard at karlquist.com
Fri May 29 15:35:29 UTC 2009


Jim Flanagan wrote:
> 
> 
> after warmup, I need to tweak the temp for a freq MIN.  Whereas, for an SC
> cut xtal osc we would be looking for a freq MAX.  For both xtal cuts the 
> turning
> point is typically set for somewhere in the 75 - 85 C range.  I see 

> Jim
> jflan at tampabay.rr.com

The majority of 10811 SC-cut crystals do not have a temperature 
turnover.  Instead they have an inflection point where the tempco is 
minimum, but not zero.  It is fairly broad, so the oven set point is
not especially critical.  If you want to tweak something in the 10811,
better to tweak the resistors that apportion heater power to the
two transistors, to maximum thermal gain.

In the case of an oscillator that does have a turnover, you do not
necessarily want to set the oven temperature to the turnover.  Instead 
you want to offset it so that there is a nonzero crystal tempco that 
happens to cancel out the tempco of the oscillator electronics.

Rick Karlquist N6RK



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