[time-nuts] Possible HP 10811 instability clue Cont’d.

[Perry Sandeen]

List,

Wrote <Some on this list mentioned having had less-than-optimal performance with their HP 10811 series oscillators.  James Miller G3RUH made a slight mention of optimizing performance by readjusting the set point temperature in one of his phase detector articles.  He said though time consuming the results were worth the effort.

Replied: <Regardless of isolated anecdotal data on one oscillator, it is probably not advisable to change the set point.

Answer: Agree.  My comments were made about someone with a “wonky” oscillator that that this MIGHT be part of the problem.

Replied: The majority of 10811 crystals do NOT have a turnover, only a region of low tempco around 82 degrees.

Answer:  I respectfully disagree.  First isn’t a region of low tempco another way of saying turning point?  Semantics aside, I believe that they do have a turning point that is selected.  This is why.   HP selects 41 separate resistance values to obtain 41 different oven temperatures between 80.0C to 84.0 C in .1 degree increments.  Now if that isn’t finding a turning point I don’t know what is.

I believe that is why they say if the oscillator fails it needs to be repaired at the factory.

Wrote: <Instead of that, change the circuit to B-mode and optimize the heat between the two heater resistors for maximum thermal gain (you should be able to get 1000).  Then change the circuit back to normal.

Answer:  I have no idea B-mode is.  Would you please expand on it and how to do it?  It could be very useful.

Regards,

Perrier