[time-nuts] compensation for resistances value changes due to temp

Paul Cianciolo paulc at snet.net
Fri Aug 26 03:56:36 UTC 2011

Hello Folks,
I have one of these C-MAC Rakon Double oven oscillators.
The oven and electronics run on a 12 vdc supply.
For this I am using 2 stages of regulation, first to 18 volts and then to 12 vdc.  Both of these are 3 term regulators, I know not the best choice.
But its a place to start.  I know there are better, quiter regulators out there and that is for the future.
The 5 volt control EFC voltage is derived from a 5 K resistor in series with a turn pot 10 turn 5 K multiturn pot'.
This method alows me to adjust the EFC voltage with resonable precision.
After a few hours I was seeing 1 part in 10-11 drift and which was control by the panel mount.
As a test I put my finger on the 5 K carbon resistor to warm it up.  After a few seconds I could see the frequency drift and acclerate.
After I moved my finger the frequecny slowly returned to normal.
Buy I would like to optimize so i guess low temp coefficient resistors.
But are the other ways to control this type of drift.??
Is there some way of knowing which way the oscillator is drifting and electrically compenate?
For  know I plan to move the 5 K resistor, after I get a precison device into the area of the oven and see what happens.
Hopfully keeping its temp constant will help a little.
Open to all suggestions
Thank you all for alloeing me to join this group and all the help you have been.

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