[time-nuts] 10811 Extra Lagging etc

SAIDJACK at aol.com SAIDJACK at aol.com
Sat Jun 17 16:47:40 EDT 2006

Hi Brian,
I went through what you are about to embark upon.
Some comments:
   * My 10811A has about +-2Hz EFC adjustment range 0-5V. I used  the 
mechanical adjust to have about 0Hz offset at 2.5V EFC.
 Make sure your voltage reference for your DAC is temperature stable  (<5ppm 
per Celcius), otherwise the error is from the DAC/Reference, not the  OCXO. It 
is best to somehow put the DAC and DAC-reference inside an oven as  well, or 
at least thermally connect it to the oven case etc, so that it doesen't  
experience your expected 35 Deg C changes.
   * Insulating the oven does help slow down the effects of  thermal changes, 
but don't overdo it because at high temperatures in the summer  you don't 
want to have the heater turn off completely, and the oven "overheat"  itself just 
from the internal power consumption of the oscillator itself. Thus  you 
always want some thermal energy to escape through your insulation even at  the 
highest expected ambient temperatures.
   * Buffer the sine output to mitigate the effects of loading on  the OCXO
   * Provide a clean, temperature compensated power supply to the  OCXO.
A trick to use: measure the oven current. It should always vary with temp  
changes, if it stops varying and stays constant while the temp is still rising  
the oven is temp-saturated.
Good luck,

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