At 6:03 PM +0100 11/11/06, Ulrich Bangert wrote: >Hi folks, > >If you look at the schematics of a Ball-Efratom FRK-L rubidium standard >you will notice that it has a fixed frequency synthesizer stage to >generate the microwave frequency from the 10 MHz OCXO. There is NO >possibility to tune anything concerning the microwave frequency of the >physics package OTHER than the C-field setting. Since the C-field >setting covers a frequency range of +/- 1E-9 relative this seems to be a >strong indication that all efects that you decribe (including a exchange >of the physics package) must be WELL below 10E-9 relative. With the >resonance frequency in the 7 GHz region +/-10E-9 makes abt. +/- 7 Hz >absolute. Note that this +/-7 Hz matches pretty much the way how the >rubidium's frequency is usually specified as x.xxxxxx +/- 4 (7)Hz for >example on TVB's pages. Up to this point I am in harmony with the world.
Ulrich, The limits of rubidium oscillator operating range is larger than you have calculated. The unit I was trying to adjust had drifted outside the range of the C-field adjustment control. This drift occurred over 13 years of use in a laboratory environment. It was a total of approximately 1.5E-9 drift. The thing that can be changed to accommodate this drift is the factory selected resistors in the C-field setting control circuit. See R10 and R11 on board 3, the 20V supply board. I don't know what the maximum variability range is, but if it was less than 1E-9 then these resistors would not be factory selected. -- --David Forbes, Tucson, AZ http://www.cathodecorner.com/ _______________________________________________ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts