Jerry, >Is this variability more likely due to the rubidium source (failing bulb) or >due to problems with the 5334B counter?
Obviously you need a third source for comparison while locking your counter to the Rb source. I gather from the web that the Lucent unit uses an Efratom module in which case there should be a lamp voltage display or at least a measurement pin for it available somewhere. I posted an old Efratom FRK manual to BAMA some time ago which may give you a clue. A good lamp will show better than 5V although this is actually the voltage on the output of the photo-detector amp. New lamps are available on the web although I replaced mine in a Racal 9475 Rb standard some time ago with no obvious improvement; it still reads 5.8V when the manual says it should be between 6 and 12V. I was told once that varnish can slowly evaporate onto the cell window thus reducing optical transparency. Don't know if this is true but it is a thought. Cheers - Joe G3LLV _______________________________________________ time-nuts mailing list [email protected] https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
