WarrenS wrote: > All very informative and useful information for sure and good to know, > But I'm thinking the real difference between a primary and secondary > standard, > Has More to do with if there is anything else more accurate and repeatable > available. > I'd guess a Rb would of made a great cave man Primary standard. > And sounds like it will NOT be long before the Freq and drift of a CS > Primary will be consider just another secondary standard that will have to > be calibrated. > (to get the 1e-16 + or whatever accuracy/repeatability it is they are now > working on.) >
Sorry but you have completely misunderstood the concept. It is admittedly a difficult concept to grasp; I know it took me a long time. A hydrogen maser with the wall shift servo'ed out will run rings around a compact Cs beam clock like the HP5062, used on submarines. (An interesting trivia item is that I don't believe the 5061 can fit through a submarine hatch). The 5062 is still a primary frequency standard and the hydrogen maser is still a secondary frequency standard. Regarding "drift" of primary cesium beam standards: the 5071A has unmeasurable drift, aging and tempco, down to a measurement limit of at least 1E-15. It has a typical *random* error of a few parts in 1E-13. The systematic error (average error of all 5071A's built) has been established to be below 1E-14. It will always be a primary standard even in the presence of longer reversible optically pumped laboratory Cs beam standards of higher accuracy and better short term stability, or cesium fountains, etc. Even the 5061A/B is considered a primary standard, albeit with reduced accuracy, even though it has a measurable tempco. We were very proud of the E1938A crystal oscillator when it was able to meet the 5061 tempco spec. It is in no way a primary frequency standard regardless of that or any other accomplishment. Primary means that the clock will meet its spec without being "calibrated" against a better clock. Secondary means that calibration against a primary standard is necessary. Rick Karlquist N6RK _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.