Magnus, That is why I said ". . . setup and properly adjusted . . "
Bill....WB6BNQ Magnus Danielson wrote: > WB6BNQ skrev: > > Well Dick, > > > > Assuming it is setup and properly adjusted, it is absolute as a > > frequency reference by "definition." It does have a given resolution > > as stated in the manufacturer's manual for the instrument. This > > resolution [or noise floor as I see it] is due to a number of factors, > > not least of which is the condition of the physics package (the actual > > Cesium tube). They do ware out ! > > Actually, Cesiums can both be offset in frequency and have drift > components in them. There are a number of systematic issues to handle. > The magnitude of these depends on how they are handled in the design as > well as how they are maintained. > > Also, general relativity comes in so the systematic error of running the > clocks above the gravity of standard sea level acceleration comes into > mind. For a relative comparision at that site it does not care that much > usually. > > There are many features of a Cesium beam which affects the precision, > but none of them actually runs at the magical number, they are all > skewed by the C-field and compensation for this needs to be done. > However, while the C-field skew can be calculated, it is hard to know > the actual C-field. Modern "digital" Cesiums use a mechanism to measure > and stabilize the C-field by measuring the position of the nearby Rabi > responses in addition to the central Rabi and Ramsey features. Such an > approach can remove the major part of the frequency error traceable to > that systematic issue. For older cesium beams you adjusted the current > in the C-field to match up, so calibration to match frequency is needed. > > Older Cesiums does not have this "digital" control loop, so it would be > inaccurate to say that they by definition is sharp on. They are not and > never really be sharp on. > > There is a number of other stability issues of various forms to add onto > this, but I think it is out of scope here. > > Cheers, > Magnus > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
