Hi..
In his message, Paul-Henning Kamp writes that a
drift-free standard has not been yet designed...
But Isn't Cesium drift-free? Since the SI second is
standardized as de duration of 9192631770 oscillation
of the hyperfine transition of the atom 133Cs?
If Cesium drifts, theren should be a more formal
definition of the second (Such as density, maximum
C-field or level of purity). Does anyone here has it?
And also, something else i don't understand: Why do
the newer GPS satellites rely on Rb standards rather
than Cs standards? Since Rubidium is known as less
precise than cesium? Is there a reliability issue
there (Rb clocks are more reliable / longer MTBF tha
Cesium clocks). I don't know...
73 de Normand Martel VE2UM
(A PLL based 9192631770 synthesizer i once
imagined...)
10 MHz ---(/250)--40000PPS-,
OCXO |
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,-------------<-----------'
|
`-(/)---[Filter]---(VCO)--*--829.08 MHz--,
| | |
`---(/20727)-----------' |
|
,---<-41454 PPS--<--(/20000)-------<-----'
|
`--(/)---[Filter]---(VCO)--*--1838.526354 MHz--,
| | |
`---(/44351)-----------' |
|
,----<--------------<--------------<-----------'
|
`-(*5 SRD)--9192631770 Hz (to physics)
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