[time-nuts] Frequency processing scheme of HP5065 vapour rubidium standard

[Normand Martel]

--- Ulrich Bangert <df6jb at ulrich-bangert.de> wrote:

> John,
> 
> > offset that changed annually.  IIRC, it was
> typically something like 
> > 300x10e-10.
> 
> Agreed! And that is what the manual says its good
> for! 
> 
> However, the question remains why different physics
> packages need
> DIFFERENT thumbwheel settings in order to achieve
> the SAME time scale.
> 
> 73 de Ulrich, DF6JB
> 
I've read the answer last week on the forum... (sorry
i don't remember who gave the answer...)

It's simple: The technology used on cesiums CAN NOT be
applioed on Rubidiums. With Cesium, high end
techniologies like fountains or beans can be used, and
if i understand well, with these technologies, PURE
CESIUM is used, so there is NOTHING that can affect or
"pull" the resonance of cesium from it's natural
resonance. (9 192 631 770 Hz).

With rubidium, buffer gases must be used, and these
gasses "pull away" the resonance away from Rubidium's
natural resonance. And that is the source of all our
problems with rubidium: Buffer gas/rubidium
evaporation/absorption will affect the frequency
"pulling", thus the drift in Rubidiums. This also
explins why two rubidiums clocks wiill have different
settings (Rb/buffer mixture tolerances). With Cesium,
no pulling, with rubidium, some pulling. That's why
Rubidiums aren't primary standards. If we could build
a Rb (or ANY OTHER element) atomic clock with the same
technology that we use with Cs (total element purity),
there wouldn't be any pulling over time and Rb's would
be considered primary standards.

Hope this explanation will help!

73 de Normand Martel VE2UM






 
____________________________________________________________________________________
Sponsored Link

$200,000 mortgage for $660/mo - 30/15 yr fixed, reduce debt, home equity - 
Click now for info http://yahoo.ratemarketplace.com