[time-nuts] Rubidium (Rb) or Caesium (Cs)

Magnus Danielson magnus at rubidium.dyndns.org
Mon Oct 3 19:13:44 EDT 2011

Dear Warren,

On 03/10/11 18:58, WarrenS wrote:
> Rubidium (Rb) or Caesium (Cs) standard reference oscillator?
> What will give the more accurate absolute Frequency source over day to day averages?
> A primary Cs (the types available to time nuts) or a optimally disciplined GPS Rb Osc?
> By definition Cs is the primary time standard,
> but there are several things that effect a time-nut's "Primary Cs Standard's" absolute frequency including how it is built and maintained, if it has the high stability option and Einstein.
> What I'd like to find out is how accurate a GPS Disciplined_Rb_Osc can be made compared to the typical Cs out there.

If you want "absolute frequency" then a GPSDO rules over any Cs a normal 
time-nut can get.

Looking only for stability, then a HP5065A will be more stable than a 
HP5061A up to about 100 ks where the HP5061A becomes more stable 
according to the ADEV charts that I have found after a quick look on the 
net (using "HP5065A ADEV" and "HP5061A ADEV" as search terms).

> I'm experimenting to find out how accurate a freq standard can be made using a LPRO Rb disciplined to a Tbolt.
> Using a  temperature compensated and tweaked LPRO Rubidium (Rb) oscillator,
> I'm getting low e-13 per deg F and day to day freq variations (compared to GPS) even before being disciplined.
> When the LPRO Rb is disciplined to GPS using a well setup Tbolt with an extended time constant of a few hours,
> their phase difference stays with-in a couple of ns RMS, and of course the difference between them long term is zero.
> What I would like to determine is how accurate that really is.

Best way is to measure against a cesium or free-running rubidiums. 
Three-cornered hat will help.


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