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

k4cle at aol.com k4cle at aol.com
Mon Oct 3 18:23:05 EDT 2011


I used to work at Efratom.  The rubidium engineers used to say that the LPRO  
did not work well with constant frequency corrections such as with GPS.   
They claimed that very slight corrections should only be made once every 24  
hours.  And then, it may take up to a week or longer to pull the frequency  
to the desired amount.  If you are constantly jerking the control voltage  
back-and-forth, the LPRO will get to where it develops jitters!
Regards, Doug, K4CLE

Connected by DROID on Verizon Wireless

-----Original message-----
From: WarrenS <warrensjmail-one at yahoo.com>
To: Discussion of precise time and frequency measurement  
<time-nuts at febo.com>
Sent: Mon, Oct 3, 2011 16:59:19 GMT+00:00
Subject: [time-nuts] Rubidium (Rb) or Caesium (Cs)

Rubidium (Rb) or Caesium (Cs) standard reference oscillator?

What will give the more accurate absolute Frequency source over day to day  
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.

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.


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