[time-nuts] Cheap Rubidium

[Bruce Griffiths]

Bob Camp wrote:
> Hi
>
> If I randomly pick up a FE 5680A data sheet, I find that it's short term stability is 1.4/sqrt(Tau) x 10-11.  Since I never doubt anything I see on a data sheet, this immediately tells me I should get 1.4x10-12 at 100 seconds, and I only have to wait for 10,000 seconds to get to 1.4x10-13.
>
> Since the temperature performance is at the 1x10-12 / C level, I would need a room that's stable to *much* better than 0.1 C over a 3 hour period to get there. I suspect that 0.01C might not be good enough ...
>
> So here's the question:
>
> Has anybody run any of the cheap rubidiums (FE or Efratom)  in a *very* stable temperature environment to see how close they get / what the floor is?  I've run through a lot of data on the web, but I haven't really found what I'm looking for.
>
> Thanks!
>
> Bob
>
>    
Figure 7 on the FE5680 page (also on the data sheet) indicates that you 
may need somewhat less than 3hours to achieve  ADEV ~1E-13.
0.01C stability should be adequate.however its not necessary to control 
the room temperature to this stability if the FE5680 is in an enclosure 
with a sufficiently high time constant whilst having a sufficiently low 
thermal resistance so as to avoid overheating the FE5680.

Bruce