[time-nuts] Cheap Rubidium

John Miles jmiles at pop.net
Wed Dec 23 02:06:42 UTC 2009


The cheap Datum LPRO-101s coming out of China appear to be capable of great
performance, no problems at all getting into the 1E-13s at t=1000 seconds.

(This plot shouldn't be taken seriously beyond t=1000s, and the flattening
effect at t=700s might be the Thunderbolt's fault.  I haven't run my
LPRO-101 long enough to see what it will do at 10000 seconds, but at some
point the ADEV curve can be expected to turn upward for real.)

-- john, KE5FX

> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com]On
> Behalf Of Bruce Griffiths
> Sent: Tuesday, December 22, 2009 5:27 PM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] Cheap Rubidium
>
>
> 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
>
>
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