sheesh! How about a right-sized water jug?
Don
----- Original Message -----
From: "Bob Camp" <[email protected]>
To: "Discussion of precise time and frequency measurement"
<[email protected]>
Sent: Tuesday, December 22, 2009 8:23 PM
Subject: Re: [time-nuts] Cheap Rubidium
Hi
I agree that if you simply bolt the rubidium to an old engine block and
toss a blanket over it, you might get some pretty good thermal stability
in the "hour to couple hours" time period. That's certainly a better
approach than putting some kind of DC heater (and it's varying magnetic
field) near the rubidium.
I'm still wondering if they do indeed hit 1x10-13 (as in almost 1x10-14)
or not. I suspect not. I'm sure that they do indeed get into the
1x10-13's, just not sure they get to the bottom of that region.
Bob
On Dec 22, 2009, at 8:26 PM, Bruce Griffiths wrote:
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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