Hi Water might work. It would take quite a bit of it.
Here's my "wild guess" level math: 1) The basement moves 0.1 to 1 C short term / over a day. 2) I want to get to < 0.01 That takes the time constant out to >= 10X the time I'm interested in. 3) The time period of interest is 3 to 30 hours. That gets to a time constant of at least 10 days. At the same time you have >10 watts coming out of the gizmo. You can't put the thermal mass inside a vacuum bottle. I suspect that some combination of thermal mass and active stabilization will be needed. So much fun .... Bob On Dec 23, 2009, at 2:18 AM, Don Latham wrote: > 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 >>> >>> >>> _______________________________________________ >>> time-nuts mailing list -- [email protected] >>> To unsubscribe, go to >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> and follow the instructions there. >>> >> >> >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
