An approach is to put just the rb unit in say the basement. Its always cooler (at least mine is) The area I work in can get pretty warm in the summer if I am gone for a week This approach solves that problem pretty well
On Sun, Feb 28, 2010 at 11:25 AM, Bob Camp <li...@rtty.us> wrote: > Hi > > A few words of caution here. > > I have run compact rubidiums for a number of years. It is *very* tempting > to skimp on the heat sink. Cooling something that's heating it's self up > sounds silly. > > Having tried the "not much heat sink" approach several times (I'm a slow > learner). The rubidium does die fairly soon. Properly cooled they last for a > long time. You need to get the baseplate below 40 C. Getting it below 30 C > might be better, but that's impractical in most settings. > > The units dump around 10 watts of heat. The number will vary depending on > the supply voltage, the exact baseplate temperature, and the exact model. If > your normal room temperature is 20 C, 10 watts and a rise to 40 gives you 2 > C/W. > > In a tightly packed rack, in the summer, at high supply voltage, the heat > sink required can easily get to < 1 C/W. My answer to that is to move the > rubidium out of the rack or simply turn it off when things get that warm. > > Fans are a good way to improve the efficiency of any heat sink. The problem > here is that rubidiums are sensitive to magnetic field. Having a device with > a magnetic motor in it right next to one probably is a bad idea. If you put > in fans, put them in the back of the case, and keep them away from the > rubidium. > > Bob > > > On Feb 28, 2010, at 10:55 AM, Joe Gwinn wrote: > > > At 2:02 AM +0000 2/28/10, time-nuts-requ...@febo.com wrote: > >> Date: Sat, 27 Feb 2010 20:02:05 -0600 > >> From: Ed Palmer <ed_pal...@sasktel.net> > >> Subject: Re: [time-nuts] Rack-mounting an LPRO? > >> To: Discussion of precise time and frequency measurement > >> <time-nuts@febo.com> > >> Message-ID: <4b89ce9d.4060...@sasktel.net> > >> Content-Type: text/plain; charset="iso-8859-1"; Format="flowed" > >> > >> Sorry, the pictures got lost. Let's try again. > >> > >> Ed Palmer wrote: > >>> What else is going to be in the rack? If your 1U enclosure is packed > >>> in tight between other devices there might be no cooling at all. You > >>> might need a fan to move some air. > >>> > >>> I don't know if you can find something like this, but I scavenged heat > >>> sinks from an old Compaq DL760 server that might fit your situation. > Here's what the heat sink looks like. The aluminum plate is about > >>> 1/4" (6.4 mm) thick. Notice the heat pipes. > >>> > >>> > >>> > >>> Here's what it looks like on the LPRO. You'll have to drill holes in > >>> the plate to match the LPRO. > >>> > >>> > >>> > >>> It's not perfect, but it certainly does the job - particularly if you > >>> had a fan blowing through the fins. The total height is about 1.75" > >>> (45 mm). > >>> > >>> But remember, the more you cool the LPRO, the more power it will draw > >>> to keep itself warm so you don't want to overdo the cooling. > >>> > >> > Ed > >>> > >> [snip] > >> -------------- next part -------------- > >> A non-text attachment was scrubbed... > >> Name: 1.jpg > >> Type: image/jpeg > >> Size: 37469 bytes > >> Desc: not available > >> URL: < > http://www.febo.com/pipermail/time-nuts/attachments/20100227/9f21a5a8/attachment.jpg > > > >> -------------- next part -------------- > >> A non-text attachment was scrubbed... > >> Name: 2.jpg > >> Type: image/jpeg > >> Size: 33025 bytes > >> Desc: not available > >> URL: < > http://www.febo.com/pipermail/time-nuts/attachments/20100227/9f21a5a8/attachment-0001.jpg > > > > > > The aluminum fin and copper pipe assembly integrated with the heatsink > plate is most likely a heat pipe of some kind, as that's what Thermacore > makes. It's a model 2644, from the nameplate, but no joy at the > Thermacore.com website. > > > > Joe Gwinn > > > > _______________________________________________ > > time-nuts mailing list -- time-nuts@febo.com > > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > and follow the instructions there. > > > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.