[NLRS] Efratom Lpro 101 Rubidium Standard

[Chris Elmquist]

I can't comment on whether or not the heatsinking is really required-- but
if you discover that it is, you might consider using something like these
Laird thermal pads between the Rubi and the inside wall of your enclosure,

http://www.digikey.com/scripts/dksearch/dksus.dll?FV=fff40012%2Cfff80067&k=laird&vendor=0&mnonly=0&newproducts=0&ptm=0&fid=0&quantity=0&PV98=2

It's otherwise known as "thermal gap filler" and it makes a nice,
compressible interface between the two surfaces and depending on the
material chosen, provides good thermal transfer as well as electrical
conductivity.  You'd use a graphite based material if you want electrical
conductivity.  The stuff's not cheap but you can cut it to size with a
scissors and save the rest for another project :-)

Chris N0JCF

On Saturday (11/17/2012 at 04:49PM -0600), tosca005 at umn.edu wrote:
> 
> 
> I am in the process of building up a rubidium standard into a die-cast 
> aluminum box. The box will contain an Efratom Lpro 101 rubidium standard, 
> power supply (24vdc direct input or 12vdc->24vdc voltage doubler boost 
> regulator), a Down East Microwave 10-4 (four-port filter/splitter for the 
> 10 MHz output), the rubidium oscillator lock signal -> LED circuit, and 
> some voltage monitoring using digital panel meter LED blocks.
> 
> I am puzzled about meeting the heat sinking requirements. Plan A was to 
> simply drill 6 holes through the bottom of the aluminum box in the 
> positions of the 6 mounting screw holes of the Lpro101, and bolt the 
> Lpro101 to the inside bottom of the box (which will become the top of the 
> box during operation, as I will put rubber feet on the "lid" and flip the 
> whole assembly over to make that the base. One web site that discussed 
> building up a standard like this claimed that this would be more than 
> satisfactory at carrying away the excess heat of the rubidium 
> lamp/oscillator. Then at the last meeting of the Roadrunners Microwave 
> Group, one of the members (sorry, I'm bad with names and callsigns, I'll 
> need a few repetitions to remember everyone) brought his homebrewed 10 MHz 
> standard which also used the Lpro 101 but he added a heat sink on the wall 
> of the box that the rubidium standard was bolted to. I didn't get a chance 
> to discuss it with him in depth. But I got to thinking if a heat sink is 
> really needed, I need to have excellent flatness on the inside of the 
> aluminum box and heat sink compound between the Lpro101 and the box, plus 
> between the box and the heat sink.
> 
> Is this really necessary? Do I need to have the inside of the aluminum box 
> milled to extreme flatness? (I am sure that without some work, it is not 
> terribly flat now.) The outside of the aluminum box looks "flat enough" to 
> me, but not the inside.
> 
> Anyone with any insight on this that they'd like to share?
> 
> John P. Toscano, W0JT/5
> EL09ro October-May
> EN34js May-September
> 
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-- 
Chris Elmquist