[NLRS] Efratom Lpro 101 Rubidium Standard

[Doug Reed]

<http://www.ka7oei.com/10meg_rubidium1.html>
This article by KA7OEI is what I was going by. He suggests he could get 
by without a heat sink beyond the die-cast box itself. I figure that if 
it gets too hot I can always add a heat since to the top over the LPRO.

I wasn't going to worry about milling it flat, but that is why he 
mounted the LPRO to the top cover rather than inside the box. The bottom 
of the box has ridges, the top is much more flat. I'll just use heat 
sink compound to help with the transfer.

Just remember that you need an extremely clean power source, else you 
will see the noise in your 10MHz output. I was leaning toward an old 
style capacitance-multiplier transistor regulator for the final stage 
with an external bulk supply feeding it. OTOH, all I really want is 
maybe 1e-10 or so....

73, Doug Reed, N0NAS.

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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