[time-nuts] Re: Rubidium oscillator : pack it in styrofoam or attach it to a heath-sink?

[Bob kb8tq]

Hi

Rubidiums are somewhat unusual beasts. They typically have two heated zones ( = two ovens) in
them. One is a bit hotter than the other. Because of the basic physics, those ovens are right next
to each other / in contact with each other. 

If you go to crazy with the insulation, the “colder” oven will heat up due to heat leakage from the
“hotter” oven.  You need a certain amount of heat coming off the package to allow this to happen.

The bigger issue is that there is a pretty big batch of electronics near the ovens in the typical telecom 
Rb. Unless you heatsink things pretty well these parts heat up. When they do their MTBF drops 
quite a bit. You save a couple of watts of heat (maybe) and loose the Rb after a year or two. Not
a great tradeoff. 

Yes, there are a lot of different designs for lab grade Rb’s. There are also some really tiny little
guys running around. Neither category is all that easy to get on the surplus market. If you want
to dive into either of those categories, there are issues, they just may not be quite the same. 

Bob

> On Oct 4, 2021, at 1:39 PM, Wim Peeters <peeters_w at scarlet.be> wrote:
> 
> Insulation decreases the power consumption.  But it will also increase the temperature of the electronics.
> 
> A heath-sink will cool the electronics but will increase the power consumption.
> 
> Or maybe insulate the  part of the case that gets hot, and put a heat-sink on the other parts?
> 
> Wim Peeters
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