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

[Dana Whitlow]

I wonder what the detailed thermal model of telecom Rb's looks like.  I
cool my PRS-10's
hear sink surface to ~55C with a heatsink, but parts of some other surfaces
of the package
run several degrees hotter.  This rather puzzles me, and worries me.

Dana


On Tue, Oct 5, 2021 at 10:46 AM Bob kb8tq <kb8tq at n1k.org> wrote:

> 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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