[time-nuts] Rb cooling

WB6BNQ wb6bnq at cox.net
Sun Jul 17 23:12:04 UTC 2011


Thinking about it Poul,

That explains why the preferred "frying pan" is made of cast iron in deference to
the modern light weight ones they sell these days; better temperature control
across the cooking area.  I knew I was saving old used cast iron pans for a
reason.  Now I know what I am going to do with them.

And I agree, people are not thinking about the reason for the heat regarding the
Rb.  Everything in its proper balance.

Bill....WB6BNQ


Poul-Henning Kamp wrote:

> Cooling Rb's is a much misunderstood discipline.
>
> Most Rb's have a specified "base plate temperature range".
>
> For instance the PRS10 specifies -20..+65°C
>
> Cooling Rb's should happen only through the base-plate.
>
> Cooling other surfaces creates unwanted temperature gradients inside
> the Rb unit.
>
> The colder you run a Rb, the more power it uses to keep important
> bits inside warm.
>
> Running it near the top end of the range wears out the electronics
> in it faster.
>
> No matter what kind of cooling, it is important that it offers
> sufficient cooling capacity for the internal ovens to have a
> margin to work with.
>
> For frequency stability, you should strive to have a constant
> baseplate temperature.
>
> Putting a fan on anything, will generally speed up and amplify the
> effects of any ambient temperature changes.
>
> For optimal frequency stability, you want to do is mount
> your Rb on a huge lump of iron which you can keep at a
> constant temperature around 35-40°C by natural convection.
>
> Iron is better than Cu/brass/Al because it conducts heat slower and
> less eagerly, thus attenuating ambient temperature fluctuations.
>
> --
> Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
> phk at FreeBSD.ORG         | TCP/IP since RFC 956
> FreeBSD committer       | BSD since 4.3-tahoe
> Never attribute to malice what can adequately be explained by incompetence.
>
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