[time-nuts] SMPS or conventional?

[Wannes Sels]

There are conflicting requirements regarding temperature in Rb's:

- For best performance, the rubidium and quartz oscillators must be kept at
a high and stable temperature.
- For reliability, the supporting electronics must be kept at a lower
temperature.

The heater takes care of the high temperature. The stability of the
temperature can be improved by increasing the thermal mass, i.e. adding a
block of aluminium or copper.
The electronics can be kept cooler with a heatsink, and forced ventilation
if needed.

When you stick both the electronics and physics in a small package, this
becomes more difficult. For the PRS-10 some form of heatsink is pretty much
required to keep the electronics cool enough. Although I seem to remember
reading somewhere that the "benchtop" heatsink they offer now is lighter
than older units.

If the room temperature is not stable enough, you might want to increase
the size of the heatsink and add a fan. This reduces the temperature swing
inside the unit, while still cooling the electronics, at the cost of
increased power draw for the heater.




On Wed, Oct 21, 2020 at 5:38 AM Hal Murray <hmurray at megapathdsl.net> wrote:

>
> > I spent a lot of years buying Rb’s and putting them on small heatsinks.
> I
> > always was disappointed in their reliability. That continued to be the
> case
> > up to the point that the baseplate temp’s got into the 40C region.  In my
> > case, that took a fan ….
>
> How well did it work if the heat sink wasn't small?  What is your version
> of
> small?
>
> Do you have any data (or vague memories) of how much it helps to orient
> the
> heat sink so the fins are vertical so they encourage warm air to flow up
> past
> the fins?
>
> --
> These are my opinions.  I hate spam.
>
>
>
>
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