[time-nuts] SMPS or conventional?

[Bob kb8tq]

Hi

> On Oct 21, 2020, at 8:40 AM, Wannes Sels <wannes.sels at gmail.com> wrote:
> 
> 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.

If you are designing the internals of the OCXO or Rb from scratch, this may
help things. If you have a part of eBay … likely not so much. 

> 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.

The PRS-10 is hardly unique in this regard. All of the small Rb’s ( = anything 
other than a 5065 sized unit) that I’ve seen really do need a heatsink in order
to live a long and happy life. 

Bob


> 
> 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.
>> 
>> 
>> 
>> 
>> _______________________________________________
>> time-nuts mailing list -- time-nuts at lists.febo.com
>> To unsubscribe, go to
>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
>> and follow the instructions there.
>> 
> _______________________________________________
> time-nuts mailing list -- time-nuts at lists.febo.com
> To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.