[time-nuts] SMPS or conventional?

[Bob kb8tq]

Hi

The only issue with the “controlled fan” approach is that you
have a variable magnetic field as a result. That and the vibration
both can impact the stability of the Rb. Some means of isolating
the fan from the immediate vicinity of the Rb sounds like a good idea. 

Bob

> On Oct 21, 2020, at 9:31 AM, Luiz Alberto Saba <las at intercat.com.br> wrote:
> 
> I am thinking in an black aluminium finned heatsink, the size of the base plate, and a fan, controlled by an electronic thermostat (sensor direct coupled to the heatsink). Is that ok?
> 
> Em 21/10/2020 09:40, Wannes Sels escreveu:
>> 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.
>>> 
>>> 
>>> 
>>> 
>>> _______________________________________________
>>> 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.
> 
> 
> _______________________________________________
> 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.