[time-nuts] Rubidium Frequency Standard FE-5680A

WB6BNQ wb6bnq at cox.net
Wed Feb 22 07:05:31 UTC 2012

Hi Ken,

The Rb systems require being heated to vaporize the Rb metal and to have a stable (more or less) temperature.  For the FE-5680 the 15 volt current should run between 750 to 850 milliamps when properly heat sinked.  Mine is riding around 840 milliamps at the moment.  The Rb is on the PCB that came with it.  I use a small 12 volt 3" x 3" fan running at 9 volts to lightly blow air across the Rb and PCB which
is slightly elevated off the bench to allow air to flow underneath.

The manual states that the 15 volt input should be at 0.8A (800 ma) under normal operating conditions at 25 degrees C.  The hotter you allow it get, the lower the 15 volt current.  However, there are limits and the PCB in its original form was much bigger and thus a larger heat sink.

So, I recommend you provide enough heat sinking or forced air to keep the 15 volt current running around 800 milliamps.  If you go to the Time-nuts archive and search through the last two or more months worth of messages you will discover and learn other interesting info for the FEI FE-5680A.

Here is the link to the archive :



Ken Kubick wrote:

> I just baught two FE-5680A Rubidium Frequency Standards.  Both units seem to work just fine.  The units I recieved are mounted to a PCB.  They both run real hot around 58 Deg. C.  Should I put them on heatsinks?  or is this normal?  The data sheet says the temperature range is -5 to +50 deg. C.  I don't want to put a heatsink on them if there is a heater inside that trys to keep them hot at 58 deg. C.
> Thankyou
> kenkubick at hotmail.com
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