On 17/07/11 22:07, Mark Spencer wrote:
I've done something similar to this. In my case the Rb out performs the 100
second adev and re trace specs from the manufacturer with the fan running. I
can't measure phase noise and I only use the rb to occasionally use as a
reference for checking the frequency of an oxco over a time span of an hour or
so.
I did notice that the current drain of the rb is slightly higher with the fan
running and probably more stable than before. I suspect the heater in the rb
is working a bit harder than before and I may be over cooling the unit. This
might be something to look at if you cool your rb with a fan.
The thing is... if you have a fan under control, you can allow the
cooling plate become hotter as you have higher capability of cooling
than just a passive radiator.
The heaters of a rubidium is there to achieve stable temperatures of
about 70 and 130 C but then need cooling to maintain stability.. but if
you modulate the cooling with a time-constant longer than the control
loop of the heater, then you can get good stability with less power
consumed.
Cheers,
Magnus
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