[time-nuts] Allan variance of Thunderbolt
Tom Van Baak
tvb at LeapSecond.com
Fri Jul 11 18:39:29 EDT 2008
> The Thunderbolt data sheet says that the unit requires 25mA at
> 12V. That spec would imply it is for a unit without an OCXO
> since the oven heater draws considerable current from the 12V
> power supply. But then, the data sheet says it draws 15 watts
> cold, 10 watts steady state. That implies the unit has a heater.
> And if you multiply the published power supply requirements out
> you get 2 watts, not 10-15 watts. It appears that some of the
> specs are for an ovenless unit, others are for the ovenized unit.
See actual power requirements for the TAPR Thunderbolt:
So, yes, these are OCXO versions. Very nice OCXO.
> The data sheet also talks about a telecom version with improved
> holdover performance... this has got to be the ovenized unit. I
> suspect the Allan variance plot is for the low end unit, but the
> shape of the curve is funny. It always slopes downward. Almost
> all GPSDO Allan variance plots show a hump in the graph around
> 100 seconds.
Right. Ignore the ADEV plot on the Trimble data sheet; it's not
quite the same unit as the TAPR deal. Please read the FAQ:
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