[time-nuts] Allan variance of Thunderbolt

[Tom Van Baak]

> 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:

http://www.leapsecond.com/pages/tbolt/power.htm

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:

http://www.leapsecond.com/tbolt-faq.htm

/tvb