[time-nuts] NTGS50AA, better than Thunderbolt?

[Mark Sims]

I got in another NTG50AA unit a couple of weeks ago and have been watching the oscillator (Trimble 34310-T2) age in and stabilize.  It started out aging at around 1E-9 parts/day.  After two weeks,  the aging rate for the last 72 hours was down to the 2E-11 range,  with the curve still flattening out.   Over the last 24 hours it is down to under 5E-12 parts per day.  

These numbers are based upon the EFC voltage and known EFC gain.   Of course,  there could be (and probably is) some aging effects to the EFC DAC/reference voltage.  The unit is running while disciplined to GPS. and is not being thermally stabilized.  The oscillator seems to be very immune to external temperature effects.   Unit temperature has varied +/- 2 degrees C and the air conditioning has been cycling quite a bit (it's been 95 degrees F outside).