[time-nuts] Surplus Rubidium Oscillator Frequency Spread

Bob Camp kb8tq at n1k.org
Fri Aug 28 11:23:41 EDT 2015


Based on looking at about 40 or so similar units - I have never seen one that was 
> 1x10^-9 off frequency. Finding one that is >5x10^-10 off after running for a few days
is rare in my experience. The makes and models ranged over several types and companies. 
I have seen no group that is any better or worse than the rest. All of the parts I have seen
apparently left the factory at one setting and never got adjusted in the field. Many of the 
date codes on mine go back into the 2000 ~ 2003 era. 

With no way to track running hours, there is not a lot you can do with this data in terms
of “power on aging”. I think it’s fair to say that in whatever environment they were in, you
didn’t see anything even remotely close to the sort of 1x10^-9 per year you see quoted as
aging numbers on these gizmos. 


> On Aug 27, 2015, at 10:37 PM, Skip Withrow <skip.withrow at gmail.com> wrote:
> Hello time-nuts,
> As an experiment I took 10 FEI FE-5650A rubidium oscillators and measured
> their frequency error (units were chosen randomly).  These were 15MHz units
> taken directly off the telecom cards with no modifications.  These units
> never went to China, and are pulls from working systems.  Each unit was
> allowed to warmup for a couple of hours before the measurement was made.
> Results were:
> Unit #       Date Code      Error
> 301302     0716               -2.87 x 10E-10
> C312570   0839              +4.16 x 10E-11
> 79119       0701               -1.01 x 10E-10
> C312324   0812               -2.54 x 10E-10
> 69008       0450               -2.52 x 10E-10
> 60495       0352               -6.05 x 10E-10
> 78894       0651               -4.30 x 10E-11
> 79287       0701               -2.77 x 10E-10
> 71379       0523               -1.80 x 10E-10
> 78871       0651               -8.58 x 10E-10
> Date code is YYWW.  The units with a 'C' in front are after production was
> moved to China.
> All but 1 of the units ran slow (my reference was a Trimble GPSTM, locked
> to GPS, so should be within a couple parts in 10E-12).  I doubt that FEI's
> reference was off by a couple parts in 10E-10, so my conclusion is that
> they tend to age slower while in service (they are disciplined to GPS in
> the application anyway).
> These oscillators can be stepped by 6.8 x 10E-13 via digital control.  When
> modified by us at RDR we set them +/-2x10E-11 (for a 00 00 00 00 control
> word).  It would be interesting to know how many hours are on each of the
> test units, but I know of no way to obtain that information (unless it is
> part of the secret information that be read out of the unit).
> Regards,
> Skip Withrow
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