[time-nuts] New 4 hints from Agilent?

Rick Karlquist richard at karlquist.com
Tue Dec 14 15:51:25 EST 2004

Three points here:

1)  The math is messed up.  They are showing an aging rate
of 1E-10 for a day, 3E-9 for a month.  Wow, the monthly aging
is 30X the daily aging, and there are 30 days in a month.
So what?  The annual aging is 2E-8, or 200X the daily aging.
So why should leaving the oscillator on all the time make any
big difference.

2)  The 10811 manufacturing process eliminates all sources
of predictable, linear, monotonically decreasing aging.  Thus,
for the 10811, there is no predictable improvement in aging
either due to total accumulated time on the oscillator, or
number of hours of continuous operation since the last power
down.  The only effect is "retrace" which happens during the
first day after being powered down.  In the old days of crystal
oscillators, and with inferior crystals, it was true that the
aging got better with time.

3)  There will always be frequency jumps.  This puts a floor on
oscillator performance regardless of aging.

Rick N6RK

Brooke Clarke said:
> Hi:
> Agilent has AN1499 where they make the case that leaving a counter on all
> the time improves the time base stability by more than an order of
> magnitude, but the numbers shown on page 3 seem to indicate that it gets
> worse.  I expect that the numbers are a typo.
> They also make the case that the counter should be calibrated in place so
> that power is not cycled.
> http://cp.literature.agilent.com/litweb/pdf/5989-1592EN.pdf
> Have Fun,
> Brooke Clarke, N6GCE
> --
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