[time-nuts] Yb clock - stability estimation procedure?

Richard Karlquist richard at karlquist.com
Tue Aug 27 17:57:25 EDT 2013


On 2013-08-27 13:35, Florian Teply wrote:

>> No, HP did not make the long tube Cs standards at NIST (as the NIST
>> guys always love to point out) and they are very different animals
>> than the ones you can buy. So, the international definition of the
>> second has always been safe from manufacturer induced common mode.

I vaguely remember the NIST guys wanting to copy some of the HP
electronics from the 5071A.  So don't be so sure.

Regarding common mode environmental drift:  When the 5071A was
introduced, an extensive set of tests was performed over the
better part of a year to determine common mode environmental
drift.  The measurements were sensitive to parts in 10^15.
No environmental sensitivity whatsoever was measurable.
This was no accident, but rather the result of careful design.
OTOH, the 5061 could change frequency noticeably by just removing
the top cover.

Whatever the merits of the big iron Cs standards, the fact of
the matter is that after the 5071A was introduced and they got
into circulation, as a group, they accounted for upwards of
80% of the weight of the TAI.


Rick Karlquist
N6RK


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