[time-nuts] Yb clock - stability estimation procedure?
Bob Camp
lists at rtty.us
Wed Aug 28 11:00:24 UTC 2013
Hi
The commonly heard comments about common mode drift very much pre-date the 5071…
Bob
On Aug 27, 2013, at 5:57 PM, Richard Karlquist <richard at karlquist.com> wrote:
> 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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