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 <[email protected]> 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 > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
