[time-nuts] Cold Rubidium over hyped?

[Michael Wouters]

I think you are missing the key selling point of this device, namely
it's long term stability and accuracy of a few parts in 10^15. From my
point of view as a national timekeeper, this is much more useful than
good short term stability. UTC reporting is at 5 day intervals so what
the clock does at 1000 s is not so important. By the way, there is
another comparison with 12 NIST masers in the current brochure:
https://spectradynamics.com/product-sheets/cRb-Clock-2019.pdf
There are evidently two models of maser here ,which politely, they do
not identify.

Cheers
Michael

On Sat, Nov 9, 2019 at 11:00 AM <cdelect at juno.com> wrote:
>
> Well I have been looking at the data in the
>
> https://www.researchgate.net/publication/325499937_A_portable_cold_87_Rb_
> atomic_clock_with_frequency_instability_at_one_day_in_the_10-15_range
>
> link and find that maybe they are overstating their performance!
>
> In the plot of figure 5 my HP 5065A almost perfectly matches the Allan
> deviation
> out to 1000 Sec.! (Although mine does have VERY good performance)
>
> Also if you look at figure 7 all the Maser data shown seems to be from
> poorly
> operating Masers so any judgement of better clock performance versus the
> Masers
> is a bit much!
>
> The figure 5 data looks much better but still is not beating a good
> active Maser.
>
> The EFOS2 a 1982 vintage Maser as well as the MHM 2010 and several other
> modern Masers
> I could find data for show between 2 and 5X10-15th at 1000 Sec.
> The MHM 2010 specs at 5X10-15th at 100Sec and 2.0X10-15th at 1000Sec
> All the Masers shown are worse than that spec!
> Also my old Kvarz passive maser has  2x10-13th at 100 Sec just shy of
> matching the top two Masers at 100Sec, which I don't believe!
>
> Something does not add up in their data!
>
> So I'm not really that impressed and would take an Active or Passive
> Maser anyday.
>
> Just wonder if some  5065A can get so impressive that they don't just
> make a modern large/cool cell classic Rubidium with modern electronics
> technology! Certainly would be cheaper and more long lived also.
>
> Just my thoughts!
>
> Cheers,
>
> Corby
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