FWIW here are plots of TAI-weight from the 'w' file for 2021.01. The
5071A's are at most 8%. Masers are >87%.
These sum up to ca 95% - not sure where the missing 5% is..
Going back to much before 2014 might show larger weight for the 5071As - I
can post python code for the figures if someone is eager to try...

AW

[image: TAI_weight_clockype.png][image: TAI_weight_lab.png]

On Sat, Mar 27, 2021 at 4:03 PM Demetrios Matsakis via time-nuts <
time-nuts@lists.febo.com> wrote:

Hi

I would guess that fountains would be in there somewhere ( at least in the
2021 version ).

Bob

Anders,

I am surprised to find that hydrogen masers was so dominant these days.
It only shows that the ALGOS improvement that handled the linear drift
that allowed their inclusion have been very effective and should have
improved the stability.

I am also surprised to find my local NMI SP clocks in as fourth weighted
laboratory. I should rig up so they have another maser to measure.

Cheers,
Magnus

On 2021-03-28 15:03, Anders Wallin wrote:

Bob,

Check the "Ground state" section of the graph.

Cheers,
Magnus

On 2021-03-28 15:15, Bob kb8tq wrote:

The pie charts that Anders created show clocks in the UTC "flywheel".
That excludes most research fountains and optical clocks because they
can't or aren't run continuously.

Of the 427 clocks [1] in that data set there are 247 5071A (58%) and 167
H-masers (39%) and 6 fountains (<1.4%). So the short answer to your
question is that there are only 6 fountains in the chart: 4 Rb fountains
at USNO and 2 Cs fountains at PTB.

When playing with charts, it's important not to confuse the number of
clocks with the weighting of clocks. And even the weighting is
misleading because for practical reasons any clock's weight in UTC is
capped at about 1%. All 4 of USNO's Rb fountains are at this level, for
example. About 60 of the H-masers are also at this level. And none of
the 5071A; not even close.

If you are a 5071A sales person you are likely to emphasize that 60% of
the clocks in UTC are 5071A. You are less likely to mention they
contribute only 8% of the weight these days.

If you are in H-maser sales you can claim 40% of the clocks in UTC are
masers and also they contribute 88% of the weight.

It's a good time to be in Microchip clock sales: they now own both the
hp 5071A and the Sigma Tau H-maser manufacturing plants. Yes, they still
make PIC chips too ;-)

/tvb

[1] https://webtai.bipm.org/database/clock.html

• clock type 35/36 are 5071A
• clock type 40/41 are H-masers
• clock type 92/93 are Cs/Rb fountain

On 3/28/2021 6:15 AM, Bob kb8tq wrote:

The BIPM’s new algorithm, implemented around 2014, weights clock by their predictability, and also estimates the frequency drift of the masers.  That’s why masers have risen to their level of prominence.  But masers do have all kinds of variations at some level, which I easily saw when I worked at the USNO and had decades of data uncorrupted by time transfer noise.  I was going to publish a paper in 2019, but I didn’t because getting approval was impossible.  It will be interesting to see what you guys can come up with using BIPM data to create long time series of frequency variations for cesiums and masers too.  Be careful because the BIPM data may not tell you when a cesium beam tube was changed, or a maser underwent repair.  Or a clock was moved.  So I would treat any data gap as a new clock.

Maybe one year ago Microsemi started advertising lower drift in their masers, and I suspect that is because they found a way to compensate for the initial drift so the user doesn’t see it.  (I have no idea if this is really true.)  Years ago in a paper I published with Mike Garvey and Paul Koppang I found the frequency drift noticeably decreased after three years.  Extending my unsupported theory, that might mean new masers pick up a drift over time.  But components change, and whatever they do can be modeled.

Another thing about the meaning of weights is that clocks used to be characterized through comparison with the EAL timescale, which does not involve primaries.  But the new algorithm characterizes them against a TT-guess which carries the frequency of the primaries.  So that in effect degrades masers, cesiums, and Rb fountains to the status of frequency interpolators between the primary standards.  (This is an observation I have made many times and no one has contradicted me, so I guess it is obvious.)

Hoi Demetrios,

Sorry for the late answer, last week was a bit crazy.

On Sat, 27 Mar 2021 09:58:30 -0400
Demetrios Matsakis via time-nuts time-nuts@lists.febo.com wrote:

Thanks! I hadn't seen this paper yet.

I actually wanted to avoid extracting the data on my own,
as there are a lot of pittfalls in this. And I'm sure I am
not even aware of half of them.

Your paper contains part of the information I was seeking.
And quite a bit that I wasn't but is very intersting. I need
to spend some quality time with it :-)

Thanks a lot and have a nice week!

		Attila Kinali

--
The driving force behind research is the question: "Why?"
There are things we don't understand and things we always
wonder about. And that's why we do research.
-- Kobayashi Makoto