Thinking outside the box a super reference
Over the past there has been talk about building from scratch high
performance references. I think consensus was that it is out of reach. In the mean
time Corby is reworking an active maser which takes a lot of know how. But
let us look at his work on the super HP5065. It is able to outperform a
passive maser in the below 100 second range! Long term a proper GPSDO should
be possible to step in. We are working on it including pressure and
temperature control. To make full use of it you also need to have the capability
to monitor, record and analyze on a continuous basis preferably with out
tying up expensive equipment. We have the pieces in place and looking forward
of combining all the pieces and compare with Corby’s active Maser. We are
back to the GPSDO after being distracted by Tbolt performance. A third party
is working combining the GPSDO data stream with the data from the unit that
generates frequency, pressure and temperature data along with time to a
USB stick, while also be able to monitor with a PC.
I know it is considered by some heresy but our lack of a Maser and in Juerg
’s case no access to one, we try to overcome it with a GPSDO tailored for
Rb and Cs and control our Cs’s C field .
There was a time that I did have a HP5065A but got rid of it when I got
some Cs’s. My best counter was A HP5345 and even with a Tracor 527 1 second
performance was not an issue. That changed when Corby introduced me to time
nuts and frankly it was the first time I learned about ADEV. But the
HP5065A was gone. Now I have a cell that Corby has plotted and time permitting
may become a project.
Let me get to the real issue. There are not enough HP5065A’s out there and
not affordable for all time nuts. Most are being kept and are not for
sale. But if a combined effort by many time nuts it MAY be possible to recreate
the guts of the HP5065A. The key word is MAY. 200 time nuts be willing to
invest $ 5000 each may get us there. The market does not justify such an
effort but time nuts keep bringing up discussions. All the other ideas kicked
around in the past will cost more. There are some among us that know what
it cost and who can make the key elements like lamps, cells, filters etc.
Just a thought outside the box and hopefully may turn in to a limited
constructive dialog. We will continue on our path, which include FRK/M100, HP5065
and Cs.
We would not be capable to contribute technically on the physics package
but I would be willing to contribute financially and with monitoring
equipment even if I would not be around when finished.
Bert Kehren
On 11/03/2016 04:07 PM, Bert Kehren via time-nuts wrote:
Over the past there has been talk about building from scratch high
performance references. I think consensus was that it is out of reach.
What about instead establishing an open-source hardware project for a
frequency standard fusor? I was researching COTS solutions for this for
my rubidium ensemble and could only find this one product, which
obviously should be exorbitant in cost:
http://vremya-ch.com/english/product/indexe817.html?Razdel=11&Id=54
-Ruslan
Hi
Since you can buy a working Rb that runs to a given level. My assumption is that
the objective is to do something that is significantly better than you can get for $100
or less. I see no point in setting up to build a device that it 10X worse and costs 10X
more money.
Making the physics package of a good Rb takes a lot of custom tooling. It also takes
a bunch of engineering experiments to get the process running on that tooling, You
also need to train the operators on how to do this or that with the setup. If good performance
is the goal, you probably need some sort of quality process backing it all up.
If you look at a modern CPU as “just a handful of sand and some stuff”, it seems
pretty easy to build one in the kitchen after an hour or two of setup. When you dig
into the nasty details the line costs rapidly spiral off into the stratosphere. Atomic
standards are not quite as complex, but there still is more than just a little custom
equipment involved. $1M sounds a bit on the low side of what it might take.
Bob
On Nov 3, 2016, at 4:37 PM, Ruslan Nabioullin rnabioullin@gmail.com wrote:
On 11/03/2016 04:07 PM, Bert Kehren via time-nuts wrote:
Over the past there has been talk about building from scratch high
performance references. I think consensus was that it is out of reach.
What about instead establishing an open-source hardware project for a frequency standard fusor? I was researching COTS solutions for this for my rubidium ensemble and could only find this one product, which obviously should be exorbitant in cost: http://vremya-ch.com/english/product/indexe817.html?Razdel=11&Id=54
-Ruslan
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
On 11/3/2016 1:07 PM, Bert Kehren via time-nuts wrote:
Over the past there has been talk about building from scratch high
performance references. I think consensus was that it is out of reach. In the mean
I was on the design team for the HP 10816 mini rubidium
which leveraged the production capabilities of the
HP 5065 such as glass blowing, etc., although what we
called "glassware" was much smaller in the 10811
than the 5065. IMHO, the glassware
is the critical item. Of the glassware, the lamp is
probably the most finicky. The glassware used some
glass type (forgot the number) that was only slightly
removed from fused quartz. Very difficult to work
with. Also, one of the Rb isotopes is slightly radioactive.
35 years ago, the guy in the next cubicle got away with
storing it under his desk. He also happily smoked
cigarettes all day at his desk. Another ERA.
HP IIRC supplied "RVFR" assemblies to customers who wanted
to roll their own electronics to use in military applications
where the 5065 wasn't suitable. I would consider approaching
current manufacturers of Rb standards to see if they would
make glassware to order.
Another thing to consider is optically pumped Rb. This is
now possible with available lasers. There are some DARPA
projects in this area that I know of. I can put you in
contact with the right person. Optical pumping gets rid of
the lamp hassle and the radioactive isotope for the filter
cell.
The rest of the standard can be built in a garage using various
contract manufacturers available online. If I can give any advice
about this project, feel free to throw me some questions.
Rick Karlquist N6RK
On Thu, 3 Nov 2016 16:07:59 -0400
Bert Kehren via time-nuts time-nuts@febo.com wrote:
Let me get to the real issue. There are not enough HP5065A’s out there and
not affordable for all time nuts. Most are being kept and are not for
sale. But if a combined effort by many time nuts it MAY be possible to recreate
the guts of the HP5065A. The key word is MAY. 200 time nuts be willing to
invest $ 5000 each may get us there. The market does not justify such an
effort but time nuts keep bringing up discussions. All the other ideas kicked
around in the past will cost more. There are some among us that know what
it cost and who can make the key elements like lamps, cells, filters etc.
Just a thought outside the box and hopefully may turn in to a limited
constructive dialog. We will continue on our path, which include FRK/M100, HP5065
and Cs.
We would not be capable to contribute technically on the physics package
but I would be willing to contribute financially and with monitoring
equipment even if I would not be around when finished.
I challenge your cost estimate! :-)
My guestimate on the cost for a Rb vapor cell standard would be somwhere
in the region of 2000€ to 5000€, per unit. If you add some experimentation
it might become something like 10k€ for the first unit. How do I come to
this number? A vapor cell is quite cheap, 300-500€ can buy you an off
the shelf cell. They will not have the best buffer gas filling, but they
will be good enough for at least to get a reasonable stability.
From here on, the analyis splits into two: dual resonance and coherent
population trapping standards.
For the dual resonance standard, a cavity is required. As the vapor cell
has a predetermined form, that cannot be changed (unless one goes for
full custom cells from the beginning), the cavity has to be adapted to the
cell. This means a cavity that is resonant at the 6.9GHz, yet fits the
cell has to be designed. My guess is, that this can be done by someone
with enough experience in microwave resonant cavities/filters and simulated
using tools like OpenEMS for verification. Producing them using aluminium
should be in the order of 200-1000€ plus cost of aluminium which I guess
to be less than 100€. Excitation of the cell can be done using either
the way the super-5065 with its filter, or tuning the laser diode. Both
way work and as far as i can tell are mostly a matter of taste with a
slightly increased complexity in the control loop for the tuned laser diode.
The detection electronics for the signal can be build for probably less
than 300€/board in batches of 10, definitely less than 1000€. Complexity
should be relatively easy to handle, as we have today access to the nice
UHF devices from Hittite, which handle all the 6.9GHz and bring it down
to easy to handle frequencies. Add a uC, some ADC and DAC and you are
basically done. For advanced features a small to medium sized FPGA (~20-50€)
can be added. If you want to be fancy, add an OCXO (like Abracon AOCJY4 or
Axtal AXIOM10HP/AXIM15) to the equation. What is missing is the magnetic
shielding, which is probably cheapest by using multiple layers of soft-iron.
Maybe using a composite of soft-iron and ferrite pads could improve things
at moderate costs. I don't think that mu-metal would be a good choice,
as it will in almost all cases need to be anealed which is not something
you can easily do (needs a furnace that goes to IIRC 800°C and can be
flooded with hydrogen)
For coherent population trapping, the cavity goes away. The excitation
is either done using a single laser that is modulated with 3.5GHz and
tuned like above, or by using two lasers that are locked to eachother
using an opto-electronic PLL (basically direct both beams at an avalance
photodiode, then use an ordinary PLL to control one of the laser).
For enhanced perfromance the two laser variant can use extenernal cavities
to narrow the laser linewidth from 10-100MHz of an "raw" laser diode
to 10-100kHz. Descriptions how to build such ECDL are available on the
net, including mechanical drawings. The price for the single diode
version is the same as the dual resonance approach, minus the cavity.
The double laser diodes add a slight cost for the OPLL (probably <100€).
An external cavity would probably be in the order of 200-500€ each.
All that said, if someone would want to tackle this project, I would
be willing to help with knowhow and electronic design. Unfortunately
due to limited finances I would not be able to invest much money.
Attila Kinali
--
Malek's Law:
Any simple idea will be worded in the most complicated way.
On a somewhat related note....
Several years ago I pondering getting a Cs standard. After considering the performance of my references and my stack of time interval counters I concluded that in practice I could more or less get the level of measurement accuracy I wanted by comparing the "device under test" to a reference and at the same time comparing the reference to several other references. I wouldn't want to use this technique in a professional setting but for my hobby use I believe it met my needs.
In hindsight though I expect I could have bought a fairly nice Cs unit for the money I sunk into the time interval counters and the various references but that wouldn't have been as much fun. The wear out aspects of used Cs standards are also a bit of a concern for me. That being said a few of my time interval counters have also stopped working properly so I seem to have just traded one set of issues for another but I'm considerably more optimistic of being able to repair / re align a couple of my HP5370's than trying to revive a dead Cs standard.
All the best
Mark S
On Nov 3, 2016, at 1:37 PM, Ruslan Nabioullin rnabioullin@gmail.com wrote:
On 11/03/2016 04:07 PM, Bert Kehren via time-nuts wrote:
Over the past there has been talk about building from scratch high
performance references. I think consensus was that it is out of reach.
What about instead establishing an open-source hardware project for a frequency standard fusor? I was researching COTS solutions for this for my rubidium ensemble and could only find this one product, which obviously should be exorbitant in cost: http://vremya-ch.com/english/product/indexe817.html?Razdel=11&Id=54
-Ruslan
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Kickstarter?
On 2016 Nov 03, at 16:07 , Bert Kehren via time-nuts time-nuts@febo.com wrote:
Over the past there has been talk about building from scratch high
performance references. I think consensus was that it is out of reach. In the mean
time Corby is reworking an active maser which takes a lot of know how. But
let us look at his work on the super HP5065. It is able to outperform a
passive maser in the below 100 second range! Long term a proper GPSDO should
be possible to step in. We are working on it including pressure and
temperature control. To make full use of it you also need to have the capability
to monitor, record and analyze on a continuous basis preferably with out
tying up expensive equipment. We have the pieces in place and looking forward
of combining all the pieces and compare with Corby’s active Maser. We are
back to the GPSDO after being distracted by Tbolt performance. A third party
is working combining the GPSDO data stream with the data from the unit that
generates frequency, pressure and temperature data along with time to a
USB stick, while also be able to monitor with a PC.
I know it is considered by some heresy but our lack of a Maser and in Juerg
’s case no access to one, we try to overcome it with a GPSDO tailored for
Rb and Cs and control our Cs’s C field .
There was a time that I did have a HP5065A but got rid of it when I got
some Cs’s. My best counter was A HP5345 and even with a Tracor 527 1 second
performance was not an issue. That changed when Corby introduced me to time
nuts and frankly it was the first time I learned about ADEV. But the
HP5065A was gone. Now I have a cell that Corby has plotted and time permitting
may become a project.
Let me get to the real issue. There are not enough HP5065A’s out there and
not affordable for all time nuts. Most are being kept and are not for
sale. But if a combined effort by many time nuts it MAY be possible to recreate
the guts of the HP5065A. The key word is MAY. 200 time nuts be willing to
invest $ 5000 each may get us there. The market does not justify such an
effort but time nuts keep bringing up discussions. All the other ideas kicked
around in the past will cost more. There are some among us that know what
it cost and who can make the key elements like lamps, cells, filters etc.
Just a thought outside the box and hopefully may turn in to a limited
constructive dialog. We will continue on our path, which include FRK/M100, HP5065
and Cs.
We would not be capable to contribute technically on the physics package
but I would be willing to contribute financially and with monitoring
equipment even if I would not be around when finished.
Bert Kehren
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
On Thu, 3 Nov 2016 16:37:06 -0400
Ruslan Nabioullin rnabioullin@gmail.com wrote:
What about instead establishing an open-source hardware project for a
frequency standard fusor? I was researching COTS solutions for this for
my rubidium ensemble and could only find this one product, which
obviously should be exorbitant in cost:
You don't need a hardware project for this, as long as a paper clock
is enough for you. Just buy a couple of kiwi-sdr (or anything similar),
provide all of them with a common clock source and you get a comparison
of all your atomic clocks with minimum effort and can build from that
a paper clock easily. The paper clock can than be used for the measurement
you do, using one of the atomic clocks (preferably the one with the lowest
phase noise) as reference.
If you really want to have a physical realization, things become quite
interesting and not easy to handle. There are two parts of the problem,
one is to steer an frequency source accurately, and the other is to
generate the steering value in realtime. Neither of those is trivial.
Especially for the latter one, there is still a lot of research going on.
Attila Kinali
--
Malek's Law:
Any simple idea will be worded in the most complicated way.
On 11/3/16 1:54 PM, Bob Camp wrote:
Hi
Since you can buy a working Rb that runs to a given level. My assumption is that
the objective is to do something that is significantly better than you can get for $100
or less. I see no point in setting up to build a device that it 10X worse and costs 10X
more money.
Making the physics package of a good Rb takes a lot of custom tooling. It also takes
a bunch of engineering experiments to get the process running on that tooling, You
also need to train the operators on how to do this or that with the setup. If good performance
is the goal, you probably need some sort of quality process backing it all up.
If you look at a modern CPU as “just a handful of sand and some stuff”, it seems
pretty easy to build one in the kitchen after an hour or two of setup. When you dig
into the nasty details the line costs rapidly spiral off into the stratosphere. Atomic
standards are not quite as complex, but there still is more than just a little custom
equipment involved. $1M sounds a bit on the low side of what it might take.
Two books everyone contemplating this should have:
Procedures in Experimental Physics, John Strong
Roll your own, in the 30s and 40s.
Building Scientific Apparatus, Moore, Davis, Coplan, and Greer
Vacuum systems, Ion optics, Temperature control, etc. etc.
https://www.amazon.com/Procedures-Experimental-Physics-John-Strong/dp/0917914562
https://www.amazon.com/Building-Scientific-Apparatus-John-Moore/dp/0521878586
I figure everyone on this list is already sufficiently knowledgeable
about oscillators, amplifiers, etc.
On Thu, 3 Nov 2016 16:54:24 -0400
Bob Camp kb8tq@n1k.org wrote:
If you look at a modern CPU as “just a handful of sand and some stuff”, it seems
pretty easy to build one in the kitchen after an hour or two of setup. When you dig
into the nasty details the line costs rapidly spiral off into the stratosphere. Atomic
standards are not quite as complex, but there still is more than just a little custom
equipment involved. $1M sounds a bit on the low side of what it might take.
Not necessarily. There is a large corpus of knowledge available on
how to build vapor cells standards and what is a good idea and what
isn't. Most of it is documented in papers of the PTTI, EFTF and IFCS.
The former two are freely available (for PTTI until 2010, but that
should be good enough). Getting access to those papers behind a
paywall, you only need to know someone with access to a university.
(not for PTTI post 2010 though, ION has quite anal access rules)
Additionally, the people in the time and frequeny community are very
open to discussion and exchange of knowledge. You can almost always
just walk up to someone and ask questions with a high chance of getting
not only answers but help in how to proceede.
Tapping into this knowhow would avoid the need to try out the whole
solution space and concentrate on the few parts that are unkown or
not well enough understood and optimize those. And by doing so safe
a lot of money.
Attila Kinali
--
Malek's Law:
Any simple idea will be worded in the most complicated way.