[time-nuts] Re. DIY atomic "resonator"

Magnus Danielson magnus at rubidium.dyndns.org
Mon Apr 17 07:49:21 EDT 2017


On that note we have Rick Karlquists article showing how he replaced the 
traditional syntheis chain with an oscillator at the target frequency, 
locked to the lower frequency. Benefit is in the phase-noise.
This was from the fine work on the 5071A.

This approach can be used for rubidiums too, if you care about phase 
noise going into the cavity.

The traditional chain has essentially only one oscillator, but one leg 
in the synthesis chain has a phase-modulation with the modulation 
frequency for the sensing of the atomic reference.


On 04/13/2017 01:19 AM, Bob kb8tq wrote:
> Hi
> There are papers from the mid 90’s talking about improving the GPS Rb’s. Those parts are
> as far as I know the best “production” Rb’s out there. The main comment seems to be that
> phase noise (in it’s various forms) is a major contributor to the stability of the Rb’s….
> Bob
>> On Apr 12, 2017, at 4:55 PM, Bert Kehren via time-nuts <time-nuts at febo.com> wrote:
>> Looking back at the dialog I started on Rb’s  and the repeated returns to
>> that subject allow me to make some comments,  observations and
>> recommendations.. I stayed on purpose away from participating  but learned a lot. It also
>> resulted in some off list dialogs with members  working on the subject off
>> list.
>> Rick’s discussion on why to use two  frequencies was for me an eye opener
>> and gives me clear directions on how to  proceed on frequency generation. The
>> single frequency project is dumped. Corby’s  work on filters again
>> influences our future steps. Using a laser diode and its  challenges again an eye
>> opener and a challenge. We have time nuts that have  working systems.
>> Let’s be honest, we have members with super  knowledge but very few have
>> the appetite to do something with it in the form of  hardware. Here is my
>> proposal that is based on walk before run.
>> FRK and M100 are next to the HP 5065A the  most promising Rb’s in what we
>> like to do. They are easy to work on specially  when you are 75/78 and in my
>> case have a macular  hole.
>> Optical Filter. Corby actually did insert a  filter in a M100 did however
>> not notice an improvement. When we discussed it  come to find out he forgot
>> to change the time constant so the cell did not  control the performance.
>> This was years ago and like many of us has his hands  full with projects. He
>> decided to pass his M100/FRK to an other time nut and  focus on HP and Maser.
>> We all benefit from these  efforts.
>> Back to filter we have dissected a FRK and a  M100 and are convinced that
>> there is a room for a filter, in case of the FRK,  very easy. Corby used a
>> M100, in my opinion more of a challenge. Will not try  it. After discussions
>> with Corby I now understand that the filter does not  filter out a particular
>> wavelength but most the noise that Rb lamps produce as  seen on optical
>> spectrum analyzers. It improves signal noise ratio after all  that is what is
>> all about. Once we have completed our current projects we may do  so.
>> We are also considering to review the  frequency generation using Rick’s
>> postings as guidance. All this needs measuring  capabilities which is what we
>> are working on. I am fortunate to have access to  Corby’s Maser but Juerg
>> does not have that. We are working on a solution.
>> There are many FRK/M100’s out there some  with low output lamps that would
>> be a natural for a Laser Diode replacement. The  mechanical makeup begs for
>> a Laser solution. The two units have a cell in size  only second to HP5065A
>> Going to  laser would also allow to reduce cell temperature again
>> contributing to an  improved signal noise ratio,
>> This is way off our expertise but it would  be nice if some one would take
>> the ball and run with it. I am convinced from off  list conversations that
>> $1000 is a reasonable  goal.
>> There is no guarantee that we will do the  filter depending what our
>> results will be on our present work so again maybe  some one would carry that
>> ball.
>> Both can be a first step for future work.  WALK
>> Bert Kehren
>> In a message dated 4/11/2017 12:02:09 P.M. Eastern Daylight Time,
>> attila at kinali.ch writes:
>> On Tue,  11 Apr 2017 07:31:01 +0000
>> Andre <Andre at Lanoe.net> wrote:
>>> Has anyone else either built an atomic clock around a bare Rb lamp
>> module  "core" or attempted
>>> to make a hydrogen maser?
>> Building  my own Rb vapor cell standard or H-maser is on my list
>> of  Things-I-have-to-do-before-I-die :-)
>> If I had to do one of those now, I  would go for a Rb vapor cell
>> with dual-resonance using an external cavity  laser diode for pumping.
>> The electronics for such a thing are  relatively easy, if you are not
>> afraid of Jiga-Hurts and using these pesky  QFN packages. But it isn't
>> cheap either. There was a discussion started by  Bert[1] where I ventured
>> a rough calculation what I think it wold cost.  Though I think I have
>> understimated the cost of an ECLD (it's more like  1k-5k from what I have
>> read)
>> Attila Kinali
>> [1] search for "thinking outside the  box" in the archives
>> --
>> It is upon moral qualities that a society  is ultimately founded. All
>> the prosperity and technological sophistication  in the world is of no
>> use without that foundation.
>> -- Miss Matheson, The Diamond Age,  Neil  Stephenson
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