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

Bob kb8tq kb8tq at n1k.org
Wed Apr 12 19:19:55 EDT 2017


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….


> 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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