Re: [time-nuts] Re. DIY atomic "resonator" 6GHz synthesizer from ADI

[Bob kb8tq]

Hi

If you make the cells in the basement (or even in most factories) the ability 
to have a wide range
synthesizer will come in handy. The whole “6.834xxx GHz” thing is dependent on 
a number of variables. 
It is not at all uncommon to produce cells that come out 10’s or 100’s of KHz 
off of the “right number”.
Wide range synthesizer = higher yield. 

Bob

> On Apr 11, 2017, at 10:00 PM, Richard (Rick) Karlquist 
>  wrote:
> 
> You always want two frequency sources.  One generates a carrier
> frequency offset many MHz from 6.834 GHz and the other frequency
> source modulates the carrier with a sideband that is at the
> exact ~6.834 GHz frequency that finds the atomic line.  The
> sideband is in turn modulated with audio to find the exact
> center of the line.  This is now the easiest section to
> design.
> 
> This architecture automatically gives you gobs of resolution.
> Of course you always have the C field for infinite resolution.
> The other thing it does is prevent RF leaks from exciting the
> atoms, since the strong LO is safely offset from 6.834.
> 
> Rick N6RK
> 
> On 4/11/2017 2:59 PM, paul swed wrote:
>> When I read about the frequency generation in the Rb or CS there are
>> normally many numbers associated with the actual frequency. Down to at
>> least the 1 Hz level. Many of these PLLs are intended for multi-KHz steps.
>> I speculate you might need 2 PLLs one thats very fine in I hz increments
>> that gets added to something like these PLLs that step in 200 KHz
>> increments.
>> Regards
>> Paul
>> WB8TSL
>> 
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Re: [time-nuts] Re. DIY atomic "resonator" 6GHz synthesizer from ADI

[Richard (Rick) Karlquist]

You always want two frequency sources.  One generates a carrier
frequency offset many MHz from 6.834 GHz and the other frequency
source modulates the carrier with a sideband that is at the
exact ~6.834 GHz frequency that finds the atomic line.  The
sideband is in turn modulated with audio to find the exact
center of the line.  This is now the easiest section to
design.

This architecture automatically gives you gobs of resolution.
Of course you always have the C field for infinite resolution.
The other thing it does is prevent RF leaks from exciting the
atoms, since the strong LO is safely offset from 6.834.

Rick N6RK

On 4/11/2017 2:59 PM, paul swed wrote:

When I read about the frequency generation in the Rb or CS there are
normally many numbers associated with the actual frequency. Down to at
least the 1 Hz level. Many of these PLLs are intended for multi-KHz steps.
I speculate you might need 2 PLLs one thats very fine in I hz increments
that gets added to something like these PLLs that step in 200 KHz
increments.
Regards
Paul
WB8TSL


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Re: [time-nuts] a link to a explanation of Rb vs Cs?

[Bob kb8tq]

HI

> On Apr 11, 2017, at 5:57 PM, jimlux  wrote:
> 
> On 4/11/17 12:59 PM, Bob kb8tq wrote:
>> Hi
>> 
>> Assuming you are doing a “conventional” Rb and Cs there are a number of 
>> differences. There is the sub set of doing a gas cell based on Cs which is
>> a lot more similar to Rb. With the Cs, you are building a very complicated 
>> vacuum tube that plays with a focused beam of ions traveling in space. With 
>> the
>> Rb you have essentially a couple of odd (Rb based) "neon bulbs" that do some 
>> cute interactions optically. Making light bulbs is easier than making
>> microwave vacuum tubes. Temperature and magnetic filed mess with both 
>> systems so they need to be controlled in both cases.
>> 
>> The more subtle issue is that we have an implicit expectation of performance 
>> when we talk about an Rb or a Cs. An ADEV of 1x10^-13 at 1,000 seconds is
>> interesting. An ADEV of 1x10^-9 at 1,000 seconds is not as interesting. 
>> Going from a level of “it works” to the point that it works reasonably well 
>> is a
>> long road with lots of zigs and zags. Teams of people do indeed spend a lot 
>> of time learning where those twists in the road are. In the case of an Rb, a 
>> half
>> dozen people working full time for a decade is probably in the range. For a 
>> Cs both the group size and time frame would be longer. In both cases there is
>> a “right” mix of skills for the team members, it’s not just a body count.
>> 
> 
> Not actually building it. I was looking for something I could point people to 
> that describes (at a high level) what the difference is between the kinds of 
> references.  Just because it says "atomic clock" on it doesn't mean that 
> they're all the same.
> (I can handle explaining why their "atomic" watch isn't really an atomic 
> standard, unless they're doing the tvb arm exercises approach)
> 
> If there's nothing folks are aware of, I'll probably see if I can find some 
> nice schematic pictures of a Cs Beam, a gas cell, and an Hg ion trap, and 
> then a AVAR plot or something.
> 

Unfortunately, a lot of this boils down to “that’s how it is”. This 
implementation of that technology works best. It has something to do with the 
underlying 
physics (trapped optical ions vs gas cells). The bigger par is what the best 
design can extract from the physics. It quickly gets messy once you look under
the hood ….

Bob

> 
> 
> 
>> Bob
>> 
>>> On Apr 11, 2017, at 10:30 AM, jimlux  wrote:
>>> 
>>> I'm looking for a link to point to an explanation (at a basic level) of the 
>>> difference between Rb and Cs references, and what the tradeoffs are.
>>> I googled a bit, but all I got were some explanations of the differences in 
>>> things like vapor pressure, etc.
>>> 
>>> Wikipedia  (Atomic_clock) has some nice words, but no block diagram of the 
>>> innards, which would be nice.
>>> 
>>> And there's plenty of charts showing the relative performance of Rb and Cs, 
>>> but not with any accompanying explanation of why.
>>> 
>>> I'm looking for something a bit more detailed, but not a 20 page tutorial 
>>> on atomic clocks.
>>> 
>>> Maybe someone has seen something on a manufacturer website or something?
>>> ___
>>> time-nuts mailing list -- time-nuts@febo.com
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>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>> and follow the instructions there.
>> 
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Re: [time-nuts] a link to a explanation of Rb vs Cs?

[Bob kb8tq]

HI

> On Apr 11, 2017, at 6:15 PM, Richard (Rick) Karlquist  
> wrote:
> 
> The "magic" of Rb in a gas cell standard is that you
> can make an optical filter cell out of radioactive
> Rb87 isotope that allows you to selectively optically pump
> to the quantum level you need.  It is just "luck"
> that the absorption line falls where you need it.
> And the RF pumping is at a doable 6.8 GHz.
> 
> I think the CSAC uses lasers

Indeed the CSAC (and the NAC) use lasers rather than a multi cell approach. 
They likely are not the first devices to
do so. The CSAC is certainly the first “production” device to run on lasers. 
The claim is made that the CSAC went 
ti a Cs based gas cell partly due to the availability of lasers at the “right” 
frequency (wavelength). 

Bob


> so all of this doesn't
> apply.
> 
> Cesium of course is part of the definition of the second,
> so it's good to use for that reason.
> 
> It is a different discussion as to why Cs was chosen
> to define the second, but the line being at 9.2 GHz might have had something 
> to do with it.  That's a doable frequency in terms
> of technology 60 years ago.
> 
> Rick N6RK
> 
> On 4/11/2017 1:54 PM, jimlux wrote:
>> On 4/11/17 12:34 PM, Attila Kinali wrote:
>>> Hoi Jim,
>>> 
>>> On Tue, 11 Apr 2017 07:30:38 -0700
>>> jimlux  wrote:
>>> 
 I'm looking for a link to point to an explanation (at a basic level) of
 the difference between Rb and Cs references, and what the tradeoffs are.
 I googled a bit, but all I got were some explanations of the differences
 in things like vapor pressure, etc.
>>> 
>>> What exactly are you looking for? A comparison of Rb vapor cell
>>> standards vs Cs vapor cell standards? Or a general comparison
>>> why different kind of standards are built with Rb and Cs?
>>> 
>>> For the former, there is a paper that has some of the details
>>> why Cs was choosen over Rb for the CSAC in one of the papers.
>>> (Which I currently cannot find...)
>>> 
>>> For the latter, there is no easy answer and a lot come from
>>> technicalities (difference in handling) and what people were
>>> able to build. There are some fundamental differences in which
>>> elements get you what kind of stability for different kinds of
>>> atomic clocks, but I have seen very little on that and it's quite
>>> spread over various papers and books.
>> 
>> precisely why I asked..
>> 
>> The wikipedia article isn't bad in terms of covering the gas cell vs
>> beam in words, but I was hoping for something with pictures..
>> 
>> Encyclopedia Brittanica, perhaps.. except that they only talk about
>> caesium beam
>> 
>> 
>> 
>> 
>>> 
>>>Attila Kinali
>>> 
>> 
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>> 
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Re: [time-nuts] Re. DIY atomic "resonator" 6GHz synthesizer from ADI

[paul swed]

When I read about the frequency generation in the Rb or CS there are
normally many numbers associated with the actual frequency. Down to at
least the 1 Hz level. Many of these PLLs are intended for multi-KHz steps.
I speculate you might need 2 PLLs one thats very fine in I hz increments
that gets added to something like these PLLs that step in 200 KHz
increments.
Regards
Paul
WB8TSL

On Tue, Apr 11, 2017 at 2:32 PM, Alex Pummer  wrote:

> the are 6GHc synthesizer chips from ADI available see here
> http://www.analog.com/en/analog-dialogue/articles/design-a-
> direct-6-ghz-local-oscillator.html
>
> 73
>
> KJ6UHN
>
> Alex
>
>
> On 4/11/2017 8:29 AM, Attila Kinali wrote:
>
>> On Tue, 11 Apr 2017 07:31:01 +
>> Andre  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
>>
>>
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Re: [time-nuts] a link to a explanation of Rb vs Cs?

[jimlux]

On 4/11/17 12:59 PM, Bob kb8tq wrote:

Hi

Assuming you are doing a “conventional” Rb and Cs there are a number of 
differences. There is the sub set of doing a gas cell based on Cs which is
a lot more similar to Rb. With the Cs, you are building a very complicated 
vacuum tube that plays with a focused beam of ions traveling in space. With the
Rb you have essentially a couple of odd (Rb based) "neon bulbs" that do some 
cute interactions optically. Making light bulbs is easier than making
microwave vacuum tubes. Temperature and magnetic filed mess with both systems 
so they need to be controlled in both cases.

The more subtle issue is that we have an implicit expectation of performance 
when we talk about an Rb or a Cs. An ADEV of 1x10^-13 at 1,000 seconds is
interesting. An ADEV of 1x10^-9 at 1,000 seconds is not as interesting. Going 
from a level of “it works” to the point that it works reasonably well is a
long road with lots of zigs and zags. Teams of people do indeed spend a lot of 
time learning where those twists in the road are. In the case of an Rb, a half
dozen people working full time for a decade is probably in the range. For a Cs 
both the group size and time frame would be longer. In both cases there is
a “right” mix of skills for the team members, it’s not just a body count.



Not actually building it. I was looking for something I could point 
people to that describes (at a high level) what the difference is 
between the kinds of references.  Just because it says "atomic clock" on 
it doesn't mean that they're all the same.
(I can handle explaining why their "atomic" watch isn't really an atomic 
standard, unless they're doing the tvb arm exercises approach)


If there's nothing folks are aware of, I'll probably see if I can find 
some nice schematic pictures of a Cs Beam, a gas cell, and an Hg ion 
trap, and then a AVAR plot or something.






Bob


On Apr 11, 2017, at 10:30 AM, jimlux  wrote:

I'm looking for a link to point to an explanation (at a basic level) of the 
difference between Rb and Cs references, and what the tradeoffs are.
I googled a bit, but all I got were some explanations of the differences in 
things like vapor pressure, etc.

Wikipedia  (Atomic_clock) has some nice words, but no block diagram of the 
innards, which would be nice.

And there's plenty of charts showing the relative performance of Rb and Cs, but 
not with any accompanying explanation of why.

I'm looking for something a bit more detailed, but not a 20 page tutorial on 
atomic clocks.

Maybe someone has seen something on a manufacturer website or something?
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Re: [time-nuts] a link to a explanation of Rb vs Cs?

[Richard (Rick) Karlquist]

The "magic" of Rb in a gas cell standard is that you
can make an optical filter cell out of radioactive
Rb87 isotope that allows you to selectively optically pump
to the quantum level you need.  It is just "luck"
that the absorption line falls where you need it.
And the RF pumping is at a doable 6.8 GHz.

I think the CSAC uses lasers so all of this doesn't
apply.

Cesium of course is part of the definition of the second,
so it's good to use for that reason.

It is a different discussion as to why Cs was chosen
to define the second, but the line being at 9.2 GHz might have had 
something to do with it.  That's a doable frequency in terms

of technology 60 years ago.

Rick N6RK

On 4/11/2017 1:54 PM, jimlux wrote:

On 4/11/17 12:34 PM, Attila Kinali wrote:

Hoi Jim,

On Tue, 11 Apr 2017 07:30:38 -0700
jimlux  wrote:


I'm looking for a link to point to an explanation (at a basic level) of
the difference between Rb and Cs references, and what the tradeoffs are.
I googled a bit, but all I got were some explanations of the differences
in things like vapor pressure, etc.


What exactly are you looking for? A comparison of Rb vapor cell
standards vs Cs vapor cell standards? Or a general comparison
why different kind of standards are built with Rb and Cs?

For the former, there is a paper that has some of the details
why Cs was choosen over Rb for the CSAC in one of the papers.
(Which I currently cannot find...)

For the latter, there is no easy answer and a lot come from
technicalities (difference in handling) and what people were
able to build. There are some fundamental differences in which
elements get you what kind of stability for different kinds of
atomic clocks, but I have seen very little on that and it's quite
spread over various papers and books.


precisely why I asked..

The wikipedia article isn't bad in terms of covering the gas cell vs
beam in words, but I was hoping for something with pictures..

Encyclopedia Brittanica, perhaps.. except that they only talk about
caesium beam






Attila Kinali



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

[jimlux]

On 4/11/17 9:22 AM, Magnus Danielson and Rick Karlquist wrote:



This is in the category of projects where if you were qualified
to do it, your time is far too valuable to do it for the amount
of money you would save.


This is the type of project you do not to save any money, but to spend
and learn.

Even if done in a much more modern fashion, avoiding several of the
traditional problems, there is plenty of issues to solve and handle.


I would agree, after watching the folks in my area doing the Cold Atom 
Lab (which makes Rb Bose Einstein Condensates in a "benchtop" unit) here 
at JPL. It's similar in many ways to building a Rb reference.. lasers, 
Rb cells, etc.; countless things to do, to figure out, and none of them 
are easy.




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Re: [time-nuts] a link to a explanation of Rb vs Cs?

[jimlux]

On 4/11/17 12:34 PM, Attila Kinali wrote:

Hoi Jim,

On Tue, 11 Apr 2017 07:30:38 -0700
jimlux  wrote:


I'm looking for a link to point to an explanation (at a basic level) of
the difference between Rb and Cs references, and what the tradeoffs are.
I googled a bit, but all I got were some explanations of the differences
in things like vapor pressure, etc.


What exactly are you looking for? A comparison of Rb vapor cell
standards vs Cs vapor cell standards? Or a general comparison
why different kind of standards are built with Rb and Cs?

For the former, there is a paper that has some of the details
why Cs was choosen over Rb for the CSAC in one of the papers.
(Which I currently cannot find...)

For the latter, there is no easy answer and a lot come from
technicalities (difference in handling) and what people were
able to build. There are some fundamental differences in which
elements get you what kind of stability for different kinds of
atomic clocks, but I have seen very little on that and it's quite
spread over various papers and books.


precisely why I asked..

The wikipedia article isn't bad in terms of covering the gas cell vs 
beam in words, but I was hoping for something with pictures..


Encyclopedia Brittanica, perhaps.. except that they only talk about 
caesium beam







Attila Kinali



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Re: [time-nuts] a link to a explanation of Rb vs Cs?

[Attila Kinali]

Hoi Jim,

On Tue, 11 Apr 2017 07:30:38 -0700
jimlux  wrote:

> I'm looking for a link to point to an explanation (at a basic level) of 
> the difference between Rb and Cs references, and what the tradeoffs are.
> I googled a bit, but all I got were some explanations of the differences 
> in things like vapor pressure, etc.

What exactly are you looking for? A comparison of Rb vapor cell
standards vs Cs vapor cell standards? Or a general comparison
why different kind of standards are built with Rb and Cs?

For the former, there is a paper that has some of the details
why Cs was choosen over Rb for the CSAC in one of the papers.
(Which I currently cannot find...)

For the latter, there is no easy answer and a lot come from
technicalities (difference in handling) and what people were
able to build. There are some fundamental differences in which
elements get you what kind of stability for different kinds of
atomic clocks, but I have seen very little on that and it's quite
spread over various papers and books.

Attila Kinali

-- 
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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Re: [time-nuts] a link to a explanation of Rb vs Cs?

[Bob kb8tq]

Hi

Assuming you are doing a “conventional” Rb and Cs there are a number of 
differences. There is the sub set of doing a gas cell based on Cs which is 
a lot more similar to Rb. With the Cs, you are building a very complicated 
vacuum tube that plays with a focused beam of ions traveling in space. With the
Rb you have essentially a couple of odd (Rb based) "neon bulbs" that do some 
cute interactions optically. Making light bulbs is easier than making 
microwave vacuum tubes. Temperature and magnetic filed mess with both systems 
so they need to be controlled in both cases. 

The more subtle issue is that we have an implicit expectation of performance 
when we talk about an Rb or a Cs. An ADEV of 1x10^-13 at 1,000 seconds is 
interesting. An ADEV of 1x10^-9 at 1,000 seconds is not as interesting. Going 
from a level of “it works” to the point that it works reasonably well is a 
long road with lots of zigs and zags. Teams of people do indeed spend a lot of 
time learning where those twists in the road are. In the case of an Rb, a half 
dozen people working full time for a decade is probably in the range. For a Cs 
both the group size and time frame would be longer. In both cases there is 
a “right” mix of skills for the team members, it’s not just a body count. 

Bob

> On Apr 11, 2017, at 10:30 AM, jimlux  wrote:
> 
> I'm looking for a link to point to an explanation (at a basic level) of the 
> difference between Rb and Cs references, and what the tradeoffs are.
> I googled a bit, but all I got were some explanations of the differences in 
> things like vapor pressure, etc.
> 
> Wikipedia  (Atomic_clock) has some nice words, but no block diagram of the 
> innards, which would be nice.
> 
> And there's plenty of charts showing the relative performance of Rb and Cs, 
> but not with any accompanying explanation of why.
> 
> I'm looking for something a bit more detailed, but not a 20 page tutorial on 
> atomic clocks.
> 
> Maybe someone has seen something on a manufacturer website or something?
> ___
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Re: [time-nuts] Re. DIY atomic "resonator" 6GHz synthesizer from ADI

[Alex Pummer]

the are 6GHc synthesizer chips from ADI available see here 
http://www.analog.com/en/analog-dialogue/articles/design-a-direct-6-ghz-local-oscillator.html


73

KJ6UHN

Alex


On 4/11/2017 8:29 AM, Attila Kinali wrote:

On Tue, 11 Apr 2017 07:31:01 +
Andre  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



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Re: [time-nuts] Re. DIY atomic "resonator"-- replacing SDRs

[Alex Pummer]

YES SDRs [step Recovery Diodes] is hard to find today, but there many-- 
PIN -- diodes, which exhibits that effect, even some standard rectifier 
diodes could be used for, despite of that Magnus is right, today are 
better solutions available e.g. PLLs with 10GHz prescalers


73

KJ6UHN

Alex


On 4/11/2017 9:22 AM, Magnus Danielson wrote:



On 04/11/2017 05:54 PM, Richard (Rick) Karlquist wrote:



On 4/11/2017 12:31 AM, Andre wrote:


Has anyone else either built an atomic clock around a bare Rb lamp
module "core" or attempted



Not a DIY project, but I was the RF designer on the HP 10816 rubidium
standard, which never made it to product introduction (a half dozen
working pilot run units were built in 1982).  I would say this task is
probably beyond the scope of a DIY project, at least for most
time-nuts.


Probably right.


The Rb lamp drive circuit (particularly getting the
lamp to light up) is very challenging.


There would be none. It would be replaced by a laser. That has its own 
set of "problems" but different.



The step recovery diode multiplier is very challenging.


Today you would not go the SRD route in synthesis.
Besides, SRDs can be hard to find these days.


The photodetector and loop integrator is non trivial.


I'd expect the loop integrator to be done in digital, which eases up 
on some of the design problems.



The synthesizer is the one thing that is easy in 2017.


Indeed-

> The oven is also no simple thing to get

low tempco.  Unlike a crystal, you have a lot of heat being
generated by the lamp, etc. The lamp needs to be at a different
temperature than the other cells.


Going down the laser-route, the balance of temperature between the 
cells is no longer a relevant problem. Further, the lamp and its heat 
is gone.



You have to keep the tip
off at the lowest temperature to keep the Rb in place and not
"flood" the cell and block the light.  Etc., etc.


You still have this problem, but not as a lamp problem but only for 
the resonance cell part.



This is in the category of projects where if you were qualified
to do it, your time is far too valuable to do it for the amount
of money you would save.


This is the type of project you do not to save any money, but to spend 
and learn.


Even if done in a much more modern fashion, avoiding several of the 
traditional problems, there is plenty of issues to solve and handle.


Cheers,
Magnus
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-
No virus found in this message.
Checked by AVG - www.avg.com
Version: 2016.0.8012 / Virus Database: 4769/14290 - Release Date: 
04/11/17


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

[Lester Veenstra]

But, in the true time nuts tradition, I would expect it is time to trap an ion.

Lester B Veenstra  K1YCM  MØYCM  W8YCM   6Y6Y
les...@veenstras.com
-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob kb8tq
Sent: Tuesday, April 11, 2017 12:50 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Re. DIY atomic "resonator"

Hi

If you are going to do a Rb, probably the best place to start is with a 
salvaged physics package out of one of the telecom Rb’s. That would let you get 
the “easy bits” worked out on your side of the design. It would also let you 
lear how to address  a few of the more complex items sorted as well. Since the 
salvaged physics package performance is likely better than what you would build 
in a basement, the performance of your device would not be impacted in a 
negative way. Indeed it’s “cheating”, but it’s about the only way to move the 
project forward.

I agree with Rick that Rb is by far the easiest one of the atomic devices to 
address. The complexity of the device / design precision goes up quite a bit 
for the other candidates. To the degree that Rb is complicated, it’s quite easy 
compared to the others. One way to view this is to take a look at the minuscule 
size of the resonance response above the noise floor on even a well made 
standard ….

Bob

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

[Bob kb8tq]

Hi

If you are going to do a Rb, probably the best place to start is with a 
salvaged physics
package out of one of the telecom Rb’s. That would let you get the “easy bits” 
worked
out on your side of the design. It would also let you lear how to address  a 
few of the 
more complex items sorted as well. Since the salvaged physics package 
performance 
is likely better than what you would build in a basement, the performance of 
your device
would not be impacted in a negative way. Indeed it’s “cheating”, but it’s about 
the only
way to move the project forward.

I agree with Rick that Rb is by far the easiest one of the atomic devices to 
address. The complexity
of the device / design precision goes up quite a bit for the other candidates. 
To the degree 
that Rb is complicated, it’s quite easy compared to the others. One way to view 
this is to
take a look at the minuscule size of the resonance response above the noise 
floor on even
a well made standard ….

Bob

> On Apr 11, 2017, at 11:54 AM, Richard (Rick) Karlquist 
>  wrote:
> 
> 
> 
> On 4/11/2017 12:31 AM, Andre wrote:
> 
>> Has anyone else either built an atomic clock around a bare Rb lamp module 
>> "core" or attempted
>> 
> 
> Not a DIY project, but I was the RF designer on the HP 10816 rubidium
> standard, which never made it to product introduction (a half dozen
> working pilot run units were built in 1982).  I would say this task is
> probably beyond the scope of a DIY project, at least for most
> time-nuts.  The Rb lamp drive circuit (particularly getting the
> lamp to light up) is very challenging.  The step recovery diode
> multiplier is very challenging.  The photodetector and loop
> integrator is non trivial.  The synthesizer is the one thing that
> is easy in 2017.  The oven is also no simple thing to get
> low tempco.  Unlike a crystal, you have a lot of heat being
> generated by the lamp, etc. The lamp needs to be at a different
> temperature than the other cells.  You have to keep the tip
> off at the lowest temperature to keep the Rb in place and not
> "flood" the cell and block the light.  Etc., etc.
> 
> This is in the category of projects where if you were qualified
> to do it, your time is far too valuable to do it for the amount
> of money you would save.
> 
> Rick N6RK
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Re: [time-nuts] Re. DIY atomic "resonator"

[Magnus Danielson]

On 04/11/2017 05:54 PM, Richard (Rick) Karlquist wrote:



On 4/11/2017 12:31 AM, Andre wrote:


Has anyone else either built an atomic clock around a bare Rb lamp
module "core" or attempted



Not a DIY project, but I was the RF designer on the HP 10816 rubidium
standard, which never made it to product introduction (a half dozen
working pilot run units were built in 1982).  I would say this task is
probably beyond the scope of a DIY project, at least for most
time-nuts.


Probably right.


The Rb lamp drive circuit (particularly getting the
lamp to light up) is very challenging.


There would be none. It would be replaced by a laser. That has its own 
set of "problems" but different.



The step recovery diode multiplier is very challenging.


Today you would not go the SRD route in synthesis.
Besides, SRDs can be hard to find these days.


The photodetector and loop integrator is non trivial.


I'd expect the loop integrator to be done in digital, which eases up on 
some of the design problems.



The synthesizer is the one thing that is easy in 2017.


Indeed-

> The oven is also no simple thing to get

low tempco.  Unlike a crystal, you have a lot of heat being
generated by the lamp, etc. The lamp needs to be at a different
temperature than the other cells.


Going down the laser-route, the balance of temperature between the cells 
is no longer a relevant problem. Further, the lamp and its heat is gone.



You have to keep the tip
off at the lowest temperature to keep the Rb in place and not
"flood" the cell and block the light.  Etc., etc.


You still have this problem, but not as a lamp problem but only for the 
resonance cell part.



This is in the category of projects where if you were qualified
to do it, your time is far too valuable to do it for the amount
of money you would save.


This is the type of project you do not to save any money, but to spend 
and learn.


Even if done in a much more modern fashion, avoiding several of the 
traditional problems, there is plenty of issues to solve and handle.


Cheers,
Magnus
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[time-nuts] a link to a explanation of Rb vs Cs?

[jimlux]

I'm looking for a link to point to an explanation (at a basic level) of 
the difference between Rb and Cs references, and what the tradeoffs are.
I googled a bit, but all I got were some explanations of the differences 
in things like vapor pressure, etc.


Wikipedia  (Atomic_clock) has some nice words, but no block diagram of 
the innards, which would be nice.


And there's plenty of charts showing the relative performance of Rb and 
Cs, but not with any accompanying explanation of why.


I'm looking for something a bit more detailed, but not a 20 page 
tutorial on atomic clocks.


Maybe someone has seen something on a manufacturer website or something?
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Re: [time-nuts] Re. DIY atomic "resonator"

[Attila Kinali]

On Tue, 11 Apr 2017 07:31:01 +
Andre  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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[time-nuts] GPS M code (was: Sinlge ADC multi-band receiver)

[Attila Kinali]

On Mon, 10 Apr 2017 16:49:24 -0700
jimlux  wrote:

> The M-code is described in a fair amount of detail here:
> www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA456656

Not really. All it says that it's a BOC(10,5) signal using some
code that allows direct aquisition. It doesn't even mention what
the rate of the data on the new signal is. From [1] one can see
that the modulation is a BOC_sin (and not a BOC_cos). And that
is all I could find out about the M code so far.

Unfortunately, all the other papers concerning the M code are
behind the ION paywal, to which I do not have access.
But guessing what else I have seen on the M code, I do not think
they contain much technical detail on the spreading code itself
or the data transmitted or the encryption.

Attila Kinali 

[1] "Design and Performance of Code Tracking for the GPS M Code Signal"
by John Betz, 2000
http://www.dtic.mil/get-tr-doc/pdf?AD=ADA460257


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

[Richard (Rick) Karlquist]

On 4/11/2017 12:31 AM, Andre wrote:


Has anyone else either built an atomic clock around a bare Rb lamp module 
"core" or attempted



Not a DIY project, but I was the RF designer on the HP 10816 rubidium
standard, which never made it to product introduction (a half dozen
working pilot run units were built in 1982).  I would say this task is
probably beyond the scope of a DIY project, at least for most
time-nuts.  The Rb lamp drive circuit (particularly getting the
lamp to light up) is very challenging.  The step recovery diode
multiplier is very challenging.  The photodetector and loop
integrator is non trivial.  The synthesizer is the one thing that
is easy in 2017.  The oven is also no simple thing to get
low tempco.  Unlike a crystal, you have a lot of heat being
generated by the lamp, etc. The lamp needs to be at a different
temperature than the other cells.  You have to keep the tip
off at the lowest temperature to keep the Rb in place and not
"flood" the cell and block the light.  Etc., etc.

This is in the category of projects where if you were qualified
to do it, your time is far too valuable to do it for the amount
of money you would save.

Rick N6RK
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Re: [time-nuts] TAPR TICC boxed (input protection)

[Charles Steinmetz]

David wrote:


If the 10pA specification is guaranteed by design, then wouldn't they
have to be testing the 1pA "A" parts?


That assumes the parts are produced by exactly the same process, which 
is very often not a safe assumption.  One of them may undergo extra 
process steps, for example, or one or more process steps may be 
modified.  That's not at all uncommon, BTW -- "A" versions are often the 
product of process tweaks, not selected "non-A" devices.


Best regards,

Charles


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Re: [time-nuts] Car Clock drift - the lowly 32kHz tuning fork

[Morris Odell]

> Most wristwatches do not have any temperature compensation. If worn, the 
> wristwatch is pretty close at the 25°C (the human body is a quite good and 
> temperature stable oven). The difference only starts to > show when the watch 
> isn't worn for long periods of time.

That explains my experience with the first microcontroller based clock I built 
years ago. I used a commercial module with a micro and some accessories 
including a watch crystal for timing. It's on a window ledge facing west in 
Australia where the temp varies during the year by 40°C. It was always a bit 
fast and I spent a lot of time checking my code to make sure I was dividing it 
by the right amount. I eventually tamed it by programming a short pause at 3:00 
am. I'm sure the temp of the watch crystal is very rarely 25°C!!

Morris

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

[paul swed]

Andre
Now I know your location. So your questions make more sense to me.
With respect to home brewing atomic standards. There have been numerous
threads on time-nuts around this.
The fact is technology has obsoleted so many technologies that things like
Rb references can be had far cheaper used then home brewed. Or GPSDOs very
cheap and there is almost always a way to sneak an antenna outside. Just
have to work at it. (Been there, done that)
H masers are even more complex and again search time-nuts for details.There
have been really good threads on rebuilding used H Masers. Wow complicated!

So all of my comments are useful but the real question is what do you want
to accomplish? A good reference for your SDR. Build an atomic standard for
fun. Nothing wrong with any of these. But useful to understand your goal.
Regards
Paul
WB8TSL


On Tue, Apr 11, 2017 at 3:31 AM, Andre  wrote:

> Hi all.
>
> As a first step, I wanted to build a specific hydrogen line (1.420 GHz)
> preamp.
>
> Seems that some fluorescent tube starters do emit a very brief burst at
> around 1.4 GHz
>
> during a specific portion of the initial switch-on surge when cold and
> actually observed this here.
>
>
> Also relevant, this same preamp can be used for GPS and if you're living
> in an RF proof flat
>
> with only one good radio station its hard to get any signal.
>
>
> Has anyone else either built an atomic clock around a bare Rb lamp module
> "core" or attempted
>
> to make a hydrogen maser?
>
> It would be a fascinating project to integrate SDR as these are (with
> modifications) very accurate
>
> and can be used to fine tune a lot of the oscillators etc with less hassle.
>
>
> Thanks, -Andre in Guernsey
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Re: [time-nuts] TAPR TICC boxed (input protection)

[Bob kb8tq]

Hi

If you go back in the thread, it started out as a “general purpose front end” 
design. One of the 
suggested parameters on that design was a high impedance input capability in 
the 1mega ohm range. 
Noise on a hi-z input is always an issue and input protection just makes it 
worse.  

About the only thing we have not dug into is the question of just how robust 
this or that protection 
approach is. A setup that will withstand being plugged into an European 250V 
wall outlet for 24 hours 
would likely be a bit more parts intensive than something that withstands the 
occasional exposure 
to +12V …. This all may seem a bit “nutty”. It’s worth noting that the HP 5335 
is not at all happy 
if you drive it with a 5V square wave and set the input attenuator to zero db 
(= you probably blow out
the input). 

Input protection does matter and getting it right is not a trivial thing. There 
will always be compromise. 

Bob

> On Apr 11, 2017, at 8:22 AM, Tim Shoppa  wrote:
> 
> I have a really naive question: how can picoamp leakage parts be relevant in 
> low impedance input pulse conditioning to an interval counter?
> 
> Tim N3QE
> 
>> On Apr 11, 2017, at 7:46 AM, Bob kb8tq  wrote:
>> 
>> Hi
>> 
>> 
>>> On Apr 11, 2017, at 7:05 AM, Charles Steinmetz  
>>> wrote:
>>> 
>>> David wrote:
>>> 
 I ended up qualifying 2N3904s based on manufacturer and lot and I
 think we ended up using ones from Motorola.  I wish detailed process
 information like National had was available from every manufacturer.
>>> 
>>> It is, if you ask the process engineers for it.  (From the Big Boys, that 
>>> is.  These days it seems discrete devices are being fabbed by dozens of 
>>> "garage" operations.  I can't speak for them, and wouldn't think of buying 
>>> product from them.)
>> 
>> If you dig into where your simple discrete part was made, you might be 
>> surprised. That’s even true of outfits you would
>> consider to be a “Big Guy” from days gone by. The real answer to selection 
>> today is to buy the automotive part.
>> That’s about the only thing anymore that locks down the sourcing, testing, 
>> and the process. If you buy a “normal” part,
>> it might have been made anywhere by just about any process. Yes, that’s 
>> scary and it raises a lot of questions. It is
>> a change that has happened over the last decade or two without a lot of 
>> publicity. 
>> 
>> Bob
>> 
>> 
>>> 
>>> Best regards,
>>> 
>>> Charles
>>> 
>>> 
>>> 
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>> 
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Re: [time-nuts] TAPR TICC boxed (input protection)

[Charles Steinmetz]

David wrote:


I ended up qualifying 2N3904s based on manufacturer and lot and I
think we ended up using ones from Motorola.  I wish detailed process
information like National had was available from every manufacturer.


It is, if you ask the process engineers for it.  (From the Big Boys, 
that is.  These days it seems discrete devices are being fabbed by 
dozens of "garage" operations.  I can't speak for them, and wouldn't 
think of buying product from them.)


Best regards,

Charles



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Re: [time-nuts] TAPR TICC boxed (input protection)

[Charles Steinmetz]

David wrote:


I ended up qualifying 2N3904s based on manufacturer and lot and I
think we ended up using ones from Motorola.  I wish detailed process
information like National had was available from every manufacturer.


It is, if you ask the process engineers for it.  (From the Big Boys, 
that is.  These days it seems discrete devices are being fabbed by 
dozens of "garage" operations.  I can't speak for them, and wouldn't 
think of buying product from them.)


Best regards,

Charles



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Re: [time-nuts] TAPR TICC boxed (input protection)

[Tim Shoppa]

I have a really naive question: how can picoamp leakage parts be relevant in 
low impedance input pulse conditioning to an interval counter?

Tim N3QE

> On Apr 11, 2017, at 7:46 AM, Bob kb8tq  wrote:
> 
> Hi
> 
> 
>> On Apr 11, 2017, at 7:05 AM, Charles Steinmetz  wrote:
>> 
>> David wrote:
>> 
>>> I ended up qualifying 2N3904s based on manufacturer and lot and I
>>> think we ended up using ones from Motorola.  I wish detailed process
>>> information like National had was available from every manufacturer.
>> 
>> It is, if you ask the process engineers for it.  (From the Big Boys, that 
>> is.  These days it seems discrete devices are being fabbed by dozens of 
>> "garage" operations.  I can't speak for them, and wouldn't think of buying 
>> product from them.)
> 
> If you dig into where your simple discrete part was made, you might be 
> surprised. That’s even true of outfits you would
> consider to be a “Big Guy” from days gone by. The real answer to selection 
> today is to buy the automotive part.
> That’s about the only thing anymore that locks down the sourcing, testing, 
> and the process. If you buy a “normal” part,
> it might have been made anywhere by just about any process. Yes, that’s scary 
> and it raises a lot of questions. It is
> a change that has happened over the last decade or two without a lot of 
> publicity. 
> 
> Bob
> 
> 
>> 
>> Best regards,
>> 
>> Charles
>> 
>> 
>> 
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Re: [time-nuts] TAPR TICC boxed (input protection)

[Bob kb8tq]

Hi

Testing can mean a lot of different things. Did they test every single part 
they shipped for every parameter?
Did they just do a sample of parts and decide the lot was good? Did they test a 
sample of parts for a sub-set
of the specs and decide they were good? Did they test them after packaging or 
at the wafer level? Did they test
a completely different (but much easier to test) part at the wafer level and 
decide the whole wafer was good?  Did
they test one wafer out of the batch and decide the rest of the day’s 
production was good?

The further down that list you go, the cheaper the part gets. I rarely go 
looking for the most expensive part when
I’m doing a sort on the distributor site. I do toss out a few outfits I don’t 
trust, but that’s about it. I doubt I’m the only
one who shops this way. That drives the whole process to ever lower cost 
approaches. 

If you *really* need a specific parameter, test it yourself. Depending on a 
supplier to 100% test this or that is *not*
a good idea. Unless you have an agreement with them to do the testing and get 
the data from the tests, there is 
no certainty that your idea of “tested” and their idea are the same thing. 

Semiconductors are by no means unique in this regard. Your wrist watch, wall 
clock, or Cesium standard has 
the same dynamics driving it’s production. They all are impacted. That’s not 
always a bad thing. We get stuff
for less money. Other approaches to QA now drive the quality of the product 
where 100% testing once ruled. 

Bob



> On Apr 11, 2017, at 7:44 AM, Charles Steinmetz  wrote:
> 
> David wrote:
> 
>> If the 10pA specification is guaranteed by design, then wouldn't they
>> have to be testing the 1pA "A" parts?
> 
> That assumes the parts are produced by exactly the same process, which is 
> very often not a safe assumption.  One of them may undergo extra process 
> steps, for example, or one or more process steps may be modified.  That's not 
> at all uncommon, BTW -- "A" versions are often the product of process tweaks, 
> not selected "non-A" devices.
> 
> Best regards,
> 
> Charles
> 
> 
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Re: [time-nuts] TAPR TICC boxed (input protection)

[Bob kb8tq]

Hi


> On Apr 11, 2017, at 7:05 AM, Charles Steinmetz  wrote:
> 
> David wrote:
> 
>> I ended up qualifying 2N3904s based on manufacturer and lot and I
>> think we ended up using ones from Motorola.  I wish detailed process
>> information like National had was available from every manufacturer.
> 
> It is, if you ask the process engineers for it.  (From the Big Boys, that is. 
>  These days it seems discrete devices are being fabbed by dozens of "garage" 
> operations.  I can't speak for them, and wouldn't think of buying product 
> from them.)

If you dig into where your simple discrete part was made, you might be 
surprised. That’s even true of outfits you would
consider to be a “Big Guy” from days gone by. The real answer to selection 
today is to buy the automotive part.
That’s about the only thing anymore that locks down the sourcing, testing, and 
the process. If you buy a “normal” part,
it might have been made anywhere by just about any process. Yes, that’s scary 
and it raises a lot of questions. It is
a change that has happened over the last decade or two without a lot of 
publicity. 

Bob


> 
> Best regards,
> 
> Charles
> 
> 
> 
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[time-nuts] Re. DIY atomic "resonator"

[Andre]

Hi all.

As a first step, I wanted to build a specific hydrogen line (1.420 GHz) preamp.

Seems that some fluorescent tube starters do emit a very brief burst at around 
1.4 GHz

during a specific portion of the initial switch-on surge when cold and actually 
observed this here.


Also relevant, this same preamp can be used for GPS and if you're living in an 
RF proof flat

with only one good radio station its hard to get any signal.


Has anyone else either built an atomic clock around a bare Rb lamp module 
"core" or attempted

to make a hydrogen maser?

It would be a fascinating project to integrate SDR as these are (with 
modifications) very accurate

and can be used to fine tune a lot of the oscillators etc with less hassle.


Thanks, -Andre in Guernsey
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[time-nuts] Sinlge ADC multi-band receiver

[Mark Sims]

I read it took less than a week to discover how to unravel the GLONASS military 
signals after they were turned on... 

--
 >  This approach is known as “security through obscurity”, and is deprecated 
 > in the professional of information security. What one invents, another can 
 > discover.
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Re: [time-nuts] TAPR TICC boxed (input protection)

[Bill Hawkins]

There are other ways that light can cause unexpected behavior.

In 1983 I worked on a process control system whose maiden installation
was in a corn processing plant, with lots of big valves and motors being
controlled. The cards that did A/D and D/A conversion of control signals
had UV erasable EPROMs for their microprocessors. There were a lot of
those cards.

One day the plant operators began complaining about the equipment
misbehaving on a large scale. The problem went away when the guy taking
flash pictures of our equipment stopped taking pictures.

We put black tape over the UV lenses.

Ob timenuts: This system later had a pulse frequency input card that I
connected to the power line. Used the operator's trending display for
process variables to watch line frequency change over time. It also had
pulse outputs, and a little work got it to play "Daisy, Daisy" like HAL
9000 in "2001: A Space Odyssey."

Bill Hawkins


-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob
kb8tq
Sent: Sunday, April 09, 2017 1:34 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] TAPR TICC boxed (input protection)

Hi

If anybody gets into this sort of thing in the future - There are black
/ optical blocking die coat materials out there. They are silicone based
and quite stable. 
We used a *lot* of the stuff on watch modules after it was discovered
that the watch died when exposed to a heavy dose of sunlight (right
through the LCD and into the chip . poof!!)

Bob


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