Re: [time-nuts] Why discipline Rubidium oscillator?

[Bob kb8tq]

Hi

Cesiums (that may be on their last legs or maybe not) are pretty common 
in the market. Prices vary, but generally are < $4,000. Bought new they are
in the $70,000 range.  Masers show up much less often. Price wise … that
depends. The cheapest working unit I have heard of was in the $30,000 range.
New, you see some with $150,000 price tags on them. 

Fountain standards for the commercial market have been a “real soon now” 
sort of thing since the 1980’s. I have yet to see anybody selling one (as 
opposed 
to building it in a lab and using it). Yes, there always has been a lot of 
talk. 
There don’t seem to be any shipments….

State of the art Ion standards are something you lock up a building full of 
very 
smart people for a good chunk of their career to come up with. Unless you have 
a budget funded by a rich uncle (or something similar)… don’t go there. 

That sounds very discouraging. Actually it’s not. There is no real need to have
a “best in the world” fountain or ion standard. One that simply works probably 
would be fine by any of us. The same is true of the Maser. Putting in a few 
years
of work to get one up and running might be an ok thing if the price was right. 

=

The bigger point is: what do you do / what can you do with this stuff? 

As you scale up the standard, the bench that goes around it probably scales
as well. The counter that was fine back when you only had a partially working 
OCXO as a standard may not be “good enough” with your maser. Watching
the second tick on your WWVB clock may no longer be “interesting” you may
want to plot signals from far away stars ….

It just keeps getting worse !!!

Bob

> On Nov 20, 2017, at 9:43 PM, Dana Whitlow  wrote:
> 
> As far as I knew, the highest level steps *actually on the market* are
> the Cesium beam clocks and the active hydrogen masers.  Are any
> of the newer technologies available for purchase today?
> 
> Dana
> 
> 
> On Mon, Nov 20, 2017 at 6:13 PM, Hal Murray  wrote:
> 
>>> aren’t too many steps after that
>> 
>> Your imagination is broken.
>> 
>> There are lots more steps.  Most of them are very expensive.
>> 
>> 
>> --
>> These are my opinions.  I hate spam.
>> 
>> 
>> 
>> 
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Re: [time-nuts] Why discipline Rubidium oscillator?

[Jerry Hancock]

Thanks, Bob, I’ll have to start looking now. 

I’ve been looking for other counters, I only have 5371a x 2 and 5335a x 2 and 
some other TeK modules.  I went back and was reading the time-nut counter 
thread from 2008 and will have to keep looking for something I want to afford.

Tonight I was plotting one of the rubidium modules Gilbert gave me against my 
Lucent GPSDO.  I was just measuring frequency and I had some glitches that I 
think are from triggering.  The stdev on some 2 hours runs were .0017 with a 
frequency of 9,999,999.956 average.  I have a new power supply coming tomorrow 
and I’ll be able to move it into a room where I can try to tweak it closer to 
10M.

The Adev plot of the Frequency was sort of weird looking, sort of like a 
flattened “U” with the dip around 10E-15.  I would have thought it should be 
more like a typical downward sloping line. I’ll have to read up and see what 
this indicates.

So much to learn, so little time.

Thanks for all the pointers. Someone should write a book, “Time-nuttery for 
dummies”.  

Jerry


> On Nov 20, 2017, at 9:54 PM, Bob Bownes  wrote:
> 
> 
> Cost of a cesium clock can go from less than you pay for a pair of doxco‘s to 
> many tens of thousands. I think 5071’s are in 
> 
>> On Nov 20, 2017, at 23:50, Jerry Hancock  wrote:
>> 
>> I read up on the GPS L1/L2 and I think there is an L5.
>> 
>> And when you say “on the market” the real question is “can be purchased for 
>> 1/20th the price of new” like all the other re-purposed toys we buy,
>> 
>> Regards,
>> 
>> Jerry
>> 
>> 
>>> On Nov 20, 2017, at 6:43 PM, Dana Whitlow  wrote:
>>> 
>>> 
>> 
>> ___
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Re: [time-nuts] Why discipline Rubidium oscillator?

[Bob Bownes]

Oops cat hit ‘send’

5071’s I’ve seen for as low as about 9k, but usually in the 15-30 range. I 
don’t want to know what they are new. 

5061’s can be had for under $1000. If you are very lucky, under $500. 

And once you have the standard, you need the counters. And other analysis 
tools...pretty soon your spouse will know you’ve gone off the deep end. 

Anyone want an sr530 lock in amplifier that eats fuses and voltage regulators?

Bob

> On Nov 20, 2017, at 23:50, Jerry Hancock  wrote:
> 
> I read up on the GPS L1/L2 and I think there is an L5.
> 
> And when you say “on the market” the real question is “can be purchased for 
> 1/20th the price of new” like all the other re-purposed toys we buy,
> 
> Regards,
> 
> Jerry
> 
> 
>> On Nov 20, 2017, at 6:43 PM, Dana Whitlow  wrote:
>> 
>> 
> 
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Re: [time-nuts] Why discipline Rubidium oscillator?

[Bob Bownes]

Cost of a cesium clock can go from less than you pay for a pair of doxco‘s to 
many tens of thousands. I think 5071’s are in 

> On Nov 20, 2017, at 23:50, Jerry Hancock  wrote:
> 
> I read up on the GPS L1/L2 and I think there is an L5.
> 
> And when you say “on the market” the real question is “can be purchased for 
> 1/20th the price of new” like all the other re-purposed toys we buy,
> 
> Regards,
> 
> Jerry
> 
> 
>> On Nov 20, 2017, at 6:43 PM, Dana Whitlow  wrote:
>> 
>> 
> 
> ___
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Re: [time-nuts] Why discipline Rubidium oscillator?

[Jerry Hancock]

I read up on the GPS L1/L2 and I think there is an L5.

And when you say “on the market” the real question is “can be purchased for 
1/20th the price of new” like all the other re-purposed toys we buy,

Regards,

Jerry


> On Nov 20, 2017, at 6:43 PM, Dana Whitlow  wrote:
> 
> 

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Re: [time-nuts] Why discipline Rubidium oscillator?

[Dana Whitlow]

As far as I knew, the highest level steps *actually on the market* are
the Cesium beam clocks and the active hydrogen masers.  Are any
of the newer technologies available for purchase today?

Dana


On Mon, Nov 20, 2017 at 6:13 PM, Hal Murray  wrote:

> > aren’t too many steps after that
>
> Your imagination is broken.
>
> There are lots more steps.  Most of them are very expensive.
>
>
> --
> These are my opinions.  I hate spam.
>
>
>
>
> ___
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> mailman/listinfo/time-nuts
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>
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Re: [time-nuts] Why discipline Rubidium oscillator?

[Jim Harman]

On Mon, Nov 20, 2017 at 7:14 PM, Jerry Hancock  wrote:

>   Have to do a cost/benefit analysis for the wife...


I hope she is not the type of person who sets her watch 5 minutes ahead so
she will arrive on time!
-- 

--Jim Harman
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Re: [time-nuts] Why discipline Rubidium oscillator?

[Bob kb8tq]

Hi

Most GPSDO’s run the GPS signal only on one “band” (L1). If you want to 
eliminate the errors in the ionosphere
correction process you go to.a double band (L1 and L2) GPS receiver. Since 
there are fewer potential errors in 
the GPS signal, you may have fewer net errors in your GPSDO.

For the Cs - the issue is a stand alone reference. How can you be sure that GPS 
is not lying to you? The only way
to check something like that is with a stand alone reference. That’s somewhere 
between priceless and worthless
depending on which half of the family you happen to ask. 

You can (or course) do a GPS disciplined Cs standard. That’s not easy to do, 
but some are attempting it ….

Lots to do…

Bob

> On Nov 20, 2017, at 7:14 PM, Jerry Hancock  wrote:
> 
> Not to junk up the mailboxes, but I have the multiple GPSDOs.  Don’t know 
> what you mean by L1/L2 GPSDO, is that a quality statement?  
> 
> Also, what would the next step cost me for a Cesium Beam?  Roughly?  And what 
> order of magnitude improvement would that be for the cost?  Have to do a 
> cost/benefit analysis for the wife...
> 
> 
>> On Nov 20, 2017, at 4:09 PM, Bob kb8tq  wrote:
>> 
>> Hi
>> 
>> Ummm ….. e ….. multiple GPSDO’s …. L1/L2 GPSDO(s) …. Cs standard (s) … 
>> Maser(s) …. Ensembles of all of the above ….
>> 
>> There’s *lots* of steps still to take ….
>> 
>> Bob
>> 
>>> On Nov 20, 2017, at 6:31 PM, Jerry Hancock  wrote:
>>> 
>>> One step at a time.
>>> 
>>> 2yrs ago when the time-bug hit, I had a crystal oscillator.  6 months 
>>> later, DOCXO then GPSDO then Rubidium soon to be with GPSDO and there 
>>> aren’t too many steps after that…
>>> 
>>> I also gave my brother the bug the other day…
>>> 
>>> 
>>> 
 On Nov 20, 2017, at 3:05 PM, Bob kb8tq  wrote:
 
 Hi
 
 It’s very much a “somewhere near that number” sort of thing with an Rb. 
 The 
 “thing” you are looking at is quantum mechanical in nature. Unfortunately 
 that
 by its self does not make it perfect. A beam tube (as opposed to a gas 
 cell) 
 isolates things better. 
 
 A 5061 is a beam tube device. A 5065 is gas cell based. It is very 
 important to note that
 accuracy and stability are two different things …. The beam tube is more 
 accurate. 
 The gas cell is more stable (over some range of tau). 
 
 A normal Rb standard has a bit of this and that in the bulb. These other 
 gasses
 help in various ways. They each also add a bit of “pull” to the frequency 
 one way
 or the other. They get you away from your “magic number” but the benefits 
 they
 deliver are worth the trouble. The exact gas mix gets into the “secret 
 sauce” of
 the Rb manufacturer. They each optimize things a bit differently. The 
 walls 
 of the bulb get into the act ….
 
 Beam standards are actually a bit old these days. The more modern approach 
 would be a fountain (toss the ion straight up and let it fall back to 
 you). An even 
 more modern approach would be a trapped ion standard. The amount of money
 involved goes up dramatically with each of those steps. You get rid of 
 this and 
 that subtle effect with each improvement. Accuracy gets better and better. 
 
 Lots of choices !!!
 
 Bob
 
> On Nov 20, 2017, at 3:28 PM, Jerry Hancock  wrote:
> 
> Bob, I was referring to the rubidium standard of 6834682610.904 Hz.  For 
> some reason I thought it was closer to 9Ghz.
> 
> I assume then rubidium standards oscillate (if that is the correct term) 
> somewhere around that number but not exact or is it in the detection 
> where things fall down?
> 
> 
> 
>> On Nov 20, 2017, at 11:40 AM, Bob kb8tq  wrote:
>> 
>> Hi
>> 
>> There is no direct relation for an Rb to 10 MYz. Cs beam tubes are what 
>> have a direct relation. 
>> Even then, the qualifier is “under standard conditions”. They are 
>> sensitive to magnetic field. Rb’s
>> also are sensitive to magnetic field. Both can be tuned by varying the 
>> field. In the case of an Rb
>> that also takes care of a multitude of other issues.
>> 
>> In the case of Rb, there is a distribution of cells coming out of the 
>> manufacturing process. Some
>> are pretty close to the “right” frequency. Others are way off (as in 
>> 100’s of KHz or more). All of them
>> are capable of meeting the required specs. DDS techniques allow those 
>> cells to be used in a 
>> production part. That increases the yield and thus drops the production 
>> cost. 
>> 
>> Since you now magically have a DDS in the Rb, you can do all sorts of 
>> interesting things. If you
>> suddenly need a 9.99900 MHz standard …. here it is … If you need to do 
>> temperature compensation 
>> via a 

Re: [time-nuts] Why discipline Rubidium oscillator?

[Hal Murray]

> aren’t too many steps after that

Your imagination is broken.

There are lots more steps.  Most of them are very expensive.


-- 
These are my opinions.  I hate spam.



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Re: [time-nuts] Why discipline Rubidium oscillator?

[Jerry Hancock]

Not to junk up the mailboxes, but I have the multiple GPSDOs.  Don’t know what 
you mean by L1/L2 GPSDO, is that a quality statement?  

Also, what would the next step cost me for a Cesium Beam?  Roughly?  And what 
order of magnitude improvement would that be for the cost?  Have to do a 
cost/benefit analysis for the wife...


> On Nov 20, 2017, at 4:09 PM, Bob kb8tq  wrote:
> 
> Hi
> 
> Ummm ….. e ….. multiple GPSDO’s …. L1/L2 GPSDO(s) …. Cs standard (s) … 
> Maser(s) …. Ensembles of all of the above ….
> 
> There’s *lots* of steps still to take ….
> 
> Bob
> 
>> On Nov 20, 2017, at 6:31 PM, Jerry Hancock  wrote:
>> 
>> One step at a time.
>> 
>> 2yrs ago when the time-bug hit, I had a crystal oscillator.  6 months later, 
>> DOCXO then GPSDO then Rubidium soon to be with GPSDO and there aren’t too 
>> many steps after that…
>> 
>> I also gave my brother the bug the other day…
>> 
>> 
>> 
>>> On Nov 20, 2017, at 3:05 PM, Bob kb8tq  wrote:
>>> 
>>> Hi
>>> 
>>> It’s very much a “somewhere near that number” sort of thing with an Rb. The 
>>> “thing” you are looking at is quantum mechanical in nature. Unfortunately 
>>> that
>>> by its self does not make it perfect. A beam tube (as opposed to a gas 
>>> cell) 
>>> isolates things better. 
>>> 
>>> A 5061 is a beam tube device. A 5065 is gas cell based. It is very 
>>> important to note that
>>> accuracy and stability are two different things …. The beam tube is more 
>>> accurate. 
>>> The gas cell is more stable (over some range of tau). 
>>> 
>>> A normal Rb standard has a bit of this and that in the bulb. These other 
>>> gasses
>>> help in various ways. They each also add a bit of “pull” to the frequency 
>>> one way
>>> or the other. They get you away from your “magic number” but the benefits 
>>> they
>>> deliver are worth the trouble. The exact gas mix gets into the “secret 
>>> sauce” of
>>> the Rb manufacturer. They each optimize things a bit differently. The walls 
>>> of the bulb get into the act ….
>>> 
>>> Beam standards are actually a bit old these days. The more modern approach 
>>> would be a fountain (toss the ion straight up and let it fall back to you). 
>>> An even 
>>> more modern approach would be a trapped ion standard. The amount of money
>>> involved goes up dramatically with each of those steps. You get rid of this 
>>> and 
>>> that subtle effect with each improvement. Accuracy gets better and better. 
>>> 
>>> Lots of choices !!!
>>> 
>>> Bob
>>> 
 On Nov 20, 2017, at 3:28 PM, Jerry Hancock  wrote:
 
 Bob, I was referring to the rubidium standard of 6834682610.904 Hz.  For 
 some reason I thought it was closer to 9Ghz.
 
 I assume then rubidium standards oscillate (if that is the correct term) 
 somewhere around that number but not exact or is it in the detection where 
 things fall down?
 
 
 
> On Nov 20, 2017, at 11:40 AM, Bob kb8tq  wrote:
> 
> Hi
> 
> There is no direct relation for an Rb to 10 MYz. Cs beam tubes are what 
> have a direct relation. 
> Even then, the qualifier is “under standard conditions”. They are 
> sensitive to magnetic field. Rb’s
> also are sensitive to magnetic field. Both can be tuned by varying the 
> field. In the case of an Rb
> that also takes care of a multitude of other issues.
> 
> In the case of Rb, there is a distribution of cells coming out of the 
> manufacturing process. Some
> are pretty close to the “right” frequency. Others are way off (as in 
> 100’s of KHz or more). All of them
> are capable of meeting the required specs. DDS techniques allow those 
> cells to be used in a 
> production part. That increases the yield and thus drops the production 
> cost. 
> 
> Since you now magically have a DDS in the Rb, you can do all sorts of 
> interesting things. If you
> suddenly need a 9.99900 MHz standard …. here it is … If you need to do 
> temperature compensation 
> via a lookup table … it just takes a bit of testing and some code to make 
> it happen. Indeed, the DDS
> does also give you some issues. Without some sort of cleanup oscillator, 
> you will have spurs and 
> phase noise on the output.
> 
> Lots of fun ….
> 
> Bob
> 
> 
>> On Nov 20, 2017, at 1:34 PM, Jerry Hancock  wrote:
>> 
>> I know this is going to sound dumb as I know many GPSDOs had rubidium 
>> oscillators in them.  I can see why, in that during holdover, they would 
>> tend to be more stable vs others, but given that there is a direct 
>> mathematical relationship between the rubidium frequency and potentially 
>> the 10Mhz desired output frequency, why do they have to be disciplined 
>> or better yet, what advantage does it bring?  Also, I can see how you 
>> discipline a DOCXO with the external 

Re: [time-nuts] Why discipline Rubidium oscillator?

[Bob kb8tq]

Hi

Ummm ….. e ….. multiple GPSDO’s …. L1/L2 GPSDO(s) …. Cs standard (s) … 
Maser(s) …. Ensembles of all of the above ….

There’s *lots* of steps still to take ….

Bob

> On Nov 20, 2017, at 6:31 PM, Jerry Hancock  wrote:
> 
> One step at a time.
> 
> 2yrs ago when the time-bug hit, I had a crystal oscillator.  6 months later, 
> DOCXO then GPSDO then Rubidium soon to be with GPSDO and there aren’t too 
> many steps after that…
> 
> I also gave my brother the bug the other day…
> 
> 
> 
>> On Nov 20, 2017, at 3:05 PM, Bob kb8tq  wrote:
>> 
>> Hi
>> 
>> It’s very much a “somewhere near that number” sort of thing with an Rb. The 
>> “thing” you are looking at is quantum mechanical in nature. Unfortunately 
>> that
>> by its self does not make it perfect. A beam tube (as opposed to a gas cell) 
>> isolates things better. 
>> 
>> A 5061 is a beam tube device. A 5065 is gas cell based. It is very important 
>> to note that
>> accuracy and stability are two different things …. The beam tube is more 
>> accurate. 
>> The gas cell is more stable (over some range of tau). 
>> 
>> A normal Rb standard has a bit of this and that in the bulb. These other 
>> gasses
>> help in various ways. They each also add a bit of “pull” to the frequency 
>> one way
>> or the other. They get you away from your “magic number” but the benefits 
>> they
>> deliver are worth the trouble. The exact gas mix gets into the “secret 
>> sauce” of
>> the Rb manufacturer. They each optimize things a bit differently. The walls 
>> of the bulb get into the act ….
>> 
>> Beam standards are actually a bit old these days. The more modern approach 
>> would be a fountain (toss the ion straight up and let it fall back to you). 
>> An even 
>> more modern approach would be a trapped ion standard. The amount of money
>> involved goes up dramatically with each of those steps. You get rid of this 
>> and 
>> that subtle effect with each improvement. Accuracy gets better and better. 
>> 
>> Lots of choices !!!
>> 
>> Bob
>> 
>>> On Nov 20, 2017, at 3:28 PM, Jerry Hancock  wrote:
>>> 
>>> Bob, I was referring to the rubidium standard of 6834682610.904 Hz.  For 
>>> some reason I thought it was closer to 9Ghz.
>>> 
>>> I assume then rubidium standards oscillate (if that is the correct term) 
>>> somewhere around that number but not exact or is it in the detection where 
>>> things fall down?
>>> 
>>> 
>>> 
 On Nov 20, 2017, at 11:40 AM, Bob kb8tq  wrote:
 
 Hi
 
 There is no direct relation for an Rb to 10 MYz. Cs beam tubes are what 
 have a direct relation. 
 Even then, the qualifier is “under standard conditions”. They are 
 sensitive to magnetic field. Rb’s
 also are sensitive to magnetic field. Both can be tuned by varying the 
 field. In the case of an Rb
 that also takes care of a multitude of other issues.
 
 In the case of Rb, there is a distribution of cells coming out of the 
 manufacturing process. Some
 are pretty close to the “right” frequency. Others are way off (as in 100’s 
 of KHz or more). All of them
 are capable of meeting the required specs. DDS techniques allow those 
 cells to be used in a 
 production part. That increases the yield and thus drops the production 
 cost. 
 
 Since you now magically have a DDS in the Rb, you can do all sorts of 
 interesting things. If you
 suddenly need a 9.99900 MHz standard …. here it is … If you need to do 
 temperature compensation 
 via a lookup table … it just takes a bit of testing and some code to make 
 it happen. Indeed, the DDS
 does also give you some issues. Without some sort of cleanup oscillator, 
 you will have spurs and 
 phase noise on the output.
 
 Lots of fun ….
 
 Bob
 
 
> On Nov 20, 2017, at 1:34 PM, Jerry Hancock  wrote:
> 
> I know this is going to sound dumb as I know many GPSDOs had rubidium 
> oscillators in them.  I can see why, in that during holdover, they would 
> tend to be more stable vs others, but given that there is a direct 
> mathematical relationship between the rubidium frequency and potentially 
> the 10Mhz desired output frequency, why do they have to be disciplined or 
> better yet, what advantage does it bring?  Also, I can see how you 
> discipline a DOCXO with the external voltage, how do you discipline a 
> rubidium?  Pulse stretching?  
> 
> I guess I don’t understand how the technology works, but it seems like an 
> RF signal is swept that would be used to detect a dip at a pretty well 
> defined frequency.  This dip can be used to discipline the oscillator to 
> something like 9Ghz or a factor of what, 900+ times better than 10Mhz.  
> So wouldn’t that be able to get your desired 10Mhz to 10,000,000.001 or 
> pretty much my level of measurement?  Or does 

Re: [time-nuts] Why discipline Rubidium oscillator?

[Jerry Hancock]

One step at a time.

2yrs ago when the time-bug hit, I had a crystal oscillator.  6 months later, 
DOCXO then GPSDO then Rubidium soon to be with GPSDO and there aren’t too many 
steps after that…

I also gave my brother the bug the other day…



> On Nov 20, 2017, at 3:05 PM, Bob kb8tq  wrote:
> 
> Hi
> 
> It’s very much a “somewhere near that number” sort of thing with an Rb. The 
> “thing” you are looking at is quantum mechanical in nature. Unfortunately that
> by its self does not make it perfect. A beam tube (as opposed to a gas cell) 
> isolates things better. 
> 
> A 5061 is a beam tube device. A 5065 is gas cell based. It is very important 
> to note that
> accuracy and stability are two different things …. The beam tube is more 
> accurate. 
> The gas cell is more stable (over some range of tau). 
> 
> A normal Rb standard has a bit of this and that in the bulb. These other 
> gasses
> help in various ways. They each also add a bit of “pull” to the frequency one 
> way
> or the other. They get you away from your “magic number” but the benefits they
> deliver are worth the trouble. The exact gas mix gets into the “secret sauce” 
> of
> the Rb manufacturer. They each optimize things a bit differently. The walls 
> of the bulb get into the act ….
> 
> Beam standards are actually a bit old these days. The more modern approach 
> would be a fountain (toss the ion straight up and let it fall back to you). 
> An even 
> more modern approach would be a trapped ion standard. The amount of money
> involved goes up dramatically with each of those steps. You get rid of this 
> and 
> that subtle effect with each improvement. Accuracy gets better and better. 
> 
> Lots of choices !!!
> 
> Bob
> 
>> On Nov 20, 2017, at 3:28 PM, Jerry Hancock  wrote:
>> 
>> Bob, I was referring to the rubidium standard of 6834682610.904 Hz.  For 
>> some reason I thought it was closer to 9Ghz.
>> 
>> I assume then rubidium standards oscillate (if that is the correct term) 
>> somewhere around that number but not exact or is it in the detection where 
>> things fall down?
>> 
>> 
>> 
>>> On Nov 20, 2017, at 11:40 AM, Bob kb8tq  wrote:
>>> 
>>> Hi
>>> 
>>> There is no direct relation for an Rb to 10 MYz. Cs beam tubes are what 
>>> have a direct relation. 
>>> Even then, the qualifier is “under standard conditions”. They are sensitive 
>>> to magnetic field. Rb’s
>>> also are sensitive to magnetic field. Both can be tuned by varying the 
>>> field. In the case of an Rb
>>> that also takes care of a multitude of other issues.
>>> 
>>> In the case of Rb, there is a distribution of cells coming out of the 
>>> manufacturing process. Some
>>> are pretty close to the “right” frequency. Others are way off (as in 100’s 
>>> of KHz or more). All of them
>>> are capable of meeting the required specs. DDS techniques allow those cells 
>>> to be used in a 
>>> production part. That increases the yield and thus drops the production 
>>> cost. 
>>> 
>>> Since you now magically have a DDS in the Rb, you can do all sorts of 
>>> interesting things. If you
>>> suddenly need a 9.99900 MHz standard …. here it is … If you need to do 
>>> temperature compensation 
>>> via a lookup table … it just takes a bit of testing and some code to make 
>>> it happen. Indeed, the DDS
>>> does also give you some issues. Without some sort of cleanup oscillator, 
>>> you will have spurs and 
>>> phase noise on the output.
>>> 
>>> Lots of fun ….
>>> 
>>> Bob
>>> 
>>> 
 On Nov 20, 2017, at 1:34 PM, Jerry Hancock  wrote:
 
 I know this is going to sound dumb as I know many GPSDOs had rubidium 
 oscillators in them.  I can see why, in that during holdover, they would 
 tend to be more stable vs others, but given that there is a direct 
 mathematical relationship between the rubidium frequency and potentially 
 the 10Mhz desired output frequency, why do they have to be disciplined or 
 better yet, what advantage does it bring?  Also, I can see how you 
 discipline a DOCXO with the external voltage, how do you discipline a 
 rubidium?  Pulse stretching?  
 
 I guess I don’t understand how the technology works, but it seems like an 
 RF signal is swept that would be used to detect a dip at a pretty well 
 defined frequency.  This dip can be used to discipline the oscillator to 
 something like 9Ghz or a factor of what, 900+ times better than 10Mhz.  So 
 wouldn’t that be able to get your desired 10Mhz to 10,000,000.001 or 
 pretty much my level of measurement?  Or does is the dip not quite that 
 precise?  If you can point me to a write-up on this I’ll go away.
 
 Thanks to Gilbert for providing me with at least one rubidium oscillator 
 that is working out of 5 though 2 others seems to stay locked for a few 
 hours during my testing.
 
 Jerry
 ___
 time-nuts 

Re: [time-nuts] Why discipline Rubidium oscillator?

[Bob kb8tq]

Hi

It’s very much a “somewhere near that number” sort of thing with an Rb. The 
“thing” you are looking at is quantum mechanical in nature. Unfortunately that
by its self does not make it perfect. A beam tube (as opposed to a gas cell) 
isolates things better. 

A 5061 is a beam tube device. A 5065 is gas cell based. It is very important to 
note that
accuracy and stability are two different things …. The beam tube is more 
accurate. 
The gas cell is more stable (over some range of tau). 

A normal Rb standard has a bit of this and that in the bulb. These other gasses
help in various ways. They each also add a bit of “pull” to the frequency one 
way
or the other. They get you away from your “magic number” but the benefits they
deliver are worth the trouble. The exact gas mix gets into the “secret sauce” of
the Rb manufacturer. They each optimize things a bit differently. The walls 
of the bulb get into the act ….

Beam standards are actually a bit old these days. The more modern approach 
would be a fountain (toss the ion straight up and let it fall back to you). An 
even 
more modern approach would be a trapped ion standard. The amount of money
involved goes up dramatically with each of those steps. You get rid of this and 
that subtle effect with each improvement. Accuracy gets better and better. 

Lots of choices !!!

Bob

> On Nov 20, 2017, at 3:28 PM, Jerry Hancock  wrote:
> 
> Bob, I was referring to the rubidium standard of 6834682610.904 Hz.  For some 
> reason I thought it was closer to 9Ghz.
> 
> I assume then rubidium standards oscillate (if that is the correct term) 
> somewhere around that number but not exact or is it in the detection where 
> things fall down?
> 
> 
> 
>> On Nov 20, 2017, at 11:40 AM, Bob kb8tq  wrote:
>> 
>> Hi
>> 
>> There is no direct relation for an Rb to 10 MYz. Cs beam tubes are what have 
>> a direct relation. 
>> Even then, the qualifier is “under standard conditions”. They are sensitive 
>> to magnetic field. Rb’s
>> also are sensitive to magnetic field. Both can be tuned by varying the 
>> field. In the case of an Rb
>> that also takes care of a multitude of other issues.
>> 
>> In the case of Rb, there is a distribution of cells coming out of the 
>> manufacturing process. Some
>> are pretty close to the “right” frequency. Others are way off (as in 100’s 
>> of KHz or more). All of them
>> are capable of meeting the required specs. DDS techniques allow those cells 
>> to be used in a 
>> production part. That increases the yield and thus drops the production 
>> cost. 
>> 
>> Since you now magically have a DDS in the Rb, you can do all sorts of 
>> interesting things. If you
>> suddenly need a 9.99900 MHz standard …. here it is … If you need to do 
>> temperature compensation 
>> via a lookup table … it just takes a bit of testing and some code to make it 
>> happen. Indeed, the DDS
>> does also give you some issues. Without some sort of cleanup oscillator, you 
>> will have spurs and 
>> phase noise on the output.
>> 
>> Lots of fun ….
>> 
>> Bob
>> 
>> 
>>> On Nov 20, 2017, at 1:34 PM, Jerry Hancock  wrote:
>>> 
>>> I know this is going to sound dumb as I know many GPSDOs had rubidium 
>>> oscillators in them.  I can see why, in that during holdover, they would 
>>> tend to be more stable vs others, but given that there is a direct 
>>> mathematical relationship between the rubidium frequency and potentially 
>>> the 10Mhz desired output frequency, why do they have to be disciplined or 
>>> better yet, what advantage does it bring?  Also, I can see how you 
>>> discipline a DOCXO with the external voltage, how do you discipline a 
>>> rubidium?  Pulse stretching?  
>>> 
>>> I guess I don’t understand how the technology works, but it seems like an 
>>> RF signal is swept that would be used to detect a dip at a pretty well 
>>> defined frequency.  This dip can be used to discipline the oscillator to 
>>> something like 9Ghz or a factor of what, 900+ times better than 10Mhz.  So 
>>> wouldn’t that be able to get your desired 10Mhz to 10,000,000.001 or pretty 
>>> much my level of measurement?  Or does is the dip not quite that precise?  
>>> If you can point me to a write-up on this I’ll go away.
>>> 
>>> Thanks to Gilbert for providing me with at least one rubidium oscillator 
>>> that is working out of 5 though 2 others seems to stay locked for a few 
>>> hours during my testing.
>>> 
>>> Jerry
>>> ___
>>> 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.
>> 
>> ___
>> 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.
> 
> ___
> time-nuts mailing list 

Re: [time-nuts] Why discipline Rubidium oscillator?

[Dana Whitlow]

And even without problems like external magnetic fields, Rb oscillators do
drift with
age. Over a period of several years they may drift as much as ~1E-9, which
is a *huge*
error for serious time nuts.

In my pre-retirement job I rode herd on an active Hydrogen maser system,
and even
that has a clear drift tendency.  Generally a couple or three times per
year I had to
make a frequency adjustment in the neighborhood of 3E-14.  And still being
privy to
its performance, I was amused to note that its drift tendency was
interrupted by the
hurricane Maria.  On the day of eye passage over the site the frequency
suddenly
decreased by a few parts in 10^14, held about constant for roughly a week,
then
resumed almost its original value and drift rate thereafter.  If anybody in
this group
can explain* that* behavior (that is, held for a week before resuming old
habits), I'd
love to learn about it.

Dana


On Mon, Nov 20, 2017 at 1:40 PM, Bob kb8tq  wrote:

> Hi
>
> There is no direct relation for an Rb to 10 MYz. Cs beam tubes are what
> have a direct relation.
> Even then, the qualifier is “under standard conditions”. They are
> sensitive to magnetic field. Rb’s
> also are sensitive to magnetic field. Both can be tuned by varying the
> field. In the case of an Rb
> that also takes care of a multitude of other issues.
>
> In the case of Rb, there is a distribution of cells coming out of the
> manufacturing process. Some
> are pretty close to the “right” frequency. Others are way off (as in 100’s
> of KHz or more). All of them
> are capable of meeting the required specs. DDS techniques allow those
> cells to be used in a
> production part. That increases the yield and thus drops the production
> cost.
>
> Since you now magically have a DDS in the Rb, you can do all sorts of
> interesting things. If you
> suddenly need a 9.99900 MHz standard …. here it is … If you need to do
> temperature compensation
> via a lookup table … it just takes a bit of testing and some code to make
> it happen. Indeed, the DDS
> does also give you some issues. Without some sort of cleanup oscillator,
> you will have spurs and
> phase noise on the output.
>
> Lots of fun ….
>
> Bob
>
>
> > On Nov 20, 2017, at 1:34 PM, Jerry Hancock  wrote:
> >
> > I know this is going to sound dumb as I know many GPSDOs had rubidium
> oscillators in them.  I can see why, in that during holdover, they would
> tend to be more stable vs others, but given that there is a direct
> mathematical relationship between the rubidium frequency and potentially
> the 10Mhz desired output frequency, why do they have to be disciplined or
> better yet, what advantage does it bring?  Also, I can see how you
> discipline a DOCXO with the external voltage, how do you discipline a
> rubidium?  Pulse stretching?
> >
> > I guess I don’t understand how the technology works, but it seems like
> an RF signal is swept that would be used to detect a dip at a pretty well
> defined frequency.  This dip can be used to discipline the oscillator to
> something like 9Ghz or a factor of what, 900+ times better than 10Mhz.  So
> wouldn’t that be able to get your desired 10Mhz to 10,000,000.001 or pretty
> much my level of measurement?  Or does is the dip not quite that precise?
> If you can point me to a write-up on this I’ll go away.
> >
> > Thanks to Gilbert for providing me with at least one rubidium oscillator
> that is working out of 5 though 2 others seems to stay locked for a few
> hours during my testing.
> >
> > Jerry
> > ___
> > 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.
>
> ___
> 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.
>
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and follow the instructions there.

Re: [time-nuts] Why discipline Rubidium oscillator?

[Gregory Maxwell]

On Mon, Nov 20, 2017 at 8:28 PM, Jerry Hancock  wrote:
> Bob, I was referring to the rubidium standard of 6834682610.904 Hz.  For some 
> reason I thought it was closer to 9Ghz.
>
> I assume then rubidium standards oscillate (if that is the correct term) 
> somewhere around that number but not exact or is it in the detection where 
> things fall down?

I think you are confused by the difference between primary and
secondary standards.

A typical rb gas cell is a secondary standard.  Its exact frequency is
distorted by a number of factors like gas pressure, interaction with
the cell walls, and ambient magnetic fields which cannot be canceled
by the design of the standard.  This is why it is useful to discipline
a telecom rb against GPS, disciplining can be accomplished through
control of a biasing magnetic field.

Something like a cesium beam standard is able to internally cancel
most of these biases "under standard conditions".  A drift free
frequency source can also be constructed using rubidium, such as
rubidium fountains just as a secondary standard could be constructed
using cs-- like cs gas cell standards (such as the sa.45 CSAC).

[Hopefully I haven't mangled things].
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Re: [time-nuts] Why discipline Rubidium oscillator?

[Jerry Hancock]

Bob, I was referring to the rubidium standard of 6834682610.904 Hz.  For some 
reason I thought it was closer to 9Ghz.

I assume then rubidium standards oscillate (if that is the correct term) 
somewhere around that number but not exact or is it in the detection where 
things fall down?



> On Nov 20, 2017, at 11:40 AM, Bob kb8tq  wrote:
> 
> Hi
> 
> There is no direct relation for an Rb to 10 MYz. Cs beam tubes are what have 
> a direct relation. 
> Even then, the qualifier is “under standard conditions”. They are sensitive 
> to magnetic field. Rb’s
> also are sensitive to magnetic field. Both can be tuned by varying the field. 
> In the case of an Rb
> that also takes care of a multitude of other issues.
> 
> In the case of Rb, there is a distribution of cells coming out of the 
> manufacturing process. Some
> are pretty close to the “right” frequency. Others are way off (as in 100’s of 
> KHz or more). All of them
> are capable of meeting the required specs. DDS techniques allow those cells 
> to be used in a 
> production part. That increases the yield and thus drops the production cost. 
> 
> Since you now magically have a DDS in the Rb, you can do all sorts of 
> interesting things. If you
> suddenly need a 9.99900 MHz standard …. here it is … If you need to do 
> temperature compensation 
> via a lookup table … it just takes a bit of testing and some code to make it 
> happen. Indeed, the DDS
> does also give you some issues. Without some sort of cleanup oscillator, you 
> will have spurs and 
> phase noise on the output.
> 
> Lots of fun ….
> 
> Bob
> 
> 
>> On Nov 20, 2017, at 1:34 PM, Jerry Hancock  wrote:
>> 
>> I know this is going to sound dumb as I know many GPSDOs had rubidium 
>> oscillators in them.  I can see why, in that during holdover, they would 
>> tend to be more stable vs others, but given that there is a direct 
>> mathematical relationship between the rubidium frequency and potentially the 
>> 10Mhz desired output frequency, why do they have to be disciplined or better 
>> yet, what advantage does it bring?  Also, I can see how you discipline a 
>> DOCXO with the external voltage, how do you discipline a rubidium?  Pulse 
>> stretching?  
>> 
>> I guess I don’t understand how the technology works, but it seems like an RF 
>> signal is swept that would be used to detect a dip at a pretty well defined 
>> frequency.  This dip can be used to discipline the oscillator to something 
>> like 9Ghz or a factor of what, 900+ times better than 10Mhz.  So wouldn’t 
>> that be able to get your desired 10Mhz to 10,000,000.001 or pretty much my 
>> level of measurement?  Or does is the dip not quite that precise?  If you 
>> can point me to a write-up on this I’ll go away.
>> 
>> Thanks to Gilbert for providing me with at least one rubidium oscillator 
>> that is working out of 5 though 2 others seems to stay locked for a few 
>> hours during my testing.
>> 
>> Jerry
>> ___
>> 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.
> 
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> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.

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Re: [time-nuts] Why discipline Rubidium oscillator?

[Bob kb8tq]

Hi

There is no direct relation for an Rb to 10 MYz. Cs beam tubes are what have a 
direct relation. 
Even then, the qualifier is “under standard conditions”. They are sensitive to 
magnetic field. Rb’s
also are sensitive to magnetic field. Both can be tuned by varying the field. 
In the case of an Rb
that also takes care of a multitude of other issues.

In the case of Rb, there is a distribution of cells coming out of the 
manufacturing process. Some
are pretty close to the “right” frequency. Others are way off (as in 100’s of 
KHz or more). All of them
are capable of meeting the required specs. DDS techniques allow those cells to 
be used in a 
production part. That increases the yield and thus drops the production cost. 

Since you now magically have a DDS in the Rb, you can do all sorts of 
interesting things. If you
suddenly need a 9.99900 MHz standard …. here it is … If you need to do 
temperature compensation 
via a lookup table … it just takes a bit of testing and some code to make it 
happen. Indeed, the DDS
does also give you some issues. Without some sort of cleanup oscillator, you 
will have spurs and 
phase noise on the output.

Lots of fun ….

Bob


> On Nov 20, 2017, at 1:34 PM, Jerry Hancock  wrote:
> 
> I know this is going to sound dumb as I know many GPSDOs had rubidium 
> oscillators in them.  I can see why, in that during holdover, they would tend 
> to be more stable vs others, but given that there is a direct mathematical 
> relationship between the rubidium frequency and potentially the 10Mhz desired 
> output frequency, why do they have to be disciplined or better yet, what 
> advantage does it bring?  Also, I can see how you discipline a DOCXO with the 
> external voltage, how do you discipline a rubidium?  Pulse stretching?  
> 
> I guess I don’t understand how the technology works, but it seems like an RF 
> signal is swept that would be used to detect a dip at a pretty well defined 
> frequency.  This dip can be used to discipline the oscillator to something 
> like 9Ghz or a factor of what, 900+ times better than 10Mhz.  So wouldn’t 
> that be able to get your desired 10Mhz to 10,000,000.001 or pretty much my 
> level of measurement?  Or does is the dip not quite that precise?  If you can 
> point me to a write-up on this I’ll go away.
> 
> Thanks to Gilbert for providing me with at least one rubidium oscillator that 
> is working out of 5 though 2 others seems to stay locked for a few hours 
> during my testing.
> 
> Jerry
> ___
> 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.

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