Re: [time-nuts] Thermal impact on OCXO

[Lars Walenius]

Thanks Azelio,

I have also thought that the EFC range probably says something. The datasheet 
for the OFC4834 says EFC range +-0.4ppm and that that should be enough for 15 
years. The OFC MC834, I have seems very similar, but without EFC. So my 68ppm 
drift is well within the +-400ppb

Lars

>From: Azelio Boriani
>Sent: den 19 november 2016 02:01
>One starting point to figure out the 10 years aging can be the
datasheet of an OCXO:
MTI240: per year, 3.0E-7, in 10 years must be less than 30.0E-7
MTI220: per year, 1.0E-6, in 10 years < 10.0E-6
Bliley NV26R: 17 years, 5.0E-6
OSA8663: per year, 3.0E-8, in 10 years < 30.0E-8

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Re: [time-nuts] Thermal impact on OCXO

[Lars Walenius]

Hi Bob,

I was afraid that the answer should be like this (smile).

One paper from MTI that probably confirms that aging prediction is difficult:

http://www.mti-milliren.com/MTIPapers/Ext_Aging_Perf_Results.pdf

Lars


From: Bob Camp
Sent: den 19 november 2016 00:23

Hi
> On Nov 18, 2016, at 1:31 PM, Lars Walenius  wrote:
>
> Hi Bob (and all others),
>
> I agree to all your points but am curious to your comment: ”that OCXO is 
> aging a lot for one that has been on that long”.
> As I have only done this test and seen no other test of OCXO´s powered over 
> at least ten years, I have no idea what is reasonable. I also guess I will 
> not do another test of an OCXO powered and measured over ten years again.
>
> Could you give some examples what is reasonable for aging after ten years? 
> Maybe others have data? I have searched internet and it isn´t easy to find 
> long-term data on OCXO’s (at least for me).

The only people I know of that have the gear and the interest to run a number 
of OCXO’s are oscillator manufacturers. They also track parts
in the field by various methods. The data takes real effort to collect and thus 
is “part of our IP”.

Bob

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Re: [time-nuts] Thermal impact on OCXO

[Azelio Boriani]

Are Oscilloquartz's Star-4 commands described somewhere? I can't find
them in the wild...

On Sat, Nov 19, 2016 at 4:34 AM, Mark Sims  wrote:
> Several years ago I replaced the OCXOs in some Tektronix DC5010 counters with 
> surplus Oscilloquartz 8663 DOCXOs.   The darn things have freaky good aging 
> characteristics.   They have been on 24/7 (except for a few brief 
> power-outages) for over 3 years.   After a month I set their freq against a 
> cesium oscillator.   They still show 10 MHz out to 8 or 9 decimal places.
>
> I just got in an Oscilloquartz Star-4 ATDC (automatic temperature / drift 
> compensation) that uses the same DOCXO.   They take 24 hours from a cold 
> start before the ATDC learning kicks in (you can fake it out by power cycling 
> during that interval and it thinks it was a brief outage and reports a 1 hour 
> learning delay).   After an unspecified time (at least several days) the 
> device learns the compensation characteristics and the holdover performance 
> status switches from POOR to IN-SPEC.   I have not yet gotten it past the 
> learning stage...
>
> Oh,  and Lady Heather now speaks Star-4 management interface commands which 
> are also used on a NEC GPSDO that shows up on Ebay... I have one of those on 
> order.
>
> ---
>
>> OSA8663: per year, 3.0E-8, in 10 years < 30.0E-8
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[time-nuts] Thermal impact on OCXO

[Mark Sims]

Several years ago I replaced the OCXOs in some Tektronix DC5010 counters with 
surplus Oscilloquartz 8663 DOCXOs.   The darn things have freaky good aging 
characteristics.   They have been on 24/7 (except for a few brief 
power-outages) for over 3 years.   After a month I set their freq against a 
cesium oscillator.   They still show 10 MHz out to 8 or 9 decimal places.

I just got in an Oscilloquartz Star-4 ATDC (automatic temperature / drift 
compensation) that uses the same DOCXO.   They take 24 hours from a cold start 
before the ATDC learning kicks in (you can fake it out by power cycling during 
that interval and it thinks it was a brief outage and reports a 1 hour learning 
delay).   After an unspecified time (at least several days) the device learns 
the compensation characteristics and the holdover performance status switches 
from POOR to IN-SPEC.   I have not yet gotten it past the learning stage...

Oh,  and Lady Heather now speaks Star-4 management interface commands which are 
also used on a NEC GPSDO that shows up on Ebay... I have one of those on order.

---

> OSA8663: per year, 3.0E-8, in 10 years < 30.0E-8
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Re: [time-nuts] Thermal impact on OCXO

[Azelio Boriani]

One starting point to figure out the 10 years aging can be the
datasheet of an OCXO:
MTI240: per year, 3.0E-7, in 10 years must be less than 30.0E-7
MTI220: per year, 1.0E-6, in 10 years < 10.0E-6
Bliley NV26R: 17 years, 5.0E-6
OSA8663: per year, 3.0E-8, in 10 years < 30.0E-8

On Fri, Nov 18, 2016 at 11:48 PM, Bob Camp  wrote:
> Hi
>
>
>
>> On Nov 18, 2016, at 1:31 PM, Lars Walenius  wrote:
>>
>> Hi Bob (and all others),
>>
>> I agree to all your points but am curious to your comment: ”that OCXO is 
>> aging a lot for one that has been on that long”.
>> As I have only done this test and seen no other test of OCXO´s powered over 
>> at least ten years, I have no idea what is reasonable. I also guess I will 
>> not do another test of an OCXO powered and measured over ten years again.
>>
>> Could you give some examples what is reasonable for aging after ten years? 
>> Maybe others have data? I have searched internet and it isn´t easy to find 
>> long-term data on OCXO’s (at least for me).
>
> The only people I know of that have the gear and the interest to run a number 
> of OCXO’s are oscillator manufacturers. They also track parts
> in the field by various methods. The data takes real effort to collect and 
> thus is “part of our IP”.
>
> Bob
>
>>
>> This oscillator drifted about 60ppm between 1month on to ten years on . Do 
>> others have figures what is reasonable over this time span?
>>
>> For point 1: Is it possible from the aging curve to have some ideas what is 
>> going on??
>>
>> Lars
>>
>> >Från: Bob Camp
>> >Skickat: den 17 november 2016 01:03
>> >Hi
>>
>> >Your data demonstrates a couple of things:
>>
>> >1) There are a number of different things going on with that OCXO and some 
>> >things are a lot less predictable than others.
>> >2) Oscillators do drop rate while on power.
>> >3) Oscillators that age a lot are easier to model (yes, that OCXO is aging 
>> >a lot for one that has been on that long).
>>
>> >Bob
>>
>> >> On Nov 16, 2016, at 2:41 PM, Lars Walenius  
>> >> wrote:
>> >>
>> >> FWIW. Between 2001 and 2011 I run a 5MHz OCXO (in a box). It is a 2x3inch 
>> >> type without EFC marked OFC MC834X4-009W with date code 97. Probably it 
>> >> was from some base station testing and it had been sitting in my shelf 
>> >> since 98. The OCXO were battery backed but at two occasions (2004 and 
>> >> 2007) we had power fails that drained the battery as can be seen in the 
>> >> graph.
>> >>
>> >> Just out of curiosity I yesterday put just the first thirty days (like in 
>> >> the pdf mentioned below) and let Excel calculate the logarithmic 
>> >> function. If I extrapolate that to 10 years it seems that the drift would 
>> >> be 6E-13/day but as can be seen in the aging graph it was more like ten 
>> >> times higher.
>> >>
>> >> Some days ago I started the OCXO again after it had been on the shelf for 
>> >> more than 4 years. Enclosed is a graph for the first 7 days. After six 
>> >> and half days it seems to be a jump of about 1.5E-10 and as I have no 
>> >> indication of anything else I believe it is from the OCXO.
>> >>
>> >> /Lars
>
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Re: [time-nuts] Thermal impact on OCXO

[Bob Camp]

Hi



> On Nov 18, 2016, at 1:31 PM, Lars Walenius  wrote:
> 
> Hi Bob (and all others),
>  
> I agree to all your points but am curious to your comment: ”that OCXO is 
> aging a lot for one that has been on that long”.
> As I have only done this test and seen no other test of OCXO´s powered over 
> at least ten years, I have no idea what is reasonable. I also guess I will 
> not do another test of an OCXO powered and measured over ten years again.
>  
> Could you give some examples what is reasonable for aging after ten years? 
> Maybe others have data? I have searched internet and it isn´t easy to find 
> long-term data on OCXO’s (at least for me).

The only people I know of that have the gear and the interest to run a number 
of OCXO’s are oscillator manufacturers. They also track parts
in the field by various methods. The data takes real effort to collect and thus 
is “part of our IP”.

Bob

>  
> This oscillator drifted about 60ppm between 1month on to ten years on . Do 
> others have figures what is reasonable over this time span?
>  
> For point 1: Is it possible from the aging curve to have some ideas what is 
> going on??
>  
> Lars
>  
> >Från: Bob Camp
> >Skickat: den 17 november 2016 01:03
> >Hi
>  
> >Your data demonstrates a couple of things:
>  
> >1) There are a number of different things going on with that OCXO and some 
> >things are a lot less predictable than others.
> >2) Oscillators do drop rate while on power.
> >3) Oscillators that age a lot are easier to model (yes, that OCXO is aging a 
> >lot for one that has been on that long).
>  
> >Bob
>  
> >> On Nov 16, 2016, at 2:41 PM, Lars Walenius  
> >> wrote:
> >>
> >> FWIW. Between 2001 and 2011 I run a 5MHz OCXO (in a box). It is a 2x3inch 
> >> type without EFC marked OFC MC834X4-009W with date code 97. Probably it 
> >> was from some base station testing and it had been sitting in my shelf 
> >> since 98. The OCXO were battery backed but at two occasions (2004 and 
> >> 2007) we had power fails that drained the battery as can be seen in the 
> >> graph.
> >>
> >> Just out of curiosity I yesterday put just the first thirty days (like in 
> >> the pdf mentioned below) and let Excel calculate the logarithmic function. 
> >> If I extrapolate that to 10 years it seems that the drift would be 
> >> 6E-13/day but as can be seen in the aging graph it was more like ten times 
> >> higher.
> >>
> >> Some days ago I started the OCXO again after it had been on the shelf for 
> >> more than 4 years. Enclosed is a graph for the first 7 days. After six and 
> >> half days it seems to be a jump of about 1.5E-10 and as I have no 
> >> indication of anything else I believe it is from the OCXO.
> >>
> >> /Lars

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Re: [time-nuts] Thermal impact on OCXO

[Lars Walenius]

Hi Bob (and all others),

I agree to all your points but am curious to your comment: ”that OCXO is aging 
a lot for one that has been on that long”.
As I have only done this test and seen no other test of OCXO´s powered over at 
least ten years, I have no idea what is reasonable. I also guess I will not do 
another test of an OCXO powered and measured over ten years again.

Could you give some examples what is reasonable for aging after ten years? 
Maybe others have data? I have searched internet and it isn´t easy to find 
long-term data on OCXO’s (at least for me).

This oscillator drifted about 60ppm between 1month on to ten years on . Do 
others have figures what is reasonable over this time span?

For point 1: Is it possible from the aging curve to have some ideas what is 
going on??

Lars

>Från: Bob Camp
>Skickat: den 17 november 2016 01:03
>Hi

>Your data demonstrates a couple of things:

>1) There are a number of different things going on with that OCXO and some 
>things are a lot less predictable than others.
>2) Oscillators do drop rate while on power.
>3) Oscillators that age a lot are easier to model (yes, that OCXO is aging a 
>lot for one that has been on that long).

>Bob

>> On Nov 16, 2016, at 2:41 PM, Lars Walenius  wrote:
>>
>> FWIW. Between 2001 and 2011 I run a 5MHz OCXO (in a box). It is a 2x3inch 
>> type without EFC marked OFC MC834X4-009W with date code 97. Probably it was 
>> from some base station testing and it had been sitting in my shelf since 98. 
>> The OCXO were battery backed but at two occasions (2004 and 2007) we had 
>> power fails that drained the battery as can be seen in the graph.
>>
>> Just out of curiosity I yesterday put just the first thirty days (like in 
>> the pdf mentioned below) and let Excel calculate the logarithmic function. 
>> If I extrapolate that to 10 years it seems that the drift would be 6E-13/day 
>> but as can be seen in the aging graph it was more like ten times higher.
>>
>> Some days ago I started the OCXO again after it had been on the shelf for 
>> more than 4 years. Enclosed is a graph for the first 7 days. After six and 
>> half days it seems to be a jump of about 1.5E-10 and as I have no indication 
>> of anything else I believe it is from the OCXO.
>>
>> /Lars

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Re: [time-nuts] Thermal impact on OCXO

[Rick Commo]

A similar practice at a small East coast microwave company back in the 60s.  
Except the product was magnetrons that were used in the Talos missile system 
(if memory serves).
 
On Nov 18, 2016, at 01:30, David  wrote:

I have only heard of and never observed the problem of manufacturers
cutting the middle out of a gaussian distribution for tighter
tolerance parts.

Robert Pease of National Semiconductor had an even better story:

I recollect the story of one of the pioneering transistor companies,
back in the '60s.  They had agreed to ship to their customers
transistors with an AQL (Acceptable Quality Level) of 2%, which was
pretty good for those days.  So the tester would test 98 good parts
and put them in the box.  Then, following her instructions, she would
add 2 bad transistors to finish off the box, thus bringing the quality
to the exact level desired.  This went on for some time, until one of
the customers got suspicious, because the two bad transistors were
always in the same corner of the box! Then things were changed ...

On Thu, 17 Nov 2016 10:34:06 -0500, you wrote:

> ...
> 
> I once herd a story from once upon a time that, if you bought a 10%
> resistor, what you ended up with is something like this in the figure
> attached.
> 
> Of course 1% percent resistors (EIA96) are manufactured in high yield
> today, but I would guess some of this still applies to OCXOs, you
> aren't likely to find a gem in the D grade parts. After pre-aging for
> a couple of weeks they are either binned, labeled D, or the ones that
> show promise are left to age some more before being tested to C grade,
> etc, etc.
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Re: [time-nuts] Thermal impact on OCXO

[David]

I have only heard of and never observed the problem of manufacturers
cutting the middle out of a gaussian distribution for tighter
tolerance parts.

Robert Pease of National Semiconductor had an even better story:

I recollect the story of one of the pioneering transistor companies,
back in the '60s.  They had agreed to ship to their customers
transistors with an AQL (Acceptable Quality Level) of 2%, which was
pretty good for those days.  So the tester would test 98 good parts
and put them in the box.  Then, following her instructions, she would
add 2 bad transistors to finish off the box, thus bringing the quality
to the exact level desired.  This went on for some time, until one of
the customers got suspicious, because the two bad transistors were
always in the same corner of the box! Then things were changed ...

On Thu, 17 Nov 2016 10:34:06 -0500, you wrote:

>...
>
>I once herd a story from once upon a time that, if you bought a 10%
>resistor, what you ended up with is something like this in the figure
>attached.
>
>Of course 1% percent resistors (EIA96) are manufactured in high yield
>today, but I would guess some of this still applies to OCXOs, you
>aren't likely to find a gem in the D grade parts. After pre-aging for
>a couple of weeks they are either binned, labeled D, or the ones that
>show promise are left to age some more before being tested to C grade,
>etc, etc.
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Re: [time-nuts] Thermal impact on OCXO

[Bob Camp]

Hi

The advent of welded packages for OCXO’s started to make the “blowtorch” 
approach obsolete back in the 1990’s. The
real problem, even backing in the 1980’s is that there is no market for 
rejects. The only high value part in an OCXO is the
crystal. It is the cause of the performance reject, so any “repair” is more 
expensive than the parts you save.

Bob

> On Nov 17, 2016, at 1:15 PM, Bob Stewart <b...@evoria.net> wrote:
> 
> Hi Bob,
> said:  "Most (> 99%) OCXO’s are made to custom specs for large OEM’s. The sort
> consists of “ship these” and “send these to the crusher”.  Needless to say,
> the emphasis is on a process that throws out as few as possible. "
> 
> We've seen a serious improvement in manufacturing yields at close tolerances 
> for small components.  IOW, they can make gazillions of 1% resistors and caps 
> today, whereas back when I was born they had to do some serious sorting to 
> just get a few.  Did this improvement in manufacturing technique carry over 
> to OCXOs such that the units we see on ebay benefited from improved 
> manufacturing ability, or was sorting still a major part of getting usable 
> yield when they were made?  This, of course, avoids the impact of using a 
> blowtorch to remove them from a board that has been removed from a larger 
> board with a bandsaw.
> 
> thanks,
> Bob - AE6RV
>  -
> AE6RV.com
> 
> GFS GPSDO list:
> groups.yahoo.com/neo/groups/GFS-GPSDOs/info
> 
>  From: Bob Camp <kb...@n1k.org>
> To: Discussion of precise time and frequency measurement <time-nuts@febo.com> 
> Sent: Thursday, November 17, 2016 11:39 AM
> Subject: Re: [time-nuts] Thermal impact on OCXO
> 
> Hi
> 
> 
> Most (> 99%) OCXO’s are made to custom specs for large OEM’s. The sort
> consists of “ship these” and “send these to the crusher”.  Needless to say,
> the emphasis is on a process that throws out as few as possible. 
> 
> Bob
> 
> 
>> 
>> On Wed, Nov 16, 2016 at 8:06 PM, Bob Camp <kb...@n1k.org> wrote:
>>> Hi
>>> 
>>> The issue in fitting over short time periods is that the noise is very much
>>> *not* gaussian. You have effects from things like temperature and warmup
>>> that *do* have trends to them. They will lead you off into all sorts of dark
>>> holes fit wise.
>>> 
>>> Bob
>>> 
>>>> On Nov 16, 2016, at 6:48 PM, Scott Stobbe <scott.j.sto...@gmail.com> wrote:
>>>> 
>>>> A few different plots. I didn't have an intuitive feel for what the B
>>>> coefficient in log term looks like on a plot, so that is the first
>>>> plot. The same aging curve is plotted three times, with the exception
>>>> of the B coefficient being scaled by 1/10, 1, 10 respectively. In hand
>>>> waving terms, it does have an enormous impact during the first 30 days
>>>> (or until Bt >>1), but from then on, it is just an additive offset.
>>>> 
>>>> The next 4 plots are just sample fits with noise added.
>>>> 
>>>> Finally the 6th plot is of just the first 30 days, the data would seem
>>>> to be cleaner than what was shown as a sample in the paper, but the
>>>> stability of the B coefficient in 10 monte-carlo runs is not great.
>>>> But when plotted over a year the results are minimal.
>>>> 
>>>> A1  A2A3
>>>> 0.022914  6.8459  0.00016743
>>>> 0.022932  6.6702  0.00058768
>>>> 0.023206  5.79690.0026103
>>>> 0.023219  4.31270.0093793
>>>> 0.02374  2.83090.016838
>>>> 0.023119  5.02140.0061557
>>>> 0.023054  5.83990.0031886
>>>> 0.022782  9.8582  -0.0074089
>>>> 0.023279  3.73920.012161
>>>> 0.02345  4.10620.0095448
>>>> 
>>>> The only other thing to point out from this, is that the A2 and A3
>>>> coefficients are highly non-orthogonal, as A2 increases, A3 drops to
>>>> make up the difference.
>>>> 
>>>> On Wed, Nov 16, 2016 at 7:38 AM, Bob Camp <kb...@n1k.org> wrote:
>>>>> Hi
>>>>> 
>>>>> The original introduction of 55310 written by a couple of *very* good 
>>>>> guys:
>>>>> 
>>>>> http://tycho.usno.navy.mil/ptti/1987papers/Vol%2019_16.pdf
>>>>> 
>>>>> A fairly current copy of 55310:
>>>>> 
>>>>> http

Re: [time-nuts] Thermal impact on OCXO

[Bob Stewart]

Hi Bob,
said:  "Most (> 99%) OCXO’s are made to custom specs for large OEM’s. The sort
consists of “ship these” and “send these to the crusher”.  Needless to say,
the emphasis is on a process that throws out as few as possible. "

We've seen a serious improvement in manufacturing yields at close tolerances 
for small components.  IOW, they can make gazillions of 1% resistors and caps 
today, whereas back when I was born they had to do some serious sorting to just 
get a few.  Did this improvement in manufacturing technique carry over to OCXOs 
such that the units we see on ebay benefited from improved manufacturing 
ability, or was sorting still a major part of getting usable yield when they 
were made?  This, of course, avoids the impact of using a blowtorch to remove 
them from a board that has been removed from a larger board with a bandsaw.

thanks,
Bob - AE6RV
 -
AE6RV.com

GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info

  From: Bob Camp <kb...@n1k.org>
 To: Discussion of precise time and frequency measurement <time-nuts@febo.com> 
 Sent: Thursday, November 17, 2016 11:39 AM
 Subject: Re: [time-nuts] Thermal impact on OCXO
   
Hi


Most (> 99%) OCXO’s are made to custom specs for large OEM’s. The sort
consists of “ship these” and “send these to the crusher”.  Needless to say,
the emphasis is on a process that throws out as few as possible. 

Bob


> 
> On Wed, Nov 16, 2016 at 8:06 PM, Bob Camp <kb...@n1k.org> wrote:
>> Hi
>> 
>> The issue in fitting over short time periods is that the noise is very much
>> *not* gaussian. You have effects from things like temperature and warmup
>> that *do* have trends to them. They will lead you off into all sorts of dark
>> holes fit wise.
>> 
>> Bob
>> 
>>> On Nov 16, 2016, at 6:48 PM, Scott Stobbe <scott.j.sto...@gmail.com> wrote:
>>> 
>>> A few different plots. I didn't have an intuitive feel for what the B
>>> coefficient in log term looks like on a plot, so that is the first
>>> plot. The same aging curve is plotted three times, with the exception
>>> of the B coefficient being scaled by 1/10, 1, 10 respectively. In hand
>>> waving terms, it does have an enormous impact during the first 30 days
>>> (or until Bt >>1), but from then on, it is just an additive offset.
>>> 
>>> The next 4 plots are just sample fits with noise added.
>>> 
>>> Finally the 6th plot is of just the first 30 days, the data would seem
>>> to be cleaner than what was shown as a sample in the paper, but the
>>> stability of the B coefficient in 10 monte-carlo runs is not great.
>>> But when plotted over a year the results are minimal.
>>> 
>>>        A1              A2            A3
>>>    0.022914      6.8459  0.00016743
>>>    0.022932      6.6702  0.00058768
>>>    0.023206      5.7969    0.0026103
>>>    0.023219      4.3127    0.0093793
>>>    0.02374      2.8309    0.016838
>>>    0.023119      5.0214    0.0061557
>>>    0.023054      5.8399    0.0031886
>>>    0.022782      9.8582  -0.0074089
>>>    0.023279      3.7392    0.012161
>>>    0.02345      4.1062    0.0095448
>>> 
>>> The only other thing to point out from this, is that the A2 and A3
>>> coefficients are highly non-orthogonal, as A2 increases, A3 drops to
>>> make up the difference.
>>> 
>>> On Wed, Nov 16, 2016 at 7:38 AM, Bob Camp <kb...@n1k.org> wrote:
>>>> Hi
>>>> 
>>>> The original introduction of 55310 written by a couple of *very* good guys:
>>>> 
>>>> http://tycho.usno.navy.mil/ptti/1987papers/Vol%2019_16.pdf
>>>> 
>>>> A fairly current copy of 55310:
>>>> 
>>>> https://nepp.nasa.gov/DocUploads/1F3275A6-9140-4C0C-864542DBF16EB1CC/MIL-PRF-55310.pdf
>>>> 
>>>> The “right” equation is on page 47. It’s the “Bt+1” in the log that messes 
>>>> up the fit. If you fit it without
>>>> the +1, the fit is *much* easier to do. The result isn’t quite right.
>>>> 
>>>> Bob
>>>> 
>>>> 
>>>>> On Nov 15, 2016, at 11:58 PM, Scott Stobbe <scott.j.sto...@gmail.com> 
>>>>> wrote:
>>>>> 
>>>>> Hi Bob,
>>>>> 
>>>>> Do you recall if you fitted with true ordinary least squares, or fit with 
>>>>> a
>>>>> recursive/iterative approach in a least squares sense. If the aging curve
>>>>> is linearizable, it isn't jumping 

Re: [time-nuts] Thermal impact on OCXO

[Bob Camp]

Hi

> On Nov 17, 2016, at 10:34 AM, Scott Stobbe  wrote:
> 
> I couldn't agree more, that, once you add a correlated disturbance or
> 1/f^a power law noise, things get even messier. Gaussian is just the
> easiest to toss in.
> 
> I once herd a story from once upon a time that, if you bought a 10%
> resistor, what you ended up with is something like this in the figure
> attached.
> 
> Of course 1% percent resistors (EIA96) are manufactured in high yield
> today, but I would guess some of this still applies to OCXOs, you
> aren't likely to find a gem in the D grade parts. After pre-aging for
> a couple of weeks they are either binned, labeled D, or the ones that
> show promise are left to age some more before being tested to C grade,
> etc, etc.

Most (> 99%) OCXO’s are made to custom specs for large OEM’s. The sort
consists of “ship these” and “send these to the crusher”.  Needless to say,
the emphasis is on a process that throws out as few as possible. 

Bob


> 
> On Wed, Nov 16, 2016 at 8:06 PM, Bob Camp  wrote:
>> Hi
>> 
>> The issue in fitting over short time periods is that the noise is very much
>> *not* gaussian. You have effects from things like temperature and warmup
>> that *do* have trends to them. They will lead you off into all sorts of dark
>> holes fit wise.
>> 
>> Bob
>> 
>>> On Nov 16, 2016, at 6:48 PM, Scott Stobbe  wrote:
>>> 
>>> A few different plots. I didn't have an intuitive feel for what the B
>>> coefficient in log term looks like on a plot, so that is the first
>>> plot. The same aging curve is plotted three times, with the exception
>>> of the B coefficient being scaled by 1/10, 1, 10 respectively. In hand
>>> waving terms, it does have an enormous impact during the first 30 days
>>> (or until Bt >>1), but from then on, it is just an additive offset.
>>> 
>>> The next 4 plots are just sample fits with noise added.
>>> 
>>> Finally the 6th plot is of just the first 30 days, the data would seem
>>> to be cleaner than what was shown as a sample in the paper, but the
>>> stability of the B coefficient in 10 monte-carlo runs is not great.
>>> But when plotted over a year the results are minimal.
>>> 
>>> A1  A2A3
>>>0.022914   6.8459   0.00016743
>>>0.022932   6.6702   0.00058768
>>>0.023206   5.79690.0026103
>>>0.023219   4.31270.0093793
>>> 0.02374   2.8309 0.016838
>>>0.023119   5.02140.0061557
>>>0.023054   5.83990.0031886
>>>0.022782   9.8582   -0.0074089
>>>0.023279   3.7392 0.012161
>>> 0.02345   4.10620.0095448
>>> 
>>> The only other thing to point out from this, is that the A2 and A3
>>> coefficients are highly non-orthogonal, as A2 increases, A3 drops to
>>> make up the difference.
>>> 
>>> On Wed, Nov 16, 2016 at 7:38 AM, Bob Camp  wrote:
 Hi
 
 The original introduction of 55310 written by a couple of *very* good guys:
 
 http://tycho.usno.navy.mil/ptti/1987papers/Vol%2019_16.pdf
 
 A fairly current copy of 55310:
 
 https://nepp.nasa.gov/DocUploads/1F3275A6-9140-4C0C-864542DBF16EB1CC/MIL-PRF-55310.pdf
 
 The “right” equation is on page 47. It’s the “Bt+1” in the log that messes 
 up the fit. If you fit it without
 the +1, the fit is *much* easier to do. The result isn’t quite right.
 
 Bob
 
 
> On Nov 15, 2016, at 11:58 PM, Scott Stobbe  
> wrote:
> 
> Hi Bob,
> 
> Do you recall if you fitted with true ordinary least squares, or fit with 
> a
> recursive/iterative approach in a least squares sense. If the aging curve
> is linearizable, it isn't jumping out at me.
> 
> If the model was hypothetically:
>   F = A ln( B*t )
> 
>   F = A ln(t) + Aln(B)
> 
> which could easily be fit as
>   F  = A' X + B', where X = ln(t)
> 
> It would appear stable32 uses an iterative approach for the non-linear
> problem
> 
> "y(t) = a·ln(bt+1), where slope = y'(t) = ab/(bt+1) Determining the
> nonlinear log fit coefficients requires an iterative procedure. This
> involves setting b to an in initial value, linearizing the equation,
> solving for the other coefficients and the sum of the squared error,
> comparing that with an error criterion, and iterating until a satisfactory
> result is found. The key aspects to this numerical analysis process are
> establishing a satisfactory iteration factor and error criterion to assure
> both convergence and small residuals."
> 
> http://www.stable32.com/Curve%20Fitting%20Features%20in%20Stable32.pdf
> 
> Not sure what others do.
> 
> 
> On Mon, Nov 14, 2016 at 7:15 AM, Bob Camp  wrote:
> 
>> Hi
>> 
>> If you already *have* data over a year (or multiple years) the fit 

Re: [time-nuts] Thermal impact on OCXO

[Attila Kinali]

On Thu, 17 Nov 2016 10:34:06 -0500
Scott Stobbe  wrote:

> I couldn't agree more, that, once you add a correlated disturbance or
> 1/f^a power law noise, things get even messier. Gaussian is just the
> easiest to toss in.

Side note: 1/f^a noise is (usually) Gaussian.
It's not white Gaussian, but it's still Gaussian[1].


Attila Kinali

[1] "Statistics of 1/f Noise", by Brophy, 1967
https://doi.org/10.1103/PhysRev.166.827

-- 
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] Thermal impact on OCXO

[Scott Stobbe]

I couldn't agree more, that, once you add a correlated disturbance or
1/f^a power law noise, things get even messier. Gaussian is just the
easiest to toss in.

I once herd a story from once upon a time that, if you bought a 10%
resistor, what you ended up with is something like this in the figure
attached.

Of course 1% percent resistors (EIA96) are manufactured in high yield
today, but I would guess some of this still applies to OCXOs, you
aren't likely to find a gem in the D grade parts. After pre-aging for
a couple of weeks they are either binned, labeled D, or the ones that
show promise are left to age some more before being tested to C grade,
etc, etc.

On Wed, Nov 16, 2016 at 8:06 PM, Bob Camp  wrote:
> Hi
>
> The issue in fitting over short time periods is that the noise is very much
> *not* gaussian. You have effects from things like temperature and warmup
> that *do* have trends to them. They will lead you off into all sorts of dark
> holes fit wise.
>
> Bob
>
>> On Nov 16, 2016, at 6:48 PM, Scott Stobbe  wrote:
>>
>> A few different plots. I didn't have an intuitive feel for what the B
>> coefficient in log term looks like on a plot, so that is the first
>> plot. The same aging curve is plotted three times, with the exception
>> of the B coefficient being scaled by 1/10, 1, 10 respectively. In hand
>> waving terms, it does have an enormous impact during the first 30 days
>> (or until Bt >>1), but from then on, it is just an additive offset.
>>
>> The next 4 plots are just sample fits with noise added.
>>
>> Finally the 6th plot is of just the first 30 days, the data would seem
>> to be cleaner than what was shown as a sample in the paper, but the
>> stability of the B coefficient in 10 monte-carlo runs is not great.
>> But when plotted over a year the results are minimal.
>>
>>  A1  A2A3
>> 0.022914   6.8459   0.00016743
>> 0.022932   6.6702   0.00058768
>> 0.023206   5.79690.0026103
>> 0.023219   4.31270.0093793
>>  0.02374   2.8309 0.016838
>> 0.023119   5.02140.0061557
>> 0.023054   5.83990.0031886
>> 0.022782   9.8582   -0.0074089
>> 0.023279   3.7392 0.012161
>>  0.02345   4.10620.0095448
>>
>> The only other thing to point out from this, is that the A2 and A3
>> coefficients are highly non-orthogonal, as A2 increases, A3 drops to
>> make up the difference.
>>
>> On Wed, Nov 16, 2016 at 7:38 AM, Bob Camp  wrote:
>>> Hi
>>>
>>> The original introduction of 55310 written by a couple of *very* good guys:
>>>
>>> http://tycho.usno.navy.mil/ptti/1987papers/Vol%2019_16.pdf
>>>
>>> A fairly current copy of 55310:
>>>
>>> https://nepp.nasa.gov/DocUploads/1F3275A6-9140-4C0C-864542DBF16EB1CC/MIL-PRF-55310.pdf
>>>
>>> The “right” equation is on page 47. It’s the “Bt+1” in the log that messes 
>>> up the fit. If you fit it without
>>> the +1, the fit is *much* easier to do. The result isn’t quite right.
>>>
>>> Bob
>>>
>>>
 On Nov 15, 2016, at 11:58 PM, Scott Stobbe  
 wrote:

 Hi Bob,

 Do you recall if you fitted with true ordinary least squares, or fit with a
 recursive/iterative approach in a least squares sense. If the aging curve
 is linearizable, it isn't jumping out at me.

 If the model was hypothetically:
F = A ln( B*t )

F = A ln(t) + Aln(B)

 which could easily be fit as
F  = A' X + B', where X = ln(t)

 It would appear stable32 uses an iterative approach for the non-linear
 problem

 "y(t) = a·ln(bt+1), where slope = y'(t) = ab/(bt+1) Determining the
 nonlinear log fit coefficients requires an iterative procedure. This
 involves setting b to an in initial value, linearizing the equation,
 solving for the other coefficients and the sum of the squared error,
 comparing that with an error criterion, and iterating until a satisfactory
 result is found. The key aspects to this numerical analysis process are
 establishing a satisfactory iteration factor and error criterion to assure
 both convergence and small residuals."

 http://www.stable32.com/Curve%20Fitting%20Features%20in%20Stable32.pdf

 Not sure what others do.


 On Mon, Nov 14, 2016 at 7:15 AM, Bob Camp  wrote:

> Hi
>
> If you already *have* data over a year (or multiple years) the fit is
> fairly easy.
> If you try to do this with data from a few days or less, the whole fit
> process is
> a bit crazy. You also have *multiple* time constants involved on most
> OCXO’s.
> The result is that an earlier fit will have a shorter time constant (and
> will ultimately
> die out). You may not be able to separate the 25 year curve from the 3
> month
> curve with only 3 months of data.
>
> Bob
>

Re: [time-nuts] Thermal impact on OCXO

[Scott Stobbe]

It sounds like you knew what I meant by linearization, but I really
should have wrote linearize in parameters. Of course functions like

F = Ax^2 + Bx + C
F = Asin(omega t) + Bcos(omega t)

fit extremely well with ordinary least squares.

Well there is no free lunch, nlsq has its own challenges, the results
you get depends on the initial conditions you provide, and can also
completely diverge, or converge on a local minima which isn't the best
fit. There don't seem to be a lot of worked examples out there so for
someone one day in the future here is some sample octave/matlab code
for nlsq.

A1 = 0.0233;
A2 = 4.4583;
A3 = 0.0082;

A = [ A1 A2 A3 ];

ts = (1:(30))';

Fage = @(A,x) A(1).*log(A(2).*x + 1) + A(3)

F = Fage(A,ts);

% Add Gaussian measurement noise
F_pn = F + 1E6*0.5e-9*randn(size(ts));

% Fit F_pn to non-linear function Fage
Ainit = [ 1 1 1 ];

options = optimset('Display','on','TolFun',1e-12, 'TolX', 1e-12);
[Aest,resnorm, e, o] = lsqcurvefit(Fage,Ainit,ts,F_pn,[],[],options);


On Thu, Nov 17, 2016 at 8:24 AM, Attila Kinali  wrote:
> On Tue, 15 Nov 2016 23:58:31 -0500
> Scott Stobbe  wrote:
>
>> Do you recall if you fitted with true ordinary least squares, or fit with a
>> recursive/iterative approach in a least squares sense. If the aging curve
>> is linearizable, it isn't jumping out at me.
>
> Least square fits to non-linear functions are almost always iterative.
> There are only very few functions for which closed formulas are known.
> Quite a few people do "linearization", but in general this does not
> work well or leads to sub-optimal solutions (aka not an least squares fit)
> without people realizing it.
>
> An alternative method that works for some functions are state-space
> methods. But I barely know about them, so I cannot really comment on them.
>
>
> 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
> ___
> 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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Re: [time-nuts] Thermal impact on OCXO

[Attila Kinali]

On Tue, 15 Nov 2016 23:58:31 -0500
Scott Stobbe  wrote:

> Do you recall if you fitted with true ordinary least squares, or fit with a
> recursive/iterative approach in a least squares sense. If the aging curve
> is linearizable, it isn't jumping out at me.

Least square fits to non-linear functions are almost always iterative.
There are only very few functions for which closed formulas are known.
Quite a few people do "linearization", but in general this does not
work well or leads to sub-optimal solutions (aka not an least squares fit)
without people realizing it.

An alternative method that works for some functions are state-space
methods. But I barely know about them, so I cannot really comment on them.


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
___
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.

Re: [time-nuts] Thermal impact on OCXO

[Bob Camp]

Hi

The issue in fitting over short time periods is that the noise is very much 
*not* gaussian. You have effects from things like temperature and warmup 
that *do* have trends to them. They will lead you off into all sorts of dark
holes fit wise. 

Bob

> On Nov 16, 2016, at 6:48 PM, Scott Stobbe  wrote:
> 
> A few different plots. I didn't have an intuitive feel for what the B
> coefficient in log term looks like on a plot, so that is the first
> plot. The same aging curve is plotted three times, with the exception
> of the B coefficient being scaled by 1/10, 1, 10 respectively. In hand
> waving terms, it does have an enormous impact during the first 30 days
> (or until Bt >>1), but from then on, it is just an additive offset.
> 
> The next 4 plots are just sample fits with noise added.
> 
> Finally the 6th plot is of just the first 30 days, the data would seem
> to be cleaner than what was shown as a sample in the paper, but the
> stability of the B coefficient in 10 monte-carlo runs is not great.
> But when plotted over a year the results are minimal.
> 
>  A1  A2A3
> 0.022914   6.8459   0.00016743
> 0.022932   6.6702   0.00058768
> 0.023206   5.79690.0026103
> 0.023219   4.31270.0093793
>  0.02374   2.8309 0.016838
> 0.023119   5.02140.0061557
> 0.023054   5.83990.0031886
> 0.022782   9.8582   -0.0074089
> 0.023279   3.7392 0.012161
>  0.02345   4.10620.0095448
> 
> The only other thing to point out from this, is that the A2 and A3
> coefficients are highly non-orthogonal, as A2 increases, A3 drops to
> make up the difference.
> 
> On Wed, Nov 16, 2016 at 7:38 AM, Bob Camp  wrote:
>> Hi
>> 
>> The original introduction of 55310 written by a couple of *very* good guys:
>> 
>> http://tycho.usno.navy.mil/ptti/1987papers/Vol%2019_16.pdf
>> 
>> A fairly current copy of 55310:
>> 
>> https://nepp.nasa.gov/DocUploads/1F3275A6-9140-4C0C-864542DBF16EB1CC/MIL-PRF-55310.pdf
>> 
>> The “right” equation is on page 47. It’s the “Bt+1” in the log that messes 
>> up the fit. If you fit it without
>> the +1, the fit is *much* easier to do. The result isn’t quite right.
>> 
>> Bob
>> 
>> 
>>> On Nov 15, 2016, at 11:58 PM, Scott Stobbe  wrote:
>>> 
>>> Hi Bob,
>>> 
>>> Do you recall if you fitted with true ordinary least squares, or fit with a
>>> recursive/iterative approach in a least squares sense. If the aging curve
>>> is linearizable, it isn't jumping out at me.
>>> 
>>> If the model was hypothetically:
>>>F = A ln( B*t )
>>> 
>>>F = A ln(t) + Aln(B)
>>> 
>>> which could easily be fit as
>>>F  = A' X + B', where X = ln(t)
>>> 
>>> It would appear stable32 uses an iterative approach for the non-linear
>>> problem
>>> 
>>> "y(t) = a·ln(bt+1), where slope = y'(t) = ab/(bt+1) Determining the
>>> nonlinear log fit coefficients requires an iterative procedure. This
>>> involves setting b to an in initial value, linearizing the equation,
>>> solving for the other coefficients and the sum of the squared error,
>>> comparing that with an error criterion, and iterating until a satisfactory
>>> result is found. The key aspects to this numerical analysis process are
>>> establishing a satisfactory iteration factor and error criterion to assure
>>> both convergence and small residuals."
>>> 
>>> http://www.stable32.com/Curve%20Fitting%20Features%20in%20Stable32.pdf
>>> 
>>> Not sure what others do.
>>> 
>>> 
>>> On Mon, Nov 14, 2016 at 7:15 AM, Bob Camp  wrote:
>>> 
 Hi
 
 If you already *have* data over a year (or multiple years) the fit is
 fairly easy.
 If you try to do this with data from a few days or less, the whole fit
 process is
 a bit crazy. You also have *multiple* time constants involved on most
 OCXO’s.
 The result is that an earlier fit will have a shorter time constant (and
 will ultimately
 die out). You may not be able to separate the 25 year curve from the 3
 month
 curve with only 3 months of data.
 
 Bob
 
> On Nov 13, 2016, at 10:59 PM, Scott Stobbe 
 wrote:
> 
> On Mon, Nov 7, 2016 at 10:34 AM, Scott Stobbe 
> wrote:
> 
>> Here is a sample data point taken from http://tycho.usno.navy.mil/ptt
>> i/1987papers/Vol%2019_16.pdf; the first that showed up on a google
 search.
>> 
>>   Year   Aging [PPB]  dF/dt [PPT/Day]
>>  1   180.51   63.884
>>  2   196.6531.93
>>  5  218   12.769
>>  9   231.69   7.0934
>> 10   234.156.384
>> 25255.5   2.5535
>> 
>> If you have a set of coefficients you believe to be representative of
 your
>> OCXO, we can give those a go.
>> 

Re: [time-nuts] Thermal impact on OCXO

[Bob Camp]

Hi

Your data demonstrates a couple of things:

1) There are a number of different things going on with that OCXO and some 
things are a lot less predictable than others.
2) Oscillators do drop rate while on power.
3) Oscillators that age a lot are easier to model (yes, that OCXO is aging a 
lot for one that has been on that long).

Bob

> On Nov 16, 2016, at 2:41 PM, Lars Walenius  wrote:
> 
> FWIW. Between 2001 and 2011 I run a 5MHz OCXO (in a box). It is a 2x3inch 
> type without EFC marked OFC MC834X4-009W with date code 97. Probably it was 
> from some base station testing and it had been sitting in my shelf since 98. 
> The OCXO were battery backed but at two occasions (2004 and 2007) we had 
> power fails that drained the battery as can be seen in the graph.
> 
> Just out of curiosity I yesterday put just the first thirty days (like in the 
> pdf mentioned below) and let Excel calculate the logarithmic function. If I 
> extrapolate that to 10 years it seems that the drift would be 6E-13/day but 
> as can be seen in the aging graph it was more like ten times higher.
> 
> Some days ago I started the OCXO again after it had been on the shelf for 
> more than 4 years. Enclosed is a graph for the first 7 days. After six and 
> half days it seems to be a jump of about 1.5E-10 and as I have no indication 
> of anything else I believe it is from the OCXO.
> 
> /Lars
> 
>> On Mon, Nov 7, 2016 at 10:34 AM, Scott Stobbe 
>> wrote:
> 
>> Here is a sample data point taken from http://tycho.usno.navy.mil/ptt
>> i/1987papers/Vol%2019_16.pdf; the first that showed up on a google search.
>> 
>> Year   Aging [PPB]  dF/dt [PPT/Day]
>>1   180.51   63.884
>>2   196.6531.93
>>5  218   12.769
>>9   231.69   7.0934
>>   10   234.156.384
>>   25255.5   2.5535
>> 
>> If you have a set of coefficients you believe to be representative of your
>> OCXO, we can give those a go.
>> 
>> 
> 
>  days.PNG> 2016.PNG>___
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Re: [time-nuts] Thermal impact on OCXO

[Scott Stobbe]

A few different plots. I didn't have an intuitive feel for what the B
coefficient in log term looks like on a plot, so that is the first
plot. The same aging curve is plotted three times, with the exception
of the B coefficient being scaled by 1/10, 1, 10 respectively. In hand
waving terms, it does have an enormous impact during the first 30 days
(or until Bt >>1), but from then on, it is just an additive offset.

The next 4 plots are just sample fits with noise added.

Finally the 6th plot is of just the first 30 days, the data would seem
to be cleaner than what was shown as a sample in the paper, but the
stability of the B coefficient in 10 monte-carlo runs is not great.
But when plotted over a year the results are minimal.

  A1  A2A3
 0.022914   6.8459   0.00016743
 0.022932   6.6702   0.00058768
 0.023206   5.79690.0026103
 0.023219   4.31270.0093793
  0.02374   2.8309 0.016838
 0.023119   5.02140.0061557
 0.023054   5.83990.0031886
 0.022782   9.8582   -0.0074089
 0.023279   3.7392 0.012161
  0.02345   4.10620.0095448

The only other thing to point out from this, is that the A2 and A3
coefficients are highly non-orthogonal, as A2 increases, A3 drops to
make up the difference.

On Wed, Nov 16, 2016 at 7:38 AM, Bob Camp  wrote:
> Hi
>
> The original introduction of 55310 written by a couple of *very* good guys:
>
> http://tycho.usno.navy.mil/ptti/1987papers/Vol%2019_16.pdf
>
> A fairly current copy of 55310:
>
> https://nepp.nasa.gov/DocUploads/1F3275A6-9140-4C0C-864542DBF16EB1CC/MIL-PRF-55310.pdf
>
> The “right” equation is on page 47. It’s the “Bt+1” in the log that messes up 
> the fit. If you fit it without
> the +1, the fit is *much* easier to do. The result isn’t quite right.
>
> Bob
>
>
>> On Nov 15, 2016, at 11:58 PM, Scott Stobbe  wrote:
>>
>> Hi Bob,
>>
>> Do you recall if you fitted with true ordinary least squares, or fit with a
>> recursive/iterative approach in a least squares sense. If the aging curve
>> is linearizable, it isn't jumping out at me.
>>
>> If the model was hypothetically:
>> F = A ln( B*t )
>>
>> F = A ln(t) + Aln(B)
>>
>> which could easily be fit as
>> F  = A' X + B', where X = ln(t)
>>
>> It would appear stable32 uses an iterative approach for the non-linear
>> problem
>>
>> "y(t) = a·ln(bt+1), where slope = y'(t) = ab/(bt+1) Determining the
>> nonlinear log fit coefficients requires an iterative procedure. This
>> involves setting b to an in initial value, linearizing the equation,
>> solving for the other coefficients and the sum of the squared error,
>> comparing that with an error criterion, and iterating until a satisfactory
>> result is found. The key aspects to this numerical analysis process are
>> establishing a satisfactory iteration factor and error criterion to assure
>> both convergence and small residuals."
>>
>> http://www.stable32.com/Curve%20Fitting%20Features%20in%20Stable32.pdf
>>
>> Not sure what others do.
>>
>>
>> On Mon, Nov 14, 2016 at 7:15 AM, Bob Camp  wrote:
>>
>>> Hi
>>>
>>> If you already *have* data over a year (or multiple years) the fit is
>>> fairly easy.
>>> If you try to do this with data from a few days or less, the whole fit
>>> process is
>>> a bit crazy. You also have *multiple* time constants involved on most
>>> OCXO’s.
>>> The result is that an earlier fit will have a shorter time constant (and
>>> will ultimately
>>> die out). You may not be able to separate the 25 year curve from the 3
>>> month
>>> curve with only 3 months of data.
>>>
>>> Bob
>>>
 On Nov 13, 2016, at 10:59 PM, Scott Stobbe 
>>> wrote:

 On Mon, Nov 7, 2016 at 10:34 AM, Scott Stobbe 
 wrote:

> Here is a sample data point taken from http://tycho.usno.navy.mil/ptt
> i/1987papers/Vol%2019_16.pdf; the first that showed up on a google
>>> search.
>
>Year   Aging [PPB]  dF/dt [PPT/Day]
>   1   180.51   63.884
>   2   196.6531.93
>   5  218   12.769
>   9   231.69   7.0934
>  10   234.156.384
>  25255.5   2.5535
>
> If you have a set of coefficients you believe to be representative of
>>> your
> OCXO, we can give those a go.
>
>
 I thought I would come back to this sample data point and see what the
 impact of using a 1st order estimate for the log function would entail.

 The coefficients supplied in the paper are the following:
A1 = 0.0233;
A2 = 4.4583;
A3 = 0.0082;

 F =  A1*ln( A2*x +1 ) + A3;  where x is time in days

Fdot = (A1*A2)/(A2*x +1)

Fdotdot = -(A1*A2^2)/(A2*x +1)^2

 When x is large, the derivatives are approximately:

Re: [time-nuts] Thermal impact on OCXO

[Tim Shoppa]

Lars,

I've broadly understood the aging in the first days to month as being
dominated by "bake-out". It's well fit with a logarithmic curve but the
effect is so large in the first weeks that it hides the true long term
aging (which could well have a different direction).

Tim N3QE

On Wed, Nov 16, 2016 at 2:41 PM, Lars Walenius 
wrote:

> FWIW. Between 2001 and 2011 I run a 5MHz OCXO (in a box). It is a 2x3inch
> type without EFC marked OFC MC834X4-009W with date code 97. Probably it was
> from some base station testing and it had been sitting in my shelf since
> 98. The OCXO were battery backed but at two occasions (2004 and 2007) we
> had power fails that drained the battery as can be seen in the graph.
>
> Just out of curiosity I yesterday put just the first thirty days (like in
> the pdf mentioned below) and let Excel calculate the logarithmic function.
> If I extrapolate that to 10 years it seems that the drift would be
> 6E-13/day but as can be seen in the aging graph it was more like ten times
> higher.
>
> Some days ago I started the OCXO again after it had been on the shelf for
> more than 4 years. Enclosed is a graph for the first 7 days. After six and
> half days it seems to be a jump of about 1.5E-10 and as I have no
> indication of anything else I believe it is from the OCXO.
>
> /Lars
>
> >On Mon, Nov 7, 2016 at 10:34 AM, Scott Stobbe 
> >wrote:
>
> > Here is a sample data point taken from http://tycho.usno.navy.mil/ptt
> > i/1987papers/Vol%2019_16.pdf; the first that showed up on a google
> search.
> >
> >  Year   Aging [PPB]  dF/dt [PPT/Day]
> > 1   180.51   63.884
> > 2   196.6531.93
> > 5  218   12.769
> > 9   231.69   7.0934
> >10   234.156.384
> >25255.5   2.5535
> >
> > If you have a set of coefficients you believe to be representative of
> your
> > OCXO, we can give those a go.
> >
> >
>
>
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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] Thermal impact on OCXO

[Lars Walenius]

Many thanks to Dan!

A question: About what temperature span has it been during these runs? Or do 
you have the temperature coefficient? Seems that the yellow line has about 
50ppt due to temperature.

For the orange it seems to me to have about 6E-12/day aging, is that high? 
Compared to the Tbolts Tom showed they seems to be very good. (Hope Tom will 
publish temperature data soon)

Lars


Från: Bob Stewart
Skickat: den 7 november 2016 22:41

My friend and mentor Dan Kemppainen's posts apparently aren't making it to the 
list so I thought I'd forward this one.
Bob

 Forwarded Message 
Subject: Re: Thermal impact on OCXO
Date: Sun, 06 Nov 2016 12:00:23 -0500
From: d...@irtelemetrics.com


For what it's worth, Some data from a few of Bob's units:

This is the EFC data for 4 separate units over the last 1120 Hours.
Since the EFC ranges are different for some of the oscillators, the EFC
value has been converted to uHz for each unit. The uHz is more
meaningful to me on the same graph.

Interestingly the Grey and Yellow traces exhibit quite a bit of wander,
but a linear best fit puts them nearly flat. Although basically
meaningless numbers the linear fit is at 8e-14 and 3e-15 in this graph.
Now, these units do exhibit a somewhat high correlation between
temperature and DAC change, but that data isn't handy right now. It's
sort of buried here, as these are long term graphs.

The Green trace looks pretty nice, even if you consider the 1.3e-12 per
day drift. This unit has basically no correlation between DAC and
temperature.

The orange trace, well lets just say this oscillator may get replaced
someday. It exhibits both exhibits a high DAC to temperature
correlation, and long term drift. It just won't settle down.

As best as I can determine from these units the temperature dependence
and long term drift is mostly from the oscillator. The long term drift
of the EFC appears to be minimal as does the thermal drift of the EFC
circuit. However as Bob Camp and others have pointed out is is not
trivial to measure such things, so take my conclusions with a grain of salt.


Dan








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Re: [time-nuts] Thermal impact on OCXO

[Lars Walenius]

FWIW. Between 2001 and 2011 I run a 5MHz OCXO (in a box). It is a 2x3inch type 
without EFC marked OFC MC834X4-009W with date code 97. Probably it was from 
some base station testing and it had been sitting in my shelf since 98. The 
OCXO were battery backed but at two occasions (2004 and 2007) we had power 
fails that drained the battery as can be seen in the graph.

Just out of curiosity I yesterday put just the first thirty days (like in the 
pdf mentioned below) and let Excel calculate the logarithmic function. If I 
extrapolate that to 10 years it seems that the drift would be 6E-13/day but as 
can be seen in the aging graph it was more like ten times higher.

Some days ago I started the OCXO again after it had been on the shelf for more 
than 4 years. Enclosed is a graph for the first 7 days. After six and half days 
it seems to be a jump of about 1.5E-10 and as I have no indication of anything 
else I believe it is from the OCXO.

/Lars

>On Mon, Nov 7, 2016 at 10:34 AM, Scott Stobbe 
>wrote:

> Here is a sample data point taken from http://tycho.usno.navy.mil/ptt
> i/1987papers/Vol%2019_16.pdf; the first that showed up on a google search.
>
>  Year   Aging [PPB]  dF/dt [PPT/Day]
> 1   180.51   63.884
> 2   196.6531.93
> 5  218   12.769
> 9   231.69   7.0934
>10   234.156.384
>25255.5   2.5535
>
> If you have a set of coefficients you believe to be representative of your
> OCXO, we can give those a go.
>
>

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Re: [time-nuts] Thermal impact on OCXO

[Bob Camp]

Hi

The original introduction of 55310 written by a couple of *very* good guys:

http://tycho.usno.navy.mil/ptti/1987papers/Vol%2019_16.pdf

A fairly current copy of 55310:

https://nepp.nasa.gov/DocUploads/1F3275A6-9140-4C0C-864542DBF16EB1CC/MIL-PRF-55310.pdf

The “right” equation is on page 47. It’s the “Bt+1” in the log that messes up 
the fit. If you fit it without 
the +1, the fit is *much* easier to do. The result isn’t quite right.

Bob


> On Nov 15, 2016, at 11:58 PM, Scott Stobbe  wrote:
> 
> Hi Bob,
> 
> Do you recall if you fitted with true ordinary least squares, or fit with a
> recursive/iterative approach in a least squares sense. If the aging curve
> is linearizable, it isn't jumping out at me.
> 
> If the model was hypothetically:
> F = A ln( B*t )
> 
> F = A ln(t) + Aln(B)
> 
> which could easily be fit as
> F  = A' X + B', where X = ln(t)
> 
> It would appear stable32 uses an iterative approach for the non-linear
> problem
> 
> "y(t) = a·ln(bt+1), where slope = y'(t) = ab/(bt+1) Determining the
> nonlinear log fit coefficients requires an iterative procedure. This
> involves setting b to an in initial value, linearizing the equation,
> solving for the other coefficients and the sum of the squared error,
> comparing that with an error criterion, and iterating until a satisfactory
> result is found. The key aspects to this numerical analysis process are
> establishing a satisfactory iteration factor and error criterion to assure
> both convergence and small residuals."
> 
> http://www.stable32.com/Curve%20Fitting%20Features%20in%20Stable32.pdf
> 
> Not sure what others do.
> 
> 
> On Mon, Nov 14, 2016 at 7:15 AM, Bob Camp  wrote:
> 
>> Hi
>> 
>> If you already *have* data over a year (or multiple years) the fit is
>> fairly easy.
>> If you try to do this with data from a few days or less, the whole fit
>> process is
>> a bit crazy. You also have *multiple* time constants involved on most
>> OCXO’s.
>> The result is that an earlier fit will have a shorter time constant (and
>> will ultimately
>> die out). You may not be able to separate the 25 year curve from the 3
>> month
>> curve with only 3 months of data.
>> 
>> Bob
>> 
>>> On Nov 13, 2016, at 10:59 PM, Scott Stobbe 
>> wrote:
>>> 
>>> On Mon, Nov 7, 2016 at 10:34 AM, Scott Stobbe 
>>> wrote:
>>> 
 Here is a sample data point taken from http://tycho.usno.navy.mil/ptt
 i/1987papers/Vol%2019_16.pdf; the first that showed up on a google
>> search.
 
Year   Aging [PPB]  dF/dt [PPT/Day]
   1   180.51   63.884
   2   196.6531.93
   5  218   12.769
   9   231.69   7.0934
  10   234.156.384
  25255.5   2.5535
 
 If you have a set of coefficients you believe to be representative of
>> your
 OCXO, we can give those a go.
 
 
>>> I thought I would come back to this sample data point and see what the
>>> impact of using a 1st order estimate for the log function would entail.
>>> 
>>> The coefficients supplied in the paper are the following:
>>>A1 = 0.0233;
>>>A2 = 4.4583;
>>>A3 = 0.0082;
>>> 
>>> F =  A1*ln( A2*x +1 ) + A3;  where x is time in days
>>> 
>>>Fdot = (A1*A2)/(A2*x +1)
>>> 
>>>Fdotdot = -(A1*A2^2)/(A2*x +1)^2
>>> 
>>> When x is large, the derivatives are approximately:
>>> 
>>>Fdot ~= A1/x
>>> 
>>>Fdotdot ~= -A1/x^2
>>> 
>>> It's worth noting that, just as it is visually apparent from the graph,
>> the
>>> aging becomes more linear as time progresses, the second, third, ...,
>>> derivatives drop off faster than the first.
>>> 
>>> A first order taylor series of the aging would be,
>>> 
>>>T1(x, xo) = A3 + A1*ln(A2*xo + 1) +  (A1*A2)(x - xo)/(A2*xo +1) + O(
>>> (x-xo)^2 )
>>> 
>>> The remainder (error) term for a 1st order taylor series of F would be:
>>> R(x) = Fdotdot(c) * ((x-xo)^2)/(2!);  where c is some value between
>> x
>>> and xo.
>>> 
>>> So, take for example, forward projecting the drift one day after the
>> 365th
>>> day using a first order model,
>>>xo = 365
>>> 
>>>Fdot(365) =  63.796 PPT/day, alternatively the approximate derivative
>>> is: 63.836 PPT/day
>>> 
>>>|R(366)| =  0.087339 PPT (more than likely, this is no where near 1
>>> DAC LSB on the EFC line)
>>> 
>>> More than likely you wouldn't try to project 7 days out, but considering
>>> only the generalized effects of aging, the error would be:
>>> 
>>>|R(372)| = 4.282 PPT (So on the 7th day, a 1st order model starts to
>>> degrade into a few DAC LSB)
>>> 
>>> In the case of forward projecting aging for one day, using a 1st order
>>> model versus the full logarithmic model, would likely be a discrepancy of
>>> less than one dac LSB.
>>> ___
>>> time-nuts mailing list -- time-nuts@febo.com
>>> 

Re: [time-nuts] Thermal impact on OCXO

[Scott Stobbe]

Hi Bob,

Do you recall if you fitted with true ordinary least squares, or fit with a
recursive/iterative approach in a least squares sense. If the aging curve
is linearizable, it isn't jumping out at me.

If the model was hypothetically:
 F = A ln( B*t )

 F = A ln(t) + Aln(B)

which could easily be fit as
 F  = A' X + B', where X = ln(t)

It would appear stable32 uses an iterative approach for the non-linear
problem

"y(t) = a·ln(bt+1), where slope = y'(t) = ab/(bt+1) Determining the
nonlinear log fit coefficients requires an iterative procedure. This
involves setting b to an in initial value, linearizing the equation,
solving for the other coefficients and the sum of the squared error,
comparing that with an error criterion, and iterating until a satisfactory
result is found. The key aspects to this numerical analysis process are
establishing a satisfactory iteration factor and error criterion to assure
both convergence and small residuals."

http://www.stable32.com/Curve%20Fitting%20Features%20in%20Stable32.pdf

Not sure what others do.


On Mon, Nov 14, 2016 at 7:15 AM, Bob Camp  wrote:

> Hi
>
> If you already *have* data over a year (or multiple years) the fit is
> fairly easy.
> If you try to do this with data from a few days or less, the whole fit
> process is
> a bit crazy. You also have *multiple* time constants involved on most
> OCXO’s.
> The result is that an earlier fit will have a shorter time constant (and
> will ultimately
> die out). You may not be able to separate the 25 year curve from the 3
> month
> curve with only 3 months of data.
>
> Bob
>
> > On Nov 13, 2016, at 10:59 PM, Scott Stobbe 
> wrote:
> >
> > On Mon, Nov 7, 2016 at 10:34 AM, Scott Stobbe 
> > wrote:
> >
> >> Here is a sample data point taken from http://tycho.usno.navy.mil/ptt
> >> i/1987papers/Vol%2019_16.pdf; the first that showed up on a google
> search.
> >>
> >> Year   Aging [PPB]  dF/dt [PPT/Day]
> >>1   180.51   63.884
> >>2   196.6531.93
> >>5  218   12.769
> >>9   231.69   7.0934
> >>   10   234.156.384
> >>   25255.5   2.5535
> >>
> >> If you have a set of coefficients you believe to be representative of
> your
> >> OCXO, we can give those a go.
> >>
> >>
> > I thought I would come back to this sample data point and see what the
> > impact of using a 1st order estimate for the log function would entail.
> >
> > The coefficients supplied in the paper are the following:
> > A1 = 0.0233;
> > A2 = 4.4583;
> > A3 = 0.0082;
> >
> > F =  A1*ln( A2*x +1 ) + A3;  where x is time in days
> >
> > Fdot = (A1*A2)/(A2*x +1)
> >
> > Fdotdot = -(A1*A2^2)/(A2*x +1)^2
> >
> > When x is large, the derivatives are approximately:
> >
> > Fdot ~= A1/x
> >
> > Fdotdot ~= -A1/x^2
> >
> > It's worth noting that, just as it is visually apparent from the graph,
> the
> > aging becomes more linear as time progresses, the second, third, ...,
> > derivatives drop off faster than the first.
> >
> > A first order taylor series of the aging would be,
> >
> > T1(x, xo) = A3 + A1*ln(A2*xo + 1) +  (A1*A2)(x - xo)/(A2*xo +1) + O(
> > (x-xo)^2 )
> >
> > The remainder (error) term for a 1st order taylor series of F would be:
> >  R(x) = Fdotdot(c) * ((x-xo)^2)/(2!);  where c is some value between
> x
> > and xo.
> >
> > So, take for example, forward projecting the drift one day after the
> 365th
> > day using a first order model,
> > xo = 365
> >
> > Fdot(365) =  63.796 PPT/day, alternatively the approximate derivative
> > is: 63.836 PPT/day
> >
> > |R(366)| =  0.087339 PPT (more than likely, this is no where near 1
> > DAC LSB on the EFC line)
> >
> > More than likely you wouldn't try to project 7 days out, but considering
> > only the generalized effects of aging, the error would be:
> >
> > |R(372)| = 4.282 PPT (So on the 7th day, a 1st order model starts to
> > degrade into a few DAC LSB)
> >
> > In the case of forward projecting aging for one day, using a 1st order
> > model versus the full logarithmic model, would likely be a discrepancy of
> > less than one dac LSB.
> > ___
> > 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] Thermal impact on OCXO

[Bob Camp]

Hi

If you already *have* data over a year (or multiple years) the fit is fairly 
easy.
If you try to do this with data from a few days or less, the whole fit process 
is
a bit crazy. You also have *multiple* time constants involved on most OCXO’s. 
The result is that an earlier fit will have a shorter time constant (and will 
ultimately
die out). You may not be able to separate the 25 year curve from the 3 month
curve with only 3 months of data.

Bob

> On Nov 13, 2016, at 10:59 PM, Scott Stobbe  wrote:
> 
> On Mon, Nov 7, 2016 at 10:34 AM, Scott Stobbe 
> wrote:
> 
>> Here is a sample data point taken from http://tycho.usno.navy.mil/ptt
>> i/1987papers/Vol%2019_16.pdf; the first that showed up on a google search.
>> 
>> Year   Aging [PPB]  dF/dt [PPT/Day]
>>1   180.51   63.884
>>2   196.6531.93
>>5  218   12.769
>>9   231.69   7.0934
>>   10   234.156.384
>>   25255.5   2.5535
>> 
>> If you have a set of coefficients you believe to be representative of your
>> OCXO, we can give those a go.
>> 
>> 
> I thought I would come back to this sample data point and see what the
> impact of using a 1st order estimate for the log function would entail.
> 
> The coefficients supplied in the paper are the following:
> A1 = 0.0233;
> A2 = 4.4583;
> A3 = 0.0082;
> 
> F =  A1*ln( A2*x +1 ) + A3;  where x is time in days
> 
> Fdot = (A1*A2)/(A2*x +1)
> 
> Fdotdot = -(A1*A2^2)/(A2*x +1)^2
> 
> When x is large, the derivatives are approximately:
> 
> Fdot ~= A1/x
> 
> Fdotdot ~= -A1/x^2
> 
> It's worth noting that, just as it is visually apparent from the graph, the
> aging becomes more linear as time progresses, the second, third, ...,
> derivatives drop off faster than the first.
> 
> A first order taylor series of the aging would be,
> 
> T1(x, xo) = A3 + A1*ln(A2*xo + 1) +  (A1*A2)(x - xo)/(A2*xo +1) + O(
> (x-xo)^2 )
> 
> The remainder (error) term for a 1st order taylor series of F would be:
>  R(x) = Fdotdot(c) * ((x-xo)^2)/(2!);  where c is some value between x
> and xo.
> 
> So, take for example, forward projecting the drift one day after the 365th
> day using a first order model,
> xo = 365
> 
> Fdot(365) =  63.796 PPT/day, alternatively the approximate derivative
> is: 63.836 PPT/day
> 
> |R(366)| =  0.087339 PPT (more than likely, this is no where near 1
> DAC LSB on the EFC line)
> 
> More than likely you wouldn't try to project 7 days out, but considering
> only the generalized effects of aging, the error would be:
> 
> |R(372)| = 4.282 PPT (So on the 7th day, a 1st order model starts to
> degrade into a few DAC LSB)
> 
> In the case of forward projecting aging for one day, using a 1st order
> model versus the full logarithmic model, would likely be a discrepancy of
> less than one dac LSB.
> ___
> 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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Re: [time-nuts] Thermal impact on OCXO

[Scott Stobbe]

On Mon, Nov 7, 2016 at 10:34 AM, Scott Stobbe 
wrote:

> Here is a sample data point taken from http://tycho.usno.navy.mil/ptt
> i/1987papers/Vol%2019_16.pdf; the first that showed up on a google search.
>
>  Year   Aging [PPB]  dF/dt [PPT/Day]
> 1   180.51   63.884
> 2   196.6531.93
> 5  218   12.769
> 9   231.69   7.0934
>10   234.156.384
>25255.5   2.5535
>
> If you have a set of coefficients you believe to be representative of your
> OCXO, we can give those a go.
>
>
I thought I would come back to this sample data point and see what the
impact of using a 1st order estimate for the log function would entail.

The coefficients supplied in the paper are the following:
 A1 = 0.0233;
 A2 = 4.4583;
 A3 = 0.0082;

F =  A1*ln( A2*x +1 ) + A3;  where x is time in days

 Fdot = (A1*A2)/(A2*x +1)

 Fdotdot = -(A1*A2^2)/(A2*x +1)^2

When x is large, the derivatives are approximately:

 Fdot ~= A1/x

 Fdotdot ~= -A1/x^2

It's worth noting that, just as it is visually apparent from the graph, the
aging becomes more linear as time progresses, the second, third, ...,
derivatives drop off faster than the first.

A first order taylor series of the aging would be,

 T1(x, xo) = A3 + A1*ln(A2*xo + 1) +  (A1*A2)(x - xo)/(A2*xo +1) + O(
(x-xo)^2 )

The remainder (error) term for a 1st order taylor series of F would be:
  R(x) = Fdotdot(c) * ((x-xo)^2)/(2!);  where c is some value between x
and xo.

So, take for example, forward projecting the drift one day after the 365th
day using a first order model,
 xo = 365

 Fdot(365) =  63.796 PPT/day, alternatively the approximate derivative
is: 63.836 PPT/day

 |R(366)| =  0.087339 PPT (more than likely, this is no where near 1
DAC LSB on the EFC line)

More than likely you wouldn't try to project 7 days out, but considering
only the generalized effects of aging, the error would be:

 |R(372)| = 4.282 PPT (So on the 7th day, a 1st order model starts to
degrade into a few DAC LSB)

In the case of forward projecting aging for one day, using a 1st order
model versus the full logarithmic model, would likely be a discrepancy of
less than one dac LSB.
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Re: [time-nuts] Thermal impact on OCXO

[Hal Murray]

kb...@n1k.org said:
> Yes, that’s a bit of a long winded reply … sorry about that. 

It was also valuable.  Thanks.


-- 
These are my opinions.  I hate spam.



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Re: [time-nuts] Thermal impact on OCXO

[Scott Stobbe]

Deeper into the rabbit hole :)

I'm not sure what specific pic you are you using but most of them have at
least one timer that will run fully asynchronously and its timer input is
usually shared with one of the 32k osc pins. Which you can then use to wake
the prossesor from one of its sleep states. Do you end up hitting a clock
sync with the pwm block?

Good old 74 series to the rescue.

On Monday, 7 November 2016, Bob Stewart <b...@evoria.net> wrote:

> Hi Scott,
>
> I wish I had some long term data, but I don't.  I had initially set out to
> build an accurate GPS frequency reference type of GPSDO.  So, aging wasn't
> an issue.  It's either on and locked or it's not.  So, I didn't worry about
> leaving a unit running for months and collecting aging data.
>
> But then I had this crackpot idea of using the latches in a 7474 to
> stabilize the 1PPS from the receiver to the OCXO.  Tom had a bit of a
> misunderstanding about what I was doing and we had a bit of a discussion
> until he caught on to what I was doing and its limitations.
>
> But, somewhere along the line, I realized that the idea was sound but my
> implementation was poor.  The basic problem with using a timer in the
> dsPIC33 is that they use a PLL to generate the internal clock - even if you
> supply a clock.  That gives you a 1-count jitter in any output pulse you
> try to create.  So, I realized that I could use the latches in a 7474 to
> latch the OCXO to the output of a timer on the PIC.  With the PIC running
> at 40MHz, I have plenty of room for the jitter without the worry of a phase
> slip.  I think I've proved that that works, so now I have the possibility
> of using my system as a time server.  And that means I now have to deal
> with such arcane matters as holdover, aging, and generating the time from
> the OCXO.  The learning curve has been a bit steep.
>
> Bob
>
> -
> AE6RV.com
>
> GFS GPSDO list:
> groups.yahoo.com/neo/groups/GFS-GPSDOs/info
>
>
> --
> *From:* Scott Stobbe <scott.j.sto...@gmail.com
> <javascript:_e(%7B%7D,'cvml','scott.j.sto...@gmail.com');>>
> *To:* Bob Camp <kb...@n1k.org
> <javascript:_e(%7B%7D,'cvml','kb...@n1k.org');>>
> *Cc:* Bob Stewart <b...@evoria.net
> <javascript:_e(%7B%7D,'cvml','b...@evoria.net');>>; Discussion of precise
> time and frequency measurement <time-nuts@febo.com
> <javascript:_e(%7B%7D,'cvml','time-nuts@febo.com');>>
> *Sent:* Monday, November 7, 2016 9:34 AM
> *Subject:* Re: [time-nuts] Thermal impact on OCXO
>
> Here is a sample data point taken from http://tycho.usno.navy.mil/
> ptti/1987papers/Vol%2019_16.pdf; the first that showed up on a google
> search.
>
>  Year   Aging [PPM]  dF/dt [PPT/Day]
> 1   180.51   63.884
> 2   196.6531.93
> 5  218   12.769
> 9   231.69   7.0934
>10   234.156.384
>25255.5   2.5535
>
> If you have a set of coefficients you believe to be representative of your
> OCXO, we can give those a go.
>
> On Mon, Nov 7, 2016 at 7:08 AM, Bob Camp <kb...@n1k.org
> <javascript:_e(%7B%7D,'cvml','kb...@n1k.org');>> wrote:
>
> Hi
>
>
> > On Nov 5, 2016, at 10:43 PM, Bob Stewart <b...@evoria.net
> <javascript:_e(%7B%7D,'cvml','b...@evoria.net');>> wrote:
> >
> > Hi Scott,
> > D'oh.  Thanks for the correction!  Like I said, I don't do these
> calculations often.
> >
> > If as Bob Camp implies, the aging isn't from the OXCO, then I'm a bit
> stumped.  I do have an op-amp in the EFC string with  a voltage divider for
> gain.  The resistors are Panasonic ERA-6AEDxxxV resistors.  Mouser says
> they're temperature stable to 25PPM/C, but of course they don't mention an
> aging rate.  I don't really see anything else, other than the OCXO, that is
> likely to be prone to a linear type of aging.
>
> OCXO’s don’t age in a linear fashion. At least 90% of them don’t. If you
> dig into the FCS papers there are various
> curves proposed as models. Mil-O-55310 has one of them as the “official”
> approach. All of them have the basic
> issue of mistakenly fitting to to short a time constraint.
>
> Bob
>
> >  The aging rate appears to be stable from unit to unit, so naturally I
> considered the OCXO first.
> >
> > There is one other bit in the EFC string that might be controversial,
> but I don't see that it would be a candidate for the symptoms of aging.
> >
> > Bob
> >  -- -- -
> > AE6RV.co

Re: [time-nuts] Thermal impact on OCXO

[Bob Stewart]

Hi Scott,
The EFC is a nominal 2.826 volts, which I removed and plotted the last 2 
decimal places.  I'd have to do a lot of fiddling to find the range, but 50uV 
looks about right from the plot.  I'm going to let this bake for another day or 
two to see if there's a time-related element to it after the thermal stuff 
averages out.  After that, I plan to take the software out of hold mode and see 
what the EFC plot looks like as the DAC voltage changes over time.  

Bob -
AE6RV.com

GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info

  From: Scott Stobbe <scott.j.sto...@gmail.com>
 To: Bob Stewart <b...@evoria.net>; Discussion of precise time and frequency 
measurement <time-nuts@febo.com> 
 Sent: Monday, November 7, 2016 2:48 PM
 Subject: Re: [time-nuts] Thermal impact on OCXO
   
Another nice plot! It looks like after 2am you see temperature swings of 1.5 
degF roughly every 30 minutes? Correspondingly, the EFC line which is nominally 
~2.8vdc sees swings of +-50 uV?


   
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Re: [time-nuts] Thermal impact on OCXO

[Scott Stobbe]

Another nice plot! It looks like after 2am you see temperature swings of
1.5 degF roughly every 30 minutes? Correspondingly, the EFC line which is
nominally ~2.8vdc sees swings of +-50 uV?

On Monday, 7 November 2016, Bob Stewart  wrote:

> Hi guys,
> First of all, thanks for the additional responses.  I was a bit angry and
> rude yesterday, and I figured this thread was over.  Thanks for staying
> with me.
> I haven't had time to look over the data etc in your responses.  I'll do
> that and get back to the list if appropriate.
>
> I spoke to Attila and Azelio offline last nite and from their input, I
> decided to hook up the 3456A and collect some data, which is in the plot
> attached.  As usual, I've modified one of my standard plot scripts, so
> there is some extraneous data that wasn't removed.
>
> First for our purposes is the thin red line, which is the DAC value locked
> at 0x734B0.  The orange trace is the temperature adjusted so that each step
> of 10 on the right hand Y tics is one degree F.  The dark blue trace is the
> EFC value read by the 3456A.  It has been multiplied by 100,000 and then
> had 282600 subtracted.  This leaves just the LSD scaled at 1:1 on the right
> hand Y tics.
> There's something interesting on the far right hand side where the
> temperature goes low and stays there.  The DVM value follows it down, but
> then recovers while the temperature stays down.  I'm not sure what to make
> of this.  Either then OCXO is making up for the temperature change by
> increasing the temperature, or the 3456 is compensating for it after the
> fact.  In either case, the EFC seems to only follow the transient
> temperature changes, and doesn't actually track the temperature on the
> board.
>
> So, to my eye, after 14 hours, there is only a dependency on thermal
> transients.  I'll leave it running for some time yet, but the EFC doesn't
> seem to be drifting in any meaningful way at this point, other than in
> relation to temperature changes.
>
> Note:  I used a shielded twisted-pair with the usual clips attached to
> ground and EFC in my GPSDO.  On the 3456, the two leads go to the
> appropriate volts inputs, and the shield goes to the ground input.  The
> "guard" switch is out, which is the off position.  There is no shield
> connector on the DUT side.
>
> Bob
>
>  -
> AE6RV.com
>
> GFS GPSDO list:
> groups.yahoo.com/neo/groups/GFS-GPSDOs/info
>
>
>
>
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Re: [time-nuts] Thermal impact on OCXO

[Bob Camp]

Hi

This is your design, and under your control. Looking at one plot here or there 
and trying to 
guess what is going on is not a really good way to do this. The whole 
sub-thread we are on
is simply a result of a “if it’s not crystal aging it can’t be anything else” 
comment way way back.
My point here is that it *can* be something else and the list of things it 
*can* be is actually quite
long. The voltage measurement stuff is simply one example out of at least a 
dozen and probably
closer to a hundred possibles. Digging through all of those possible things is 
a lot of work. It’s work 
that can only be done “hands on” with a set of units and test gear.  My first 
step would be to toss
the setup into an environmental chamber and do some 48 hour temperature sweeps. 

Aging is a “long term” drift. It goes on for years. Warmup is a very short term 
effect. It goes on for hours
or days. Retrace is the process of re-settilitg to the previous long term aging 
line. It can take days / weeks /
months depending on the oscillator. If you were buying the OCXO’s as an OEM, 
the specs you 
bought them to would be a function of what you asked for and how much you were 
willing to pay. It
is unlikely that as an OEM you would have requirements on  retrace and warmup, 
and aging. If you 
did have a spec it would be under fairly specific conditions (on power for 
three months, measure
frequency, off power at XX C for 24 hours, on power again for 24 hours at YY C, 
measure delta
frequency. That would cover warmup, but really says nothing about aging or 
retrace. 

Regardless of if an OCXO is spec’d for this or that issue or not, it 
experiences it. There are a lot of 
other things that OCXO’s do that many or may not be spec’d. When using one and 
digging into it, 
you have to deal with all the issues, regardless of if there is a spec or not. 
That assumes you want 
to dig in at this level. A *very* reasonable question is - what level do you 
want to dig into? That is 
why I bring up the good old “what is the goal?” question on a regular basis. 
Without a goal in mind, 
you will keep digging ever deeper. The number of issues you need to look into 
grows exponentially 
as you dig deeper. The time, learning, equipment, experiments, and number of 
test units each go 
up rapidly. It is work, equipment, and experiments that only apply to your 
design. It is not a piggyback 
process as you go deeper. 

Yes, that’s a bit of a long winded reply … sorry about that.

Bob




> On Nov 7, 2016, at 2:23 PM, Bob Stewart <b...@evoria.net> wrote:
> 
> Hi Bob,
> 
> OK, given that, what is your view of the plot I presented?  Let's remember 
> that I plotted this because I was trying to discover whether the EFC 
> circuitry has a time-related drift, or  whether the DAC value drift I plotted 
> with the GPSDO locked to the GPS was caused by the OCXO.
> 
> In one of your posts today, you talked about a long-term retrace lasting some 
> months.  I've been using the term "aging".  Has my choice of terms caused the 
> discussion to take a turn that it wouldn't have taken if I had used the term 
> "retrace"?  The fact is that I don't know whether it's aging or retrace.  I'm 
> not really clear on how to tell the difference.  I'm especially handicapped 
> by not having the mfg specs for the OCXOs I use.  It could be that I simply 
> haven't had the test unit under power for long enough to let the OCXO settle 
> out.  And for sure when I added the test lead to the EFC (breaking a trace in 
> the process) there was enough off time to thoroughly insult the OCXO.
> 
> Bob
>  
> -
> AE6RV.com
> 
> GFS GPSDO list:
> groups.yahoo.com/neo/groups/GFS-GPSDOs/info
> 
> 
> From: Bob Camp <kb...@n1k.org>
> To: Bob Stewart <b...@evoria.net>; Discussion of precise time and frequency 
> measurement <time-nuts@febo.com> 
> Sent: Monday, November 7, 2016 1:01 PM
> Subject: Re: [time-nuts] Thermal impact on OCXO
> 
> Hi
> 
> Thermocouples in test leads are nasty because they operate on the temperature
> delta rather than the absolute temperature. It’s the gradient you have to 
> worry about.
> Until you have run out a few dozen sensors around your bench (or test 
> chamber) and
> monitored them for a few days … you won’t believe just how little “point A” 
> has in common
> with “point B”.
> 
> Bob
> 
> > On Nov 7, 2016, at 1:44 PM, Bob Stewart <b...@evoria.net> wrote:
> > 
> > -accidentally omitted timenuts from my reply to bob-
> > Hi Bob,
> > The data is at the 10uV level.  As to whether I've plotted "data" or data, 
> > I can only report what I have.  It seems to be consistent over the long 
> > ru

Re: [time-nuts] Thermal impact on OCXO

[Attila Kinali]

On Mon, 7 Nov 2016 17:47:19 + (UTC)
Bob Stewart  wrote:

> When you say that OCXOs don't age in a linear fashion, what does that mean?  
> IOW, is this a case where it's almost linear over a week, and the non-
> linearity is only detectable when you consider the longer term?  If that's 
> the case, then it seems reasonable to use the past 3 or so days of data 
> collection to project the near-term behavior; where near-term is less than 3 
> days into the future

Have a look at John Vig's tutorial. There are 2-3 slides on aging and retrace
with references to papers for details.

Attila Kinali

-- 
Malek's Law:
Any simple idea will be worded in the most complicated way.
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Re: [time-nuts] Thermal impact on OCXO

[Attila Kinali]

On Mon, 7 Nov 2016 17:20:58 + (UTC)
Bob Stewart  wrote:

> There's something interesting on the far right hand side where the 
> temperature goes low and stays there.  The DVM value follows it down, but 
> then recovers while the temperature stays down.  I'm not sure what to make 
> of this.  Either then OCXO is making up for the temperature change by 
> increasing the temperature, or the 3456 is compensating for it after the 
> fact.  In either case, the EFC seems to only follow the transient 
> temperature changes, and doesn't actually track the temperature on the board.

These are most likely caused by temperature gradients due to temperature
changes. Once the temperature is (almost) constant, these differences
equalize and the effect goes away. Where that gradient is and what part
of the circuit it affects is not clear. It could be your circuit,
or it could be the measurement.

At least the measurment looks like that temperature dependence is low
enough that it shouldn't be much of an issue. 

Attila Kinali
-- 
Malek's Law:
Any simple idea will be worded in the most complicated way.
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Re: [time-nuts] Thermal impact on OCXO

[Bob Stewart]

Hi Bob,
OK, given that, what is your view of the plot I presented?  Let's remember that 
I plotted this because I was trying to discover whether the EFC circuitry has a 
time-related drift, or  whether the DAC value drift I plotted with the GPSDO 
locked to the GPS was caused by the OCXO.

In one of your posts today, you talked about a long-term retrace lasting some 
months.  I've been using the term "aging".  Has my choice of terms caused the 
discussion to take a turn that it wouldn't have taken if I had used the term 
"retrace"?  The fact is that I don't know whether it's aging or retrace.  I'm 
not really clear on how to tell the difference.  I'm especially handicapped by 
not having the mfg specs for the OCXOs I use.  It could be that I simply 
haven't had the test unit under power for long enough to let the OCXO settle 
out.  And for sure when I added the test lead to the EFC (breaking a trace in 
the process) there was enough off time to thoroughly insult the OCXO.

Bob -
AE6RV.com

GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info

  From: Bob Camp <kb...@n1k.org>
 To: Bob Stewart <b...@evoria.net>; Discussion of precise time and frequency 
measurement <time-nuts@febo.com> 
 Sent: Monday, November 7, 2016 1:01 PM
 Subject: Re: [time-nuts] Thermal impact on OCXO
   
Hi

Thermocouples in test leads are nasty because they operate on the temperature
delta rather than the absolute temperature. It’s the gradient you have to worry 
about.
Until you have run out a few dozen sensors around your bench (or test chamber) 
and
monitored them for a few days … you won’t believe just how little “point A” has 
in common
with “point B”.

Bob

> On Nov 7, 2016, at 1:44 PM, Bob Stewart <b...@evoria.net> wrote:
> 
> -accidentally omitted timenuts from my reply to bob-
> Hi Bob,
> The data is at the 10uV level.  As to whether I've plotted "data" or data, I 
> can only report what I have.  It seems to be consistent over the long run.  I 
> would expect to see something else if it were just noise.  If the 4 
> attachments were strongly thermocoupled, wouldn't the data have a stronger 
> correlation to temperature, rather than just to temperature transients?
> 
> Bob -
> AE6RV.com
> 
> GFS GPSDO list:
> groups.yahoo.com/neo/groups/GFS-GPSDOs/info
> 
>      From: Bob Camp <kb...@n1k.org>
> To: Bob Stewart <b...@evoria.net> 
> Cc: Discussion of Precise Time and Frequency Measurement <time-nuts@febo.com>
> Sent: Monday, November 7, 2016 11:54 AM
> Subject: Re: [time-nuts] Thermal impact on OCXO
> 
> Hi
> 
> I would suggest you read the papers on the subject. They are out there. Even 
> over a few days
> OCXO aging is likely to be non-linear ( => curved, not straight line). On an 
> OCXO that is 
> warming up, your are dealing with retrace rather than aging. This can have an 
> impact for a 
> few months after turn on. I have one unit in the basement that took 9 months 
> to come out
> of retrace after being in storage for “a while”. It was an eBay item so no 
> idea just how long 
> the power off time was. 
> 
> Bob
> 
> 
>> On Nov 7, 2016, at 12:47 PM, Bob Stewart <b...@evoria.net> wrote:
>> 
>> Hi Bob,
>> 
>> When you say that OCXOs don't age in a linear fashion, what does that mean?  
>> IOW, is this a case where it's almost linear over a week, and the 
>> non-linearity is only detectable when you consider the longer term?  If 
>> that's the case, then it seems reasonable to use the past 3 or so days of 
>> data collection to project the near-term behavior; where near-term is less 
>> than 3 days into the future.
>> 
>> Bob
>>  
>> -
>> AE6RV.com
>> 
>> GFS GPSDO list:
>> groups.yahoo.com/neo/groups/GFS-GPSDOs/info
>> 
>> 
>> From: Bob Camp <kb...@n1k.org>
>> To: Bob Stewart <b...@evoria.net>; Discussion of precise time and frequency 
>> measurement <time-nuts@febo.com> 
>> Cc: Scott Stobbe <scott.j.sto...@gmail.com>
>> Sent: Monday, November 7, 2016 6:08 AM
>> Subject: Re: [time-nuts] Thermal impact on OCXO
>> 
>> Hi
>> 
>> 
>>> On Nov 5, 2016, at 10:43 PM, Bob Stewart <b...@evoria.net> wrote:
>>> 
>>> Hi Scott,
>>> D'oh.  Thanks for the correction!  Like I said, I don't do these 
>>> calculations often.  
>>> 
>>> If as Bob Camp implies, the aging isn't from the OXCO, then I'm a bit 
>>> stumped.  I do have an op-amp in the EFC string with  a volt

Re: [time-nuts] Thermal impact on OCXO

[Bob Camp]

Hi

Thermocouples in test leads are nasty because they operate on the temperature
delta rather than the absolute temperature. It’s the gradient you have to worry 
about.
Until you have run out a few dozen sensors around your bench (or test chamber) 
and
monitored them for a few days … you won’t believe just how little “point A” has 
in common
with “point B”.

Bob

> On Nov 7, 2016, at 1:44 PM, Bob Stewart <b...@evoria.net> wrote:
> 
> -accidentally omitted timenuts from my reply to bob-
> Hi Bob,
> The data is at the 10uV level.  As to whether I've plotted "data" or data, I 
> can only report what I have.  It seems to be consistent over the long run.  I 
> would expect to see something else if it were just noise.  If the 4 
> attachments were strongly thermocoupled, wouldn't the data have a stronger 
> correlation to temperature, rather than just to temperature transients?
> 
> Bob -
> AE6RV.com
> 
> GFS GPSDO list:
> groups.yahoo.com/neo/groups/GFS-GPSDOs/info
> 
>  From: Bob Camp <kb...@n1k.org>
> To: Bob Stewart <b...@evoria.net> 
> Cc: Discussion of Precise Time and Frequency Measurement <time-nuts@febo.com>
> Sent: Monday, November 7, 2016 11:54 AM
> Subject: Re: [time-nuts] Thermal impact on OCXO
> 
> Hi
> 
> I would suggest you read the papers on the subject. They are out there. Even 
> over a few days
> OCXO aging is likely to be non-linear ( => curved, not straight line). On an 
> OCXO that is 
> warming up, your are dealing with retrace rather than aging. This can have an 
> impact for a 
> few months after turn on. I have one unit in the basement that took 9 months 
> to come out
> of retrace after being in storage for “a while”. It was an eBay item so no 
> idea just how long 
> the power off time was. 
> 
> Bob
> 
> 
>> On Nov 7, 2016, at 12:47 PM, Bob Stewart <b...@evoria.net> wrote:
>> 
>> Hi Bob,
>> 
>> When you say that OCXOs don't age in a linear fashion, what does that mean?  
>> IOW, is this a case where it's almost linear over a week, and the 
>> non-linearity is only detectable when you consider the longer term?  If 
>> that's the case, then it seems reasonable to use the past 3 or so days of 
>> data collection to project the near-term behavior; where near-term is less 
>> than 3 days into the future.
>> 
>> Bob
>>   
>> -
>> AE6RV.com
>> 
>> GFS GPSDO list:
>> groups.yahoo.com/neo/groups/GFS-GPSDOs/info
>> 
>> 
>> From: Bob Camp <kb...@n1k.org>
>> To: Bob Stewart <b...@evoria.net>; Discussion of precise time and frequency 
>> measurement <time-nuts@febo.com> 
>> Cc: Scott Stobbe <scott.j.sto...@gmail.com>
>> Sent: Monday, November 7, 2016 6:08 AM
>> Subject: Re: [time-nuts] Thermal impact on OCXO
>> 
>> Hi
>> 
>> 
>>> On Nov 5, 2016, at 10:43 PM, Bob Stewart <b...@evoria.net> wrote:
>>> 
>>> Hi Scott,
>>> D'oh.  Thanks for the correction!  Like I said, I don't do these 
>>> calculations often.  
>>> 
>>> If as Bob Camp implies, the aging isn't from the OXCO, then I'm a bit 
>>> stumped.  I do have an op-amp in the EFC string with  a voltage divider for 
>>> gain.  The resistors are Panasonic ERA-6AEDxxxV resistors.  Mouser says 
>>> they're temperature stable to 25PPM/C, but of course they don't mention an 
>>> aging rate.  I don't really see anything else, other than the OCXO, that is 
>>> likely to be prone to a linear type of aging.
>> 
>> OCXO’s don’t age in a linear fashion. At least 90% of them don’t. If you dig 
>> into the FCS papers there are various
>> curves proposed as models. Mil-O-55310 has one of them as the “official” 
>> approach. All of them have the basic 
>> issue of mistakenly fitting to to short a time constraint.
>> 
>> Bob
>> 
>>>   The aging rate appears to be stable from unit to unit, so naturally I 
>>> considered the OCXO first.  
>>> 
>>> There is one other bit in the EFC string that might be controversial, but I 
>>> don't see that it would be a candidate for the symptoms of aging.
>>> 
>>> Bob
>>>   -
>>> AE6RV.com
>>> 
>>> GFS GPSDO list:
>>> groups.yahoo.com/neo/groups/GFS-GPSDOs/info
>>> 
>>>   From: Scott Stobbe <scott.j.sto...@gmail.com>
>>> To: Bob Stewart <b...@evoria.net>

Re: [time-nuts] Thermal impact on OCXO

[Bob Stewart]

-accidentally omitted timenuts from my reply to bob-
Hi Bob,
The data is at the 10uV level.  As to whether I've plotted "data" or data, I 
can only report what I have.  It seems to be consistent over the long run.  I 
would expect to see something else if it were just noise.  If the 4 attachments 
were strongly thermocoupled, wouldn't the data have a stronger correlation to 
temperature, rather than just to temperature transients?

Bob -
AE6RV.com

GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info

  From: Bob Camp <kb...@n1k.org>
 To: Bob Stewart <b...@evoria.net> 
Cc: Discussion of Precise Time and Frequency Measurement <time-nuts@febo.com>
 Sent: Monday, November 7, 2016 11:54 AM
 Subject: Re: [time-nuts] Thermal impact on OCXO
   
Hi

I would suggest you read the papers on the subject. They are out there. Even 
over a few days
OCXO aging is likely to be non-linear ( => curved, not straight line). On an 
OCXO that is 
warming up, your are dealing with retrace rather than aging. This can have an 
impact for a 
few months after turn on. I have one unit in the basement that took 9 months to 
come out
of retrace after being in storage for “a while”. It was an eBay item so no idea 
just how long 
the power off time was. 

Bob


> On Nov 7, 2016, at 12:47 PM, Bob Stewart <b...@evoria.net> wrote:
> 
> Hi Bob,
> 
> When you say that OCXOs don't age in a linear fashion, what does that mean?  
> IOW, is this a case where it's almost linear over a week, and the 
> non-linearity is only detectable when you consider the longer term?  If 
> that's the case, then it seems reasonable to use the past 3 or so days of 
> data collection to project the near-term behavior; where near-term is less 
> than 3 days into the future.
> 
> Bob
>  
> -
> AE6RV.com
> 
> GFS GPSDO list:
> groups.yahoo.com/neo/groups/GFS-GPSDOs/info
> 
> 
> From: Bob Camp <kb...@n1k.org>
> To: Bob Stewart <b...@evoria.net>; Discussion of precise time and frequency 
> measurement <time-nuts@febo.com> 
> Cc: Scott Stobbe <scott.j.sto...@gmail.com>
> Sent: Monday, November 7, 2016 6:08 AM
> Subject: Re: [time-nuts] Thermal impact on OCXO
> 
> Hi
> 
> 
> > On Nov 5, 2016, at 10:43 PM, Bob Stewart <b...@evoria.net> wrote:
> > 
> > Hi Scott,
> > D'oh.  Thanks for the correction!  Like I said, I don't do these 
> > calculations often.  
> > 
> > If as Bob Camp implies, the aging isn't from the OXCO, then I'm a bit 
> > stumped.  I do have an op-amp in the EFC string with  a voltage divider for 
> > gain.  The resistors are Panasonic ERA-6AEDxxxV resistors.  Mouser says 
> > they're temperature stable to 25PPM/C, but of course they don't mention an 
> > aging rate.  I don't really see anything else, other than the OCXO, that is 
> > likely to be prone to a linear type of aging.
> 
> OCXO’s don’t age in a linear fashion. At least 90% of them don’t. If you dig 
> into the FCS papers there are various
> curves proposed as models. Mil-O-55310 has one of them as the “official” 
> approach. All of them have the basic 
> issue of mistakenly fitting to to short a time constraint.
> 
> Bob
> 
> >  The aging rate appears to be stable from unit to unit, so naturally I 
> >considered the OCXO first.  
> > 
> > There is one other bit in the EFC string that might be controversial, but I 
> > don't see that it would be a candidate for the symptoms of aging.
> > 
> > Bob
> >  -
> > AE6RV.com
> > 
> > GFS GPSDO list:
> > groups.yahoo.com/neo/groups/GFS-GPSDOs/info
> > 
> >      From: Scott Stobbe <scott.j.sto...@gmail.com>
> > To: Bob Stewart <b...@evoria.net> 
> > Cc: Discussion of Precise Time and Frequency Measurement 
> > <time-nuts@febo.com>
> > Sent: Saturday, November 5, 2016 9:19 PM
> > Subject: Re: [time-nuts] Thermal impact on OCXO
> > 
> > If your DAC spans the full EFC range than 1LSB is 1/2^20 ~ 1 PPM of the EFC 
> > range, and the EFC tuning range is 8/10E6 ~ 1 PPM full scale, so 1 LSB is 
> > ~1PPT. So, if everything else is stable the DAC code reflects changes 
> > solely due to the OCXO, which would be an aging of 24 PPT/day. 
> > On Sat, Nov 5, 2016 at 9:57 PM, Bob Stewart <b...@evoria.net> wrote:
> > 
> > Hi Scott,
> > The 20 bits span about 6 volts.  The EFC range spans about 8Hz (+/-4Hz).  I 
> > don't do these calculations every day, but that's about 4.5PPT?
> > Bob  -- 

Re: [time-nuts] Thermal impact on OCXO

[Bob Camp]

Hi

I would suggest you read the papers on the subject. They are out there. Even 
over a few days
OCXO aging is likely to be non-linear ( => curved, not straight line). On an 
OCXO that is 
warming up, your are dealing with retrace rather than aging. This can have an 
impact for a 
few months after turn on. I have one unit in the basement that took 9 months to 
come out
of retrace after being in storage for “a while”. It was an eBay item so no idea 
just how long 
the power off time was. 

Bob


> On Nov 7, 2016, at 12:47 PM, Bob Stewart <b...@evoria.net> wrote:
> 
> Hi Bob,
> 
> When you say that OCXOs don't age in a linear fashion, what does that mean?  
> IOW, is this a case where it's almost linear over a week, and the 
> non-linearity is only detectable when you consider the longer term?  If 
> that's the case, then it seems reasonable to use the past 3 or so days of 
> data collection to project the near-term behavior; where near-term is less 
> than 3 days into the future.
> 
> Bob
>  
> -
> AE6RV.com
> 
> GFS GPSDO list:
> groups.yahoo.com/neo/groups/GFS-GPSDOs/info
> 
> 
> From: Bob Camp <kb...@n1k.org>
> To: Bob Stewart <b...@evoria.net>; Discussion of precise time and frequency 
> measurement <time-nuts@febo.com> 
> Cc: Scott Stobbe <scott.j.sto...@gmail.com>
> Sent: Monday, November 7, 2016 6:08 AM
> Subject: Re: [time-nuts] Thermal impact on OCXO
> 
> Hi
> 
> 
> > On Nov 5, 2016, at 10:43 PM, Bob Stewart <b...@evoria.net> wrote:
> > 
> > Hi Scott,
> > D'oh.  Thanks for the correction!  Like I said, I don't do these 
> > calculations often.  
> > 
> > If as Bob Camp implies, the aging isn't from the OXCO, then I'm a bit 
> > stumped.  I do have an op-amp in the EFC string with  a voltage divider for 
> > gain.  The resistors are Panasonic ERA-6AEDxxxV resistors.  Mouser says 
> > they're temperature stable to 25PPM/C, but of course they don't mention an 
> > aging rate.  I don't really see anything else, other than the OCXO, that is 
> > likely to be prone to a linear type of aging.
> 
> OCXO’s don’t age in a linear fashion. At least 90% of them don’t. If you dig 
> into the FCS papers there are various
> curves proposed as models. Mil-O-55310 has one of them as the “official” 
> approach. All of them have the basic 
> issue of mistakenly fitting to to short a time constraint.
> 
> Bob
> 
> >  The aging rate appears to be stable from unit to unit, so naturally I 
> > considered the OCXO first.  
> > 
> > There is one other bit in the EFC string that might be controversial, but I 
> > don't see that it would be a candidate for the symptoms of aging.
> > 
> > Bob
> >  -
> > AE6RV.com
> > 
> > GFS GPSDO list:
> > groups.yahoo.com/neo/groups/GFS-GPSDOs/info
> > 
> >  From: Scott Stobbe <scott.j.sto...@gmail.com>
> > To: Bob Stewart <b...@evoria.net> 
> > Cc: Discussion of Precise Time and Frequency Measurement 
> > <time-nuts@febo.com>
> > Sent: Saturday, November 5, 2016 9:19 PM
> > Subject: Re: [time-nuts] Thermal impact on OCXO
> > 
> > If your DAC spans the full EFC range than 1LSB is 1/2^20 ~ 1 PPM of the EFC 
> > range, and the EFC tuning range is 8/10E6 ~ 1 PPM full scale, so 1 LSB is 
> > ~1PPT. So, if everything else is stable the DAC code reflects changes 
> > solely due to the OCXO, which would be an aging of 24 PPT/day. 
> > On Sat, Nov 5, 2016 at 9:57 PM, Bob Stewart <b...@evoria.net> wrote:
> > 
> > Hi Scott,
> > The 20 bits span about 6 volts.  The EFC range spans about 8Hz (+/-4Hz).  I 
> > don't do these calculations every day, but that's about 4.5PPT?
> > Bob  -- -- -
> > AE6RV.com
> > 
> > GFS GPSDO list:
> > groups.yahoo.com/neo/groups/ GFS-GPSDOs/info
> > 
> > 
> > 
> > From: Scott Stobbe <scott.j.sto...@gmail.com>
> > To: Bob Stewart <b...@evoria.net>; Discussion of precise time and frequency 
> > measurement <time-nuts@febo.com> 
> > Sent: Saturday, November 5, 2016 8:38 PM
> > Subject: Re: [time-nuts] Thermal impact on OCXO
> > 
> > I think that's a nice plot, it looks like you have stepped 160 LSB over 7 
> > days or roughly 1 LSB per hour. With a 20bit dac you are trimming maybe 1 
> > ppt/LSB to 4 ppt/LSB? In allan devation terms, the case of 1ppt/LSB, solely 
> > due to drift, you're at 1E-12 at 3600*sqrt(2) = 5000 s, in the case of

Re: [time-nuts] Thermal impact on OCXO

[Bob Camp]

Hi

> On Nov 7, 2016, at 12:45 PM, Chris Caudle  wrote:
> 
> On Mon, November 7, 2016 11:41 am, Chris Caudle wrote:
>> On Mon, November 7, 2016 11:20 am, Bob Stewart wrote:
>>> Either then OCXO is making up for the temperature change
>>> by increasing the temperature
>> 
>> Isn't that the entire point of an OCXO?
> 
> Actually, that is not very precise language on my part.  The OCXO does not
> increase the temperature, it increases the heat input to the oven to
> counteract the decrease in ambient temperature, i.e. attempts to keep the
> internal oven temperature constant.

…. and as it does so, it pulls more current (or less) which changes the voltage
on the ground pin which hits the EFC reference which impacts things to a 
greater or lesser extent depending on the board layout.

Bob


> 
> -- 
> Chris Caudle
> 
> 
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Re: [time-nuts] Thermal impact on OCXO

[Bob Camp]

Hi

Ok, You have a thermocouple junction at the + post on the DVM. You have one at 
the - post on the DVM.
You have a junction at the + connection to the board. You have a junction at 
the - connection to the board. 
There are indeed more than that, but those four are pretty much a sure thing. 
The ones near the hot OCXO
are also worth looking at. 

The metals involved are unknown, so we have to guess a bit. You *can* get some 
alarming junctions with 
very normal test lead materials. Getting low thermal EMF connections requires 
special attention. 
If your junctions have a 1 mV / K coefficient, then you need temperature data 
that is good to 0.001C at each
junction to work out what is going on at the junctions. That assumes you are 
after 1 uV on your “data” plot. 
It’s not terribly hard to get a contact at one (or more than one) junction that 
messes you up.

Bob

> On Nov 7, 2016, at 12:20 PM, Bob Stewart  wrote:
> 
> Hi guys,
> First of all, thanks for the additional responses.  I was a bit angry and 
> rude yesterday, and I figured this thread was over.  Thanks for staying with 
> me.
> I haven't had time to look over the data etc in your responses.  I'll do that 
> and get back to the list if appropriate.
> 
> I spoke to Attila and Azelio offline last nite and from their input, I 
> decided to hook up the 3456A and collect some data, which is in the plot 
> attached.  As usual, I've modified one of my standard plot scripts, so there 
> is some extraneous data that wasn't removed.
> 
> First for our purposes is the thin red line, which is the DAC value locked at 
> 0x734B0.  The orange trace is the temperature adjusted so that each step of 
> 10 on the right hand Y tics is one degree F.  The dark blue trace is the EFC 
> value read by the 3456A.  It has been multiplied by 100,000 and then had 
> 282600 subtracted.  This leaves just the LSD scaled at 1:1 on the right hand 
> Y tics.
> There's something interesting on the far right hand side where the 
> temperature goes low and stays there.  The DVM value follows it down, but 
> then recovers while the temperature stays down.  I'm not sure what to make of 
> this.  Either then OCXO is making up for the temperature change by increasing 
> the temperature, or the 3456 is compensating for it after the fact.  In 
> either case, the EFC seems to only follow the transient temperature changes, 
> and doesn't actually track the temperature on the board.
> 
> So, to my eye, after 14 hours, there is only a dependency on thermal 
> transients.  I'll leave it running for some time yet, but the EFC doesn't 
> seem to be drifting in any meaningful way at this point, other than in 
> relation to temperature changes.
> 
> Note:  I used a shielded twisted-pair with the usual clips attached to ground 
> and EFC in my GPSDO.  On the 3456, the two leads go to the appropriate volts 
> inputs, and the shield goes to the ground input.  The "guard" switch is out, 
> which is the off position.  There is no shield connector on the DUT side.
> 
> Bob
> 
>  -
> AE6RV.com
> 
> GFS GPSDO list:
> groups.yahoo.com/neo/groups/GFS-GPSDOs/info
> 
> 
> 
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> time-nuts mailing list -- time-nuts@febo.com
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Re: [time-nuts] Thermal impact on OCXO

[Chris Caudle]

On Mon, November 7, 2016 11:41 am, Chris Caudle wrote:
> On Mon, November 7, 2016 11:20 am, Bob Stewart wrote:
>> Either then OCXO is making up for the temperature change
>> by increasing the temperature
>
> Isn't that the entire point of an OCXO?

Actually, that is not very precise language on my part.  The OCXO does not
 increase the temperature, it increases the heat input to the oven to
counteract the decrease in ambient temperature, i.e. attempts to keep the
internal oven temperature constant.

-- 
Chris Caudle


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Re: [time-nuts] Thermal impact on OCXO

[Chris Caudle]

On Mon, November 7, 2016 11:20 am, Bob Stewart wrote:
> Either then OCXO is making up for the temperature change
> by increasing the temperature

Isn't that the entire point of an OCXO?

-- 
Chris Caudle




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Re: [time-nuts] Thermal impact on OCXO

[Bob Stewart]

Hi Scott,
I wish I had some long term data, but I don't.  I had initially set out to 
build an accurate GPS frequency reference type of GPSDO.  So, aging wasn't an 
issue.  It's either on and locked or it's not.  So, I didn't worry about 
leaving a unit running for months and collecting aging data.

But then I had this crackpot idea of using the latches in a 7474 to stabilize 
the 1PPS from the receiver to the OCXO.  Tom had a bit of a misunderstanding 
about what I was doing and we had a bit of a discussion until he caught on to 
what I was doing and its limitations.  

But, somewhere along the line, I realized that the idea was sound but my 
implementation was poor.  The basic problem with using a timer in the dsPIC33 
is that they use a PLL to generate the internal clock - even if you supply a 
clock.  That gives you a 1-count jitter in any output pulse you try to create.  
So, I realized that I could use the latches in a 7474 to latch the OCXO to the 
output of a timer on the PIC.  With the PIC running at 40MHz, I have plenty of 
room for the jitter without the worry of a phase slip.  I think I've proved 
that that works, so now I have the possibility of using my system as a time 
server.  And that means I now have to deal with such arcane matters as 
holdover, aging, and generating the time from the OCXO.  The learning curve has 
been a bit steep.
Bob -
AE6RV.com

GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info

  From: Scott Stobbe <scott.j.sto...@gmail.com>
 To: Bob Camp <kb...@n1k.org> 
Cc: Bob Stewart <b...@evoria.net>; Discussion of precise time and frequency 
measurement <time-nuts@febo.com>
 Sent: Monday, November 7, 2016 9:34 AM
 Subject: Re: [time-nuts] Thermal impact on OCXO
   
Here is a sample data point taken from 
http://tycho.usno.navy.mil/ptti/1987papers/Vol%2019_16.pdf; the first that 
showed up on a google search.

         Year   Aging [PPM]  dF/dt [PPT/Day]
            1       180.51       63.884
            2       196.65        31.93
            5          218       12.769
            9       231.69       7.0934
           10       234.15        6.384
           25        255.5       2.5535
If you have a set of coefficients you believe to be representative of your 
OCXO, we can give those a go.
On Mon, Nov 7, 2016 at 7:08 AM, Bob Camp <kb...@n1k.org> wrote:

Hi


> On Nov 5, 2016, at 10:43 PM, Bob Stewart <b...@evoria.net> wrote:
>
> Hi Scott,
> D'oh.  Thanks for the correction!  Like I said, I don't do these calculations 
> often.
>
> If as Bob Camp implies, the aging isn't from the OXCO, then I'm a bit 
> stumped.  I do have an op-amp in the EFC string with  a voltage divider for 
> gain.  The resistors are Panasonic ERA-6AEDxxxV resistors.  Mouser says 
> they're temperature stable to 25PPM/C, but of course they don't mention an 
> aging rate.  I don't really see anything else, other than the OCXO, that is 
> likely to be prone to a linear type of aging.

OCXO’s don’t age in a linear fashion. At least 90% of them don’t. If you dig 
into the FCS papers there are various
curves proposed as models. Mil-O-55310 has one of them as the “official” 
approach. All of them have the basic
issue of mistakenly fitting to to short a time constraint.

Bob

>  The aging rate appears to be stable from unit to unit, so naturally I 
>considered the OCXO first.
>
> There is one other bit in the EFC string that might be controversial, but I 
> don't see that it would be a candidate for the symptoms of aging.
>
> Bob
>  -- -- -
> AE6RV.com
>
> GFS GPSDO list:
> groups.yahoo.com/neo/groups/ GFS-GPSDOs/info
>
>      From: Scott Stobbe <scott.j.sto...@gmail.com>
> To: Bob Stewart <b...@evoria.net>
> Cc: Discussion of Precise Time and Frequency Measurement <time-nuts@febo.com>
> Sent: Saturday, November 5, 2016 9:19 PM
> Subject: Re: [time-nuts] Thermal impact on OCXO
>
> If your DAC spans the full EFC range than 1LSB is 1/2^20 ~ 1 PPM of the EFC 
> range, and the EFC tuning range is 8/10E6 ~ 1 PPM full scale, so 1 LSB is 
> ~1PPT. So, if everything else is stable the DAC code reflects changes solely 
> due to the OCXO, which would be an aging of 24 PPT/day.
> On Sat, Nov 5, 2016 at 9:57 PM, Bob Stewart <b...@evoria.net> wrote:
>
> Hi Scott,
> The 20 bits span about 6 volts.  The EFC range spans about 8Hz (+/-4Hz).  I 
> don't do these calculations every day, but that's about 4.5PPT?
> Bob   -- -- -
> AE6RV.com
>
> GFS GPSDO list:
> groups.yahoo.com/neo/groups/ GFS-GPSDOs/info
>
>
>
> From: Scott Stobbe <scott.j.sto...@gmail.com>
> To: Bob Stewart <b...@evoria.net>; Discussion of prec

Re: [time-nuts] Thermal impact on OCXO

[Bob Stewart]

Hi guys,
First of all, thanks for the additional responses.  I was a bit angry and rude 
yesterday, and I figured this thread was over.  Thanks for staying with me.
I haven't had time to look over the data etc in your responses.  I'll do that 
and get back to the list if appropriate.

I spoke to Attila and Azelio offline last nite and from their input, I decided 
to hook up the 3456A and collect some data, which is in the plot attached.  As 
usual, I've modified one of my standard plot scripts, so there is some 
extraneous data that wasn't removed.

First for our purposes is the thin red line, which is the DAC value locked at 
0x734B0.  The orange trace is the temperature adjusted so that each step of 10 
on the right hand Y tics is one degree F.  The dark blue trace is the EFC value 
read by the 3456A.  It has been multiplied by 100,000 and then had 282600 
subtracted.  This leaves just the LSD scaled at 1:1 on the right hand Y tics.
There's something interesting on the far right hand side where the temperature 
goes low and stays there.  The DVM value follows it down, but then recovers 
while the temperature stays down.  I'm not sure what to make of this.  Either 
then OCXO is making up for the temperature change by increasing the 
temperature, or the 3456 is compensating for it after the fact.  In either 
case, the EFC seems to only follow the transient temperature changes, and 
doesn't actually track the temperature on the board.

So, to my eye, after 14 hours, there is only a dependency on thermal 
transients.  I'll leave it running for some time yet, but the EFC doesn't seem 
to be drifting in any meaningful way at this point, other than in relation to 
temperature changes.

Note:  I used a shielded twisted-pair with the usual clips attached to ground 
and EFC in my GPSDO.  On the 3456, the two leads go to the appropriate volts 
inputs, and the shield goes to the ground input.  The "guard" switch is out, 
which is the off position.  There is no shield connector on the DUT side.

Bob

 -
AE6RV.com

GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info



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Re: [time-nuts] Thermal impact on OCXO

[Scott Stobbe]

Typo, "Aging [PPM]" should read "Aging [PPB]".

On Mon, Nov 7, 2016 at 10:34 AM, Scott Stobbe <scott.j.sto...@gmail.com>
wrote:

> Here is a sample data point taken from http://tycho.usno.navy.mil/
> ptti/1987papers/Vol%2019_16.pdf; the first that showed up on a google
> search.
>
>  Year   Aging [PPM]  dF/dt [PPT/Day]
> 1   180.51   63.884
> 2   196.6531.93
> 5  218   12.769
> 9   231.69   7.0934
>10   234.156.384
>25255.5   2.5535
>
> If you have a set of coefficients you believe to be representative of your
> OCXO, we can give those a go.
>
> On Mon, Nov 7, 2016 at 7:08 AM, Bob Camp <kb...@n1k.org> wrote:
>
>> Hi
>>
>>
>> > On Nov 5, 2016, at 10:43 PM, Bob Stewart <b...@evoria.net> wrote:
>> >
>> > Hi Scott,
>> > D'oh.  Thanks for the correction!  Like I said, I don't do these
>> calculations often.
>> >
>> > If as Bob Camp implies, the aging isn't from the OXCO, then I'm a bit
>> stumped.  I do have an op-amp in the EFC string with  a voltage divider for
>> gain.  The resistors are Panasonic ERA-6AEDxxxV resistors.  Mouser says
>> they're temperature stable to 25PPM/C, but of course they don't mention an
>> aging rate.  I don't really see anything else, other than the OCXO, that is
>> likely to be prone to a linear type of aging.
>>
>> OCXO’s don’t age in a linear fashion. At least 90% of them don’t. If you
>> dig into the FCS papers there are various
>> curves proposed as models. Mil-O-55310 has one of them as the “official”
>> approach. All of them have the basic
>> issue of mistakenly fitting to to short a time constraint.
>>
>> Bob
>>
>> >  The aging rate appears to be stable from unit to unit, so naturally I
>> considered the OCXO first.
>> >
>> > There is one other bit in the EFC string that might be controversial,
>> but I don't see that it would be a candidate for the symptoms of aging.
>> >
>> > Bob
>> >  -
>> > AE6RV.com
>> >
>> > GFS GPSDO list:
>> > groups.yahoo.com/neo/groups/GFS-GPSDOs/info
>> >
>> >  From: Scott Stobbe <scott.j.sto...@gmail.com>
>> > To: Bob Stewart <b...@evoria.net>
>> > Cc: Discussion of Precise Time and Frequency Measurement <
>> time-nuts@febo.com>
>> > Sent: Saturday, November 5, 2016 9:19 PM
>> > Subject: Re: [time-nuts] Thermal impact on OCXO
>> >
>> > If your DAC spans the full EFC range than 1LSB is 1/2^20 ~ 1 PPM of the
>> EFC range, and the EFC tuning range is 8/10E6 ~ 1 PPM full scale, so 1 LSB
>> is ~1PPT. So, if everything else is stable the DAC code reflects changes
>> solely due to the OCXO, which would be an aging of 24 PPT/day.
>> > On Sat, Nov 5, 2016 at 9:57 PM, Bob Stewart <b...@evoria.net> wrote:
>> >
>> > Hi Scott,
>> > The 20 bits span about 6 volts.  The EFC range spans about 8Hz
>> (+/-4Hz).  I don't do these calculations every day, but that's about 4.5PPT?
>> > Bob   -- --
>> -
>> > AE6RV.com
>> >
>> > GFS GPSDO list:
>> > groups.yahoo.com/neo/groups/ GFS-GPSDOs/info
>> >
>> >
>> >
>> > From: Scott Stobbe <scott.j.sto...@gmail.com>
>> > To: Bob Stewart <b...@evoria.net>; Discussion of precise time and
>> frequency measurement <time-nuts@febo.com>
>> > Sent: Saturday, November 5, 2016 8:38 PM
>> > Subject: Re: [time-nuts] Thermal impact on OCXO
>> >
>> > I think that's a nice plot, it looks like you have stepped 160 LSB over
>> 7 days or roughly 1 LSB per hour. With a 20bit dac you are trimming maybe 1
>> ppt/LSB to 4 ppt/LSB? In allan devation terms, the case of 1ppt/LSB, solely
>> due to drift, you're at 1E-12 at 3600*sqrt(2) = 5000 s, in the case of
>> 4ppt/hour your at 1E-12 at 1280 s. Seems reasonable.
>> > On Sat, Nov 5, 2016 at 2:47 PM, Bob Stewart <b...@evoria.net> wrote:
>> >
>> > Oh dear.  I attached the wrong file.  Here's the correct one.
>> >  - -- --
>> > AE6RV.com
>> >
>> > GFS GPSDO list:
>> > groups.yahoo.com/neo/groups/ GFS-GPSDOs/info
>> >
>> >
>> >
>> > __ _
>> > 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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>> ailman/listinfo/time-nuts
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Re: [time-nuts] Thermal impact on OCXO

[Scott Stobbe]

Here is a sample data point taken from
http://tycho.usno.navy.mil/ptti/1987papers/Vol%2019_16.pdf; the first that
showed up on a google search.

 Year   Aging [PPM]  dF/dt [PPT/Day]
1   180.51   63.884
2   196.6531.93
5  218   12.769
9   231.69   7.0934
   10   234.156.384
   25255.5   2.5535

If you have a set of coefficients you believe to be representative of your
OCXO, we can give those a go.

On Mon, Nov 7, 2016 at 7:08 AM, Bob Camp <kb...@n1k.org> wrote:

> Hi
>
>
> > On Nov 5, 2016, at 10:43 PM, Bob Stewart <b...@evoria.net> wrote:
> >
> > Hi Scott,
> > D'oh.  Thanks for the correction!  Like I said, I don't do these
> calculations often.
> >
> > If as Bob Camp implies, the aging isn't from the OXCO, then I'm a bit
> stumped.  I do have an op-amp in the EFC string with  a voltage divider for
> gain.  The resistors are Panasonic ERA-6AEDxxxV resistors.  Mouser says
> they're temperature stable to 25PPM/C, but of course they don't mention an
> aging rate.  I don't really see anything else, other than the OCXO, that is
> likely to be prone to a linear type of aging.
>
> OCXO’s don’t age in a linear fashion. At least 90% of them don’t. If you
> dig into the FCS papers there are various
> curves proposed as models. Mil-O-55310 has one of them as the “official”
> approach. All of them have the basic
> issue of mistakenly fitting to to short a time constraint.
>
> Bob
>
> >  The aging rate appears to be stable from unit to unit, so naturally I
> considered the OCXO first.
> >
> > There is one other bit in the EFC string that might be controversial,
> but I don't see that it would be a candidate for the symptoms of aging.
> >
> > Bob
> >  -
> > AE6RV.com
> >
> > GFS GPSDO list:
> > groups.yahoo.com/neo/groups/GFS-GPSDOs/info
> >
> >  From: Scott Stobbe <scott.j.sto...@gmail.com>
> > To: Bob Stewart <b...@evoria.net>
> > Cc: Discussion of Precise Time and Frequency Measurement <
> time-nuts@febo.com>
> > Sent: Saturday, November 5, 2016 9:19 PM
> > Subject: Re: [time-nuts] Thermal impact on OCXO
> >
> > If your DAC spans the full EFC range than 1LSB is 1/2^20 ~ 1 PPM of the
> EFC range, and the EFC tuning range is 8/10E6 ~ 1 PPM full scale, so 1 LSB
> is ~1PPT. So, if everything else is stable the DAC code reflects changes
> solely due to the OCXO, which would be an aging of 24 PPT/day.
> > On Sat, Nov 5, 2016 at 9:57 PM, Bob Stewart <b...@evoria.net> wrote:
> >
> > Hi Scott,
> > The 20 bits span about 6 volts.  The EFC range spans about 8Hz
> (+/-4Hz).  I don't do these calculations every day, but that's about 4.5PPT?
> > Bob   -- -- -
> > AE6RV.com
> >
> > GFS GPSDO list:
> > groups.yahoo.com/neo/groups/ GFS-GPSDOs/info
> >
> >
> >
> > From: Scott Stobbe <scott.j.sto...@gmail.com>
> > To: Bob Stewart <b...@evoria.net>; Discussion of precise time and
> frequency measurement <time-nuts@febo.com>
> > Sent: Saturday, November 5, 2016 8:38 PM
> > Subject: Re: [time-nuts] Thermal impact on OCXO
> >
> > I think that's a nice plot, it looks like you have stepped 160 LSB over
> 7 days or roughly 1 LSB per hour. With a 20bit dac you are trimming maybe 1
> ppt/LSB to 4 ppt/LSB? In allan devation terms, the case of 1ppt/LSB, solely
> due to drift, you're at 1E-12 at 3600*sqrt(2) = 5000 s, in the case of
> 4ppt/hour your at 1E-12 at 1280 s. Seems reasonable.
> > On Sat, Nov 5, 2016 at 2:47 PM, Bob Stewart <b...@evoria.net> wrote:
> >
> > Oh dear.  I attached the wrong file.  Here's the correct one.
> >  - -- --
> > AE6RV.com
> >
> > GFS GPSDO list:
> > groups.yahoo.com/neo/groups/ GFS-GPSDOs/info
> >
> >
> >
> > __ _
> > 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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> mailman/listinfo/time-nuts
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Re: [time-nuts] Thermal impact on OCXO

[Bob Camp]

Hi


> On Nov 5, 2016, at 10:43 PM, Bob Stewart <b...@evoria.net> wrote:
> 
> Hi Scott,
> D'oh.  Thanks for the correction!  Like I said, I don't do these calculations 
> often.  
> 
> If as Bob Camp implies, the aging isn't from the OXCO, then I'm a bit 
> stumped.  I do have an op-amp in the EFC string with  a voltage divider for 
> gain.  The resistors are Panasonic ERA-6AEDxxxV resistors.  Mouser says 
> they're temperature stable to 25PPM/C, but of course they don't mention an 
> aging rate.  I don't really see anything else, other than the OCXO, that is 
> likely to be prone to a linear type of aging.

OCXO’s don’t age in a linear fashion. At least 90% of them don’t. If you dig 
into the FCS papers there are various
curves proposed as models. Mil-O-55310 has one of them as the “official” 
approach. All of them have the basic 
issue of mistakenly fitting to to short a time constraint.

Bob

>  The aging rate appears to be stable from unit to unit, so naturally I 
> considered the OCXO first.  
> 
> There is one other bit in the EFC string that might be controversial, but I 
> don't see that it would be a candidate for the symptoms of aging.
> 
> Bob
>  -
> AE6RV.com
> 
> GFS GPSDO list:
> groups.yahoo.com/neo/groups/GFS-GPSDOs/info
> 
>  From: Scott Stobbe <scott.j.sto...@gmail.com>
> To: Bob Stewart <b...@evoria.net> 
> Cc: Discussion of Precise Time and Frequency Measurement <time-nuts@febo.com>
> Sent: Saturday, November 5, 2016 9:19 PM
> Subject: Re: [time-nuts] Thermal impact on OCXO
> 
> If your DAC spans the full EFC range than 1LSB is 1/2^20 ~ 1 PPM of the EFC 
> range, and the EFC tuning range is 8/10E6 ~ 1 PPM full scale, so 1 LSB is 
> ~1PPT. So, if everything else is stable the DAC code reflects changes solely 
> due to the OCXO, which would be an aging of 24 PPT/day. 
> On Sat, Nov 5, 2016 at 9:57 PM, Bob Stewart <b...@evoria.net> wrote:
> 
> Hi Scott,
> The 20 bits span about 6 volts.  The EFC range spans about 8Hz (+/-4Hz).  I 
> don't do these calculations every day, but that's about 4.5PPT?
> Bob   -- -- -
> AE6RV.com
> 
> GFS GPSDO list:
> groups.yahoo.com/neo/groups/ GFS-GPSDOs/info
> 
> 
> 
> From: Scott Stobbe <scott.j.sto...@gmail.com>
> To: Bob Stewart <b...@evoria.net>; Discussion of precise time and frequency 
> measurement <time-nuts@febo.com> 
> Sent: Saturday, November 5, 2016 8:38 PM
> Subject: Re: [time-nuts] Thermal impact on OCXO
> 
> I think that's a nice plot, it looks like you have stepped 160 LSB over 7 
> days or roughly 1 LSB per hour. With a 20bit dac you are trimming maybe 1 
> ppt/LSB to 4 ppt/LSB? In allan devation terms, the case of 1ppt/LSB, solely 
> due to drift, you're at 1E-12 at 3600*sqrt(2) = 5000 s, in the case of 
> 4ppt/hour your at 1E-12 at 1280 s. Seems reasonable.
> On Sat, Nov 5, 2016 at 2:47 PM, Bob Stewart <b...@evoria.net> wrote:
> 
> Oh dear.  I attached the wrong file.  Here's the correct one.
>  - -- --
> AE6RV.com
> 
> GFS GPSDO list:
> groups.yahoo.com/neo/groups/ GFS-GPSDOs/info
> 
> 
>
> __ _
> 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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Re: [time-nuts] Thermal impact on OCXO

[Scott Stobbe]

Well bob's comments & caution are accurate, everything drifts. In your
case, if the OCXO is rock solid then you would see a 160 PPM change on the
EFC line over 7 days which is a 1mV change on your 6 V full scale, which is
fairly easy to measure if you have a 6 1/2 digit DMM.

On Sat, Nov 5, 2016 at 10:43 PM, Bob Stewart <b...@evoria.net> wrote:

> Hi Scott,
>
> D'oh.  Thanks for the correction!  Like I said, I don't do these
> calculations often.
>
> If as Bob Camp implies, the aging isn't from the OXCO, then I'm a bit
> stumped.  I do have an op-amp in the EFC string with  a voltage divider for
> gain.  The resistors are Panasonic ERA-6AEDxxxV resistors.  Mouser says
> they're temperature stable to 25PPM/C, but of course they don't mention an
> aging rate.  I don't really see anything else, other than the OCXO, that is
> likely to be prone to a linear type of aging.  The aging rate appears to be
> stable from unit to unit, so naturally I considered the OCXO first.
>
> There is one other bit in the EFC string that might be controversial, but
> I don't see that it would be a candidate for the symptoms of aging.
>
> Bob
>
>
> -
> AE6RV.com
>
> GFS GPSDO list:
> groups.yahoo.com/neo/groups/GFS-GPSDOs/info
>
>
> --
> *From:* Scott Stobbe <scott.j.sto...@gmail.com>
> *To:* Bob Stewart <b...@evoria.net>
> *Cc:* Discussion of Precise Time and Frequency Measurement <
> time-nuts@febo.com>
> *Sent:* Saturday, November 5, 2016 9:19 PM
> *Subject:* Re: [time-nuts] Thermal impact on OCXO
>
> If your DAC spans the full EFC range than 1LSB is 1/2^20 ~ 1 PPM of the
> EFC range, and the EFC tuning range is 8/10E6 ~ 1 PPM full scale, so 1 LSB
> is ~1PPT. So, if everything else is stable the DAC code reflects
> changes solely due to the OCXO, which would be an aging of 24 PPT/day.
>
> On Sat, Nov 5, 2016 at 9:57 PM, Bob Stewart <b...@evoria.net> wrote:
>
> Hi Scott,
>
> The 20 bits span about 6 volts.  The EFC range spans about 8Hz (+/-4Hz).
> I don't do these calculations every day, but that's about 4.5PPT?
>
> Bob
>
> -- -- -
> AE6RV.com
>
> GFS GPSDO list:
> groups.yahoo.com/neo/groups/ GFS-GPSDOs/info
> <http://groups.yahoo.com/neo/groups/GFS-GPSDOs/info?soc_src=mail_trk=ma>
>
>
>
>
> --
> *From:* Scott Stobbe <scott.j.sto...@gmail.com>
> *To:* Bob Stewart <b...@evoria.net>; Discussion of precise time and
> frequency measurement <time-nuts@febo.com>
> *Sent:* Saturday, November 5, 2016 8:38 PM
> *Subject:* Re: [time-nuts] Thermal impact on OCXO
>
> I think that's a nice plot, it looks like you have stepped 160 LSB over 7
> days or roughly 1 LSB per hour. With a 20bit dac you are trimming maybe 1
> ppt/LSB to 4 ppt/LSB? In allan devation terms, the case of 1ppt/LSB, solely
> due to drift, you're at 1E-12 at 3600*sqrt(2) = 5000 s, in the case of
> 4ppt/hour your at 1E-12 at 1280 s. Seems reasonable.
>
> On Sat, Nov 5, 2016 at 2:47 PM, Bob Stewart <b...@evoria.net> wrote:
>
> Oh dear.  I attached the wrong file.  Here's the correct one.
>  - -- --
> AE6RV.com
>
> GFS GPSDO list:
> groups.yahoo.com/neo/groups/ GFS-GPSDOs/info
> <http://groups.yahoo.com/neo/groups/GFS-GPSDOs/info?soc_src=mail_trk=ma>
>
>
>
>
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> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/
> mailman/listinfo/time-nuts
> <https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts>
> and follow the instructions there.
>
>
>
>
>
>
>
>
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Re: [time-nuts] Thermal impact on OCXO

[Bob Stewart]

Hi Bob,
Sadly, all I have is what I have.  The GSPDOs are in an unvented Hammond 
aluminum case.  I've got a thermistor on the bottom side of the board.  
Actually, it's right below the PIC, so the temperature from the PIC would seem 
to be the driver of what I see.  Except that I've also done some experiments 
with putting a thermistor on the receiver plugin, as well as on the OCXO, and 
right next to the EFC amp.  I didn't see anything obviously different in the 
temperature swings.  So, from my POV, since the drift is about the same on each 
unit, it's either from the OCXO or the voltage divider; which is a 15K/16K 
divider.
Bob
 -
AE6RV.com

GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info

  From: Bob Camp <kb...@n1k.org>
 To: Bob Stewart <b...@evoria.net> 
Cc: Discussion of Precise Time and Frequency Measurement <time-nuts@febo.com>
 Sent: Saturday, November 5, 2016 9:43 PM
 Subject: Re: [time-nuts] Thermal impact on OCXO
   
Hi

If you go back to my previous list, all the things that have a tempco also age. 
Holding temperature
over weeks or months is not at all easy …. You have gradients between parts so 
it is impossible to
look at temperature (or aging) as a single effect. In the case of a fairly 
normal room, temperature may
well peak in one area when it hits minimum in another area. Everything has 
hysteresis so it’s a never
ending process of perturbation and response. 

The 3456 is not immune to any of this. It’s only rated as an 8 ppm device over 
24 hours. Over 90 days 
it’s about 3X that.  The leads you connect it up to the DUT with are not easy 
to do. Coming 
up with a “perfect” answer at the 20 bit level is tough. A proper solution 
would take the sum of the errors
down below 0.2 ppm. That can be done, but it’s a *lot* of work. 

Bob


> On Nov 5, 2016, at 10:06 PM, Bob Stewart <b...@evoria.net> wrote:
> 
> Hi Bob,
> 
> Could you expound on "so far below a number of issues"?
> 
> In any case, your post implies that something else is aging.  I'm using an 
> ADR4533A as my voltage reference.  That feeds an AD8638 op-amp driving an 
> MMBTA pass transistor.  That pretty much leaves the divider resistors on 
> an AD8638 in the EFC string.  But, aging is aging from my point of view.  I 
> guess I could prove that by hooking the EFC to my 3456A and plotting that 
> over a few days.
> 
> Bob
>  
> -
> AE6RV.com
> 
> GFS GPSDO list:
> groups.yahoo.com/neo/groups/GFS-GPSDOs/info
> 
> 
> From: Bob Camp <kb...@n1k.org>
> To: Bob Stewart <b...@evoria.net> 
> Sent: Saturday, November 5, 2016 8:46 PM
> Subject: Re: [time-nuts] Thermal impact on OCXO
> 
> Hi
> 
> My experience is that the aging on these oscillators is so far below a number 
> of issues
> that you will not be able to see it in under a year on a > 10 year old unit. 
> 
> Bob
> 
> > On Nov 5, 2016, at 9:06 PM, Bob Stewart <b...@evoria.net> wrote:
> > 
> > Hi Bob,
> > 
> > But will any of the things you mentioned show up as a more or less linear 
> > march downhill at about 1 step per hour over the course of 7 days?  In 
> > fact, I think Dan's units show about the same -1 per hour, and he's had 
> > them running continuously for many months.  I believe you use these same 
> > OCXOs, Bob.  They're Trimble 34310-T units salvaged from China.  What's 
> > been your experience with them over the long run as far as aging is 
> > concerned?
> > 
> > Bob
> > 
> > -
> > AE6RV.com
> > 
> > GFS GPSDO list:
> > groups.yahoo.com/neo/groups/GFS-GPSDOs/info
> > 
> > 
> > From: Bob Camp <kb...@n1k.org>
> > To: Discussion of precise time and frequency measurement 
> > <time-nuts@febo.com> 
> > Sent: Saturday, November 5, 2016 7:37 PM
> > Subject: Re: [time-nuts] Thermal impact on OCXO
> > 
> > Hi
> > 
> > 2^20 is roughly 1 ppm. It is about 5 uV on a 5V line or 2.5 uV on a 2.5 V 
> > EFC center. 
> > 
> >    A DAC that does 100 ppm / C is a pretty typical part. 10 ppm / C is 
> >unusually good
> >    A “good” voltage reference might do 2 ppm / C
> >    A very typical room will swing around +/- 2C without much going on.
> >    Open the door in the room or open a window and 10C is not unusual. 
> >    Grabbing a normal banana plug with your fingers will give you > 10 uV, 
> >other thermocouples are running around
> >    A DAC with < 10 uV of noise in the 0.01 to 1 Hz region is unusually good
> > 
> > That’s just look

Re: [time-nuts] Thermal impact on OCXO

[Bob Stewart]

Hi Scott,
D'oh.  Thanks for the correction!  Like I said, I don't do these calculations 
often.  

If as Bob Camp implies, the aging isn't from the OXCO, then I'm a bit stumped.  
I do have an op-amp in the EFC string with  a voltage divider for gain.  The 
resistors are Panasonic ERA-6AEDxxxV resistors.  Mouser says they're 
temperature stable to 25PPM/C, but of course they don't mention an aging rate.  
I don't really see anything else, other than the OCXO, that is likely to be 
prone to a linear type of aging.  The aging rate appears to be stable from unit 
to unit, so naturally I considered the OCXO first.  

There is one other bit in the EFC string that might be controversial, but I 
don't see that it would be a candidate for the symptoms of aging.

Bob
 -
AE6RV.com

GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info

  From: Scott Stobbe <scott.j.sto...@gmail.com>
 To: Bob Stewart <b...@evoria.net> 
Cc: Discussion of Precise Time and Frequency Measurement <time-nuts@febo.com>
 Sent: Saturday, November 5, 2016 9:19 PM
 Subject: Re: [time-nuts] Thermal impact on OCXO
   
If your DAC spans the full EFC range than 1LSB is 1/2^20 ~ 1 PPM of the EFC 
range, and the EFC tuning range is 8/10E6 ~ 1 PPM full scale, so 1 LSB is 
~1PPT. So, if everything else is stable the DAC code reflects changes solely 
due to the OCXO, which would be an aging of 24 PPT/day. 
On Sat, Nov 5, 2016 at 9:57 PM, Bob Stewart <b...@evoria.net> wrote:

Hi Scott,
The 20 bits span about 6 volts.  The EFC range spans about 8Hz (+/-4Hz).  I 
don't do these calculations every day, but that's about 4.5PPT?
Bob   -- -- -
AE6RV.com

GFS GPSDO list:
groups.yahoo.com/neo/groups/ GFS-GPSDOs/info

 

 From: Scott Stobbe <scott.j.sto...@gmail.com>
 To: Bob Stewart <b...@evoria.net>; Discussion of precise time and frequency 
measurement <time-nuts@febo.com> 
 Sent: Saturday, November 5, 2016 8:38 PM
 Subject: Re: [time-nuts] Thermal impact on OCXO
  
I think that's a nice plot, it looks like you have stepped 160 LSB over 7 days 
or roughly 1 LSB per hour. With a 20bit dac you are trimming maybe 1 ppt/LSB to 
4 ppt/LSB? In allan devation terms, the case of 1ppt/LSB, solely due to drift, 
you're at 1E-12 at 3600*sqrt(2) = 5000 s, in the case of 4ppt/hour your at 
1E-12 at 1280 s. Seems reasonable.
On Sat, Nov 5, 2016 at 2:47 PM, Bob Stewart <b...@evoria.net> wrote:

Oh dear.  I attached the wrong file.  Here's the correct one.
 - -- --
AE6RV.com

GFS GPSDO list:
groups.yahoo.com/neo/groups/ GFS-GPSDOs/info


   
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Re: [time-nuts] Thermal impact on OCXO

[Bob Camp]

Hi

If you go back to my previous list, all the things that have a tempco also age. 
Holding temperature
over weeks or months is not at all easy …. You have gradients between parts so 
it is impossible to
look at temperature (or aging) as a single effect. In the case of a fairly 
normal room, temperature may
well peak in one area when it hits minimum in another area. Everything has 
hysteresis so it’s a never
ending process of perturbation and response. 

The 3456 is not immune to any of this. It’s only rated as an 8 ppm device over 
24 hours. Over 90 days 
it’s about 3X that.  The leads you connect it up to the DUT with are not easy 
to do. Coming 
up with a “perfect” answer at the 20 bit level is tough. A proper solution 
would take the sum of the errors
down below 0.2 ppm. That can be done, but it’s a *lot* of work. 

Bob


> On Nov 5, 2016, at 10:06 PM, Bob Stewart <b...@evoria.net> wrote:
> 
> Hi Bob,
> 
> Could you expound on "so far below a number of issues"?
> 
> In any case, your post implies that something else is aging.  I'm using an 
> ADR4533A as my voltage reference.  That feeds an AD8638 op-amp driving an 
> MMBTA pass transistor.  That pretty much leaves the divider resistors on 
> an AD8638 in the EFC string.  But, aging is aging from my point of view.  I 
> guess I could prove that by hooking the EFC to my 3456A and plotting that 
> over a few days.
> 
> Bob
>  
> -
> AE6RV.com
> 
> GFS GPSDO list:
> groups.yahoo.com/neo/groups/GFS-GPSDOs/info
> 
> 
> From: Bob Camp <kb...@n1k.org>
> To: Bob Stewart <b...@evoria.net> 
> Sent: Saturday, November 5, 2016 8:46 PM
> Subject: Re: [time-nuts] Thermal impact on OCXO
> 
> Hi
> 
> My experience is that the aging on these oscillators is so far below a number 
> of issues
> that you will not be able to see it in under a year on a > 10 year old unit. 
> 
> Bob
> 
> > On Nov 5, 2016, at 9:06 PM, Bob Stewart <b...@evoria.net> wrote:
> > 
> > Hi Bob,
> > 
> > But will any of the things you mentioned show up as a more or less linear 
> > march downhill at about 1 step per hour over the course of 7 days?  In 
> > fact, I think Dan's units show about the same -1 per hour, and he's had 
> > them running continuously for many months.  I believe you use these same 
> > OCXOs, Bob.  They're Trimble 34310-T units salvaged from China.  What's 
> > been your experience with them over the long run as far as aging is 
> > concerned?
> > 
> > Bob
> > 
> > -
> > AE6RV.com
> > 
> > GFS GPSDO list:
> > groups.yahoo.com/neo/groups/GFS-GPSDOs/info
> > 
> > 
> > From: Bob Camp <kb...@n1k.org>
> > To: Discussion of precise time and frequency measurement 
> > <time-nuts@febo.com> 
> > Sent: Saturday, November 5, 2016 7:37 PM
> > Subject: Re: [time-nuts] Thermal impact on OCXO
> > 
> > Hi
> > 
> > 2^20 is roughly 1 ppm. It is about 5 uV on a 5V line or 2.5 uV on a 2.5 V 
> > EFC center. 
> > 
> >A DAC that does 100 ppm / C is a pretty typical part. 10 ppm / C is 
> > unusually good
> >A “good” voltage reference might do 2 ppm / C
> >A very typical room will swing around +/- 2C without much going on.
> >Open the door in the room or open a window and 10C is not unusual. 
> >Grabbing a normal banana plug with your fingers will give you > 10 uV, 
> > other thermocouples are running around
> >A DAC with < 10 uV of noise in the 0.01 to 1 Hz region is unusually good
> > 
> > That’s just looking at the easy to measure part of the system. A few 
> > hundred uV delta on
> > the PCB between the OCXO ground pin and “ground” from grabbing the OCXO is 
> > harder
> > to measure, but also pretty typical. It sums right into the EFC line. 
> > 
> > It’s not a rabbit hole so much as the details of the design at the level 
> > you have chosen
> > to look at. 
> > 
> > Bob
> > 
> > > On Nov 5, 2016, at 8:10 PM, Bob Stewart <b...@evoria.net> wrote:
> > > 
> > > This seems to be turning into a rabbit hole from which there can be no 
> > > possible return.  With no evidence, you question my competence and cast 
> > > aspersions on my testing methodology.  I give up.  
> > > 
> > > Have a nice day.
> > > 
> > > Bob -
> > > AE6RV.com
> > > 
> > > GFS GPSDO list:
> > > groups.yahoo.co

Re: [time-nuts] Thermal impact on OCXO

[Scott Stobbe]

If your DAC spans the full EFC range than 1LSB is 1/2^20 ~ 1 PPM of the EFC
range, and the EFC tuning range is 8/10E6 ~ 1 PPM full scale, so 1 LSB is
~1PPT. So, if everything else is stable the DAC code reflects
changes solely due to the OCXO, which would be an aging of 24 PPT/day.

On Sat, Nov 5, 2016 at 9:57 PM, Bob Stewart <b...@evoria.net> wrote:

> Hi Scott,
>
> The 20 bits span about 6 volts.  The EFC range spans about 8Hz (+/-4Hz).
> I don't do these calculations every day, but that's about 4.5PPT?
>
> Bob
>
> -
> AE6RV.com
>
> GFS GPSDO list:
> groups.yahoo.com/neo/groups/GFS-GPSDOs/info
>
>
>
>
> --
> *From:* Scott Stobbe <scott.j.sto...@gmail.com>
> *To:* Bob Stewart <b...@evoria.net>; Discussion of precise time and
> frequency measurement <time-nuts@febo.com>
> *Sent:* Saturday, November 5, 2016 8:38 PM
> *Subject:* Re: [time-nuts] Thermal impact on OCXO
>
> I think that's a nice plot, it looks like you have stepped 160 LSB over 7
> days or roughly 1 LSB per hour. With a 20bit dac you are trimming maybe 1
> ppt/LSB to 4 ppt/LSB? In allan devation terms, the case of 1ppt/LSB, solely
> due to drift, you're at 1E-12 at 3600*sqrt(2) = 5000 s, in the case of
> 4ppt/hour your at 1E-12 at 1280 s. Seems reasonable.
>
> On Sat, Nov 5, 2016 at 2:47 PM, Bob Stewart <b...@evoria.net> wrote:
>
> Oh dear.  I attached the wrong file.  Here's the correct one.
>  - -- --
> AE6RV.com
>
> GFS GPSDO list:
> groups.yahoo.com/neo/groups/ GFS-GPSDOs/info
> <http://groups.yahoo.com/neo/groups/GFS-GPSDOs/info?soc_src=mail_trk=ma>
>
>
>
>
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> mailman/listinfo/time-nuts
> <https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts>
> and follow the instructions there.
>
>
>
>
>
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Re: [time-nuts] Thermal impact on OCXO

[Bob Stewart]

Hi Bob,
Could you expound on "so far below a number of issues"?
In any case, your post implies that something else is aging.  I'm using an 
ADR4533A as my voltage reference.  That feeds an AD8638 op-amp driving an 
MMBTA pass transistor.  That pretty much leaves the divider resistors on an 
AD8638 in the EFC string.  But, aging is aging from my point of view.  I guess 
I could prove that by hooking the EFC to my 3456A and plotting that over a few 
days.

Bob
 -
AE6RV.com

GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info

  From: Bob Camp <kb...@n1k.org>
 To: Bob Stewart <b...@evoria.net> 
 Sent: Saturday, November 5, 2016 8:46 PM
 Subject: Re: [time-nuts] Thermal impact on OCXO
   
Hi

My experience is that the aging on these oscillators is so far below a number 
of issues
that you will not be able to see it in under a year on a > 10 year old unit. 

Bob

> On Nov 5, 2016, at 9:06 PM, Bob Stewart <b...@evoria.net> wrote:
> 
> Hi Bob,
> 
> But will any of the things you mentioned show up as a more or less linear 
> march downhill at about 1 step per hour over the course of 7 days?  In fact, 
> I think Dan's units show about the same -1 per hour, and he's had them 
> running continuously for many months.  I believe you use these same OCXOs, 
> Bob.  They're Trimble 34310-T units salvaged from China.  What's been your 
> experience with them over the long run as far as aging is concerned?
> 
> Bob
> 
> -
> AE6RV.com
> 
> GFS GPSDO list:
> groups.yahoo.com/neo/groups/GFS-GPSDOs/info
> 
> 
> From: Bob Camp <kb...@n1k.org>
> To: Discussion of precise time and frequency measurement <time-nuts@febo.com> 
> Sent: Saturday, November 5, 2016 7:37 PM
> Subject: Re: [time-nuts] Thermal impact on OCXO
> 
> Hi
> 
> 2^20 is roughly 1 ppm. It is about 5 uV on a 5V line or 2.5 uV on a 2.5 V EFC 
> center. 
> 
>    A DAC that does 100 ppm / C is a pretty typical part. 10 ppm / C is 
>unusually good
>    A “good” voltage reference might do 2 ppm / C
>    A very typical room will swing around +/- 2C without much going on.
>    Open the door in the room or open a window and 10C is not unusual. 
>    Grabbing a normal banana plug with your fingers will give you > 10 uV, 
>other thermocouples are running around
>    A DAC with < 10 uV of noise in the 0.01 to 1 Hz region is unusually good
> 
> That’s just looking at the easy to measure part of the system. A few hundred 
> uV delta on
> the PCB between the OCXO ground pin and “ground” from grabbing the OCXO is 
> harder
> to measure, but also pretty typical. It sums right into the EFC line. 
> 
> It’s not a rabbit hole so much as the details of the design at the level you 
> have chosen
> to look at. 
> 
> Bob
> 
> > On Nov 5, 2016, at 8:10 PM, Bob Stewart <b...@evoria.net> wrote:
> > 
> > This seems to be turning into a rabbit hole from which there can be no 
> > possible return.  With no evidence, you question my competence and cast 
> > aspersions on my testing methodology.  I give up.  
> > 
> > Have a nice day.
> > 
> > Bob -
> > AE6RV.com
> > 
> > GFS GPSDO list:
> > groups.yahoo.com/neo/groups/GFS-GPSDOs/info
> > 
> >      From: Azelio Boriani <azelio.bori...@gmail.com>
> > To: Discussion of precise time and frequency measurement 
> > <time-nuts@febo.com> 
> > Sent: Saturday, November 5, 2016 7:02 PM
> > Subject: Re: [time-nuts] Thermal impact on OCXO
> > 
> > ...with a 20bit DAC, a suitable voltage reference for that DAC and an 
> > HP3458...
> > 
> > On Sun, Nov 6, 2016 at 12:39 AM, Bob Stewart <b...@evoria.net> wrote:
> >> Hi Hal,
> >> 
> >> With a 20 bit DAC, even a small aging rate is going to show up.  I'll let 
> >> the one GPSDO cook for a month or so and see what it shows then.  I'll 
> >> also pull the data from the log file and see if I can see any correlation 
> >> between the temperature and the EFC over time.  IOW, for data points 
> >> separated by 3.5 days, does the temperature difference between the two 
> >> point seem to play a large part of the change in the recorded DAC value.
> >> 
> >> The graph was made from the logging data sent to the PC.  But, the 
> >> firmware doesn't have access to historical data on the PC, so something is 
> >> needed for aging calculations.  Tom mentioned here recently about the 
> >> 58503A GPSDO saving 64 hours of data for it's aging ca

Re: [time-nuts] Thermal impact on OCXO

[Bob Stewart]

Hi Scott,
The 20 bits span about 6 volts.  The EFC range spans about 8Hz (+/-4Hz).  I 
don't do these calculations every day, but that's about 4.5PPT?
Bob   -
AE6RV.com

GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info

 

 From: Scott Stobbe <scott.j.sto...@gmail.com>
 To: Bob Stewart <b...@evoria.net>; Discussion of precise time and frequency 
measurement <time-nuts@febo.com> 
 Sent: Saturday, November 5, 2016 8:38 PM
 Subject: Re: [time-nuts] Thermal impact on OCXO
  
I think that's a nice plot, it looks like you have stepped 160 LSB over 7 days 
or roughly 1 LSB per hour. With a 20bit dac you are trimming maybe 1 ppt/LSB to 
4 ppt/LSB? In allan devation terms, the case of 1ppt/LSB, solely due to drift, 
you're at 1E-12 at 3600*sqrt(2) = 5000 s, in the case of 4ppt/hour your at 
1E-12 at 1280 s. Seems reasonable.
On Sat, Nov 5, 2016 at 2:47 PM, Bob Stewart <b...@evoria.net> wrote:

Oh dear.  I attached the wrong file.  Here's the correct one.
 - -- --
AE6RV.com

GFS GPSDO list:
groups.yahoo.com/neo/groups/ GFS-GPSDOs/info


   
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Re: [time-nuts] Thermal impact on OCXO

[Scott Stobbe]

I think that's a nice plot, it looks like you have stepped 160 LSB over 7
days or roughly 1 LSB per hour. With a 20bit dac you are trimming maybe 1
ppt/LSB to 4 ppt/LSB? In allan devation terms, the case of 1ppt/LSB, solely
due to drift, you're at 1E-12 at 3600*sqrt(2) = 5000 s, in the case of
4ppt/hour your at 1E-12 at 1280 s. Seems reasonable.

On Sat, Nov 5, 2016 at 2:47 PM, Bob Stewart  wrote:

> Oh dear.  I attached the wrong file.  Here's the correct one.
>  -
> AE6RV.com
>
> GFS GPSDO list:
> groups.yahoo.com/neo/groups/GFS-GPSDOs/info
>
>
>
>
> ___
> 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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Re: [time-nuts] Thermal impact on OCXO

[Bob Stewart]

Hi Bob,
But will any of the things you mentioned show up as a more or less linear march 
downhill at about 1 step per hour over the course of 7 days?  In fact, I think 
Dan's units show about the same -1 per hour, and he's had them running 
continuously for many months.  I believe you use these same OCXOs, Bob.  
They're Trimble 34310-T units salvaged from China.  What's been your experience 
with them over the long run as far as aging is concerned?

Bob

-
AE6RV.com

GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info

  From: Bob Camp <kb...@n1k.org>
 To: Discussion of precise time and frequency measurement <time-nuts@febo.com> 
 Sent: Saturday, November 5, 2016 7:37 PM
 Subject: Re: [time-nuts] Thermal impact on OCXO
   
Hi

2^20 is roughly 1 ppm. It is about 5 uV on a 5V line or 2.5 uV on a 2.5 V EFC 
center. 

    A DAC that does 100 ppm / C is a pretty typical part. 10 ppm / C is 
unusually good
    A “good” voltage reference might do 2 ppm / C
    A very typical room will swing around +/- 2C without much going on.
    Open the door in the room or open a window and 10C is not unusual. 
    Grabbing a normal banana plug with your fingers will give you > 10 uV, 
other thermocouples are running around
    A DAC with < 10 uV of noise in the 0.01 to 1 Hz region is unusually good

That’s just looking at the easy to measure part of the system. A few hundred uV 
delta on
the PCB between the OCXO ground pin and “ground” from grabbing the OCXO is 
harder
to measure, but also pretty typical. It sums right into the EFC line. 

It’s not a rabbit hole so much as the details of the design at the level you 
have chosen
to look at. 

Bob

> On Nov 5, 2016, at 8:10 PM, Bob Stewart <b...@evoria.net> wrote:
> 
> This seems to be turning into a rabbit hole from which there can be no 
> possible return.  With no evidence, you question my competence and cast 
> aspersions on my testing methodology.  I give up.  
> 
> Have a nice day.
> 
> Bob -
> AE6RV.com
> 
> GFS GPSDO list:
> groups.yahoo.com/neo/groups/GFS-GPSDOs/info
> 
>      From: Azelio Boriani <azelio.bori...@gmail.com>
> To: Discussion of precise time and frequency measurement <time-nuts@febo.com> 
> Sent: Saturday, November 5, 2016 7:02 PM
> Subject: Re: [time-nuts] Thermal impact on OCXO
> 
> ...with a 20bit DAC, a suitable voltage reference for that DAC and an 
> HP3458...
> 
> On Sun, Nov 6, 2016 at 12:39 AM, Bob Stewart <b...@evoria.net> wrote:
>> Hi Hal,
>> 
>> With a 20 bit DAC, even a small aging rate is going to show up.  I'll let 
>> the one GPSDO cook for a month or so and see what it shows then.  I'll also 
>> pull the data from the log file and see if I can see any correlation between 
>> the temperature and the EFC over time.  IOW, for data points separated by 
>> 3.5 days, does the temperature difference between the two point seem to play 
>> a large part of the change in the recorded DAC value.
>> 
>> The graph was made from the logging data sent to the PC.  But, the firmware 
>> doesn't have access to historical data on the PC, so something is needed for 
>> aging calculations.  Tom mentioned here recently about the 58503A GPSDO 
>> saving 64 hours of data for it's aging calculations.  So, I just added a few 
>> hours to that to get to 3.5 days of history in the GPSDO.
>> Bob -
>> AE6RV.com
>> 
>> GFS GPSDO list:
>> groups.yahoo.com/neo/groups/GFS-GPSDOs/info
>> 
>>      From: Hal Murray <hmur...@megapathdsl.net>
>>  To: Bob Stewart <b...@evoria.net>
>> Cc: Hal Murray <hmur...@megapathdsl.net>
>>  Sent: Saturday, November 5, 2016 6:23 PM
>>  Subject: Re: [time-nuts] Thermal impact on OCXO
>> 
>>> The OCXO has been hot for a number of months.
>> 
>> Then I don't understand why it is still aging that much.
>> 
>> 
>>> I changed the firmware to save the DAC voltage every 30 minutes for 3.5
>>> day
>> 
>> That's not very long.
>> 
>> How did you make the graph?  You had to get the data out to a place where you
>> can plot it somehow.  If you can do that, why are you "saving" the data?  I
>> assume you have a serial port to a PC or something like that.
>> 
>> 
>>> The fuzz in the temperature line is, indeed, the HVAC cycling
>> 
>> You could try putting a box over the unit to see if that slows down the
>> temperature changes.
>> 
>> Mostly, you are trying to block air flow.
>> 
>> 
>> 
>> --
&

Re: [time-nuts] Thermal impact on OCXO

[Bob Camp]

Hi

2^20 is roughly 1 ppm. It is about 5 uV on a 5V line or 2.5 uV on a 2.5 V EFC 
center. 

 A DAC that does 100 ppm / C is a pretty typical part. 10 ppm / C is 
unusually good
 A “good” voltage reference might do 2 ppm / C
 A very typical room will swing around +/- 2C without much going on.
 Open the door in the room or open a window and 10C is not unusual. 
 Grabbing a normal banana plug with your fingers will give you > 10 uV, 
other thermocouples are running around
 A DAC with < 10 uV of noise in the 0.01 to 1 Hz region is unusually good

That’s just looking at the easy to measure part of the system. A few hundred uV 
delta on
the PCB between the OCXO ground pin and “ground” from grabbing the OCXO is 
harder
to measure, but also pretty typical. It sums right into the EFC line. 

It’s not a rabbit hole so much as the details of the design at the level you 
have chosen
to look at. 

Bob

> On Nov 5, 2016, at 8:10 PM, Bob Stewart <b...@evoria.net> wrote:
> 
> This seems to be turning into a rabbit hole from which there can be no 
> possible return.  With no evidence, you question my competence and cast 
> aspersions on my testing methodology.  I give up.  
> 
> Have a nice day.
> 
> Bob -
> AE6RV.com
> 
> GFS GPSDO list:
> groups.yahoo.com/neo/groups/GFS-GPSDOs/info
> 
>  From: Azelio Boriani <azelio.bori...@gmail.com>
> To: Discussion of precise time and frequency measurement <time-nuts@febo.com> 
> Sent: Saturday, November 5, 2016 7:02 PM
> Subject: Re: [time-nuts] Thermal impact on OCXO
> 
> ...with a 20bit DAC, a suitable voltage reference for that DAC and an 
> HP3458...
> 
> On Sun, Nov 6, 2016 at 12:39 AM, Bob Stewart <b...@evoria.net> wrote:
>> Hi Hal,
>> 
>> With a 20 bit DAC, even a small aging rate is going to show up.  I'll let 
>> the one GPSDO cook for a month or so and see what it shows then.  I'll also 
>> pull the data from the log file and see if I can see any correlation between 
>> the temperature and the EFC over time.  IOW, for data points separated by 
>> 3.5 days, does the temperature difference between the two point seem to play 
>> a large part of the change in the recorded DAC value.
>> 
>> The graph was made from the logging data sent to the PC.  But, the firmware 
>> doesn't have access to historical data on the PC, so something is needed for 
>> aging calculations.  Tom mentioned here recently about the 58503A GPSDO 
>> saving 64 hours of data for it's aging calculations.  So, I just added a few 
>> hours to that to get to 3.5 days of history in the GPSDO.
>> Bob -
>> AE6RV.com
>> 
>> GFS GPSDO list:
>> groups.yahoo.com/neo/groups/GFS-GPSDOs/info
>> 
>>   From: Hal Murray <hmur...@megapathdsl.net>
>>   To: Bob Stewart <b...@evoria.net>
>> Cc: Hal Murray <hmur...@megapathdsl.net>
>>   Sent: Saturday, November 5, 2016 6:23 PM
>>   Subject: Re: [time-nuts] Thermal impact on OCXO
>> 
>>> The OCXO has been hot for a number of months.
>> 
>> Then I don't understand why it is still aging that much.
>> 
>> 
>>> I changed the firmware to save the DAC voltage every 30 minutes for 3.5
>>> day
>> 
>> That's not very long.
>> 
>> How did you make the graph?  You had to get the data out to a place where you
>> can plot it somehow.  If you can do that, why are you "saving" the data?  I
>> assume you have a serial port to a PC or something like that.
>> 
>> 
>>> The fuzz in the temperature line is, indeed, the HVAC cycling
>> 
>> You could try putting a box over the unit to see if that slows down the
>> temperature changes.
>> 
>> Mostly, you are trying to block air flow.
>> 
>> 
>> 
>> --
>> These are my opinions.  I hate spam.
>> 
>> 
>> 
>> 
>> 
>> 
>> ___
>> 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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Re: [time-nuts] Thermal impact on OCXO

[Bob Stewart]

This seems to be turning into a rabbit hole from which there can be no possible 
return.  With no evidence, you question my competence and cast aspersions on my 
testing methodology.  I give up.  

Have a nice day.

Bob -
AE6RV.com

GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info

  From: Azelio Boriani <azelio.bori...@gmail.com>
 To: Discussion of precise time and frequency measurement <time-nuts@febo.com> 
 Sent: Saturday, November 5, 2016 7:02 PM
 Subject: Re: [time-nuts] Thermal impact on OCXO
   
...with a 20bit DAC, a suitable voltage reference for that DAC and an HP3458...

On Sun, Nov 6, 2016 at 12:39 AM, Bob Stewart <b...@evoria.net> wrote:
> Hi Hal,
>
> With a 20 bit DAC, even a small aging rate is going to show up.  I'll let the 
> one GPSDO cook for a month or so and see what it shows then.  I'll also pull 
> the data from the log file and see if I can see any correlation between the 
> temperature and the EFC over time.  IOW, for data points separated by 3.5 
> days, does the temperature difference between the two point seem to play a 
> large part of the change in the recorded DAC value.
>
> The graph was made from the logging data sent to the PC.  But, the firmware 
> doesn't have access to historical data on the PC, so something is needed for 
> aging calculations.  Tom mentioned here recently about the 58503A GPSDO 
> saving 64 hours of data for it's aging calculations.  So, I just added a few 
> hours to that to get to 3.5 days of history in the GPSDO.
> Bob -
> AE6RV.com
>
> GFS GPSDO list:
> groups.yahoo.com/neo/groups/GFS-GPSDOs/info
>
>      From: Hal Murray <hmur...@megapathdsl.net>
>  To: Bob Stewart <b...@evoria.net>
> Cc: Hal Murray <hmur...@megapathdsl.net>
>  Sent: Saturday, November 5, 2016 6:23 PM
>  Subject: Re: [time-nuts] Thermal impact on OCXO
>
>> The OCXO has been hot for a number of months.
>
> Then I don't understand why it is still aging that much.
>
>
>> I changed the firmware to save the DAC voltage every 30 minutes for 3.5
>> day
>
> That's not very long.
>
> How did you make the graph?  You had to get the data out to a place where you
> can plot it somehow.  If you can do that, why are you "saving" the data?  I
> assume you have a serial port to a PC or something like that.
>
>
>> The fuzz in the temperature line is, indeed, the HVAC cycling
>
> You could try putting a box over the unit to see if that slows down the
> temperature changes.
>
> Mostly, you are trying to block air flow.
>
>
>
> --
> These are my opinions.  I hate spam.
>
>
>
>
>
>
> ___
> 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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Re: [time-nuts] Thermal impact on OCXO

[Azelio Boriani]

...with a 20bit DAC, a suitable voltage reference for that DAC and an HP3458...

On Sun, Nov 6, 2016 at 12:39 AM, Bob Stewart <b...@evoria.net> wrote:
> Hi Hal,
>
> With a 20 bit DAC, even a small aging rate is going to show up.  I'll let the 
> one GPSDO cook for a month or so and see what it shows then.  I'll also pull 
> the data from the log file and see if I can see any correlation between the 
> temperature and the EFC over time.  IOW, for data points separated by 3.5 
> days, does the temperature difference between the two point seem to play a 
> large part of the change in the recorded DAC value.
>
> The graph was made from the logging data sent to the PC.  But, the firmware 
> doesn't have access to historical data on the PC, so something is needed for 
> aging calculations.  Tom mentioned here recently about the 58503A GPSDO 
> saving 64 hours of data for it's aging calculations.  So, I just added a few 
> hours to that to get to 3.5 days of history in the GPSDO.
> Bob -
> AE6RV.com
>
> GFS GPSDO list:
> groups.yahoo.com/neo/groups/GFS-GPSDOs/info
>
>   From: Hal Murray <hmur...@megapathdsl.net>
>  To: Bob Stewart <b...@evoria.net>
> Cc: Hal Murray <hmur...@megapathdsl.net>
>  Sent: Saturday, November 5, 2016 6:23 PM
>  Subject: Re: [time-nuts] Thermal impact on OCXO
>
>> The OCXO has been hot for a number of months.
>
> Then I don't understand why it is still aging that much.
>
>
>> I changed the firmware to save the DAC voltage every 30 minutes for 3.5
>> day
>
> That's not very long.
>
> How did you make the graph?  You had to get the data out to a place where you
> can plot it somehow.  If you can do that, why are you "saving" the data?  I
> assume you have a serial port to a PC or something like that.
>
>
>> The fuzz in the temperature line is, indeed, the HVAC cycling
>
> You could try putting a box over the unit to see if that slows down the
> temperature changes.
>
> Mostly, you are trying to block air flow.
>
>
>
> --
> These are my opinions.  I hate spam.
>
>
>
>
>
>
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Re: [time-nuts] Thermal impact on OCXO

[Bob Stewart]

Hi Hal,

With a 20 bit DAC, even a small aging rate is going to show up.  I'll let the 
one GPSDO cook for a month or so and see what it shows then.  I'll also pull 
the data from the log file and see if I can see any correlation between the 
temperature and the EFC over time.  IOW, for data points separated by 3.5 days, 
does the temperature difference between the two point seem to play a large part 
of the change in the recorded DAC value.

The graph was made from the logging data sent to the PC.  But, the firmware 
doesn't have access to historical data on the PC, so something is needed for 
aging calculations.  Tom mentioned here recently about the 58503A GPSDO saving 
64 hours of data for it's aging calculations.  So, I just added a few hours to 
that to get to 3.5 days of history in the GPSDO.
Bob -
AE6RV.com

GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info

  From: Hal Murray <hmur...@megapathdsl.net>
 To: Bob Stewart <b...@evoria.net> 
Cc: Hal Murray <hmur...@megapathdsl.net>
 Sent: Saturday, November 5, 2016 6:23 PM
 Subject: Re: [time-nuts] Thermal impact on OCXO
   
> The OCXO has been hot for a number of months.

Then I don't understand why it is still aging that much.


> I changed the firmware to save the DAC voltage every 30 minutes for 3.5
> day

That's not very long.

How did you make the graph?  You had to get the data out to a place where you 
can plot it somehow.  If you can do that, why are you "saving" the data?  I 
assume you have a serial port to a PC or something like that.


> The fuzz in the temperature line is, indeed, the HVAC cycling

You could try putting a box over the unit to see if that slows down the 
temperature changes.

Mostly, you are trying to block air flow.



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Re: [time-nuts] Thermal impact on OCXO

[Bob Stewart]

Oh dear.  I attached the wrong file.  Here's the correct one.
 -
AE6RV.com

GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info


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Re: [time-nuts] Thermal impact on OCXO

[Bob Stewart]

Hi Hal,
I don't think I understand your question.  So, I've attached a plot and you can 
tell me if that gives you anything to work with.  This uses my standard 
plotting script, so there are things you aren't interested in.  But, this is a 
plot of one unit from startup on the night of 10/29 through right now.

The blue band is the plot of the TIC in my GPSDO.  The TIC is affected by 
noise, which is filtered by the PID software, as well as an LPF in the EFC 
line.  So, the OCXO output is much more stable than the blue band would 
indicate.  The red trace (the DAC voltage in hex as read on the left) is what's 
important for this discussion.  Notice the steady decrease in the DAC voltage 
over time.  The orange trace is the temperature.  For scaling, use the right 
side numbers divided by 10 to get delta degrees F.  IOW, from 0 to 10 would be 
a 1 degree Fahrenheit temperature change.  Other items of interest on the plot 
are TDOP, number of sats seen, and number of sats used.

So, looking at the plot, it seems clear that time dominates the change in the 
DAC voltage.  But, there is a noticeable impact from temperature change.  That 
impact is not linear, except that small changes do seem to affect it in a 
linear manner.
As to how I'm calibrating this:  I've got several GPSDOs running.  One is being 
used as the 10MHz reference for the 5370A.  Another is being used as the 1PPS 
reference for the one I'm testing.  Since these are essentially identical 
units, though with different firmware, the impact of ionospheric change on the 
results is muted.  So, what the testing boils down to is bringing up a unit 
with the firmware to be tested, and allowing it to be well locked before 
disconnecting the antenna.  Generally I leave it overnight and reconnect the 
antenna some time in the morning.  So, this gives me two figures:  One is how 
far the unit drifts over some time period, as well as the rate of recovery once 
the antenna is restored.  

I'd include a Timelab plot except that I don't have the two units skewed enough 
in time to allow for 1uS of drift.  So, the time reported on Timelab would be 
misleading due to the 5370 slipping into "one sample every two seconds" mode as 
the phase difference exceeds the time skew.  For the next test I think I'll 
skew the DUT by 2uS so that I can get a clean plot.

Anyway, does any of this answer your question?  If not, let me know what's 
missing.

Bob -
AE6RV.com

GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info

  From: Hal Murray <hmur...@megapathdsl.net>
 To: Bob Stewart <b...@evoria.net>; Discussion of precise time and frequency 
measurement <time-nuts@febo.com> 
Cc: hmur...@megapathdsl.net
 Sent: Saturday, November 5, 2016 12:55 PM
 Subject: Re: [time-nuts] Thermal impact on OCXO
   

> At 12 hours of holdover...
> I think I'll need a lot more understanding of the impact of aging vs 
> temperature

At that timescale, I'd expect aging to be lost in the noise.

How are you calibrating things?


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PlotCal.sh
Description: application/shellscript
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Re: [time-nuts] Thermal impact on OCXO

[Hal Murray]

> At 12 hours of holdover...
> I think I'll need a lot more understanding of the impact of aging vs 
> temperature

At that timescale, I'd expect aging to be lost in the noise.

How are you calibrating things?


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Re: [time-nuts] Thermal impact on OCXO

[Bob Stewart]

Hi Bob,
Ugh!  40C to 70C is not something I plan to deal with.  If I were selling to a 
commercial market, that would be a different story.  But at my price point, not 
gonna happen.  But it does bring up the point that I need to have some sort of 
idea of what I'm willing to manage.

Bob -
AE6RV.com

GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info

  From: Bob Camp <kb...@n1k.org>
 To: Bob Stewart <b...@evoria.net>; Discussion of precise time and frequency 
measurement <time-nuts@febo.com> 
 Sent: Saturday, November 5, 2016 11:54 AM
 Subject: Re: [time-nuts] Thermal impact on OCXO
   
Hi

Remember - most holdover specs also include a delta temperature (like 40 to 
70C) during the 
holdover period ….

Bob

> On Nov 5, 2016, at 12:15 PM, Bob Stewart <b...@evoria.net> wrote:
> 
> Hi Scott and Bob and others,
> I keep telling myself that I won't get involved with the temperature problem, 
> and yet for some reason I keep going down that rabbit hole.  It seems to me 
> that it's one thing to correct well enough to stay on frequency within some 
> degree of accuracy, and yet another to try to also correct for phase.  The 
> reality is that what I have is good enough for now.  At 12 hours of holdover, 
> I'm usually a bit over 1uS out of phase.  Maybe I could better that, but I 
> think I'll need a lot more understanding of the impact of aging vs 
> temperature before I can get there.
> 
> Bob -
> AE6RV.com
> 
> GFS GPSDO list:
> groups.yahoo.com/neo/groups/GFS-GPSDOs/info
> 
>      From: Scott Stobbe <scott.j.sto...@gmail.com>
> To: Bob Stewart <b...@evoria.net>; Discussion of precise time and frequency 
> measurement <time-nuts@febo.com> 
> Sent: Saturday, November 5, 2016 10:54 AM
> Subject: Re: [time-nuts] Thermal impact on OCXO
> 
> Sounds like you already realized this. Phase is the integral of frequency and 
> the derivative of phase (phase rate) is frequency. So if you go from nominal 
> frequency - slow - nominal or equivalently nominal frequency - fast - nominal 
> the phase integrates up/down.
> It would be a little more complicated for an ocxo since it is servoing the xo 
> temperature, you would need to know the disturbance rejection (gain, time 
> constant for a simple Pi controller) to try and feedfoward correct the phase 
> error.
> 
> On Friday, 4 November 2016, Bob Stewart <b...@evoria.net> wrote:
> 
> OK, never mind.  I see the obvious.  Phase changes faster at a higher 
> frequency than it does at a lower frequency.
> 
> Bob
>  - -- --
> AE6RV.com
> 
> GFS GPSDO list:
> groups.yahoo.com/neo/groups/ GFS-GPSDOs/info
> 
>      From: Bob Stewart <b...@evoria.net>
>  To: Discussion of Precise Time and Frequency Measurement <time-nuts@febo.com>
>  Sent: Friday, November 4, 2016 8:56 PM
>  Subject: [time-nuts] Thermal impact on OCXO
> 
> In the general case, is the impact of changing the ambient temperature around 
> an OCXO from, say, 40C to 41C the same as changing it from 41C to 40C all 
> else being equal?  IOW, if I somehow have the same temperature ramp over the 
> same time period in both directions, will I wind up with the same frequency 
> and phase, or will the frequency revert but at some phase difference?
> 
> Bob - AE6RV
>  - -- --
> AE6RV.com
> 
> GFS GPSDO list:
> groups.yahoo.com/neo/groups/ GFS-GPSDOs/info
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Re: [time-nuts] Thermal impact on OCXO

[Bob Camp]

Hi

Remember - most holdover specs also include a delta temperature (like 40 to 
70C) during the 
holdover period ….

Bob

> On Nov 5, 2016, at 12:15 PM, Bob Stewart <b...@evoria.net> wrote:
> 
> Hi Scott and Bob and others,
> I keep telling myself that I won't get involved with the temperature problem, 
> and yet for some reason I keep going down that rabbit hole.  It seems to me 
> that it's one thing to correct well enough to stay on frequency within some 
> degree of accuracy, and yet another to try to also correct for phase.  The 
> reality is that what I have is good enough for now.  At 12 hours of holdover, 
> I'm usually a bit over 1uS out of phase.  Maybe I could better that, but I 
> think I'll need a lot more understanding of the impact of aging vs 
> temperature before I can get there.
> 
> Bob -
> AE6RV.com
> 
> GFS GPSDO list:
> groups.yahoo.com/neo/groups/GFS-GPSDOs/info
> 
>  From: Scott Stobbe <scott.j.sto...@gmail.com>
> To: Bob Stewart <b...@evoria.net>; Discussion of precise time and frequency 
> measurement <time-nuts@febo.com> 
> Sent: Saturday, November 5, 2016 10:54 AM
> Subject: Re: [time-nuts] Thermal impact on OCXO
> 
> Sounds like you already realized this. Phase is the integral of frequency and 
> the derivative of phase (phase rate) is frequency. So if you go from nominal 
> frequency - slow - nominal or equivalently nominal frequency - fast - nominal 
> the phase integrates up/down.
> It would be a little more complicated for an ocxo since it is servoing the xo 
> temperature, you would need to know the disturbance rejection (gain, time 
> constant for a simple Pi controller) to try and feedfoward correct the phase 
> error.
> 
> On Friday, 4 November 2016, Bob Stewart <b...@evoria.net> wrote:
> 
> OK, never mind.  I see the obvious.  Phase changes faster at a higher 
> frequency than it does at a lower frequency.
> 
> Bob
>  - -- --
> AE6RV.com
> 
> GFS GPSDO list:
> groups.yahoo.com/neo/groups/ GFS-GPSDOs/info
> 
>   From: Bob Stewart <b...@evoria.net>
>  To: Discussion of Precise Time and Frequency Measurement <time-nuts@febo.com>
>  Sent: Friday, November 4, 2016 8:56 PM
>  Subject: [time-nuts] Thermal impact on OCXO
> 
> In the general case, is the impact of changing the ambient temperature around 
> an OCXO from, say, 40C to 41C the same as changing it from 41C to 40C all 
> else being equal?  IOW, if I somehow have the same temperature ramp over the 
> same time period in both directions, will I wind up with the same frequency 
> and phase, or will the frequency revert but at some phase difference?
> 
> Bob - AE6RV
>  - -- --
> AE6RV.com
> 
> GFS GPSDO list:
> groups.yahoo.com/neo/groups/ GFS-GPSDOs/info
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> 
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Re: [time-nuts] Thermal impact on OCXO

[Bob Stewart]

Hi Scott and Bob and others,
I keep telling myself that I won't get involved with the temperature problem, 
and yet for some reason I keep going down that rabbit hole.  It seems to me 
that it's one thing to correct well enough to stay on frequency within some 
degree of accuracy, and yet another to try to also correct for phase.  The 
reality is that what I have is good enough for now.  At 12 hours of holdover, 
I'm usually a bit over 1uS out of phase.  Maybe I could better that, but I 
think I'll need a lot more understanding of the impact of aging vs temperature 
before I can get there.

Bob -
AE6RV.com

GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info

  From: Scott Stobbe <scott.j.sto...@gmail.com>
 To: Bob Stewart <b...@evoria.net>; Discussion of precise time and frequency 
measurement <time-nuts@febo.com> 
 Sent: Saturday, November 5, 2016 10:54 AM
 Subject: Re: [time-nuts] Thermal impact on OCXO
   
Sounds like you already realized this. Phase is the integral of frequency and 
the derivative of phase (phase rate) is frequency. So if you go from nominal 
frequency - slow - nominal or equivalently nominal frequency - fast - nominal 
the phase integrates up/down.
It would be a little more complicated for an ocxo since it is servoing the xo 
temperature, you would need to know the disturbance rejection (gain, time 
constant for a simple Pi controller) to try and feedfoward correct the phase 
error.

On Friday, 4 November 2016, Bob Stewart <b...@evoria.net> wrote:

OK, never mind.  I see the obvious.  Phase changes faster at a higher frequency 
than it does at a lower frequency.

Bob
 - -- --
AE6RV.com

GFS GPSDO list:
groups.yahoo.com/neo/groups/ GFS-GPSDOs/info

      From: Bob Stewart <b...@evoria.net>
 To: Discussion of Precise Time and Frequency Measurement <time-nuts@febo.com>
 Sent: Friday, November 4, 2016 8:56 PM
 Subject: [time-nuts] Thermal impact on OCXO

In the general case, is the impact of changing the ambient temperature around 
an OCXO from, say, 40C to 41C the same as changing it from 41C to 40C all else 
being equal?  IOW, if I somehow have the same temperature ramp over the same 
time period in both directions, will I wind up with the same frequency and 
phase, or will the frequency revert but at some phase difference?

Bob - AE6RV
 - -- --
AE6RV.com

GFS GPSDO list:
groups.yahoo.com/neo/groups/ GFS-GPSDOs/info
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Re: [time-nuts] Thermal impact on OCXO

[Scott Stobbe]

Sounds like you already realized this. Phase is the integral of frequency
and the derivative of phase (phase rate) is frequency. So if you go from
nominal frequency - slow - nominal or equivalently nominal frequency - fast
- nominal the phase integrates up/down.

It would be a little more complicated for an ocxo since it is servoing the
xo temperature, you would need to know the disturbance rejection (gain,
time constant for a simple Pi controller) to try and feedfoward correct the
phase error.

On Friday, 4 November 2016, Bob Stewart <b...@evoria.net> wrote:

> OK, never mind.  I see the obvious.  Phase changes faster at a higher
> frequency than it does at a lower frequency.
>
> Bob
>  -
> AE6RV.com
>
> GFS GPSDO list:
> groups.yahoo.com/neo/groups/GFS-GPSDOs/info
>
>   From: Bob Stewart <b...@evoria.net <javascript:;>>
>  To: Discussion of Precise Time and Frequency Measurement <
> time-nuts@febo.com <javascript:;>>
>  Sent: Friday, November 4, 2016 8:56 PM
>  Subject: [time-nuts] Thermal impact on OCXO
>
> In the general case, is the impact of changing the ambient temperature
> around an OCXO from, say, 40C to 41C the same as changing it from 41C to
> 40C all else being equal?  IOW, if I somehow have the same temperature ramp
> over the same time period in both directions, will I wind up with the same
> frequency and phase, or will the frequency revert but at some phase
> difference?
>
> Bob - AE6RV
>  -
> AE6RV.com
>
> GFS GPSDO list:
> groups.yahoo.com/neo/groups/GFS-GPSDOs/info
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Re: [time-nuts] Thermal impact on OCXO

[Bob Camp]

Hi

You have a first order, second order and third order coefficient to the 
temperature rate dependance
on a crystal.  Since the second order term is a square, it does not care about 
the sign of the 
rate.

Bob

> On Nov 4, 2016, at 9:56 PM, Bob Stewart  wrote:
> 
> In the general case, is the impact of changing the ambient temperature around 
> an OCXO from, say, 40C to 41C the same as changing it from 41C to 40C all 
> else being equal?  IOW, if I somehow have the same temperature ramp over the 
> same time period in both directions, will I wind up with the same frequency 
> and phase, or will the frequency revert but at some phase difference?
> 
> Bob - AE6RV
>  -
> AE6RV.com
> 
> GFS GPSDO list:
> groups.yahoo.com/neo/groups/GFS-GPSDOs/info
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Re: [time-nuts] Thermal impact on OCXO

[jimlux]

On 11/4/16 6:56 PM, Bob Stewart wrote:

In the general case, is the impact of changing the ambient temperature around 
an OCXO from, say, 40C to 41C the same as changing it from 41C to 40C all else 
being equal?  IOW, if I somehow have the same temperature ramp over the same 
time period in both directions, will I wind up with the same frequency and 
phase, or will the frequency revert but at some phase difference?

most oscillators exhibit some degree of hysteresis - the mechanical 
mounting puts stresses on the crystal, if nothing else.




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Re: [time-nuts] Thermal impact on OCXO

[Bob Stewart]

OK, never mind.  I see the obvious.  Phase changes faster at a higher frequency 
than it does at a lower frequency.

Bob
 -
AE6RV.com

GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info

  From: Bob Stewart <b...@evoria.net>
 To: Discussion of Precise Time and Frequency Measurement <time-nuts@febo.com> 
 Sent: Friday, November 4, 2016 8:56 PM
 Subject: [time-nuts] Thermal impact on OCXO
   
In the general case, is the impact of changing the ambient temperature around 
an OCXO from, say, 40C to 41C the same as changing it from 41C to 40C all else 
being equal?  IOW, if I somehow have the same temperature ramp over the same 
time period in both directions, will I wind up with the same frequency and 
phase, or will the frequency revert but at some phase difference?

Bob - AE6RV
 -
AE6RV.com

GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info
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[time-nuts] Thermal impact on OCXO

[Bob Stewart]

In the general case, is the impact of changing the ambient temperature around 
an OCXO from, say, 40C to 41C the same as changing it from 41C to 40C all else 
being equal?  IOW, if I somehow have the same temperature ramp over the same 
time period in both directions, will I wind up with the same frequency and 
phase, or will the frequency revert but at some phase difference?

Bob - AE6RV
 -
AE6RV.com

GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info
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