[time-nuts] This may be my new favorite old oscillator

[Mark Sims]

If you connect the Thunderbolt EFC voltage up to the oscillator,  Lady 
Heather's oscillator autotune () command does a good job of characterizing 
the EFC slope/gain (Hz/volt) characteristics of a 10 MHz oscillator.  It will 
step the EFC voltage up and down a few millivolts around the 10 MHz point and 
calculate the oscillator EFC gain.

-

> I love using a Thunderbolt/NTBW50AA for making frequency measurements this
way.  I remove the OCXO, and insert the 10MHz from the DUT.  Then disable
disciplining so the DAC voltage doesn't try to chase the open loop
oscillator
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Re: [time-nuts] Subject: Re: I love the smell of tantalum in the morning

[Charles Steinmetz]

Jeremy wrote:


Amazon indicates the different lenses simply snap in and out. Any idea how
easy/practical this is? It it better to have two completely different
visors each holding different magnification lenses?


Quite easy -- the lens plates are held onto the front of the visor by 
two plastic pins that just snap in and out.  You can see the heads from 
the outside (as opposed to the eye-side) at the far left and right of 
the lens plate.


That said, IMO it is always more convenient to have each lens plate 
mounted in its own visor.


I have to say that contrary to the original post, I find the 3.5x lenses 
WAY too strong for SMD work.  The working distance is only 3-4" -- not 
nearly enough to work safely with hot tools, or comfortably.  Even the 
2.5x lenses, with 6-8" of working distance, are too strong for me.  For 
anything that requires working on the object you're looking at (as 
opposed to just examining it), I recommend staying at 2x and below (2x, 
1.75x, 1.5x).


Finally, Donegan makes two series of lenses -- rectangular plastic 
frames with optical glass lenses, and rectangular plastic frames with 
molded-in plastic lenses.  The glass lenses are more expensive, but the 
large difference in optical quality makes them the only real choice, IMO.


At substantially greater cost, you can get "surgical loupes" (a/k/a 
"dental loupes").  These have compound optical systems, so you can get 
longer working distances at a particular magnification than you can with 
a single lens (like the OptiVisor has).


Best regards,

Charles


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[time-nuts] This may be my new favorite old oscillator

[Skip Withrow]

Hello Time-Nuts,

I recently acquired an HP 5065A rubidium oscillator (with 10811 10MHz
OCXO). I think I pretty much have it running now and have been letting it
cook for the last couple of weeks.  I offset the C-field + and - and
measured the frequency to calculate the C-field sensitivity. My unit came
out to 1.96x10E-12 per dial unit, which agrees with the manual stated
2x10E-12. So, calculated the on frequency C-field value and dialed it in.

Attached is a Lady Heather plot of the frequency over the last 3 days.  The
purple line is the 1pps plot with the vertical scale being 20ns per
division.  So, the unit is off about 125ns over the last 72 hours (running
about 4.92x10E-13 slow).  So my C-field setting is off about 1/4 of a
division, but I think I'm going to leave well enough alone.

The yellow line is the NTBW50AA temperature sensor, and you can clearly see
when the furnace cycles.  I was away for the weekend, and you can also
clearly see when I came home this evening and turned up the heat.  At the
very end of the plot is the spike when I turned on the lights in the shop.

I love using a Thunderbolt/NTBW50AA for making frequency measurements this
way.  I remove the OCXO, and insert the 10MHz from the DUT.  Then disable
disciplining so the DAC voltage doesn't try to chase the open loop
oscillator.  Of course the short-term performance looks worse than it
actually is because of measuring against GPS, but the long-term
measurements are very good.

I want to log this unit at regular intervals to see what the aging looks
like.  Also need to do some measurements against the cesium to see what the
short-term performance might be.  But, I think this oscillator will be a
good reference in many cases in lieu of using the cesium.

Regards,
Skip Withrow
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Re: [time-nuts] Subject: Re: I love the smell of tantalum in the morning

[Jeremy Nichols]

Amazon indicates the different lenses simply snap in and out. Any idea how
easy/practical this is? It it better to have two completely different
visors each holding different magnification lenses?

Jeremy


On Monday, November 7, 2016, Scott Hamilton  wrote:

> https://www.amazon.com/Donegan-OptiVISOR-Headband-
> Magnifier-Magnification/dp/B0068OSIIS/ref=sr_1_4?ie=UTF8&
> qid=1478548961=8-4=headset+magnifiers
>
> Finally, I can offer a contribution to this list. I have found the Donegan
> magnifiers in the above Amazon link with 3.5X lenses to be very comfortable
> and indespensible for SMD work. Different lenses can be obtained for other
> work but the 3.5X is a minimum for me.
>
> Scott Hamilton
> W3SEH
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> and follow the instructions there.
>


-- 
Sent from Gmail Mobile
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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  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  >
> *To:* Bob Camp  >
> *Cc:* Bob Stewart  >; Discussion of precise
> time and frequency measurement  >
> *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  > wrote:
>
> Hi
>
>
> > On Nov 5, 2016, at 10:43 PM, Bob Stewart  > 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  >
> > To: Bob Stewart  >
> > Cc: Discussion of Precise Time and Frequency 

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 
 To: Bob Stewart ; Discussion of precise time and frequency 
measurement  
 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] Questionable content webcomic channels some time nuttery

[Andy ZL3AG via time-nuts]

At first, I avoided clicking the link as seeing it posted there with no hint as 
to the content, it screamed "this person's email account has been hijacked by a 
virus".

Once someone replied +1, I took a look and had a wee chortle.

On 8/11/2016, at 9:57 AM, Don Latham wrote:

> glad there are some other readers out there…
> 
>> On Nov 7, 2016, at 8:33 AM, Christopher Hoover  wrote:
>> 
>> +1
>> 
>> On Nov 7, 2016 4:05 PM, "Gregory Maxwell"  wrote:
>> 
>>> http://questionablecontent.net/view.php?comic=3346
>>> ___


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[time-nuts] Subject: Re: I love the smell of tantalum in the morning

[Scott Hamilton]

https://www.amazon.com/Donegan-OptiVISOR-Headband-Magnifier-Magnification/dp/B0068OSIIS/ref=sr_1_4?ie=UTF8=1478548961=8-4=headset+magnifiers

Finally, I can offer a contribution to this list. I have found the Donegan 
magnifiers in the above Amazon link with 3.5X lenses to be very comfortable and 
indespensible for SMD work. Different lenses can be obtained for other work but 
the 3.5X is a minimum for me.

Scott Hamilton
W3SEH
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Re: [time-nuts] Questionable content webcomic channels some time nuttery

[Don Latham]

glad there are some other readers out there…

> On Nov 7, 2016, at 8:33 AM, Christopher Hoover  wrote:
> 
> +1
> 
> On Nov 7, 2016 4:05 PM, "Gregory Maxwell"  wrote:
> 
>> http://questionablecontent.net/view.php?comic=3346
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> 

Felix qui potuit rerum cognoscere causas.
Lucky is he who has been able to understand the causes of things.
Virgil
---
"Noli sinere nothos te opprimere"

Dr. Don Latham, AJ7LL
Six Mile Systems LLC, 17850 Six Mile Road
Huson, MT, 59846
mailing address:  POBox 404
Frenchtown MT 59834-0404

VOX 406-626-4304
CEL 406-241-5093
Skype: buffler2
www.lightningforensics.com 
www.sixmilesystems.com 
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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  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 
> To: Bob Stewart ; Discussion of precise time and frequency 
> measurement  
> 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  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 

Re: [time-nuts] I love the smell of tantalum in the morning

[Clint Jay]

Definitely, for a proven bad or dirt cheap leaded part when the board is
valuable cut the legs. gives you an added advantage when removing the part
as well as you can apply heat to both sides of the leg if it's through
hole.

On 5 November 2016 at 21:56, Mark Sims  wrote:

> Tom's method is what I use when replacing commodity parts that I don't
> care about salvaging.  Much less chance of damaging anything.   Hack the
> part apart,  cut the leads on gull wing packages, etc.  Don't waste your
> time with tweezers,  lifting one end, etc.   I have a very nice set of hot
> tweezers and almost never use them.
>
> And for DIP packages cut the package free from the leads first...  even
> though I have a $6000+ vacuum desoldering station,  trying to get all the
> leads unsoldered cleanly and prying out the chip always risks tearing out a
> feed through... particularly on multi-layer boards with out thermal
> isolation vias on power/ground connections.
>
> -
>
> >  I usually nibble away at the center of the part until it is two separate
> pieces. Then unsolder each piece. Clean the pads off with wick then install
> the new part.
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-- 
Clint.

*No trees were harmed in the sending of this mail. However, a large number
of electrons were greatly inconvenienced.*
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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 
 To: Bob Stewart ; Discussion of precise time and frequency 
measurement  
 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  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 
> To: Bob Stewart  
> Cc: Discussion of Precise Time and Frequency Measurement 
> 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  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 
>> To: Bob Stewart ; Discussion of precise time and frequency 
>> measurement  
>> Cc: Scott Stobbe 
>> 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  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 

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  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 
> To: Bob Stewart  
> Cc: Discussion of Precise Time and Frequency Measurement 
> 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  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 
>> To: Bob Stewart ; Discussion of precise time and frequency 
>> measurement  
>> Cc: Scott Stobbe 
>> 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  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 
>>> To: Bob Stewart  
>>> Cc: Discussion of Precise Time and Frequency Measurement 
>>> 
>>> 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  wrote:
>>> 
>>> Hi Scott,
>>> The 20 bits span about 6 volts.  The EFC range spans about 8Hz (+/-4Hz).  I 
>>> don't do these 

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 
 To: Bob Stewart  
Cc: Discussion of Precise Time and Frequency Measurement 
 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  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 
> To: Bob Stewart ; Discussion of precise time and frequency 
> measurement  
> Cc: Scott Stobbe 
> 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  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 
> > To: Bob Stewart  
> > Cc: Discussion of Precise Time and Frequency Measurement 
> > 
> > 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  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 
> > To: Bob Stewart ; Discussion of precise time and frequency 
> > measurement  
> > 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 

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  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 
> To: Bob Stewart ; Discussion of precise time and frequency 
> measurement  
> Cc: Scott Stobbe 
> 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  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 
> > To: Bob Stewart  
> > Cc: Discussion of Precise Time and Frequency Measurement 
> > 
> > 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  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 
> > To: Bob Stewart ; Discussion of precise time and frequency 
> > measurement  
> > 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  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/ 
> > 

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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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 
 To: Bob Camp  
Cc: Bob Stewart ; Discussion of precise time and frequency 
measurement 
 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  wrote:

Hi


> On Nov 5, 2016, at 10:43 PM, Bob Stewart  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 
> To: Bob Stewart 
> Cc: Discussion of Precise Time and Frequency Measurement 
> 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  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 
> To: Bob Stewart ; Discussion of precise time and frequency 
> measurement 
> 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 

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] I love the smell of tantalum in the morning

[Everett B. Fulton]

I also use the double-iron method over hot air for tiny components. I use them 
like tweezers, yet with an improvement in dexterity.

Liberal use of liquid or paste flux, in addition to what might be in the solder 
itself, is very helpful in obtaining good results.  If you have the "SMT 
solder paste" with tiny spheres of solder mixed in with rosin paste, that also 
works well.

Obviously, a hot air machine with assortment of nozzles is the easiest way to 
handle components with a large lead count.  Under "field conditions" I've 
actually used a common heat gun and a watchful eye on the phase change.  Since 
leaving the 2-way radio field a dozen years ago, I only get to work on my own 
gear.  I still like maintaining the ability, although the eyesight is becoming 
an issue.  Time for those glasses I've been avoiding...

First post for me, despite a few years of lurking.  Always one of my favorite 
reads!

On Saturday, November 05, 2016 12:55:55 PM Hal Murray wrote:
> t...@leapsecond.com said:
> > Having not done SMT before, how should I do it with minimal risk to the
> > very precious PCB. Or, what equipment should I use this as a good excuse
> > to buy?
> 
> If you can get at it, 2 soldering irons, one on each end, works reasonably
> well.  When both ends are melted, just push the part out of the way.
> Small/light things like 0805 resistors will frequently stick to one of the
> tops by surface tension of the liquid solder.

-- 
Everett B. Fulton, AF5OK
eful...@rackspace.com
DNS/NTP Engineer
(the other time-nuts guy from the Spring Branch TX area)
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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 
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  wrote:
>
>> Hi
>>
>>
>> > On Nov 5, 2016, at 10:43 PM, Bob Stewart  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 
>> > To: Bob Stewart 
>> > 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  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 
>> > To: Bob Stewart ; Discussion of precise time and
>> frequency measurement 
>> > 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  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.
>> >
>> >
>> >
>> >
>> >
>> >
>> >
>> >
>> >
>> > ___
>> > time-nuts mailing list -- time-nuts@febo.com
>> > To unsubscribe, go to https://www.febo.com/cgi-bin/m
>> ailman/listinfo/time-nuts
>> > and follow the instructions there.
>>
>>
>
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Re: [time-nuts] Questionable content webcomic channels some time nuttery

[Christopher Hoover]

+1

On Nov 7, 2016 4:05 PM, "Gregory Maxwell"  wrote:

> http://questionablecontent.net/view.php?comic=3346
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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  wrote:

> Hi
>
>
> > On Nov 5, 2016, at 10:43 PM, Bob Stewart  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 
> > To: Bob Stewart 
> > 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  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 
> > To: Bob Stewart ; Discussion of precise time and
> frequency measurement 
> > 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  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] Time nut soon to be in Shenzhen

[Mark Kahrs]

I think you need "The Essential Guide to Electronics in Shenzhen" by Bunnie
Huang.



On Sun, Nov 6, 2016 at 8:37 PM, Li Ang <379...@qq.com> wrote:

> Hi
>Welcome to Shenzhen. As far as I know there is no market that you can
> see pile of OCXO. They were taken off from equipments, and the process is
> done in the Qingyuan or Shanwei city Guangdong province. The seller might
> be in Shenzhen, but the source is in Qingyuan/Shanwei. These city have a
> lot of people doing the disassembly , recycle and alchemy work.
>
> However, there are a lot of eletronics markets near Huaqiangbei. I think
> you should pay a visit there. There are some 2nd-hand test equipment
> sellers in Duhui,  Xinyazhou market. Since the rental price is quite high
> in Huaqiangbei, most 2nd-hand test equipment selles and warehouses are not
> there.
> If you are interested in some other things, maybe I can give you more
> detailed info.(place to buy, reference price, etc.).
>
>
>
> ---Original---
> From: "Christopher Hoover"
> Date: 2016/11/6 23:13:55
> To: "Discussion of precise time and frequency measurement" com>;
> Subject: [time-nuts] Time nut soon to be in Shenzhen
>
>
> I'm in Shanghai now but will be leaving for Shenzhen in a few days.  Any
> one know of any special time nutty stuff to check out in Shenzhen?  I
> expect if I can find the right place I might see piles of OCXO's.
>
> Thanks, Christopher and 73 de AI6KG
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Re: [time-nuts] Thermal impact on OCXO

[Bob Camp]

Hi


> On Nov 5, 2016, at 10:43 PM, Bob Stewart  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 
> To: Bob Stewart  
> Cc: Discussion of Precise Time and Frequency Measurement 
> 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  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 
> To: Bob Stewart ; Discussion of precise time and frequency 
> measurement  
> 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  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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> and follow the instructions there.
> 
> 
> 
> 
> 
> 
> 
> 
> 
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Re: [time-nuts] Man with too many clocks.

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 4 Nov 2016 17:48, "Bob Camp"  wrote:
>
> Hi
>
> The only practical way to set the 10811 or 10544 is with a >= 10 turn pot
on the EFC. I
> never have worked out just why there are so many instruments that don’t
have a pot on
> the EFC.
>
> Bob

I'm amazed my 18 GHz HP 5342A counter has no pot. IIRC the standard TCXO
does, but the counter drifts a lot with that.  After fitting the optional
10811A OCXO, I discovered it is almost impossible to set the frequency from
the mechanical control. I guess I should modify the counter and add a
control. It really is odd that there's no such facility.

That said,  the difference in value between this old counter and the newer
microwave counters like the 5351B has fallen.  The newer ones are much more
sensitive too.

Dave.
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