[time-nuts] Microscope for SMT work...

[Burt I. Weiner]

Ian,

You have a very nice setup.  I also bought an AM-Scope about three 
years ago.  Mine has the associated 8-bazillion ton white stand on 
the edge of the bench with double arms that lets me swing it over to 
where I'm working.  As I recall, it has a zoom range of about 3.5 to 
45x which is more than enough range for SMT work.  Not only is it 
great for SMT work, it's great for removing slivers from my 
fingers.  The optics on the AM Scope instruments are excellent.  I 
was fortunate in that a friend of mine works in a lab that builds 
satellite LNB's, so I was able to go play with the microscope before 
going to the Minister of Finance to get a blessing on purchasing 
it.  It was amazing that even the slightest suggestion of using it to 
be able to repair the smallest of jewelry resulted in a blessing of 
the proposed purchase  :>


See: 
http://www.amscope.com/stereo-microscopes/3-5x-45x-trinocular-stereo-boom-zoom-microscope-fluorescent-light.html


Burt, K6OQK


  Also, a recent addition that makes SMT so easy, the title of the manual is,
"Instruction Manual for SE400, SE400-LED,  Long Working Distance 
Stereo Microscope",

about $200.

  With a working distance of nine inches or so, it beats the pants off my
previous magnifier, Optivisor 10x where I have to have my face less than two
inches from the soldering area.

  .. got the microscope from description from W7ZOI web site.
http://w7zoi.net/micscope.html

Ian, G4ICV, AB2GR

Burt I. Weiner Associates
Broadcast Technical Services
Glendale, California U.S.A.
b...@att.net
K6OQK 


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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  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 
> *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
> 
>
>
>
>
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>
>
>
>
>
>
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Re: [time-nuts] Thinking outside the box a super reference

[Attila Kinali]

On Sat, 05 Nov 2016 12:25:35 +
"Poul-Henning Kamp"  wrote:


> >Active maser like the hydrogen would be possible naturally, but would 
> >require the resonator.
> 
> I don't think they are.

They are. It took a while, but they have been a thing since '64.
Though all of them have been using vapor cells.

> As I understand it not all excited modes of all atoms and molecules
> have the not-quite-pinned-down quantum-thaumagic property to do that.
> 
> And I remember reading somewhere that the alkali atoms have been
> poked and prodded to no end about this, in the hope of creating
> active Cs, Rb or Sr frequency standards, but the very reluctant
> (and expensive) conclusion was that hydrogen is the only one in the
> family which knows the trick.

Nope, the problem, as far as I understand it, is not that you cannot
get the atoms to emit, but to keep them in one place without perturbing
them. For hydrogen, a teflon coating does a very good job and the atom
can go for many wall collisions without losing its state/phase. Even the
early hydrogen maser got to >10^4 collisions and modern coatings offer
something like 10^6 IIRC, ie the life time is measured in seconds
to minutes.

Until recently, there didn't exist such a coating for Rb or Cs [1] and
relaxation time was measured in milliseconds. For comparison, have a look at
page 37 of Bandi's dissertation[2], the broadening due to wall collisions
is stated as 300Hz for the wall coated, evacuated cell, while the buffer
gas collision broadening is a mere 10Hz (yes, I am cheating here, the
correct comparison would be the total broadening which is 350Hz vs 600Hz).
Yes, the wall shift is smaller than the buffer gas shift (4000Hz vs 300Hz)
but this is in first order approximation a constant. 

Additionally, all the coatings have rather low temperature limits
(the hydrocarbon coatings are very similar to parafin wax) and the
high temperatures that were needed for the Rb lamps didn't work togheter.
And even for modern laser pumped systems, you still need a rather high
temperature (40-90°C are usual) to get a high enough amount or Rb in the cell.

I guess you can understand that people have not been using vapor cell
active masers because they do not offer the long term stability one
seeks (due to buffer gas changes) and their short term stability is
not any better than the passive masers (limited by buffer gas relaxation).

Probably, with the new coatings and laser pumping one could build a usable
Rb active maser with evacuated cells instead of buffer gas. But sofar
nobody has tried that yet (as far as I am aware of). I guess it's more
sexy to investigate optical standards than something as old as Rb.
Especially as there are already Rb fountains[3] which offer quite a
high stability already.


Attila Kinali


[1] "Polarized Alkali-Metal Vapor with Minute-Long Transverse
Spin-Relaxation Time", by Balabas, Kraulanov, Ledbetter, Budker, 2010
http://dx.doi.org/10.1103/PhysRevLett.105.070801

[2] "Double-Resonance Studies on Compact, High-performance Rubidium Cell
Frequency Standards", by Thejesh Bandi, 2013
https://doc.rero.ch/record/32317/files/2318.pdf

[3] "The USNO rubidium fountains", by Peil et al. 2015
http://dx.doi.org/10.1088/1742-6596/723/1/012004
-- 
Malek's Law:
Any simple idea will be worded in the most complicated way.
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Re: [time-nuts] Thinking outside the box a super reference

[Attila Kinali]

On Sat, 5 Nov 2016 06:53:45 -0700
jimlux  wrote:

> On 11/5/16 2:59 AM, Attila Kinali wrote:
>   But we still need to ensure that the field is properly
> > oriented and homogenous over the whole vapor cell. For this you need
> > a cavity that is properly designed and most likely will be resonant at 
> > 6.9GHz.
> > (I don't know whether it is possible to design a non-resonant cavity with
> > the above properties)
> 
> isn't a TEM cell, as used in EMI/EMC testing, something like this?  It's 
> a tapered transmission line and produces a uniform field within an area 
> inside the line.

Yes, they fullfill the "constant field" condition, but not the "properly
oriented" condition. The field in these cells has still a quite considerable
curl. One can of course minimize that by building a larger one, but
then there are smaller structures with similar properties, when one does
not need the the wideband property of those TEM cells.

Attila Kinali

-- 
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Any simple idea will be worded in the most complicated way.
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[time-nuts] Corby Dawson Super 5065a work can I use a miniature Rubidium

[cdelect]

Anton,

To answer both questions:
 
You can use a Laser in place of the Rubidium lamp, however assuming the
problem is the lamp it would be cheaper to buy several LPRO units to
scavenge for a replacement lamp.
 
How did you determine it's the lamp that is dead?
 
Using a Laser is more complicated than it sounds. The Laser frequency has
to be stabilized at the proper wavelength. This usually requires a
combination of selecting the proper diode current as well as the proper
temperature. Even then the diode ages and drifts away from the proper
spot. Sometimes a separate Rubidium vapor cell is used to stabilize the
frequency of the diode.
 
The equipment to run the diode would take up MUCH more room than the
LPRO!
 
This is why you don't find commercial Rubidiums using Laser diodes! (YET)
 
The Super modification will not work on the miniature Rubidiums.
(although some do filter the lamp to get a better SN, however performance
is not anywhere near a Super.)
 
The 5065A has a large cell and runs at a low temperature, this offers the
ideal stability and the chance to Super it.
 
Even so not all 5065A can be Supered!
 
Cheers,
 
Corby Dawson

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

Re: [time-nuts] Man with too many clocks.

[EB4APL]

I agree that FE-5680 is a whole family of products with very different 
features and these can not deducted from the labels.


In my case I own a FE-5680A which outputs 1 PPS and a fixed (but 
slightly tunable) 10 MHz and needs 2 power supply voltages, +5 V and + 15 V.


I am sending directly to you the information of the breakout board that 
I use and it includes the pinout of this unit.  A caution here, some of 
the FE-5680 variations have different pinouts.


Regards,

Ignacio EB4APL


El 05/11/2016 a las 2:01, Peter Reilley escribió:
It is a FE-5680B.   It is my understanding that these were made in 
many variations
of features but that what features were present or absent could not be 
known
from the model numbers of other external identifying information. This 
one

has the 1 PPS apparently.

Pete.



On 11/4/2016 1:07 PM, EB4APL wrote:
A bit OT, but regarding your Rb, some units needs to be powered thru 
2 pins, one is used only for the 10 MHz output buffer, if remember it 
correctly. Which is your model number?


Ignacio EB4APL


El 04/11/2016 a las 16:35, Peter Reilley escribió:
I gave up on trying to use the GPS 1 PPS signal to calibrate the 10 
MHz OCXO's that
I have.   The reason that others have pointed out is that the 
uncorrected 1 PPS
signal from the GPS is has just a little too much a jitter to use it 
for calibration
with your eye using a scope.   If it were sawtooth corrected then it 
would be better

but you really need a GPS disciplined oscillator.

Not to be outdone, I brought out a rubidium oscillator that I had 
put away because
it did not appear to work properly.   It only put out a 1 PPS signal 
and nothing else.
I compared that with the GPS PPS and could get a good comparison on 
the scope.
The rubidium drifted about 40 nS over 12 hours.   So it seemed to be 
good.


With that I could adjust the OCXO's in my 5370's.   The spec for the 
HP 5370B with
a HP 10811 OCXO is better than 1 X 10^-10 RMS for 1 sec average. 
That is, it should
take more than 1,000 seconds for one 10 MHz wave to shift by 360 
degrees.   That
is very hard to do using the screw adjustment in the OCXO. Even the 
slightest
movement possible will cause a frequency change greater that is 
spec'ed.   How

do cal labs do it?

My HP 5370A has a 10544 OCXO which is spec'ed for short term 
stability of
better than 1 X 10^11 for 1 second.   Even better than the 5370B! 
The adjustment
screw is much coarser and it is not possible to get any better than 
a few seconds for
one cycle phase shift of the 10 MHz OCXO against the standard. It 
seems that I can't

get even close to the spec.

These have been running for a few days.   It that enough?

Pete.



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Re: [time-nuts] Man with too many clocks.

[Bob Camp]

Hi

A ten or twenty turn pot on a normal EFC will get you past the point that 
you can reasonably set the oscillator. The typical (not GPS version) EFC is down
around 1 to 2 x 10^-7. A 20 turn pot will be running 1x10^-8 per turn. 100 to 
200
points per turn is a pretty typical “set” number for a pot. That gets you into 
the 
sub 1x10^-10 region. The OCXO’s we are talking about have a temperature,
 pressure and humidity coefficient that each are well above that level.

Bob 

> On Nov 4, 2016, at 2:31 PM, Scott Stobbe  wrote:
> 
> I'm not sure if there is a reason counters don't let you digitally
> calibrate beyond that, the 10 MHz ref out on the rear panel would still be
> out of cal.
> 
> On Fri, Nov 4, 2016 at 1:48 PM, 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
>> 
>>> On Nov 4, 2016, at 11:35 AM, Peter Reilley 
>> wrote:
>>> 
>>> I gave up on trying to use the GPS 1 PPS signal to calibrate the 10 MHz
>> OCXO's that
>>> I have.   The reason that others have pointed out is that the
>> uncorrected 1 PPS
>>> signal from the GPS is has just a little too much a jitter to use it for
>> calibration
>>> with your eye using a scope.   If it were sawtooth corrected then it
>> would be better
>>> but you really need a GPS disciplined oscillator.
>>> 
>>> Not to be outdone, I brought out a rubidium oscillator that I had put
>> away because
>>> it did not appear to work properly.   It only put out a 1 PPS signal and
>> nothing else.
>>> I compared that with the GPS PPS and could get a good comparison on the
>> scope.
>>> The rubidium drifted about 40 nS over 12 hours.   So it seemed to be
>> good.
>>> 
>>> With that I could adjust the OCXO's in my 5370's.   The spec for the HP
>> 5370B with
>>> a HP 10811 OCXO is better than 1 X 10^-10 RMS for 1 sec average. That
>> is, it should
>>> take more than 1,000 seconds for one 10 MHz wave to shift by 360
>> degrees.   That
>>> is very hard to do using the screw adjustment in the OCXO.   Even the
>> slightest
>>> movement possible will cause a frequency change greater that is
>> spec'ed.   How
>>> do cal labs do it?
>>> 
>>> My HP 5370A has a 10544 OCXO which is spec'ed for short term stability of
>>> better than 1 X 10^11 for 1 second.   Even better than the 5370B! The
>> adjustment
>>> screw is much coarser and it is not possible to get any better than a
>> few seconds for
>>> one cycle phase shift of the 10 MHz OCXO against the standard.   It
>> seems that I can't
>>> get even close to the spec.
>>> 
>>> These have been running for a few days.   It that enough?
>>> 
>>> Pete.
>>> 
>>> 
>>> 
>>> On 11/3/2016 8:20 AM, Peter Reilley wrote:
 I am the proverbial man with too many clocks and I don't know what time
>> it is.
 To correct this situation I have decided to calibrate everything.
 
 I have a HP 5370B, a HP 6370A, and a HP 5328A all with the TCXO
>> option.   I also
 have some TCXO modules.   I figured that I would calibrate them against
>> my Trimble
 Resolution T GPS receiver.
 
 I put the 1 PPS signal in one channel of my scope and one of the 10 MHz
>> TCXO
 signals in the other channel and look at the phase relationship. The
>> TCXO's are
 already close enough that I should not be out by more than a fraction
>> of a waveform.
 I understand that I have to deal with the 1 PPS without sawtooth
>> correction.
 
 I expected to see the 10 MHz signal bounce around but not move more
>> than 1/2
 of a wave length.   Instead I see the 10 MHz waveform appear steady for
>> a few seconds
 then jump a significant portion of the wave.   The jump is too much to
>> be confident
 that I have not slipped one cycle.
 
 Can I do what I am trying to do or am I missing something?
 
 Pete.
 
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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:
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Re: [time-nuts] Man with too many clocks.

[Clint Jay]

I own a 5680b and while it only outputs a PPS signal there is a very stable
30MHz signal available inside the unit IIRC.

I can dig mine out and find the signal if that's of use?

I believe they can be modded for 10MHz output on the 15p D type  but I've
just not managed to find time to get around to that yet.

On 5 Nov 2016 13:33, "EB4APL"  wrote:

I agree that FE-5680 is a whole family of products with very different
features and these can not deducted from the labels.

In my case I own a FE-5680A which outputs 1 PPS and a fixed (but slightly
tunable) 10 MHz and needs 2 power supply voltages, +5 V and + 15 V.

I am sending directly to you the information of the breakout board that I
use and it includes the pinout of this unit.  A caution here, some of the
FE-5680 variations have different pinouts.

Regards,

Ignacio EB4APL



El 05/11/2016 a las 2:01, Peter Reilley escribió:

> It is a FE-5680B.   It is my understanding that these were made in many
> variations
> of features but that what features were present or absent could not be
> known
> from the model numbers of other external identifying information. This one
> has the 1 PPS apparently.
>
> Pete.
>
>
>
> On 11/4/2016 1:07 PM, EB4APL wrote:
>
>> A bit OT, but regarding your Rb, some units needs to be powered thru 2
>> pins, one is used only for the 10 MHz output buffer, if remember it
>> correctly. Which is your model number?
>>
>> Ignacio EB4APL
>>
>>
>> El 04/11/2016 a las 16:35, Peter Reilley escribió:
>>
>>> I gave up on trying to use the GPS 1 PPS signal to calibrate the 10 MHz
>>> OCXO's that
>>> I have.   The reason that others have pointed out is that the
>>> uncorrected 1 PPS
>>> signal from the GPS is has just a little too much a jitter to use it for
>>> calibration
>>> with your eye using a scope.   If it were sawtooth corrected then it
>>> would be better
>>> but you really need a GPS disciplined oscillator.
>>>
>>> Not to be outdone, I brought out a rubidium oscillator that I had put
>>> away because
>>> it did not appear to work properly.   It only put out a 1 PPS signal and
>>> nothing else.
>>> I compared that with the GPS PPS and could get a good comparison on the
>>> scope.
>>> The rubidium drifted about 40 nS over 12 hours.   So it seemed to be
>>> good.
>>>
>>> With that I could adjust the OCXO's in my 5370's.   The spec for the HP
>>> 5370B with
>>> a HP 10811 OCXO is better than 1 X 10^-10 RMS for 1 sec average. That
>>> is, it should
>>> take more than 1,000 seconds for one 10 MHz wave to shift by 360
>>> degrees.   That
>>> is very hard to do using the screw adjustment in the OCXO. Even the
>>> slightest
>>> movement possible will cause a frequency change greater that is
>>> spec'ed.   How
>>> do cal labs do it?
>>>
>>> My HP 5370A has a 10544 OCXO which is spec'ed for short term stability of
>>> better than 1 X 10^11 for 1 second.   Even better than the 5370B! The
>>> adjustment
>>> screw is much coarser and it is not possible to get any better than a
>>> few seconds for
>>> one cycle phase shift of the 10 MHz OCXO against the standard. It seems
>>> that I can't
>>> get even close to the spec.
>>>
>>> These have been running for a few days.   It that enough?
>>>
>>> Pete.
>>>
>>
>>
>> ---
>> El software de antivirus Avast ha analizado este correo electrónico en
>> busca de virus.
>> https://www.avast.com/antivirus
>>
>>
>>
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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  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 >
>  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] Man with too many clocks.

[Bob Camp]

HI

If you use a good wire wound pot and run it off of and oscillator EFC source 
(not
all have them), the temperature effect is pretty much zero. You are using the 
pot
as a ratio device. 

A mechanical cap that is part of the heated region of the OCXO (the normal case)
has already been taken into consideration when the OCXO set point is adjusted to
compensate it.

Bob

> On Nov 4, 2016, at 3:34 PM, Hal Murray  wrote:
> 
> 
> kb...@n1k.org said:
>> 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. 
> 
> How would temperature effect that?  For that matter, how does temperature 
> effect the typical mechanical capacitor?  Does anybody play fancy tricks to 
> cancel out the mechanical motions?  (like the mercury pendulum - as the 
> pendulum rod expands the mercury expands in the other direction to keep the 
> CG the same)
> 
> -- 
> These are my opinions.  I hate spam.
> 
> 
> 
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Re: [time-nuts] Newbie With a Z3801 Problem

[Bill Riches]

Hi Mark,

Thank you for working with the KS24361.  Looking forward to when the program 
will be available.  

Any ideas on being able to use the 1 PPS signal out of the KS24361 to drive SL 
sound card calibration?  It is a weird pulse and someone mentioned the timing 
is wrong.  I use the pulse out of a Jackson unit with SL and it works fine.

73, 

Bill, WA2DVU

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Re: [time-nuts] Thinking outside the box a super reference

[Poul-Henning Kamp]

In message <0e976194-3cc1-2bc7-1289-0d9433132...@rubidium.dyndns.org>, Magnus D
anielson writes:

>> They won't be coherent photons, like in a Hydrogen maser, but we
>> don't need them to be, in fact that just causes the same exact
>> problems as the tuned cavity anyway, as long as we can measure
>> the frequency well enough.
>
>Active maser like the hydrogen would be possible naturally, but would 
>require the resonator.

I don't think they are.

With hydrogen, hitting the excited electron with the right frequency
increases the probability of coherent emission of the photon enough
that you get to the "SE" we know from LASER and MASER.

As I understand it not all excited modes of all atoms and molecules
have the not-quite-pinned-down quantum-thaumagic property to do that.

And I remember reading somewhere that the alkali atoms have been
poked and prodded to no end about this, in the hope of creating
active Cs, Rb or Sr frequency standards, but the very reluctant
(and expensive) conclusion was that hydrogen is the only one in the
family which knows the trick.

-- 
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
p...@freebsd.org | TCP/IP since RFC 956
FreeBSD committer   | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
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Re: [time-nuts] Thinking outside the box a super reference

[Richard (Rick) Karlquist]

One of the main limiting factors in the 5061 was
microwave leakage.  An excellent Italian engineer
named DiMarchi mastered the so called "top cover
effect", where removing the top cover changed the
frequency.  He had a small business going refurbishing
5061's by cleaning up the waveguide gasketing, etc.
If any 9192.63177 reaches the beam at one end or
the other, it will upset the phase balance.  In
the 5071, phase balance is the main limiting factor
in accuracy.  They go to extreme measures to make
the cavity absolutely symmetrical using fabrication
techniques analogous to "self aligning" IC masking.
In the 5071, the only place 9192 shows up is in the
microwave module that is directly attached to the
coax to waveguide transition into the cavity.
There are no frequencies anywhere that are sub
harmonics of 9192.  Incidentally, there are no
frequencies anywhere that are coherent with
50 Hz, 60 Hz, etc line frequencies.  Nothing
is by accident when Len Cutler is involved.

In terms of basic synthesizer architecture, the
mix from 9280 to 9192 using 87 is described by
the technical term "free lunch" :-)  We pick
up two decades of resolution.  Furthermore, we
don't have to filter out 9280 or 9367 because
they are ignored by the CBT.  One of the reasons
for going up from 12 to 87 was to get these
spurs safely removed from anything that would
interact quantum mechanically with the cesium
line tail.  With the increased accuracy, 12
was no longer high enough.

Rick

On 11/5/2016 7:39 AM, Attila Kinali wrote:

Hoi Rick,

On Sat, 5 Nov 2016 07:17:21 -0700
"Richard (Rick) Karlquist"  wrote:


I think this is all described in the 1992 FCS papers,
but the executive summary is that a direct synthesizer
on 9192.63177 is to be avoided at all costs because
of the danger of it leaking into the CBT cavity.
This is also the reason why you don't multiply up
a subharmonic of this frequency.



I don't get what you mean with "danger of leaking into the CBT cavity"?
When signal leakage into the cavity is a problem, shouldn't that also
exist for the signal after the mixer? And what does this leaking actually
mean? The 9192.63177 is supposed to end up in the cavity anyways.

Attila Kinali


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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 
 To: Bob Stewart ; Discussion of precise time and frequency 
measurement  
 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  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 
 To: Discussion of Precise Time and Frequency Measurement 
 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  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 
> To: Bob Stewart ; Discussion of precise time and frequency 
> measurement  
> 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  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 
>  To: Discussion of Precise Time and Frequency Measurement 
>  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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> 
> 
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Re: [time-nuts] I love the smell of tantalum in the morning

[jimlux]

On 11/5/16 12:12 PM, Tom Van Baak wrote:

See C13 in the attached photo. I need to replace some blown caps on a few 
boards [1]. In one instance the cap got so hot it melted itself off the board. 
Quiet convenient, actually -- it acts like its own fuse -- but I don't think 
the 5071 designers had that clever feature in mind.

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?



Suitable hot tweezers would do this just fine, for both the removal and 
the replacement.


this kind of thing
http://www.weller-toolsus.com/weller-t0051317199-wta-50-tweezers-smd-desoldering.html
https://www.amazon.com/WMRT-Desoldering-Tweezers-Soldering-Stations/dp/B000UMMUII

It's what I've used at work, with a wx2021
Here's the complete set:
http://www.weller-toolsus.com/soldering/systems/weller-wx2021-solder-stat-wxmpms-wxmtms-wdh51-wdh60-120v.html

The tips heat basically instantly. It makes it easy to remove/replace 
even tiny stuff, although 0402 is just too small for me.


You need a good magnifier or stereo microscope, and some orange sticks 
to hold things in place while you solder, etc.



However, I've been given to understand that there is another superior 
brand (on this list.. )





Thanks,
/tvb

[0] http://www.imdb.com/title/tt0078788/quotes
[1] http://leapsecond.com/museum/hp5071a/A1-mother.htm



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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?


-- 
These are my opinions.  I hate spam.



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Re: [time-nuts] Thinking outside the box a super reference

[Ruslan Nabioullin]

On 11/03/2016 06:10 PM, Attila Kinali wrote:

On Thu, 3 Nov 2016 16:37:06 -0400
Ruslan Nabioullin  wrote:


What about instead establishing an open-source hardware project for a
frequency standard fusor?  I was researching COTS solutions for this for
my rubidium ensemble and could only find this one product, which
obviously should be exorbitant in cost:


You don't need a hardware project for this, as long as a paper clock
is enough for you. Just buy a couple of kiwi-sdr (or anything similar),
provide all of them with a common clock source and you get a comparison
of all your atomic clocks with minimum effort and can build from that
a paper clock easily. The paper clock can than be used for the measurement
you do, using one of the atomic clocks (preferably the one with the lowest
phase noise) as reference.


If it's so relatively straightforward, then why not establish such a 
project instead of reinventing the wheel by attempting to perform atomic 
standard R and fabrication on a shoestring?  It should be much more 
practical, even considering the fact that one will obtain diminishing 
returns on the ensemble's n, and furthermore should be extremely 
successful---apparently only a single Russian company holds a global 
monopoly on this product, apart from custom-fabricated setups in 
national metrology labs, and numerous people would benefit (why purchase 
an exorbitantly-expensive and short-lifespan cesium standard when one 
can fuse a redundant ensemble of rubidium standards?  Or for 
lower-budget and/or higher-MTBF setups, the same for a rubidium standard 
and OCXO standards, resp.)


Another project, much simpler in comparison but even more useful, would 
be a rack-mount standard for an OCXO or rubidium physics package, which 
should consist of just a chassis, power supply, thermal structure, and a 
monitoring subsystem with interfaces (LEDs, an LCD display, and 
RS-232/USB/GPIB/Ethernet).  The used market is flooded with cheap 
physics packages, yet actual standards are uncommon and expensive.


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

[John Ackermann N8UR]

Either hot tweezers or a hot air rework station are the best/easiest 
ways to remove dead parts.  But two fine-tip soldering irons will also 
work and are a lot cheaper.  The idea is to heat both ends of the part 
at once, and when the solder flows, lift or flip the part off.  Then, 
use some liquid flux and narrow solder wick to suck off the excess 
solder, and you should end up with nice smooth pads ready for the 
replacement part.


The key thing to avoid damage is to make sure the solder is really 
flowing on both pads before you try to lift the part.  Sometimes ground 
pads have enough thermal mass that it takes a while to get them hot 
enough.  Be patient.


Good luck!
John


On 11/05/2016 03:12 PM, Tom Van Baak wrote:

See C13 in the attached photo. I need to replace some blown caps on a few 
boards [1]. In one instance the cap got so hot it melted itself off the board. 
Quiet convenient, actually -- it acts like its own fuse -- but I don't think 
the 5071 designers had that clever feature in mind.

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?

Thanks,
/tvb

[0] http://www.imdb.com/title/tt0078788/quotes
[1] http://leapsecond.com/museum/hp5071a/A1-mother.htm



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

[Bryan _]

Surprisingly the 852D+ which is a very cheap rework station is quite good. 
Quite a few reviews on the EEVblog.


-=Bryan=-



From: time-nuts  on behalf of Bob Stewart 

Sent: November 5, 2016 12:18 PM
To: Tom Van Baak; Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] I love the smell of tantalum in the morning

Hi Tom,
Personally, I wouldn't touch this without a hot air gun.  I don't know what 
your budget is.  What I consider reasonable may be an order of magnitude 
smaller than for you.  So, I use a generically labeled 852D+ rework combo.  It 
has both solder pencil and hot air gun.  There are better hot air guns for a 
reasonable price that have a better system for changing the nozzles.  OTOH, 
I've heard some complaints about this "better" system where the nozzle has 
fallen off.  If you've got a Pace soldering system, then you already know what 
to do.  =)

Bob




  From: Tom Van Baak 
 To: Discussion of precise time and frequency measurement 
 Sent: Saturday, November 5, 2016 2:12 PM
 Subject: [time-nuts] I love the smell of tantalum in the morning

See C13 in the attached photo. I need to replace some blown caps on a few 
boards [1]. In one instance the cap got so hot it melted itself off the board. 
Quiet convenient, actually -- it acts like its own fuse -- but I don't think 
the 5071 designers had that clever feature in mind.

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?

Thanks,
/tvb

[0] http://www.imdb.com/title/tt0078788/quotes
[https://images-na.ssl-images-amazon.com/images/M/MV5BYWNjNjZjYmMtOTRjOC00ZGIwLWI2YzEtMjkxNTAzODkzZDRlXkEyXkFqcGdeQXVyNjUwNzk3NDc@._V1_UY98_CR0]

Apocalypse Now (1979) - Quotes - 
IMDb
www.imdb.com
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[1] http://leapsecond.com/museum/hp5071a/A1-mother.htm
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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] I love the smell of tantalum in the morning

[Bob Stewart]

Hi Tom,
Personally, I wouldn't touch this without a hot air gun.  I don't know what 
your budget is.  What I consider reasonable may be an order of magnitude 
smaller than for you.  So, I use a generically labeled 852D+ rework combo.  It 
has both solder pencil and hot air gun.  There are better hot air guns for a 
reasonable price that have a better system for changing the nozzles.  OTOH, 
I've heard some complaints about this "better" system where the nozzle has 
fallen off.  If you've got a Pace soldering system, then you already know what 
to do.  =)

Bob




  From: Tom Van Baak 
 To: Discussion of precise time and frequency measurement  
 Sent: Saturday, November 5, 2016 2:12 PM
 Subject: [time-nuts] I love the smell of tantalum in the morning
   
See C13 in the attached photo. I need to replace some blown caps on a few 
boards [1]. In one instance the cap got so hot it melted itself off the board. 
Quiet convenient, actually -- it acts like its own fuse -- but I don't think 
the 5071 designers had that clever feature in mind.

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?

Thanks,
/tvb

[0] http://www.imdb.com/title/tt0078788/quotes
[1] http://leapsecond.com/museum/hp5071a/A1-mother.htm
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Re: [time-nuts] I love the smell of tantalum in the morning

[Adrian Godwin]

Metcal /OKI might be that other brand. I'd certainly recommend them, but
the tweezers are not as fast to heat as the single tip devices.

I've had little success personally with the hot air devices. I seem to
toast the board before I melt the solder, and when it does melt it's not
limited to one component. Doubtless it's my technique at fault, but I
prefer the tweezers.






On Sat, Nov 5, 2016 at 7:20 PM, jimlux  wrote:

> On 11/5/16 12:12 PM, Tom Van Baak wrote:
>
>> See C13 in the attached photo. I need to replace some blown caps on a few
>> boards [1]. In one instance the cap got so hot it melted itself off the
>> board. Quiet convenient, actually -- it acts like its own fuse -- but I
>> don't think the 5071 designers had that clever feature in mind.
>>
>> 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?
>>
>>
> Suitable hot tweezers would do this just fine, for both the removal and
> the replacement.
>
> this kind of thing
> http://www.weller-toolsus.com/weller-t0051317199-wta-50-twee
> zers-smd-desoldering.html
> https://www.amazon.com/WMRT-Desoldering-Tweezers-Soldering-
> Stations/dp/B000UMMUII
>
> It's what I've used at work, with a wx2021
> Here's the complete set:
> http://www.weller-toolsus.com/soldering/systems/weller-wx202
> 1-solder-stat-wxmpms-wxmtms-wdh51-wdh60-120v.html
>
> The tips heat basically instantly. It makes it easy to remove/replace even
> tiny stuff, although 0402 is just too small for me.
>
> You need a good magnifier or stereo microscope, and some orange sticks to
> hold things in place while you solder, etc.
>
>
> However, I've been given to understand that there is another superior
> brand (on this list.. )
>
>
>
> Thanks,
>> /tvb
>>
>> [0] http://www.imdb.com/title/tt0078788/quotes
>> [1] http://leapsecond.com/museum/hp5071a/A1-mother.htm
>>
>>
>>
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Re: [time-nuts] Thinking outside the box a super reference

[Tom Van Baak]

Attila, PHK, et al --

Rb maser proposal, including some photos. 3 PDF's, 175 pages of weekend reading:

https://archive.org/details/NASA_NTRS_Archive_19720025867

https://archive.org/details/NASA_NTRS_Archive_19730017775

https://archive.org/details/NASA_NTRS_Archive_19750006044

/tvb

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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 
 To: Bob Stewart ; Discussion of precise time and frequency 
measurement  
 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  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 
> To: Bob Stewart ; Discussion of precise time and frequency 
> measurement  
> 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  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 
>  To: Discussion of Precise Time and Frequency Measurement 
>  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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> 
> 
> 
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Re: [time-nuts] Thinking outside the box a super reference

[Magnus Danielson]

On 11/05/2016 03:16 PM, Attila Kinali wrote:

On Sat, 05 Nov 2016 12:25:35 +
"Poul-Henning Kamp"  wrote:



Active maser like the hydrogen would be possible naturally, but would
require the resonator.


I don't think they are.


They are. It took a while, but they have been a thing since '64.
Though all of them have been using vapor cells.


As I understand it not all excited modes of all atoms and molecules
have the not-quite-pinned-down quantum-thaumagic property to do that.

And I remember reading somewhere that the alkali atoms have been
poked and prodded to no end about this, in the hope of creating
active Cs, Rb or Sr frequency standards, but the very reluctant
(and expensive) conclusion was that hydrogen is the only one in the
family which knows the trick.


Nope, the problem, as far as I understand it, is not that you cannot
get the atoms to emit, but to keep them in one place without perturbing
them. For hydrogen, a teflon coating does a very good job and the atom
can go for many wall collisions without losing its state/phase. Even the
early hydrogen maser got to >10^4 collisions and modern coatings offer
something like 10^6 IIRC, ie the life time is measured in seconds
to minutes.


Hydrogren maser is really a development out of the beam device, through 
the intermediary step of a beam device who's beam is extended with a 
"bounce box" to increase the time between the two Ramsey interegation 
zones. The quick decorrelation due to the wall-bounces for many atoms 
made this impractical except for the hydrogen, and the hydrogen maser is 
a refined variant of it.


In the end of the day, many of the classicial atomic clocks and the 
choice of elements for them is really dependent on what is "practical".


Cheers,
Magnus
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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 
 To: Bob Stewart ; Discussion of precise time and frequency 
measurement  
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?


-- 
These are my opinions.  I hate spam.





   

PlotCal.sh
Description: application/shellscript
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Re: [time-nuts] Thinking outside the box a super reference

[Poul-Henning Kamp]

In message , "Tom Van Baak" writes:
>Attila, PHK, et al --
>
>Rb maser proposal, including some photos. 3 PDF's, 175 pages of weekend 
>reading:
>
>https://archive.org/details/NASA_NTRS_Archive_19720025867
>
>https://archive.org/details/NASA_NTRS_Archive_19730017775
>
>https://archive.org/details/NASA_NTRS_Archive_19750006044


Interesting!

As is this:

https://arxiv.org/abs/physics/0508227

-- 
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
p...@freebsd.org | TCP/IP since RFC 956
FreeBSD committer   | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
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Re: [time-nuts] I love the smell of tantalum in the morning

[Bruce Griffiths]

On Saturday, November 05, 2016 12:12:18 PM Tom Van Baak wrote:
> See C13 in the attached photo. I need to replace some blown caps on a 
few
> boards [1]. In one instance the cap got so hot it melted itself off the
> board. Quiet convenient, actually -- it acts like its own fuse -- but I
> don't think the 5071 designers had that clever feature in mind.
> 
> 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?
> 
> Thanks,
> /tvb
> 
> [0] http://www.imdb.com/title/tt0078788/quotes
> [1] http://leapsecond.com/museum/hp5071a/A1-mother.htm
Tom

Either a hot air jet as used for smt desoldering will work.
A variety of nozzle shapes and sizes are available.

or

One can use a fine tip iron to alloy the solder with a low melting point 
solder alloy making it very easy to remove the component and then 
cleanup the pads using fluxed copper braid or even a cotton bud. Its 
essential to remove the low melting point alloy before resoldering.
 
CHIPQUIK SMD N1 works well with both leaded and unleaded soldered SMT 
parts
Bob Pease touted RF induction heated irons. Hakko makes a nice one 
(FX100) now the patent has expired.

Bruce
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Re: [time-nuts] Logging SPAD pulses on synced devices (was: Linux PPS clues?)

[Ilia Platone]

Hi, and thank you for these suggestions.

Currently this project becomes reality (slowly): this kind of 
synchronization/grabbing is very interesting, but I need something fast 
(I expect the SPAD with active quenching circuitry could output 30ns 
pulses, and the quantization frequency I hope to run at is 350/450MHz 
range).
Anyway, I found some FPGA code for so fast UART, not difficult to 
implement, and using these kind of devices this system you propose can 
be built from scratch, including a small buffer.


Can I post an LTSpice drawing for review here describing the active 
quenching circuitry?


Best Regards,
Ilia

On 11/05/16 04:48, Casey L. Jones wrote:
Yes, you might need a separate dedicated chip to take in the serial 
input steadily. Although you may not. Many serial ports have a small 
buffer to prevent missed serial input when the operating system gets 
distracted with something other than processing serial data.

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--
Ilia Platone
via Ferrara 54
47841
Cattolica (RN), Italy
Cell +39 349 1075999

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Re: [time-nuts] Logging SPAD pulses on synced devices (was: Linux PPS clues?)

[Bruce Griffiths]

Ilia
Circuit diagrams are  posted here from time to time, so it should be OK.
Bruce 

On Saturday, 5 November 2016 7:02 PM, Ilia Platone  
wrote:
 

 Hi, and thank you for these suggestions.

Currently this project becomes reality (slowly): this kind of 
synchronization/grabbing is very interesting, but I need something fast 
(I expect the SPAD with active quenching circuitry could output 30ns 
pulses, and the quantization frequency I hope to run at is 350/450MHz 
range).
Anyway, I found some FPGA code for so fast UART, not difficult to 
implement, and using these kind of devices this system you propose can 
be built from scratch, including a small buffer.

Can I post an LTSpice drawing for review here describing the active 
quenching circuitry?

Best Regards,
Ilia

On 11/05/16 04:48, Casey L. Jones wrote:
> Yes, you might need a separate dedicated chip to take in the serial 
> input steadily. Although you may not. Many serial ports have a small 
> buffer to prevent missed serial input when the operating system gets 
> distracted with something other than processing serial data.
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-- 
Ilia Platone
via Ferrara 54
47841
Cattolica (RN), Italy
Cell +39 349 1075999

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Re: [time-nuts] Logging SPAD pulses on synced devices

[Ilia Platone]

Attached to this mail there are three files: the APD.asc LTSpice4 
simulation schematics, a model for the AD8561 comparator, a model for 
the VN2210 mosfet transistor, and a model for the BF959 bipolar transistor.


Please note that the APD model included into the schematics may have 
errors: I took it from an LTSpice demo and adapted on the APDs I have, 
some Marktech MTAPD, and observations made with them.


Unfortunately the boards have been ordered, but components shortening or 
value editing can be done. (the real value of the capacitor of the psu 
is 47uF, for faster rendering I dropped it to a lower value.


Best Regards,
Ilia.

On 11/05/16 06:10, Bruce Griffiths wrote:

Ilia
Circuit diagrams are  posted here from time to time, so it should be OK.
Bruce

 On Saturday, 5 November 2016 7:02 PM, Ilia Platone  
wrote:
  


  Hi, and thank you for these suggestions.

Currently this project becomes reality (slowly): this kind of
synchronization/grabbing is very interesting, but I need something fast
(I expect the SPAD with active quenching circuitry could output 30ns
pulses, and the quantization frequency I hope to run at is 350/450MHz
range).
Anyway, I found some FPGA code for so fast UART, not difficult to
implement, and using these kind of devices this system you propose can
be built from scratch, including a small buffer.

Can I post an LTSpice drawing for review here describing the active
quenching circuitry?

Best Regards,
Ilia

On 11/05/16 04:48, Casey L. Jones wrote:

Yes, you might need a separate dedicated chip to take in the serial
input steadily. Although you may not. Many serial ports have a small
buffer to prevent missed serial input when the operating system gets
distracted with something other than processing serial data.
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--
Ilia Platone
via Ferrara 54
47841
Cattolica (RN), Italy
Cell +39 349 1075999

.MODEL VN2210 NMOS (LEVEL=3 RS=0.02 NSUB=3.0E15 DELTA=1.0 KAPPA=1.20 TPG=1 
CGDO=1.61E-10 RD=0.03 VTO=1.650 VMAX=5.0E6 ETA=0.053089 NFS=6.6E10 TOX=725E-10 
LD=1.698E-9 UO=862.425 XJ=6.4666E-7 THETA=1.0E-5 CGSO=4.850E-9 L=4.0E-6 W=85E-3)

.MODEL BF959 NPN(IS=10.2e-15 BF=78.00 NF=1.000 VAF=80.50 IKF=60.00m ISE=16.80p 
NE=2.000 BR=4.000 NR=1.000 VAR=12.00 IKR=90.00m ISC=0.000 NC=2.000 RB=2.060 
IRB=0.000 RBM=0.000 RE=515.0m RC=206.0m CJE=1.740p VJE=1.100 MJE=500.0m 
TF=227.0p XTF=0.000 VTF=0.000 ITF=0.000 PTF=0.000 CJC=2.250p VJC=300.0m 
MJC=300.0m XCJC=1.000 TR=158.0n CJS=0.000 VJS=750.0m MJS=0.000 XTB=1.500 
EG=1.110 XTI=3.000 KF=0.000 AF=1.000 FC=500.0m TNOM=27.00)

* AD8561 SPICE Macro-Model Typical Values
* 4/98, Ver. 1.0
* TAM / ADSC
*
* Node assignments
*   non-inverting input
*   |   inverting input
*   |   |   positive supply
*   |   |   |   negative supply
*   |   |   |   |   Latch
*   |   |   |   |   |   DGND
*   |   |   |   |   |   |   Q
*   |   |   |   |   |   |   |   QNOT
*   |   |   |   |   |   |   |   |
.SUBCKT AD8561  1   2   99  50  80  51  45  65
*
* INPUT STAGE
*
*
Q1 4  3 5 PIX
Q2 6  2 5 PIX
IBIAS 99  5 800E-6
RC14 50 1E3
RC26 50 1E3
CL14  6 1E-12
CIN1  2 3E-12
VCM1  99  7 1
D1 5  7 DX
EOS3  1 POLY(1) (31,98) 1E-3 1
*
* Reference Voltage
*
EREF 98 0 POLY(2) (99,0) (50,0) 0 0.5 0.5
RREF 98 0 100E3
*
* CMRR=80dB, ZERO AT 1kHz
*
ECM1 30 98 POLY(2) (1,98) (2,98) 0 0.5 0.5
RCM1 30 31 10E3
RCM2 31 98 1
CCM1 30 31 15.9E-9
*
* Latch Section
*
RX 80 51 100E3
E1 10 98 (4,6) 1
S1 10 11 (80,51) SLATCH1
R2 11 12 1
C3 12 98 10E-12
E2 13 98 (12,98) 1
R3 12 13 500
*
* Power Supply Section
*
GSY1 99 52 POLY(1) (99,50) 4E-3 -2.6E-4
GSY2 52 50 POLY(1) (99,50) 3.7E-3 -.6E-3
RSY  52 51 10
*
* Gain Stage Av=250 fp=100MHz
*
G2 98 20 (12,98) 0.25
R1 20 98 1000
C1 20 98 10E-13
D2 20 21 DX
D3 22 20 DX
V1 99 21 DC 0.8
V2 22 50 DC 0.8
*
* Q Output
*
Q3  99 41 46 NOX
Q4  47 42 50 NOX
RB1 43 41 200
RB2 40 42 5E3
CB1 99 41 10E-12
CB2 42 50 5E-12
RO1 46 45 2E3
RO2 47 45 500
EO1 98 43 POLY(1) (20,98) 0 1
EO2 40 98 POLY(1) (20,98) 0 1
*
* Q NOT Output
*
Q5  99 61 66 NOX
Q6  67 62 50 NOX
RB3 63 61 200
RB4 60 62 5E3
CB3 99 61 10E-12
CB4 62 50 5E-12
RO3 66 65 2E3
RO4 67 65 500
EO3 63 98 POLY(1) (20,98) 0 1
EO4 98 60 POLY(1) (20,98) 0 1
*
* MODELS
*
.MODEL PIX PNP(BF=100,IS=1E-16)
.MODEL NOX NPN(BF=100,VAF=130,IS=1E-14)
.MODEL DX D(IS=1E-16)
.MODEL SLATCH1 VSWITCH(ROFF=1E6,RON=500,VOFF=2.1,VON=1.4)
.ENDS AD8561
Version 4
SHEET 1 2888 1012
WIRE 208 0 -592 0
WIRE 1456 0 224 0
WIRE 1936 0 1472 0
WIRE 16 144 -64 144
WIRE 112 144 80 144
WIRE 128 144 112 144
WIRE 1216 144 1072 144

Re: [time-nuts] Thinking outside the box a super reference

[Poul-Henning Kamp]

In message <768ee5a7-1c53-06cf-cf36-ec75e2901...@karlquist.com>, "Richard 
(Rick) Karlquist" w
rites:

>Reminds me of an interesting Jack Kusters story.
>There was some customer who was having problems with
>his atomic clocks being noisy (I don't remember exactly
>the story) but the bottom line was that they determined
>it was because of helium contamination.

How would helium make his clocks noisy ?

Isn't it more likely that it was the alphas from the
radon decay that did it by their charge ?


-- 
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
p...@freebsd.org | TCP/IP since RFC 956
FreeBSD committer   | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
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[time-nuts] Calibrating a HP 5370B Oscillator

[Perry Sandeen via time-nuts]

Hi,
Wrote:I am the proverbial man with too many clocks and I don'tknow what time

it is.


To correct this situation I have decided to calibrateeverything.


 
I have a HP 5370B, a HP6370A, and a HP 5328A all with the TCXO 

option. 
Hi Peter,
You can't really calibrate the 5370B oscillator.  I tried.
All that you can do is adjust the mechanical adjustment as the EFC pin is 
grounded on the edge connector.
I thought about making the EFC pin available but it required cutting some of 
the bottom sheet metal.  Then one would have to cut the trace on the MB and add 
a highly regulated PS for the EFC with an adjustment control.
Also the PS for the oscillator is primitive and would need to be upgraded.
IMNSHO, the reason they left out doing this is the variations of airflow rate, 
airflow temperature and vibration from the cooling fan.
In the 5370A they used a less expensive oscillator.
I think that in the B model HP just wanted better stability to achieve the 
better pico-second  resolution rating.
An interesting experiment would be to run the B, take the 10 MHz output and 
compare it to a GPSDO or Rb standard and see how many variances that would 
occur.
IMNSHO, I drive the B with an its 10811 externally powered in a better 
enclosure.
I cant comment on the other gear.
Regards,
Perrier   
 
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Re: [time-nuts] Gentlemen: Synchronize Your Watches!

[Attila Kinali]

On Sat, 5 Nov 2016 04:19:08 + (UTC)
Perry Sandeen via time-nuts  wrote:

> Time may be relative, but physicists are a stickler for accuracy.

Ok.. the story without out the whole media mambojambo and mixup
of things can be found at [1]. A description of the setup they used
can be found at [2] and [3]. What they basically do is to use two
fs frequency combs running at 200MHz, each on the transmitter and
receiver side and implement a two-way frequency and  time transfer
using those pulses.

Attila Kinali


[1] "Synchronization of clocks through 12km of strongly turbulent air
over a city", by Sinclari et al. 2016
http://dx.doi.org/10.1063/1.4963130

[2] "Synchronization of Distant Optical Clocks at the Femtosecond Level",
by Deschenes et al. 2016
http://dx.doi.org/10.1103/PhysRevX.6.021016
https://arxiv.org/abs/1509.07888

[3] "Tight real-time synchronization of a microwave clock to an optical
clock across a turbulent air path", by Bergeron et al. 2016
http://dx.doi.org/10.1364/OPTICA.3.000441


-- 
Malek's Law:
Any simple idea will be worded in the most complicated way.
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Re: [time-nuts] Satellite TV messed up, how is GPS time

[David J Taylor]

Satellite TV (Dish, Direct, etc) has been having trouble for 10 hours or so, 
sometimes losing some channels and occasionally all of them.


Fox News is consistently down, so it could have a human cause, but Space 
Weather says we have unusual solar activity.


I no longer have GPS time receivers, so I wonder how GPS is doing.

Thanks for any comments.
Bill Hawkins
___

Bill,

GPS is fine here in Edinburgh:

 http://www.satsignal.eu/mrtg/performance_gps.php

Cheers,
David
--
SatSignal Software - Quality software written to your requirements
Web: http://www.satsignal.eu
Email: david-tay...@blueyonder.co.uk
Twitter: @gm8arv 


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

[Hal Murray]

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.

-- 
These are my opinions.  I hate spam.



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

[Bob Stewart]

Hi John,

I've never used the hot tweezers.  I'm going to have to look into them.  
Normally, for desoldering, I use a narrower nozzle with an elevated temperature 
- usually between 280C and 350C.  That blows the part completely off the pads 
just as soon as the solder flows, with little impact on adjacent components.  
For soldering, since I use a 240C leaded solder paste, i use a larger nozzle 
with slower air flow at about 245C-260C depending on what I'm soldering.  
Desoldering against a copper plane is always a problem regardless of the 
thermal pad's shape.  I'd think you'd need a pretty hot set of tweezers to get 
a big 1210 sized tantalum off the board if there's a ground plane.

Bob
 -
AE6RV.com

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

  From: John Ackermann N8UR 
 To: time-nuts@febo.com 
 Sent: Saturday, November 5, 2016 2:35 PM
 Subject: Re: [time-nuts] I love the smell of tantalum in the morning
   
Either hot tweezers or a hot air rework station are the best/easiest 
ways to remove dead parts.  But two fine-tip soldering irons will also 
work and are a lot cheaper.  The idea is to heat both ends of the part 
at once, and when the solder flows, lift or flip the part off.  Then, 
use some liquid flux and narrow solder wick to suck off the excess 
solder, and you should end up with nice smooth pads ready for the 
replacement part.

The key thing to avoid damage is to make sure the solder is really 
flowing on both pads before you try to lift the part.  Sometimes ground 
pads have enough thermal mass that it takes a while to get them hot 
enough.  Be patient.

Good luck!
John


On 11/05/2016 03:12 PM, Tom Van Baak wrote:
> See C13 in the attached photo. I need to replace some blown caps on a few 
> boards [1]. In one instance the cap got so hot it melted itself off the 
> board. Quiet convenient, actually -- it acts like its own fuse -- but I don't 
> think the 5071 designers had that clever feature in mind.
>
> 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?
>
> Thanks,
> /tvb
>
> [0] http://www.imdb.com/title/tt0078788/quotes
> [1] http://leapsecond.com/museum/hp5071a/A1-mother.htm
>
>
>
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Re: [time-nuts] I love the smell of tantalum in the morning

[Andrea Baldoni]

On Sat, Nov 05, 2016 at 12:12:18PM -0700, Tom Van Baak wrote:

> 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?

Hello Tom.
I do this kind of repairs quite often and as you have already read from others,
almost every method like hot air, hot tweezers and two irons is suitable.

However, if you have not previous experience of smd reworking and, being
lucky that the component has only two leads, if you can have someone who
will help you and there is enough clearance around the components, I suggest
you use two irons of normal power (> 50W) with flat tip.

Hot air is a much better way to do this work, but it's also more risky:
the temperature and air flux should be right (too low and you will heat too
much everything before desoldering the component, too high and you do the same).
You can end up with melted plastic parts in other components around the area.
In some cases when sensitive components are very near, I build little fences
out of sheet metal to lay on board around the component, letting just the space
to pull up it with tweezers.

To solder back, clean the pads with solder wick, then with some form of
liquid cleaner to remove traces of rosin (I use alcohol, or thinner in some
stubborn cases). Hold the component in position pushing down to the board and
solder it manually at the sides. Forget to use SMD paste and hot air for
soldering. This has not any sense with parts so big and with only two pins
and it's trickier than desoldering about temperature and airflow...

There is another thing to look at. In some process, mainly time ago, the SMD
components were glued before soldering, so the component, even if solder is
already melt, need some force to be pulled up.

Best regards,
Andrea Baldoni
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Re: [time-nuts] I love the smell of tantalum in the morning

[Tom Miller]

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.


Use a good sharp pair of flush cut side cutters.

Tom


- Original Message - 
From: "Bob Camp" 
To: "Tom Van Baak" ; "Discussion of precise time and 
frequency measurement" 

Sent: Saturday, November 05, 2016 4:24 PM
Subject: Re: [time-nuts] I love the smell of tantalum in the morning



Hi

A *lot* depends on how many planes there are in that board. The weight of 
he copper
also maters a bit. If there is enough thermal mass, you will need a 
pre-heat process.
There are lots of ways to do it ranging from the kitchen oven to various 
“frame and

lightbulb” setups and on into ever more complex heating approaches.

If the hot tweezers / soldering iron / hot air tool does not reflow the 
solder quickly (10 seconds
or less) stop. Get a pre-heat setup and try again. With proper heat you 
should have the part
off in under 4 seconds. People don’t tend to use stopwatches when 
soldering. 4 seconds is quite

a while on a joint. Ten seconds is pretty much forever ….

Bob


On Nov 5, 2016, at 3:12 PM, Tom Van Baak  wrote:

See C13 in the attached photo. I need to replace some blown caps on a few 
boards [1]. In one instance the cap got so hot it melted itself off the 
board. Quiet convenient, actually -- it acts like its own fuse -- but I 
don't think the 5071 designers had that clever feature in mind.


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?


Thanks,
/tvb

[0] http://www.imdb.com/title/tt0078788/quotes
[1] http://leapsecond.com/museum/hp5071a/A1-mother.htm
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Re: [time-nuts] I love the smell of tantalum in the morning

[Magnus Danielson]

Dear Tom,

On 11/05/2016 08:12 PM, Tom Van Baak wrote:

See C13 in the attached photo. I need to replace some blown caps on a few 
boards [1]. In one instance the cap got so hot it melted itself off the board. 
Quiet convenient, actually -- it acts like its own fuse -- but I don't think 
the 5071 designers had that clever feature in mind.


You're clearly lucky, one failure mode is short-circuit, and they can 
bring other stuff with them as they fail, and hence hated by some.



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?


Now, for these caps, you can use a normal soldering-iron without too 
much trouble, but I strongly recommend pre-heating the board with a 
hot-air gun.


The trick is to pre-heat the board widely so it becomes hot, but not 
enough to melt any solder. As you now apply your soldering iron, the 
heat-transfer won't be as large as if you had a room-temperature board, 
simply because the lower temperature gradient.
The effect is that your heating up goes quicker and that part of the 
board won't experience excess heat for too long.


Another trick I use is to solder new solder onto the joints. This breaks 
through the oxide layer, which is a poor heat conductor. I solder onto 
the joints and let them cool. Then I come back again and now the 
soldering iron melts it all up nicely.


I still do SMD with my Weller WECP-20, but it's not optimal.
At work we moved the otherwise so high valued (over-valued) Metcal to 
the side as the new JBC stations is much better. Metcal's doesn't keep 
the temperature good enough and the new JBCs is beeter. Metcal's also 
have a failure-mode in their tips which makes them break way to early. 
There exist replacement tips which is in fact better than the original.


So, if you need an excuse to buy a new toy, look at the JBC-stuff:
http://www.jbctools.com/

However, I would probably be able to replace that cap before your get 
your new and shiny toy on the table.


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

[Chris Waldrup]

Hi Tom,

I'm a SMT rework technician for a large satcom and defense company. 
I have a shop at home too and all the equipment to repair this if I can be 
provided with the replacement cap. 
Please let me know if I can be of help. 

Chris
KD4PBJ

> On Nov 5, 2016, at 14:12, Tom Van Baak  wrote:
> 
> See C13 in the attached photo. I need to replace some blown caps on a few 
> boards [1]. In one instance the cap got so hot it melted itself off the 
> board. Quiet convenient, actually -- it acts like its own fuse -- but I don't 
> think the 5071 designers had that clever feature in mind.
> 
> 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?
> 
> Thanks,
> /tvb
> 
> [0] http://www.imdb.com/title/tt0078788/quotes
> [1] http://leapsecond.com/museum/hp5071a/A1-mother.htm
> 
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Re: [time-nuts] I love the smell of tantalum in the morning

[Bob Camp]

Hi

A *lot* depends on how many planes there are in that board. The weight of he 
copper
also maters a bit. If there is enough thermal mass, you will need a pre-heat 
process. 
There are lots of ways to do it ranging from the kitchen oven to various “frame 
and 
lightbulb” setups and on into ever more complex heating approaches. 

If the hot tweezers / soldering iron / hot air tool does not reflow the solder 
quickly (10 seconds 
or less) stop. Get a pre-heat setup and try again. With proper heat you should 
have the part
off in under 4 seconds. People don’t tend to use stopwatches when soldering. 4 
seconds is quite 
a while on a joint. Ten seconds is pretty much forever ….

Bob

> On Nov 5, 2016, at 3:12 PM, Tom Van Baak  wrote:
> 
> See C13 in the attached photo. I need to replace some blown caps on a few 
> boards [1]. In one instance the cap got so hot it melted itself off the 
> board. Quiet convenient, actually -- it acts like its own fuse -- but I don't 
> think the 5071 designers had that clever feature in mind.
> 
> 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?
> 
> Thanks,
> /tvb
> 
> [0] http://www.imdb.com/title/tt0078788/quotes
> [1] http://leapsecond.com/museum/hp5071a/A1-mother.htm
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Re: [time-nuts] I love the smell of tantalum in the morning

[paul swed]

So much information from so many that have obviously run into the smell of
a burnt part.
I do the cut the part to pieces and unsolder each leg. Also the 2 iron
approach.
The absolute goal, do not damage the board.
I have a hot air station also and much like the comments made not impressed.
I did grab a scrap board to play with as I was learning.
Since your cap looks like it already split in half 50% of the jobs done.
As everyone focuses on the soldering part. The damaged board is equally
critical.
The stuff in tantalums is nasty. I clean the whole area with alcohol. And
at times actually carve out some of the carbon if I can measure some level
of resistance from each trace to the center point.
Your problem looks simple enough Tom.
Just remember this. I hate caps. But have received some of my best
equipment because they fail for $/pound. Kind of a love hate thing.
Regards
Paul
WB8TSL

On Sat, Nov 5, 2016 at 4:37 PM, Tom Miller  wrote:

> 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.
>
> Use a good sharp pair of flush cut side cutters.
>
> Tom
>
>
> - Original Message - From: "Bob Camp" 
> To: "Tom Van Baak" ; "Discussion of precise time and
> frequency measurement" 
> Sent: Saturday, November 05, 2016 4:24 PM
> Subject: Re: [time-nuts] I love the smell of tantalum in the morning
>
>
> Hi
>>
>> A *lot* depends on how many planes there are in that board. The weight of
>> he copper
>> also maters a bit. If there is enough thermal mass, you will need a
>> pre-heat process.
>> There are lots of ways to do it ranging from the kitchen oven to various
>> “frame and
>> lightbulb” setups and on into ever more complex heating approaches.
>>
>> If the hot tweezers / soldering iron / hot air tool does not reflow the
>> solder quickly (10 seconds
>> or less) stop. Get a pre-heat setup and try again. With proper heat you
>> should have the part
>> off in under 4 seconds. People don’t tend to use stopwatches when
>> soldering. 4 seconds is quite
>> a while on a joint. Ten seconds is pretty much forever ….
>>
>> Bob
>>
>> On Nov 5, 2016, at 3:12 PM, Tom Van Baak  wrote:
>>>
>>> See C13 in the attached photo. I need to replace some blown caps on a
>>> few boards [1]. In one instance the cap got so hot it melted itself off the
>>> board. Quiet convenient, actually -- it acts like its own fuse -- but I
>>> don't think the 5071 designers had that clever feature in mind.
>>>
>>> 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?
>>>
>>> Thanks,
>>> /tvb
>>>
>>> [0] http://www.imdb.com/title/tt0078788/quotes
>>> [1] http://leapsecond.com/museum/hp5071a/A1-mother.htm
>>> ___
>>> 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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>
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Re: [time-nuts] I love the smell of tantalum in the morning

[Tom Van Baak]

Ok, thanks, Chris! Some day I'll learn SMT but I don't think it's wise for me 
to use a 5071 main board as my first mistake. So I'll follow-up with your 
generous offer off-list.

/tvb

  - Original Message - 
  From: Chris Waldrup 
  To: Tom Van Baak ; Discussion of precise time and frequency measurement 
  Sent: Saturday, November 05, 2016 12:58 PM
  Subject: Re: [time-nuts] I love the smell of tantalum in the morning


  Hi Tom,


  I'm a SMT rework technician for a large satcom and defense company. 
  I have a shop at home too and all the equipment to repair this if I can be 
provided with the replacement cap. 
  Please let me know if I can be of help. 


  Chris
  KD4PBJ

  On Nov 5, 2016, at 14:12, Tom Van Baak  wrote:


See C13 in the attached photo. I need to replace some blown caps on a few 
boards [1]. In one instance the cap got so hot it melted itself off the board. 
Quiet convenient, actually -- it acts like its own fuse -- but I don't think 
the 5071 designers had that clever feature in mind.

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?

Thanks,
/tvb

[0] http://www.imdb.com/title/tt0078788/quotes
[1] http://leapsecond.com/museum/hp5071a/A1-mother.htm


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

[Mark Sims]

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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Re: [time-nuts] Thinking outside the box a super reference

[jimlux]

On 11/5/16 2:59 AM, Attila Kinali wrote:
 But we still need to ensure that the field is properly

oriented and homogenous over the whole vapor cell. For this you need
a cavity that is properly designed and most likely will be resonant at 6.9GHz.
(I don't know whether it is possible to design a non-resonant cavity with
the above properties)


isn't a TEM cell, as used in EMI/EMC testing, something like this?  It's 
a tapered transmission line and produces a uniform field within an area 
inside the line.




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Re: [time-nuts] Thinking outside the box a super reference

[Richard (Rick) Karlquist]

I think this is all described in the 1992 FCS papers,
but the executive summary is that a direct synthesizer
on 9192.63177 is to be avoided at all costs because
of the danger of it leaking into the CBT cavity.
This is also the reason why you don't multiply up
a subharmonic of this frequency.
It would also have made the synthesizer a lot more
complicated.  We multiplied 10 to 320 and then used
an SRD to get to 9280 and applied a sideband at 87.36
MHz to it.  The 87.36 MHz synthesizer was a phase
locked VCXO using a 5th OT crystal.

It took me a long time for me to sell this to Len Cutler.
It was pretty advanced for 1989.

Rick

On 11/4/2016 7:12 PM, paul swed wrote:

Rick on the pll DRO I agree with you for today.
So is it built for 9180 and then the 12.63 is mixed with it? Or is it
actually a direct PLL precisely at the frequency so not even the
synthesizer is used?
Regards
Paul
WB8TSL

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Re: [time-nuts] Thinking outside the box a super reference

[Richard (Rick) Karlquist]

On 11/5/2016 12:18 AM, Poul-Henning Kamp wrote:


In message <768ee5a7-1c53-06cf-cf36-ec75e2901...@karlquist.com>, "Richard (Rick) 
Karlquist" w
rites:


Reminds me of an interesting Jack Kusters story.
There was some customer who was having problems with
his atomic clocks being noisy (I don't remember exactly
the story) but the bottom line was that they determined
it was because of helium contamination.


How would helium make his clocks noisy ?

Isn't it more likely that it was the alphas from the
radon decay that did it by their charge ?


I probably am not remembering the story exactly, but
I do definitely remember it had to do with unexplained
helium, which they tried to blame Kusters company for.
He said there was a simple explanation, namely radon
gas emitting alpha particles that turn into helium
and helium can diffuse into "sealed" containers.
He basically told them that if they dropped the issue,
it wouldn't be necessary for him to publicize the fact
that their plant was full of radon.  It was really
funny when Jack himself told it.

Rick

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Re: [time-nuts] Thinking outside the box a super reference

[Attila Kinali]

Hoi Rick,

On Sat, 5 Nov 2016 07:17:21 -0700
"Richard (Rick) Karlquist"  wrote:

> I think this is all described in the 1992 FCS papers,
> but the executive summary is that a direct synthesizer
> on 9192.63177 is to be avoided at all costs because
> of the danger of it leaking into the CBT cavity.
> This is also the reason why you don't multiply up
> a subharmonic of this frequency.


I don't get what you mean with "danger of leaking into the CBT cavity"?
When signal leakage into the cavity is a problem, shouldn't that also
exist for the signal after the mixer? And what does this leaking actually
mean? The 9192.63177 is supposed to end up in the cavity anyways.

Attila Kinali

-- 
Malek's Law:
Any simple idea will be worded in the most complicated way.
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Re: [time-nuts] I love the smell of tantalum in the morning

[Scott Stobbe]

For through hole parts sure, but I would not recommend that on SMD parts,
the copper foil of a little pad is pretty easy to tear off and it's a royal
pain if you have to mount a device missing some of its landing pads.

On Sat, Nov 5, 2016 at 4:37 PM, Tom Miller  wrote:

> 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.
>
> Use a good sharp pair of flush cut side cutters.
>
> Tom
>
>
> - Original Message - From: "Bob Camp" 
> To: "Tom Van Baak" ; "Discussion of precise time and
> frequency measurement" 
> Sent: Saturday, November 05, 2016 4:24 PM
> Subject: Re: [time-nuts] I love the smell of tantalum in the morning
>
>
> Hi
>>
>> A *lot* depends on how many planes there are in that board. The weight of
>> he copper
>> also maters a bit. If there is enough thermal mass, you will need a
>> pre-heat process.
>> There are lots of ways to do it ranging from the kitchen oven to various
>> “frame and
>> lightbulb” setups and on into ever more complex heating approaches.
>>
>> If the hot tweezers / soldering iron / hot air tool does not reflow the
>> solder quickly (10 seconds
>> or less) stop. Get a pre-heat setup and try again. With proper heat you
>> should have the part
>> off in under 4 seconds. People don’t tend to use stopwatches when
>> soldering. 4 seconds is quite
>> a while on a joint. Ten seconds is pretty much forever ….
>>
>> Bob
>>
>> On Nov 5, 2016, at 3:12 PM, Tom Van Baak  wrote:
>>>
>>> See C13 in the attached photo. I need to replace some blown caps on a
>>> few boards [1]. In one instance the cap got so hot it melted itself off the
>>> board. Quiet convenient, actually -- it acts like its own fuse -- but I
>>> don't think the 5071 designers had that clever feature in mind.
>>>
>>> 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?
>>>
>>> Thanks,
>>> /tvb
>>>
>>> [0] http://www.imdb.com/title/tt0078788/quotes
>>> [1] http://leapsecond.com/museum/hp5071a/A1-mother.htm
>>> ___
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>>> ailman/listinfo/time-nuts
>>> and follow the instructions there.
>>>
>>
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>> and follow the instructions there.
>>
>
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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 
 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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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 
 To: Bob Stewart  
 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  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 
> To: Discussion of precise time and frequency measurement  
> 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  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 
> > To: Discussion of precise time and frequency measurement 
> >  
> > 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  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 
> >>  To: Bob Stewart 
> >> Cc: Hal Murray 
> >>  Sent: Saturday, November 5, 2016 6:23 PM
> >>  Subject: Re: [time-nuts] 

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

[Andy ZL3AG via time-nuts]

Yes. Unless you're grinding it away with a dremel (which I wouldn't recommend 
as far as chemical dust is concerned), nibbling away with sidecutters would be 
trying to force the 2 ends of the component apart. That may be stressing the 
pads they're soldered to, leading to a possible pad lifting at some stage.

Any of the methods mentioned that heat both ends at the same time - allowing 
the component to be wiped off the board - would have to be the best, 
stress-wise.

On 6/11/2016, at 3:00 PM, Scott Stobbe wrote:

> For through hole parts sure, but I would not recommend that on SMD parts,
> the copper foil of a little pad is pretty easy to tear off and it's a royal
> pain if you have to mount a device missing some of its landing pads.
> 
> On Sat, Nov 5, 2016 at 4:37 PM, Tom Miller  wrote:
> 
>> 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.
>> 
>> Use a good sharp pair of flush cut side cutters.
>> 
>> Tom
>> 
>> 

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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  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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> 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 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  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 
> To: Bob Stewart  
> 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  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 
> > To: Discussion of precise time and frequency measurement 
> >  
> > 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  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 
> > > To: Discussion of precise time and frequency measurement 
> > >  
> > > 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  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 

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

[Ian Stirling]

On 11/05/2016 03:12 PM, Tom Van Baak wrote:

> 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?

Tom, I used the obvious but never read about using two soldering irons,
invented it myself, or co-discovered.

  Also, a recent addition that makes SMT so easy, the title of the manual is,
"Instruction Manual for SE400, SE400-LED,  Long Working Distance Stereo 
Microscope",
about $200.

  With a working distance of nine inches or so, it beats the pants off my
previous magnifier, Optivisor 10x where I have to have my face less than two
inches from the soldering area.

  .. got the microscope from description from W7ZOI web site.
http://w7zoi.net/micscope.html

Ian, G4ICV, AB2GR
--


 

  

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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  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 
>  To: Bob Stewart 
> Cc: Hal Murray 
>  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
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Re: [time-nuts] Lady Heather and LeapSecond

[Chris Arnold via time-nuts]

Where will the file go?




-Original Message-
From: Mark Sims 
To: time-nuts 
Sent: Fri, Nov 4, 2016 2:37 pm
Subject: [time-nuts] Lady Heather and LeapSecond

Yes,  and it will also automatically do a screen dump to the file 
"leap_sec.gif" That all assume that the GPS device reports a leap second as 
23:59:60.   Some devices duplicate 23:59:59 or 00:00:00   I have also seen one 
say 00:00:60

The next version of Lady Heather internally handles time differently.  Instead 
of dragging around variables for 
year,month,day,hours,minutes,seconds,fractions-of-second, it now keeps time in 
double precision Julian date variables (for gps, utc, local, and astronomical 
times).  When those are converted to hours/minutes/seconds for display the 
23:59:60 was coming out 00:00:00 .  I had to implement a special flag that says 
to show it as 23:59:60  ...  hopefully that all works...  it did when my Z3801A 
did a false leap-second at the end of September.

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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  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 
> To: Discussion of precise time and frequency measurement  
> 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  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 
>>   To: Bob Stewart 
>> Cc: Hal Murray 
>>   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
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> 
> 
> 
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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 
 To: Discussion of precise time and frequency measurement  
 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  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 
> To: Discussion of precise time and frequency measurement  
> 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  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 
>>  To: Bob Stewart 
>> Cc: Hal Murray 
>>  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
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>> and follow the instructions there.
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> and 

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
>
>
>
>
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> mailman/listinfo/time-nuts
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>
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Re: [time-nuts] I love the smell of tantalum in the morning

[Alexander Pummer]

metcal has a "hot twizer " to remove SMD components it heats the 
component on both end


73

Alex


On 11/5/2016 12:55 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.



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

[David]

On Sat, 5 Nov 2016 20:57:11 +0100, you wrote:

>> 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?
>
>Now, for these caps, you can use a normal soldering-iron without too 
>much trouble, but I strongly recommend pre-heating the board with a 
>hot-air gun.
>
>The trick is to pre-heat the board widely so it becomes hot, but not 
>enough to melt any solder. As you now apply your soldering iron, the 
>heat-transfer won't be as large as if you had a room-temperature board, 
>simply because the lower temperature gradient.
>The effect is that your heating up goes quicker and that part of the 
>board won't experience excess heat for too long.

I have never had a problem removing surface mount parts like that with
just a single soldering iron.  If access is good so that a large heat
capacity tip can be applied, then each solder joint can be heated up
very quickly preventing damage to the board.

Through hole parts on multilayer boards which have a high heat
capacity are a different manner.

>Another trick I use is to solder new solder onto the joints. This breaks 
>through the oxide layer, which is a poor heat conductor. I solder onto 
>the joints and let them cool. Then I come back again and now the 
>soldering iron melts it all up nicely.

On newer boards this is also a great way to dilute the lead free
solder lowering the melting point making removal easier without
damaging the board.

Add some leaded solder and flux to each joint, then remove most of the
solder from each joint with braid, and then a little heat will allow
each side of the part to pop off.

>I still do SMD with my Weller WECP-20, but it's not optimal.
>At work we moved the otherwise so high valued (over-valued) Metcal to 
>the side as the new JBC stations is much better. Metcal's doesn't keep 
>the temperature good enough and the new JBCs is beeter. Metcal's also 
>have a failure-mode in their tips which makes them break way to early. 
>There exist replacement tips which is in fact better than the original.
>
>So, if you need an excuse to buy a new toy, look at the JBC-stuff:
>http://www.jbctools.com/
>
>However, I would probably be able to replace that cap before your get 
>your new and shiny toy on the table.
>
>Cheers,
>Magnus

I still use my ancient Weller Magnestat irons but have quite a
collection of tips including my overpowered vacuum desoldering head.
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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 
 To: Bob Stewart  
Cc: Hal Murray 
 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] Newbie With a Z3801 Problem

[Gerhard Hoffmann]

Am 05.11.2016 um 12:51 schrieb Bill Riches:

Hi Mark,

Thank you for working with the KS24361.  Looking forward to when the program 
will be available.

Any ideas on being able to use the 1 PPS signal out of the KS24361 to drive SL 
sound card calibration?  It is a weird pulse and someone mentioned the timing 
is wrong.  I use the pulse out of a Jackson unit with SL and it works fine.



In  ,

I have described a 1pps-Buffer, frequency doubler 5->10MHz and 
distribution amplifier
for the KS24361.  You may not want to build it, but there are pictures 
of the

1pps timing of the Lucent and and also a pic that shows where you can get
the internal 1pps in LVCMOS / TTL level. Buffer it to your taste and 
feed it

to a new BNC / SMA / whatever on the front plate.

73, Gerhard, DK4XP

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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 
 To: Discussion of precise time and frequency measurement  
 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  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 
>  To: Bob Stewart 
> Cc: Hal Murray 
>  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
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[time-nuts] Corby Watson Super 5065a work can I use a miniature Rubidium

[Anton Moehammad via time-nuts]

Hi all,a few day ago I read "super HP5065A" from Mr Corby and I wondering if 
any one has done same thing with "telecom" Rubidium pack ? I found an optical 
bandpass filter cost is cheap enough to a third country people like me but if 
any one has tried before and know a lot more than what I know I really 
appreciate if You can share it 
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[time-nuts] Lady Heather and LeapSecond

[Mark Sims]

It should wind up in the standard Lady Heather directory...  depends upon the 
operating system and how the program was started.   From the keyboard in Lady 
Heather, type ?  That will bring up the command line option help.  Scroll/page 
down to the end of the info and there will be a line that says something like 
"Put heather.cfg in directory... "

---

>   Where will the file go?
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Re: [time-nuts] Thinking outside the box a super reference

[Attila Kinali]

On Fri, 04 Nov 2016 23:04:22 +
"Poul-Henning Kamp"  wrote:

> First:  Yes, but if you pick a sensible vibration mode for your
> microwave resonance, that can be done with an screw-in endcap.
> 
> Second:  No, I would actually not need to tune it.
> 
> Historically resonance cavities were used so that step/avalance
> diode multipliers had enough power to excite them.  Today we have
> semiconductors which work at those frequencies.

Yes, it is easier to create the required frequencies with high power
(getting 7GHz with 10dBm is trivial and 30dBm can be readily achieved
with single chip amplifiers) and the signal will be cleaner than what
an SRD setup can achieve (no spurs, comparable close-in phase noise
characteristic). Thus we can use cavities with lower Q which are easier
to build and tune. But we still need to ensure that the field is properly
oriented and homogenous over the whole vapor cell. For this you need
a cavity that is properly designed and most likely will be resonant at 6.9GHz.
(I don't know whether it is possible to design a non-resonant cavity with
the above properties)
 
> But the resonanance leads to all sorts of trouble, including frequency
> pulling, temperature sensitivities etc.

Frequency pulling is not so much of an issue for a vapor cell standard
as it is for hydrogen masers or the primary standards. The shifts due
to buffer gas and wall collisions are so large that a calibration is
needed anyways. Frequency pulling just adds another term. Temperature
sensitivity is IIRC lower for frequency pulling than for buffer gas shift,
but I could be mistaken. For high stability applications, temperature
stabilization of the cavity and the cell are advised anyways.

> Third:  A lot of the "everybody knows" about which atoms can be
> used for active vs. passive atomic standards comes from the
> state of the art electronics about 30 years ago.

A lot of the "everybody knows" has been challenged and rewritten
in the past 10-20 years. Although, it looks like the vapor cell
standards have not changed in 50 years, there has been a lot of
research going on and people optimized old ideas and came up with
new ones. Yes, a lot of the electronics design is rather crude,
but most of the people working in the field a physicists or electrical
engineers that just graduated, one cannot expect the level of skill
and expertise of someone who has been doing RF designs for 30 years.
Beside, these people are there to do research, not to design electronics.
The circuits are just a tool for the research, not their main topic.
Hence they rather spend 100k€ on a synthesiser from keysight instead
of spending 6 months for designing their own to save money.

 
> Using laser-pumping and modern semiconductors, it might actually
> be possible to detect the 6.8GHz photons from the Rb.

You mean an optically pumped active maser? (our vapor cell standards
are passive masers allready) This has been already done in the 60's[1]
and studied later again (eg [2]). I guess this isn't popular because
the short term stability of Rb vapor cell standards is already quite
good and the long term stability does not get improved. So it does not
justify the additional complexity.


> They won't be coherent photons, like in a Hydrogen maser, but we
> don't need them to be, in fact that just causes the same exact
> problems as the tuned cavity anyway, as long as we can measure
> the frequency well enough.

If you mean to detect the decay from the 5S hyperfine splitting,
then i have to disapoint you. There will not be much radiation to detect.
On one hand, the lifetime of the hyperfine splitting is quite long, thus
the electrons will just get stuck on the upper level after they fell
down from the 5P state (it's a forbidden transition after all).
A photon to stimulate the fall to the lower state is required, either
provided by spontaneous emission from other Rb atoms or from an external
source. On the other hand, if the photons are not coherent, they will
not build up a signal that one could detect. They will just be spikes
that get burried in noise. Yes, one could build a spectrometer which would
average over a lot of these photons, but that would require a stable
frequency source to be able to avearge for a long time. And I don't think
a simple OCXO is up to this task. 


Attila Kinali

[1] "The Optically Pumped Rubidium Maser", by Davidovits and Novik, 1966
http://dx.doi.org/10.1109/PROC.1966.4628

[2] "Experimental Study of the Laser Diode Pumped Rubidium Maser",
by Michaud Tremblay and Tetu, 1991
http://dx.doi.org/10.1109/TIM.1990.1032908
https://arxiv.org/abs/physics/0508227

-- 
Malek's Law:
Any simple idea will be worded in the most complicated way.
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Re: [time-nuts] Thinking outside the box a super reference

[Gerhard Hoffmann]

Am 05.11.2016 um 00:45 schrieb David:

On Fri, 04 Nov 2016 14:39:54 -0700, you wrote:

87-Rb has a half life of something like 4.9e10 years — you'll be waiting
a while for that strontium. /gp

Various online sources say that natural rubidium is radioactive enough
to fog photographic film in 1 to 2 months but that is also the case
with unprocessed uranium ore so I would not worry about it at all.

That's next to nothing. A friend of mine with interest in minerals found a
piece of Pechblende (Uranit) simply laying on the street near 
St.Joachimsthal
where they used to dig for silver over the centuries and after 1945 for 
uranium.


We put it on a sheet of Polaroid film for the Tektronix scope cameras and
sure enough, next morning we could see the silhouette of the stone,
completely white, probably way overexposed.

regards, Gerhard
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