[time-nuts] HP5061B Square Wave Modulation Evaluation

[cdelect]

Attached is a plot showing the measured floor of the sine wave loop 
in the 5061A/B and also in the 5065A, along with plot of an HP 5061B
with a high performance tube.

The tube is the limiting factor.
As you can see the margin provided by the current design is substantial.

Also if you look at the FTS 4050 and 4060 that use square wave modulation
they are a bit noisier than the HP 5061A/B.

If you can provide an Allan deviation plot using the existing sine wave
system along with a plot of the square wave modified system doing better
I'll be surprised!

If you really want to make your Cesiums STS better then I'd suggest
building a disciplined clean up oscillator like the Microsemi 4145C.
If you look at the Allan deviation plot of the combined 5071A and 4145C
you can see it works pretty good. However I'm not sure how good a 
"cherry-picked" 10811 or FTS 1200 at 6 parts in 10-13th or so will
compare to the BVA!

Corby___
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Re: [time-nuts] Three-cornered hat on timelab?

[Bob kb8tq]

Hi

There are a number of papers from the 70’s and 80’s digging into three corner 
hat data. The net result often
would turn out to be “less than zero” noise on one of the DUT’s. Since that’s 
physically impossible the technique
got a bit of “attention”.  The Cliff Notes version of the results is that 
simultaneous measurements were the key
to getting decent results. The closer to “same time” (as in microseconds or 
nanoseconds) the better. Even with very careful 
data collection, odd things can still happen. Phase noise pops up at crazy low 
levels or ADEV goes to bizarre
numbers. In many ways a TimePod (or other ADC based setup) is ideal for getting 
the data synchronized. Running
all three devices on one is by far the best way I have seen to make the 
technique work. It still can have problems, 
but less so that other ways of doing it. 

Bob



> On Apr 13, 2017, at 7:16 PM, Bob Stewart  wrote:
> 
> Hi John,
> I had a chance to think about this some more after I pressed the send key.  
> The ionospheric effects are certainly going to be different if the distance 
> in time between tests is large.  And, of course, there is the fact that the 
> KS has a pretty old receiver compared the Ublox I use, so that even the 
> reaction to the ionosphere is likely to be different.  So, I thought I'd 
> experiment with some runs with both GPSDOs in holdover to see if that would 
> even the score, so to speak.  Of course then I have the temperature variable, 
> so it's never going to be perfect.
> Anyway, thanks for the help.  If I get anything that seems useful out of 
> this, I'll post links to the data.
> Bob 
> 
>  From: John Miles 
> To: 'Discussion of precise time and frequency measurement' 
>  
> Sent: Thursday, April 13, 2017 6:01 PM
> Subject: Re: [time-nuts] Three-cornered hat on timelab?
> 
> Longer runs would be better to the extent that they give you smaller error 
> bars in your tau range of interest, certainly.  But any effects that 
> influence one of your runs but not the others will render the 3-cornered hat 
> solution questionable, if not outright invalid.  Only through many repeated 
> runs can you learn to tell the bogus data from the good stuff.  So I'd make 
> shorter runs at first, until you're sure you know what you're looking at.
> 
> 
> 
> It doesn't matter which source is applied to the start versus stop channel, 
> as long as the assignments are consistent with the source labels you apply.  
> I would use frequency-count mode to simplify things, at least at first.  This 
> is already a very challenging measurement for all the reasons mentioned. 
> 
> 
> 
> -- john, KE5FX
> 
> Miles Design LLC
> 
> 
> 
> 
> 
> From: Bob Stewart [mailto:b...@evoria.net] 
> Sent: Thursday, April 13, 2017 8:41 AM
> To: Discussion of precise time and frequency measurement; John Miles
> Subject: Re: [time-nuts] Three-cornered hat on timelab?
> 
> 
> 
> Hi John,
> 
> 
> 
> Thanks!  With lesser equipment, such as the 5370A, would longer runs be 
> better?  I used a set of 1 hr runs and the result wasn't quite what I had 
> expected.  However, it may be that I had mislabeled the files, and thus got 
> the sources confused.  Of course, it may be that the ionospheric effect was 
> grossly different between the three tests.  So, with a 5370, Source A would 
> be the START input and Source B would be the STOP input, right?  For my 
> testing, the sources are all 10MHz signals, and I'm driving the EXT input 
> with 1PPS from a GPSDO.
> 
> 
> 
> 
> 
> Bob 
> 
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> 
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Re: [time-nuts] Three-cornered hat on timelab?

[Bob Stewart]

Hi John,
I had a chance to think about this some more after I pressed the send key.  The 
ionospheric effects are certainly going to be different if the distance in time 
between tests is large.  And, of course, there is the fact that the KS has a 
pretty old receiver compared the Ublox I use, so that even the reaction to the 
ionosphere is likely to be different.  So, I thought I'd experiment with some 
runs with both GPSDOs in holdover to see if that would even the score, so to 
speak.  Of course then I have the temperature variable, so it's never going to 
be perfect.
Anyway, thanks for the help.  If I get anything that seems useful out of this, 
I'll post links to the data.
Bob 

  From: John Miles 
 To: 'Discussion of precise time and frequency measurement' 
 
 Sent: Thursday, April 13, 2017 6:01 PM
 Subject: Re: [time-nuts] Three-cornered hat on timelab?
   
Longer runs would be better to the extent that they give you smaller error bars 
in your tau range of interest, certainly.  But any effects that influence one 
of your runs but not the others will render the 3-cornered hat solution 
questionable, if not outright invalid.  Only through many repeated runs can you 
learn to tell the bogus data from the good stuff.  So I'd make shorter runs at 
first, until you're sure you know what you're looking at.

 

It doesn't matter which source is applied to the start versus stop channel, as 
long as the assignments are consistent with the source labels you apply.  I 
would use frequency-count mode to simplify things, at least at first.  This is 
already a very challenging measurement for all the reasons mentioned. 

 

-- john, KE5FX

Miles Design LLC

 

 

From: Bob Stewart [mailto:b...@evoria.net] 
Sent: Thursday, April 13, 2017 8:41 AM
To: Discussion of precise time and frequency measurement; John Miles
Subject: Re: [time-nuts] Three-cornered hat on timelab?

 

Hi John,

 

Thanks!  With lesser equipment, such as the 5370A, would longer runs be better? 
 I used a set of 1 hr runs and the result wasn't quite what I had expected.  
However, it may be that I had mislabeled the files, and thus got the sources 
confused.  Of course, it may be that the ionospheric effect was grossly 
different between the three tests.  So, with a 5370, Source A would be the 
START input and Source B would be the STOP input, right?  For my testing, the 
sources are all 10MHz signals, and I'm driving the EXT input with 1PPS from a 
GPSDO.



 

Bob 

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Re: [time-nuts] Three-cornered hat on timelab?

[John Miles]

Longer runs would be better to the extent that they give you smaller error bars 
in your tau range of interest, certainly.  But any effects that influence one 
of your runs but not the others will render the 3-cornered hat solution 
questionable, if not outright invalid.  Only through many repeated runs can you 
learn to tell the bogus data from the good stuff.  So I'd make shorter runs at 
first, until you're sure you know what you're looking at.

 

It doesn't matter which source is applied to the start versus stop channel, as 
long as the assignments are consistent with the source labels you apply.  I 
would use frequency-count mode to simplify things, at least at first.  This is 
already a very challenging measurement for all the reasons mentioned. 

 

-- john, KE5FX

Miles Design LLC

 

 

From: Bob Stewart [mailto:b...@evoria.net] 
Sent: Thursday, April 13, 2017 8:41 AM
To: Discussion of precise time and frequency measurement; John Miles
Subject: Re: [time-nuts] Three-cornered hat on timelab?

 

Hi John,

 

Thanks!  With lesser equipment, such as the 5370A, would longer runs be better? 
 I used a set of 1 hr runs and the result wasn't quite what I had expected.  
However, it may be that I had mislabeled the files, and thus got the sources 
confused.  Of course, it may be that the ionospheric effect was grossly 
different between the three tests.  So, with a 5370, Source A would be the 
START input and Source B would be the STOP input, right?  For my testing, the 
sources are all 10MHz signals, and I'm driving the EXT input with 1PPS from a 
GPSDO.



 

Bob 

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[time-nuts] HP5061B Square Wave Modulation Evalukation

[Donald E. Pauly]

https://www.febo.com/pipermail/time-nuts/2017-April/thread.html

We did some testing to evaluate the advantages of square wave
modulation instead of sine waves for locking to the atomic resonance
peak.  We drove J1 on the A3 board with a 2.8 Volt peak to peak
triangle at 20 cps from a signal generator.  The crystal oscillator
fine frequency was adjusted downward for below resonance. See
http://gonascent.com/papers/hp/hp5061/waveform/sqrmod.jpg .

The frequency out of the phase modulator is proportional to the
derivative of the varicap voltage drive.  For the triangle rising
slope, the varicap is linearly increasing in capacitance with an
constantly increasing phase lag.  For the falling slope it is linearly
decreasing in capacitance and a constantly increasing phase lead.
This results in a lower and higher frequency for the positive and
negative slope of the triangle respectively.   The frequency shifts
suddenly from about 300 cps below resonance to about 100 cps above
resonance.  We performed the same measurements with the fine frequency
centered and above resonance but did not photograph them.

Back of the envelope calculations predict a 10:1 improvement in jitter
with square wave lock for average measurement times of 1 second.  Beam
current was injected directly into the scope with its 1 Meg resistance
being the load for the electron multiplier.   The scope was inverted
to give a positive appearing beam current of 5 nA per division.  Peak
beam current is about 22 nA. (nA=Beam I meter reading)  Note that the
beam current is slightly delayed from the triangle and contains
positive spikes at both transitions.  This originates from the 1
millisecond or so travel time of the beam from the start of the
microwave path to its end.  During the rising portion of the triangle,
the frequency out of the phase modulator is lowest and slightly below
resonance.  During the falling portion, it is the highest and slightly
above resonance.

When the frequency suddenly shifts, the beam cannot react instantly
because it is only traveling at the speed of sound and must travel a
foot or so in the microwave path.  This takes on the order of a
millisecond. A positive spike is created  as the frequency passes thru
the resonance peak at 22 nA. This occurs at both the low to high
transition and the high to low transition.   The frequency changes so
fast that the voltage cannot reach 22 nA.  As the center frequency is
reduced, the negative half of the square wave becomes more negative
and the positive half becomes more positive.  As the center frequency
is increased the square wave negative half becomes less negative and
the positive half becomes less positive.

When the center frequency is at the resonance of the cesium line the
square wave disappears except for the spikes.  Above center frequency,
it reverses phase and gradually gets bigger.  This type of lock is
nearly 100% efficient and should be far lower noise.

πθ°μΩω±√·Γλ
WB0KVV
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Re: [time-nuts] OCXO Soft-Start

[Bob kb8tq]

Hi

If your MCU has a POR that resets the internal oscillator that’s an unusual 
part. Most
of them I’ve seen simply reset the CPU…..Once the 8 MHz crystal oscillator is 
running 
at 37 to 53 MHz (or KHz) it may or may not ever return to 8 MHz on it’s own. 
Yes, you 
need to get into some nutty (as in volt per second) rates to see a lot of this 
kind of thing. 
It’s not a common thing to run into on a real design and it is even less common 
to see
it tested for. Unfortunately there are a few fields / companies where really 
slow supply ramps are
“the way it’s done”.  Needless to say, they have a lot of fun getting stuff to 
work right.

Bob

> On Apr 13, 2017, at 1:41 PM, Scott Stobbe  wrote:
> 
> I can't say I have run into that issue with a MCU as most 21st century ones
> have a decent POR and Brown out detect (which typically burns 10x more
> current than a 32k XO + RTC, and may get switched off in battery
> applications, and then problems can occur). What does seem to come up is
> stuff hanging off non-always on power rails (ADC,DAC,Sensors,etc), leakage
> and back-feeding onto their dedicated supply has them try to startup on
> leakage but there isn't enough leakage to actually power the device. They
> may issue the on die reset once and then the supply collapses all the flops
> lose their reset state, but the IC dosen't try to reset again.
> 
> Fortunately, you can buy a bunch of LDOs which include a small discharge
> FET to help this case as well as others.
> 

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Re: [time-nuts] OCXO Soft-Start

[Scott Stobbe]

I can't say I have run into that issue with a MCU as most 21st century ones
have a decent POR and Brown out detect (which typically burns 10x more
current than a 32k XO + RTC, and may get switched off in battery
applications, and then problems can occur). What does seem to come up is
stuff hanging off non-always on power rails (ADC,DAC,Sensors,etc), leakage
and back-feeding onto their dedicated supply has them try to startup on
leakage but there isn't enough leakage to actually power the device. They
may issue the on die reset once and then the supply collapses all the flops
lose their reset state, but the IC dosen't try to reset again.

Fortunately, you can buy a bunch of LDOs which include a small discharge
FET to help this case as well as others.


On Thu, Apr 13, 2017 at 9:17 AM, Bob kb8tq  wrote:

> Hi
>
> It’s a good bet that there is at least one regulator IC inside any modern
> OCXO.
> As you slowly ramp the input voltage on a regulator, various odd things may
> or may not happen. A 1 mv / s ramp on the outside can be “who knows what”
> at the oscillator level. That said, slow voltage ramps are a really good
> way to put
> all sorts of oscillator circuits into really odd modes. Clock oscillators
> (XO’s) and MCU
> built in clock circuits very definitely fall into this category.
>
> The same sort of “who knows what” problem also gets into the rest of the
> circuit.
> A limited supply might work fine nine times out of ten or 99 out of 100.
> On the
> odd time out, something goes poof !
>
> Bob
>
> > On Apr 12, 2017, at 11:40 PM, Scott Stobbe 
> wrote:
> >
> > Bob, Rick, my use of modes vs overtones was loose, you guys are spot on.
> >
> >
> > That's a fun challenge, suppressing a mode 10% higher in frequency.
> That's
> > a bit of a fussy LC filter/trap.
> >
> > So if I assume the tempCo of the B-mode to be 20 ppm/degC, that would
> mean
> > the heater servo has a sustained oscillation of about 250 udegC all day
> > long.
> >
> > Power cycling for 100 ms isn't long enough for the crystal motion to die
> > out, 200 ms seems to do it, which ~2 MCycles. At which point it runs on
> the
> > 10MHz C-Mode as desired.
> >
> > I couldn't say who Trimble went with, to me its an ebay special :), but
> > photo attached anyways.
> >
> > When the supply is current or power limited the effective supply slew
> rate
> > is something like 1 mV/s, and under these conditions, at least this
> > particular unit starts up on B-mode every time.
> >
> > Running one of these on a USB supply (5V, 500mA = 2.5W) is looking
> > plausible.
> >
> > On Wed, Apr 12, 2017 at 9:30 PM, Bob kb8tq  wrote:
> >
> >> Hi
> >>
> >> A SC cut crystal has multiple resonance “modes” in can operate on. This
> is
> >> in addition to the
> >> normal set of fundamental, third overtone, fifth overtone and so on. For
> >> various interesting reasons
> >> the SC modes are called A, B and C.  On a normal 10 MHz crystal, the
> “main
> >> mode” is the C mode. The
> >> A mode is well below this mode both in frequency and amplitude. The B
> mode
> >> is more problematic, It is
> >> 8 to 12% above the C mode in frequency and may be higher in amplitude
> >> (lower resistance) than the
> >> desired mode.
> >>
> >> The C mode has a “useful” third order temperature characteristic. The B
> >> mode has a fairly steep linear
> >> temp co. One of the classic design experiments on a SC based design is
> to
> >> force the oscillator onto the
> >> B mode. This lets you investigate the oven gain while running a
> >> temperature run. What you have likely
> >> done is to put the unit onto the B mode.
> >>
> >> Oscillators tend to be fractal when switching between modes. Minor
> startup
> >> issues can drive the circuit
> >> one way or the other. Once it gets onto a mode, it may be quite
> difficult
> >> to get it off of that mode ….
> >>
> >> Bob
> >>
> >>> On Apr 12, 2017, at 5:38 PM, Scott Stobbe 
> >> wrote:
> >>>
> >>> Hello,
> >>>
> >>> I wanted to see if I could soft-start a used OCXO (Trimble 34310)
> during
> >>> warm-up. By default with an appropriately rated 12 VDC supply, the OCXO
> >>> starts the heater at about 8 W, and eventually settles down to 2 W for
> >>> 20-25 degC ambient temperature. Figure Attached.
> >>>
> >>> The good news is it does startup with either a current limited or power
> >>> limited supply. Albeit, for the constant current case the start-up time
> >> is
> >>> dramatically longer. Figures Attached.
> >>>
> >>> The bad news, but interesting tangent is that when this particular OCXO
> >> is
> >>> soft-started, it doesn't oscillate at 10 MHz! It starts up on a
> spurious
> >>> overtone at 10.9 MHz. There isn't even a hint of 10 MHz in the output
> >>> spectrum just the 10.9 MHz tone (and some noise from the banana
> >> clip-leads
> >>> loop-antenna). So this is a bit of a pain for soft-starting because,
> >>> although the oven eventually comes into regulation, 

[time-nuts] Last notice for live online class, Phase Noise Fundamentals

[Gary Giust]

For anyone interested in a fundamentals class on phase noise, I'm 
teaching an online class with live instruction (including video 
recordings in case you miss a class) titled "Phase Noise Fundamentals."


https://www.jitterlabs.com/support/training/phasenoiseclass

Register with the coupon code TIMENUTS1704 to receive 10% off (coupon is 
only valid for the April class).


If any questions, please call or message me at

https://www.jitterlabs.com/company/contact

Best regards,
Gary Giust
JitterLabs

 Class syllabus follows --

PART 1: BASIC CONCEPTS

Measures of Quality

Precision. Stability. Accuracy. Crystal oscillators. Drift. Allan 
deviation. Time error. Time interval error (TIE). Wander. Phase Noise.


Phase Noise and Jitter

Digital versus RF. Phase noise versus jitter. Power-law model of phase 
noise. Stability metrics. Sources of phase noise.


PART 2: ANALYSIS

Phasor representation. Effect of changing temperature, signal power, and 
carrier frequency on phase noise. Leeson's equation. Amplifiers. Random 
versus spurious phase noise. Spur-detection algorithms. Convert from 
dBc/Hz to seconds RMS, and from dBc to seconds peak-peak. Compute phase 
jitter from phase noise. Select the right offset-frequency range for 
integration. Spur analysis. Determine dominant noise sources.


PART 3: MEASUREMENT

Spectrum analyzers. IF-filter resolution bandwidth. Phase noise 
analyzers. Eliminating AM. Additive, multiplicative, and residual noise. 
Phase-detector method. PLL with reference-source method. Cross 
correlation to reduce instrument noise floor. Delay-line discriminator 
method. Effect of power supply noise. Measuring differential signals. 
Balun artifacts and how to minimize them. Measurement tradeoffs and best 
practices.


PART 4: APPLICATIONS

Phase-locked Loops (PLLs)

Analog PLL operation and model. Transfer functions. Effect of bandwidth 
on phase noise. Sources of spurious and random phase noise. Impact of 
frequency division, and integer-N versus fractional-N architectures, on 
phase noise.


SERDES Reference Clocks

Anatomy of a serial link. PLL jitter transfer. Receiver observed jitter 
transfer. Reference-clock analysis. Converting phase noise into jitter 
at a given BER.


RF Transceivers (QAM)

Role of LO phase noise in RF up/down conversion. I-Q modulation. 
Constellation diagrams. I-Q demodulation. Phase errors. Phase noise 
budgeting. Effect of phase noise on symbol error rate (SER), and error 
vector magnitude (EVM). Testing.


Analog Data Converters (ADCs)

Operation. Aperture and phase jitter. Signal-to-noise ratio. 
Offset-frequency range for integration. Effect of clock spurs.

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Re: [time-nuts] Three-cornered hat on timelab?

[Bob Stewart]

Hi John,
Thanks!  With lesser equipment, such as the 5370A, would longer runs be better? 
 I used a set of 1 hr runs and the result wasn't quite what I had expected.  
However, it may be that I had mislabeled the files, and thus got the sources 
confused.  Of course, it may be that the ionospheric effect was grossly 
different between the three tests.  So, with a 5370, Source A would be the 
START input and Source B would be the STOP input, right?  For my testing, the 
sources are all 10MHz signals, and I'm driving the EXT input with 1PPS from a 
GPSDO.

Bob 


  From: John Miles 
 To: 'Discussion of precise time and frequency measurement' 
 
 Sent: Thursday, April 13, 2017 1:07 AM
 Subject: Re: [time-nuts] Three-cornered hat on timelab?
   
> It was mentioned that Timelab can do a three-cornered hat.  I can't find it.  
> Is
> this something that can only be done with multiple Timepods connected, or
> is there an option that I'm missing?  Or is there some other tool that needs
> to be used?  For the record, I want to create the 3c-hat from data that was
> run at different times, and I understand (at least somewhat) the
> shortcomings of doing that.  But, it would be interesting to see what would
> result.  And, not having three 5370s in good condition, it's the best I can 
> do.

Hi, Bob --

N-cornered hat measurement is a beta feature, not in the docs yet.  A single 
TimePod can generate the required three plots simultaneously, but you can use 
individual plots from TICs and frequency counters as long as you start with 
highly-reproducible measurements and are careful with your interpretation of 
the results.  If your setup returns inconsistent results from one run to the 
next, then any attempt at a separated-variance plot will be GIGO.

You can see some examples at http://www.ke5fx.com/gpscomp.htm .  Various 
finicky conditions need to be met before the 3-cornered hat display will become 
available; check out 
https://www.febo.com/pipermail/time-nuts/2015-September/094039.html for some 
tips.  

-- john, KE5FX
Miles Design LLC


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Re: [time-nuts] OCXO Soft-Start

[jimlux]

On 4/13/17 6:17 AM, Bob kb8tq wrote:

Hi

It’s a good bet that there is at least one regulator IC inside any modern OCXO.
As you slowly ramp the input voltage on a regulator, various odd things may
or may not happen. A 1 mv / s ramp on the outside can be “who knows what”
at the oscillator level. That said, slow voltage ramps are a really good way to 
put
all sorts of oscillator circuits into really odd modes. Clock oscillators 
(XO’s) and MCU
built in clock circuits very definitely fall into this category.

The same sort of “who knows what” problem also gets into the rest of the 
circuit.
A limited supply might work fine nine times out of ten or 99 out of 100. On the
odd time out, something goes poof !

Bob


This is a known problem with many FPGAs, particularly those which 
configure themselves from on or off-board flash memory.


They have all sorts of little sequencers internally which are driven by 
(very non-time-nuts-quality) oscillators.


And even some non-flash based anti-fuse parts:
https://www.microsemi.com/document-portal/doc_view/130010-ac344-board-level-considerations-for-power-up-and-power-down-of-rtax-s-sl-fpgas

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Re: [time-nuts] Mini-circuits ZFSC-8-1 a a reference distribution

[Bob kb8tq]

Hi

If the circulators are good to 10 MHz and you have eight of them to play with, 
then certainly they can 
be turned into isolators. Unless you have a really unique source of them, that 
kind of gets this out of 
the cheap seats.

The “why” of isolation is very application dependent. Without knowing what you 
are trying to do, there is 
no way to tell if it’s an issue or not. To some degree it’s one of those “if I 
can do it cheap why not” sort of
things. You do run into back feed issues in all sorts of setups. They can be a 
major pain to track down. 
My main reason for mentioning it is because normal mixer isolation numbers 
assume pretty darn good
terminations. There are unterminated combos that also give good isolation. 
There are some that give
really rotten isolation. That’s right back to being a pain to track down ….

Bob


> On Apr 13, 2017, at 1:29 AM, Jerry Hancock  wrote:
> 
> I have circulators but not on the splitter.  Since there are no mixers down 
> stream, would reverse isolation be necessary in this application?
> 
> 
>> On Apr 12, 2017, at 7:39 PM, Mark Sims  wrote:
>> 
>> My UCT-2008 rubidium reference uses the same splitter.  It is driven by a 
>> LPRO rubidium through an amplifier circuit which also drives a divider chain 
>> for producing several TTL level frequencies.   One issue to be aware of with 
>> splitters can be poor reverse isolation of the outputs.  I have not seen any 
>> issues with mine, but I don't use it for anything where that is likely to be 
>> a problem.
>> 
>> 
>>> I recently purchased the subject device, Mini-circuits ZFSC-8-1
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Re: [time-nuts] OCXO Soft-Start

[Bob kb8tq]

Hi

It’s a good bet that there is at least one regulator IC inside any modern OCXO. 
As you slowly ramp the input voltage on a regulator, various odd things may 
or may not happen. A 1 mv / s ramp on the outside can be “who knows what”
at the oscillator level. That said, slow voltage ramps are a really good way to 
put
all sorts of oscillator circuits into really odd modes. Clock oscillators 
(XO’s) and MCU
built in clock circuits very definitely fall into this category. 

The same sort of “who knows what” problem also gets into the rest of the 
circuit. 
A limited supply might work fine nine times out of ten or 99 out of 100. On the
odd time out, something goes poof ! 

Bob

> On Apr 12, 2017, at 11:40 PM, Scott Stobbe  wrote:
> 
> Bob, Rick, my use of modes vs overtones was loose, you guys are spot on.
> 
> 
> That's a fun challenge, suppressing a mode 10% higher in frequency. That's
> a bit of a fussy LC filter/trap.
> 
> So if I assume the tempCo of the B-mode to be 20 ppm/degC, that would mean
> the heater servo has a sustained oscillation of about 250 udegC all day
> long.
> 
> Power cycling for 100 ms isn't long enough for the crystal motion to die
> out, 200 ms seems to do it, which ~2 MCycles. At which point it runs on the
> 10MHz C-Mode as desired.
> 
> I couldn't say who Trimble went with, to me its an ebay special :), but
> photo attached anyways.
> 
> When the supply is current or power limited the effective supply slew rate
> is something like 1 mV/s, and under these conditions, at least this
> particular unit starts up on B-mode every time.
> 
> Running one of these on a USB supply (5V, 500mA = 2.5W) is looking
> plausible.
> 
> On Wed, Apr 12, 2017 at 9:30 PM, Bob kb8tq  wrote:
> 
>> Hi
>> 
>> A SC cut crystal has multiple resonance “modes” in can operate on. This is
>> in addition to the
>> normal set of fundamental, third overtone, fifth overtone and so on. For
>> various interesting reasons
>> the SC modes are called A, B and C.  On a normal 10 MHz crystal, the “main
>> mode” is the C mode. The
>> A mode is well below this mode both in frequency and amplitude. The B mode
>> is more problematic, It is
>> 8 to 12% above the C mode in frequency and may be higher in amplitude
>> (lower resistance) than the
>> desired mode.
>> 
>> The C mode has a “useful” third order temperature characteristic. The B
>> mode has a fairly steep linear
>> temp co. One of the classic design experiments on a SC based design is to
>> force the oscillator onto the
>> B mode. This lets you investigate the oven gain while running a
>> temperature run. What you have likely
>> done is to put the unit onto the B mode.
>> 
>> Oscillators tend to be fractal when switching between modes. Minor startup
>> issues can drive the circuit
>> one way or the other. Once it gets onto a mode, it may be quite difficult
>> to get it off of that mode ….
>> 
>> Bob
>> 
>>> On Apr 12, 2017, at 5:38 PM, Scott Stobbe 
>> wrote:
>>> 
>>> Hello,
>>> 
>>> I wanted to see if I could soft-start a used OCXO (Trimble 34310) during
>>> warm-up. By default with an appropriately rated 12 VDC supply, the OCXO
>>> starts the heater at about 8 W, and eventually settles down to 2 W for
>>> 20-25 degC ambient temperature. Figure Attached.
>>> 
>>> The good news is it does startup with either a current limited or power
>>> limited supply. Albeit, for the constant current case the start-up time
>> is
>>> dramatically longer. Figures Attached.
>>> 
>>> The bad news, but interesting tangent is that when this particular OCXO
>> is
>>> soft-started, it doesn't oscillate at 10 MHz! It starts up on a spurious
>>> overtone at 10.9 MHz. There isn't even a hint of 10 MHz in the output
>>> spectrum just the 10.9 MHz tone (and some noise from the banana
>> clip-leads
>>> loop-antenna). So this is a bit of a pain for soft-starting because,
>>> although the oven eventually comes into regulation, the oscillator is
>>> running on the wrong frequency.
>>> 
>>> I'm not sure what the tempCo of the 10.9 MHz crystal mode is, but its a
>>> pretty great temperature probe of the crystal (literally). You can see
>> the
>>> sinusoidal frequency disturbance of this tone has the same periodicity as
>>> that of the heater current (~50 s). So I don't know if the heater is
>>> oscillating at the uK level or mK level, will need to find out the tempCo
>>> of this crystal mode. Neat to see the oven dynamics.
>>> 
>>> Hopefully once the oven is settled at temp, I can load switch the OCXO
>> for
>>> 10 or 100 ms and get it to startup on the correct 10 MHz mode. With a
>> 10+ W
>>> rated supply it starts up on 10 MHz every time.
>>> <
>> TrimbleSpur_Spectrum.png>___
>> 
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>> mailman/listinfo/time-nuts
>>> and follow the instructions there.
>> 
>> 

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

[Bob kb8tq]

Hi

You likely would get more noise density out of the NE-2 than the incandescent 
bulb. The
advantage of the incandescent is that you can estimate the temperature fairly 
accurately 
and thus come up with the noise by calculation. We did the build as part of a 
radio club 
meeting back in the 60’s. I was still in high school and will not in any way 
claim I followed
the zigs and zags of the physics between the various candidate sources as that 
was all presented. 
My only focus was on “what goes where to make it work” :) 

Bob

> On Apr 12, 2017, at 11:16 PM, jimlux  wrote:
> 
> On 4/12/17 6:33 PM, Bob kb8tq wrote:
>> Hi
>> 
>> Back in the day (1960’s) noise diodes were quite a bit more expensive than 
>> they are today. Even
>> today, a miniature lightbulb is quite a bit less expensive than a noise 
>> diode. You don’t go that way
>> because it’s better. You go that way because it’s cheap ….
>> 
> yeah, but I'd think something like a NE2 might be better, but maybe the noise 
> properties of a glow discharge aren't as good.
> 
> 
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Re: [time-nuts] UltrAtomic® Clock

[Jeremy Nichols]

My LaCrosse UltrAtomic® clock arrived yesterday from Amazon. In my case, 
the clock wasn't assembled on a Monday or a Friday, so nothing rattled, 
and the packaging defeated the animals in shipping. The clock was 
stopped, of course, at exactly 12:00. I installed four C-cells (big 
spender!), replaced the battery cover, and turned the clock over. The 
hands moved around to 4:00 and stopped. I hung the clock on an inside 
wall (facing west in my single-story northern California home) and I 
went about my business. Ten minutes later I checked back and the clock 
had set itself to the correct time. Happy camper!


Jeremy, N6WFO


On 4/12/2017 10:34 AM, Gregory Beat wrote:

My long-time (and accurate) 12-inch analog kitchen clock (24 years) dropped to 
floor in March, as I was adjusting for Daylight Savings Time.  Of course, the 
polycarbonate lens cover cracked and I could not find a replacement.  The 
manufacturer, General Time of Athens, GA (handled Seth Thomas, others) closed 
their operations in 2000.
===
So, I decided to order the LaCrosse UltrAtomic® clock.
My experience, in setting it up this clock, was the same as noted by Larry.
Took less than 90 minutes ... and agrees with my GPS/NTP server with IRIG 
displays.

One caveat, while the clock was well packed, I heard a "rattle".
Sometime, during this clock's assembly, the portion of the plastic retention 
lip for the glass/aluminum frame was broken off at the top (aggressive 
assembler or flaw in plastic molding?).
Since I purchased the clock directly from LaCrosse, I sent them photos.
They are sending a replacement clock with a return label for this one.

greg
w9gb
Sent from iPad Air
--
From: Larry McDavid 
Subject: [time-nuts] UltrAtomic® Clock

When I got home after my Thursday Lunch meeting today, my new La Crosse 404-1235UA-SS 
UltrAtomic® clock was waiting. I unpacked it and installed two (of 4 possible) C-cells 
and set it on the floor upstairs near the center of my home, fully under the radiant 
barrier insulation that has foiled (that's a pun!) all my previous "Atomic" 
clocks. The hands moved around 4 hours and stopped. I left.

Returning about an hour later, the clock had set itself correctly!

I verified the displayed time against my (Tindie) GPS Clock and the seconds and 
seconds-tick match as closely as I can determine visually.
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Re: [time-nuts] Mini-circuits ZFSC-8-1 a a reference distribution

[Jerry Hancock]

I have circulators but not on the splitter.  Since there are no mixers down 
stream, would reverse isolation be necessary in this application?


> On Apr 12, 2017, at 7:39 PM, Mark Sims  wrote:
> 
> My UCT-2008 rubidium reference uses the same splitter.  It is driven by a 
> LPRO rubidium through an amplifier circuit which also drives a divider chain 
> for producing several TTL level frequencies.   One issue to be aware of with 
> splitters can be poor reverse isolation of the outputs.  I have not seen any 
> issues with mine, but I don't use it for anything where that is likely to be 
> a problem.
> 
> 
>> I recently purchased the subject device, Mini-circuits ZFSC-8-1
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Re: [time-nuts] Three-cornered hat on timelab?

[John Miles]

> It was mentioned that Timelab can do a three-cornered hat.  I can't find it.  
> Is
> this something that can only be done with multiple Timepods connected, or
> is there an option that I'm missing?  Or is there some other tool that needs
> to be used?  For the record, I want to create the 3c-hat from data that was
> run at different times, and I understand (at least somewhat) the
> shortcomings of doing that.  But, it would be interesting to see what would
> result.  And, not having three 5370s in good condition, it's the best I can 
> do.

Hi, Bob --

N-cornered hat measurement is a beta feature, not in the docs yet.  A single 
TimePod can generate the required three plots simultaneously, but you can use 
individual plots from TICs and frequency counters as long as you start with 
highly-reproducible measurements and are careful with your interpretation of 
the results.  If your setup returns inconsistent results from one run to the 
next, then any attempt at a separated-variance plot will be GIGO.

You can see some examples at http://www.ke5fx.com/gpscomp.htm .   Various 
finicky conditions need to be met before the 3-cornered hat display will become 
available; check out 
https://www.febo.com/pipermail/time-nuts/2015-September/094039.html for some 
tips.  

-- john, KE5FX
Miles Design LLC


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Re: [time-nuts] OCXO Soft-Start

[jimlux]

On 4/12/17 7:14 PM, Richard (Rick) Karlquist wrote:

10.9 MHz is likely the B-mode of the SC cut.
(It's a different mode, not a different overtone).
This mode has a tempco of 20 ppm and is used
to do thermometry.

IMHO, there is NO excuse for the oscillator
designer to design an oscillator that doesn't
oscillate unconditionally in the right mode.
NONE!  What was the actual manufacturer of
the OCXO? (AFAIK, Trimble doesn't make their
own).

My old boss at Zeta Labs (a really great boss)
used to walk up to people who were testing
their latest circuit and momentarily turn
down the current limit on each of the power
supplies to see if the circuit recovered
correctly.  It often didn't, and then it
was back to the drawing board...



These days, a common trap is when you've got a DC/DC converter on the 
input - with a soft start, the current goes huge, causing all kinds of 
problems.


(I'm in the middle of closing a failure report on just such a 
sensitivity - an unexpected interaction between the source DC/DC 
converter and the load DC/DC converter..)



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