Re: [time-nuts] Raw phase data of super-5065

[Attila Kinali]

On Thu, 14 Jun 2018 15:14:55 +0200
Magnus Danielson  wrote:

> Do we have the raw measurements in a readable format?

Yes, you can find them at
http://time.kinali.ch/phase_data/luciano/

    Attila Kinali
-- 
It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
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Re: [time-nuts] a newbie question: where can I purchase 794.7nm VCSEL for building CPT rubidium clock?

[Attila Kinali]

On Mon, 11 Jun 2018 22:29:42 +0800
mimitech mimitech  wrote:

> I think your information is very interesting. I didn't realize which type
> of common LDs can do GHz level modulation (anyway I didn’t have much
> knowledge on laser diode before). 

Hehe. Same here. When I looked into CPT I thought that one needs
a fast laser diode as well. Then, a few years ago, I had the chance
to talk to John Kitching who corrected a few of my assumptions.

> It would be great If you could recommend
> several good Laser diodes (which vendor/part number) with possible 1-2GHz
> modulation bandwidth. Thanks!

Sorry, unfortunately I do not have any reliable data on the bandwidth
of standard laser diodes. The easiest would be probably if you select
some diodes that you can easily acquire, then contact the manufacturer.
Manufacturers almost always have more data on their devices than they
put into the datasheet. They do not include it because they can either
not sufficiently control those parameters during production, cannot 
test for it or testing would be too expensive.

        Attila Kinali

-- 
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the prosperity and technological sophistication in the world is of no 
use without that foundation.
 -- Miss Matheson, The Diamond Age, Neil Stephenson
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Re: [time-nuts] Raw phase data of super-5065

[Attila Kinali]

On Wed, 13 Jun 2018 08:19:58 -0700
 wrote:

> Would be interesting to see a long plot of the two 5065 against each
> other!

I had a look at Luciano's data and it's probably safe to say, that
the instability of the super-5065 would be the limit. The unmodified
5065 is incredibly stable (once you remove drift).

Attached are the two phase plots, both with quadratic drift removed.
The unmodified 5065A has a kind of weird ~18day undulation. I would
say it's an environmental effect, but the two cycles are too similar,
so I do not know what to think of it.

The super-5065 (5065B) has quite a few bigger frequency jumps, with
pretty stable phases in-between. My guess here would be that there
are no environmental effects and it is limited by instabilities in
the frequency discriminator electronics, ie offsets that show (close to)
discrete jumps. or that the lamp brightness changes.

    Attila Kinali

-- 
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the prosperity and technological sophistication in the world is of no 
use without that foundation.
 -- Miss Matheson, The Diamond Age, Neil Stephenson
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Re: [time-nuts] Raw phase data of super-5065

[Attila Kinali]

Ciao Luciano,

On Fri,  8 Jun 2018 14:05:24 +0200
"tim...@timeok.it"  wrote:


>Here a ten days simultaneously run of the A and B version compared with my 
> HP Z3816A GPSDO.

Thanks a lot!
Unfortunately, I have no application that can read XPS files available.
Can you send it as something more standard?

        Attila Kinali
-- 
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the prosperity and technological sophistication in the world is of no 
use without that foundation.
 -- Miss Matheson, The Diamond Age, Neil Stephenson
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Re: [time-nuts] a newbie question: where can I purchase 794.7nm VCSEL for building CPT rubidium clock?

[Attila Kinali]

On Sat, 9 Jun 2018 16:54:15 +0800
mimitech mimitech  wrote:

> I prefer the 780/795nm VCSEL scheme for its simplicity. After some
> searching, looks like the 780nm VCSELs are also not easy to source,
> although other types of 780nm LD are common.

Why are you focusing on VCSEL anyways? Standard laser diodes already
have a modulation bandwidth that goes into several 100MHz, the better
ones should give you 1-2GHz. With that, you should be within 6dB,
maybe 10dB of the CW power. Given that you only need a few 10µW to 100µW
of laser power, and that those diodes are in the 1-30mW range should
give you enough margin.


        Attila Kinali
-- 
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the prosperity and technological sophistication in the world is of no 
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Re: [time-nuts] a newbie question: where can I purchase 794.7 nm VCSEL for building CPT rubidium clock?

[Attila Kinali]

On Sat, 9 Jun 2018 23:28:29 +0800
mimitech mimitech  wrote:

> Just do a little bit research on 1560nm telecom laser transceiver. The
> closest wavelength is 1560.61nm (DWDM channel 21) as defined by ITU.
> Usually telecom laser transceiver module uses DFB (distributed feedback)
> type laser diode instead of VCSEL laser. However, the DFB LD should be
> capable of direct modulation, so there maybe not much difference with VCSEL
> in terms of usage. For the modulation bandwidth, I guess a 2.5Gbps module
> should be OK for 1.71GHz analog modulation.

A 2.5Gbps module should be good even for 3.4GHz modulation. The 3dB frequency
of should be higher than the baud rate used. Besides, even if the 3dB frequency
is below 3.4GHz, that does not matter, it just means that your sidebands will
be damped (second order low pass, IIRC), but you don't need that much power
anyways.

> So, imagine I modulated 1.71GHz microwave signal onto 1560nm laser wave,
> then used a KPT non-linear optical crystal to double the frequency,
> hopefully I could get 780nm laser with +/-3.42GHz sideband spectrum, that
> should be suitable to shine on a Rubidium vapor cell and trigger CPT
> effect. I don't know if I understand this process correctly, many details
> must be missed.

Using a non-linear element will give you lots of intermodulation products.
Ie, your sidebands will be +/-1.71GHz, +/-3.42GHz, +/-6.84GHz,...
So you will have to be a bit carefull with the laser tuning in order to
get the right harmonics. 

An alternative approach would be to use an EOM after the doubler
to get the sidebands. These have bandwidths in the order of 10-20GHz,
so applying 3.42GHz shouldn't be a problem.

BTW: a lot of the frequency doubler architectures for high stability
lasers use resonant cavities, to increase efficiency and decrease noise.
You will either have to tune the free spectral range of the cavity
to a divisor of 6.84GHz or use a non-resonant one.

> Another question is, after passing through the KPT doubler crystal, whether
> the light remains single mode and linear polarization mode or not? If
> someone could provide any relevant information and suggestion, thanks very
> much.

If I understood the optical process correctly (disclaimer: I'm not
a physicst and have never worked with optical systems), then the multiple
modes are a problem of the laser source, not of the doubler. As multi-modes
are a problem for high speed communication, I expect telecom lasers to
be quite clean. You will have to ensure that you are not operating it
close to a mode jump, though.

A side note on the doubler approach: The group at UniNE around Gaetano
Mileti and Christoph Affolderbach focuses only on double-resonant
Rb standards. That means they do not modulate the laser. As they
have gotten the whole standard to the SNR limit, they are now focusing
on getting the shifts due to laser (frequency and intensity shift)
and cavity (low Q cavity to avoid pulling) down. The current state
of affairs is quite nicely documented in their two papers at 8FSM[1,2,3].

Attila Kinali


[1] Proceedings of the 8th Symposium on Frequency Standards and Metrology
http://conferenceseries.iop.org/conferenceseries/issue/1742-6596/723/1

[2] "High performance vapour-cell frequency standards", 
Gharavipour, Affolderbach, Kang, Bandi, Buret, Pellaton, Mileti, 2015
http://iopscience.iop.org/1742-6596/723/1/012006/pdf/1742-6596_723_1_012006.pdf

[3] "Pulsed Optically Pumped Rb clock", 
Micalizio, Levi, Godone, Calosso, François, Boudot, Affolderbach, Kang,
Gharavipour, Gruet and Mileti, 2015
http://iopscience.iop.org/1742-6596/723/1/012015/pdf/1742-6596_723_1_012015.pdf

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Re: [time-nuts] ?==?utf-8?q? a newbie question: where can I purchase 794.7 nm VCSEL for building CPT rubidium clock?

[Attila Kinali]

On Mon, 11 Jun 2018 06:53:49 +0200
Magnus Danielson  wrote:

> One might then ask what the availability and pricetag is for nonlinear
> chrystal needed for frequency doubling.

It cannot be too much, given the fact that these are used in
green laser pointers.

Though, I have to say I am astonished how expensive those VCSEL are.
I would have guessed they are below $100/pcs, given that "normal"
laser diodes are usually in the order of $10-$20.


        Attila Kinali
-- 
It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
 -- Miss Matheson, The Diamond Age, Neil Stephenson
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Re: [time-nuts] a newbie question: where can I purchase 794.7 nm VCSEL for building CPT rubidium clock?

[Attila Kinali]

On Mon, 4 Jun 2018 21:31:56 +0800
mimitech mimitech  wrote:

> I'm planning to build a CPT (coherent-population-trapping) rubidium clock
> as my next hobby project. The main purpose is to learn the principles
> behind CPT rubidium clock, and hopefully got similar or better performance
> than commercial miniature rubidium clock such as FE-5680A.

Building a CPT clock is slightly more involved than you might think
at first. The laser diode is only one part of it. You will most likely
be able to improve on the short-term stability of the FE-5680 (which
is rather poor). But I doubt you will be able to improve much on
the long term stability, which is where things actually become interesting,
if you use a naive approach.

Nevertheless, I have not seen many 794/795nm diodes around. The only
one that I have the datasheet of is the one from Vixar.
You might want want to consider going for the D2 line instead of the
D1 line, as 780nm diodes are more commonly available than 795nm. You will
also need to buy several of those and select the ones that come closest
to the wavelength at the desired opearating conditions (usuall spread
is +/-1nm to +/-10nm). Do not assume you can tune more than 0.1nm with
temperature and current (rule of thumb is that you get about 10GHz
per °C and mA). If you need more tuning range, you will need to add an
external cavity (can give you up to 5nm range), which then needs to be
tuned to the 3.45GHz (ie it's length needs to be approximately 8-9cm).

Alternatively, you can get two S1-0780-XXX from Sacher Laser
(cost IIRC 2500€ each) and keep them 6.9GHz apart (using an optical PLL).
If you have enough money to spend, I'd go for two Cateye diode laser CEL's
from Moglabs (cost AFAIK 5000€ each)

No matter what you choose, you will need some wavelength stabilization
scheme. You can either do that with the vapor cell itself or use
an additional cell and do a DVALL or a saturated absorption locking.
Note that this addtional cell will need to be without buffer gas.
An external cell will offer better stability and thus lower noise,
which directly translates into higher stability.

As polarisation scheme, I suggest using σ+/σ- as it seems to be more
robust than the lin/lin schemes.

    Attila Kinali
-- 
It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
 -- Miss Matheson, The Diamond Age, Neil Stephenson
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[time-nuts] Raw phase data of super-5065

[Attila Kinali]

Hoi zäme!

Would one (preferably multiple) of the owners of a super-5065 be so kind
and share the raw phase data of an super-5065 against a stable reference
with me? The longer the data trace, the better.

Thanks in advance!

Attila Kinali

-- 
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the prosperity and technological sophistication in the world is of no 
use without that foundation.
 -- Miss Matheson, The Diamond Age, Neil Stephenson
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[time-nuts] Traveling to the US west coast

[Attila Kinali]

Hi,

Some of you might already know, I will fly to the US west coast
to attend IFCS. Afterwards, I will be in Seattle for a couple of
days (from 25th to 31st). If you are in the area and want to meet up,
please drop me an email (off-list).


Attila Kinali
-- 
It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
 -- Miss Matheson, The Diamond Age, Neil Stephenson
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Re: [time-nuts] 4046 replacement

[Attila Kinali]

On Wed, 18 Apr 2018 20:04:02 +1200
donald collie <donaldbcol...@gmail.com> wrote:

> I have 4  frequency synthesiser projects, each using HEF4046BCN`s, but have
> recently read that this CMOS IC has a design flaw. What would be a better
> chip to retrofit? I`m thinking perhaps a HEF74HC4046AN [that`s if it
> doesn`t have the same bug], or a 74HC7046AN - which is similar. Both these
> chips are more-or-less pin compatable TIA for any

What design flaw are you talking about?

        Attila Kinali

-- 
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Re: [time-nuts] suggestions on getting 24 Mhz ?

[Attila Kinali]

On Wed, 11 Apr 2018 03:00:23 -0700
Pete Lancashire <p...@petelancashire.com> wrote:

> Needed for SDR project as external clock source.

If your goal is, as Jim guessed, to get 24MHz from 10MHz and
you are using something like an RTL-SDR, then how about just
passing the 10MHz through a CMOS gate to square it up and
get nice harmonics, then pass a wire close to the crystal.
This should injection lock the crystal to right frequency.
It wont be a strong lock due to the 5:12 ratio, but for something
like a crystal that is already quite close, that should do the trick.

Alternatively, using an ADF4002 with a small uC to configure it
and a VCXO/VCO should also work.

        Attila Kinali
-- 
The bad part of Zurich is where the degenerates
throw DARK chocolate at you.
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Re: [time-nuts] femtosecond jitter

[Attila Kinali]

On Fri, 13 Apr 2018 08:54:41 -0700
John Larkin <jjlar...@highlandtechnology.com> wrote:

> If you walk the differential data and clock inputs of an NB7V52  CML 
> flipflop across one another in time, the equivalent jitter is below 20 
> fs RMS. That's what we're measuring, but our test rig may well dominate 
> the jitter, so the flop is probably better.

I heard similar numbers for the NB7V52 last week at EFTF. So you
cannot be that far off.

        Attila Kinali

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Re: [time-nuts] Help improving impedance measurement by having a better clock

[Attila Kinali]

On Sat, 7 Apr 2018 22:54:42 -0300
Daniel Mendes <dmend...@gmail.com> wrote:

> I´m a long time time-nuts lurker (I posted here just a dozen times). I make
> a few impedance measurement systems for material analysis (i´m a single man
> shop doing custom hardware for clients). Usually they´re based around a
> STM32F4 / F7 microprocessor: DAC generates sine signal (1-400KHz), ADCs
> measure them back, a few calculations later we have modulus / phase. I
> always used internal ADCs and DACs (12 bits each).

The STM32's are known for their poorly performing ADCs and DACs,
even using an external one with the same bit width will increase
your performance. That said, what is your actual sample rate?
I would guess, if you use the timer unit to generate the pulses,
your jitter would be less than 10ps rms, probably even less than 1ps rms.
10ps rms limits your resolution to something like 14-15bit @500kHz,
1ps rms should be around 18bits, if I'm not mistaken. 

To measure the performance, I would just build the device and feed it
with an appropriate sine wave. Then analyze the SNR and spurs of the
sampled signal.

        Attila Kinali

-- 
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the prosperity and technological sophistication in the world is of no 
use without that foundation.
 -- Miss Matheson, The Diamond Age, Neil Stephenson
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Re: [time-nuts] Cheap jitter measurements

[Attila Kinali]

On Tue, 3 Apr 2018 10:47:37 -0700
"Gary E. Miller" <g...@rellim.com> wrote:

> What would you guys suggest as the cheapest way to see jitter down to
> around 1 nano second?  

Look at Nick Sayers GPSDO and his interpolator. You wont get any
cheaper than that. Next best thing is to use a TDC7200 like in
the TICC.

Of course, you will need a standard that is stable enough on the
time scales you are looking at. Which is for short taus (<100s)
a good OCXO and for 1s to 10ks an Rb, and beyond that a Cs beam
standard or hydrogen maser.

        Attila Kinali

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Re: [time-nuts] quartz / liquid nitrogen

[Attila Kinali]

On Mon, 2 Apr 2018 12:46:26 -0700
"Tom Van Baak" <t...@leapsecond.com> wrote:

> Has anyone tried running a quartz oscillator at liquid nitrogen 
> temperatures: -196 C (-321F, 77K)? It's probably impractical commercially, 
> but maybe something of value to a time nut. Would that dramatically lower 
> temperature improve phase noise & short-term performance? Is there a crystal 
> cut that could be optimized for 77 K instead of ~25 C (room) or 60 C (oven)?
> 
> If not Nitrogen, how about dry ice (-109F -78C)?

Yes, it has been done. Down to liquid helium tempratures even.
The main benefit is that the Q of the crystal increses with
decreasing temperatures, but the effect is not as large as with
dielectric resonators (aka whispering galery mode CSO). 

Of course thermal noise decreases as well, but usually quartz
oscillators are limited by their amplifiers and the 50 Ohm system
for termal noise. I do not remember reading anything about flicker
noise, but my guess would be that it decreases as well.

I am sure I have some paper on this somewhere in my collection,
if you want I can dig it out.

Attila Kinali


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Re: [time-nuts] Timestamping audio waveforms

[Attila Kinali]

On Sat, 31 Mar 2018 10:41:45 -0400
Tim Shoppa <tsho...@gmail.com> wrote:

> Can Audacity do this kind of timestamping for me based on the system clock?

I don't know about audacity, but writing a small program in c that
reads from the soundcard and does the timestamping is pretty easy.
Should be less than 50 lines of code, with error checking and all.
You can use [1] as a decent starting point.

One important point: Switch off all other applications that access
the soundcard, as some of these are pretty nasty when it comes
to their behaviour. Especially pulseaudio is known to mess with
all kinds of settings while running Oh, and don't even try
to run anything ontop of pulseaudio, it is known to mess up
audio timing by several 10ms, sometimes even over 100ms.

        Attila Kinali


[1] https://gist.github.com/albanpeignier/104902

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[time-nuts] Open Access (was: WWV/CHU)

[Attila Kinali]

On Sat, 31 Mar 2018 12:25:34 +0100
"Dr. David Kirkby" <drkir...@kirkbymicrowave.co.uk> wrote:

> Alexandra Elbakyan makes the very valid point that authors do not get paid
> for submitting papers, reviewers do not get paid for reviewing them, yet
> the publishers charge significant amounts of money for distribution of
> electronic copies of papers. This is VERY different to books or music,
> where authors get royalties from copies sold.

And just to drive another nail into this coffin:
Writing an easy paper takes something like a week (after the research
is done). Writing a difficult one can easily take one or two months until
it's in a form that can be understood. Reviewing takes anything between
half a day (easy, experimental paper) to a week (100 pages of proofs),
for each reviewer! Then there is the guy in India who gets paid a dollar
a day to make the paper's layout fit the journals general rules (and often
botches the whole paper in the process, to the point where the author has
to prohibit its publication). If you want to have it as Open Access, then
publication can cost anything between 1000€ and 5000€, depending on the
publisher and journal. In most countries, that in the order of a months
salary... for what? So far, the only value I have seen, that these
publishers provide is the organisation of double blind reviews. 
Everything else is just make pretend. There is not even have any form
of quality control of the reviews. Heck, I've seen one line reviews of
the form "This paper is stuipd." And I am not talking yet about the
butchoring they do in the name of editing (like replacing minus signs
with dashes or changing the number format such that you cannot distinguish
between a decimal separator and an item separator).

>From all the venues I've seen so far, IEEE was the least hassle.
They demand you to use their LaTeX template. They check whether
you "optimized" it upon upload, and that's it. Yes, their Open Access
fee is still significant, though lower than most others. But at least
they do not pretend to know better than the authors how to format a
paper. And, unlike Springer and Elsevier, IEEE does not seem to care
when an author puts their own papers on their website (though, officially
the copyright asignment prohibits that).

I don't like that sci-hub has to work in a legal dark gray area.
But the way publishers work these days, borders on extortion and is 
IMHO a big waste of tax money (we are talking about several 10's of
millions per year, country and publisher). Honestly, I couldn't care
less if Springer and Elsevier would go bancrupt and didn't exist
anymore, if it wouldn't be for the papers they hold hostage, which
would become completely inaccessible over night. As such, I am glad
that the Open Access movement has got so much traction these days.
It gives me hope that in future, our knowledge will be accessible
to everyone, not just a select few who can afford the fees.

As a researcher, I do not really care where my paper is published,
as long as people can read it (the more people read my paper,
the better). A paper published at a venue that actively seeks
to prevent people from reading papers (I am looking at you, ION!)
is a place I will not publish at. And from personal experience
I can say that it's much more likely that easily available papers
get cited than one that is behind an inpenetrable pay-wall.



Attila Kinali
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Re: [time-nuts] WWV/CHU

[Attila Kinali]

On Thu, 29 Mar 2018 03:12:24 -0700
Hal Murray <hmur...@megapathdsl.net> wrote:

> What do I need in in order to get time from WWV or CHU?
> 
> Do I need a fancy receiver as a front end?  Do I have a chance with one of 
> the low cost USB thumb drive size receivers?
> 
> Is there an obvious software package to start with?  (Linux)

I think the easiest is GnuRadio... A quick googling lead
to https://github.com/jasonabele/gr-wwvb
I don't know anything about it so use at own risk :)
But at least it seems like something that can be done easily
on a rainy evening.

Normal RTL-SDR's do not work for WWVB as they have a lower cut of
frequency in the range of 20-50MHz...unless you bypass the tuner
chip and feed the signal directly to the ADC. As IIRC all RTL-SDR
give you something like 2Msps, that should be more than plenty to
decode WWVB and related signals. If you feed the RTL-SDR from an
external frequency source, you should be able to related that
frequency source to WWV.

        Attila Kinali

-- 
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the prosperity and technological sophistication in the world is of no 
use without that foundation.
 -- Miss Matheson, The Diamond Age, Neil Stephenson
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Re: [time-nuts] What does determine the short term stability of an Rb vapor cell standard?

[Attila Kinali]

On Sun, 25 Mar 2018 15:28:10 -0400
Bob kb8tq <kb...@n1k.org> wrote:

> Well, magnetic shielding, temperature coupling between cells, photo detector
> noise floor, phase noise of the various signals, basic stability of the 
> “ocxo” and 
> I’m sure a few other issues as well……

The effects of those seem not to be that big. If you look at the
phase noise plot of the measurements that John Miles did [1],
it looks like the PRS10 comes very close to the 5065 for everything
shorter than 1s. Which suggests, that they might have missed something
in the control loop or set its constant too long.

        Attila Kinali


[1] http://www.ke5fx.com/rb.htm

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Re: [time-nuts] What does determine the short term stability of an Rb vapor cell standard?

[Attila Kinali]

On Sun, 25 Mar 2018 14:13:56 -0500
Dana Whitlow <k8yumdoo...@gmail.com> wrote:

> Could it be that with the narrow-band laser emission the dip in
> light transmission of the Rb cell is significantly improved?   I know
> that diode lasers are generally not paragons of virtue when it comes
> to intensity noise, so I'm wondering what accounts for the claims of
> better SNR with laser illumination.

Those who use lasers, seem to mostly use a variant of saturated
absorption spectroscopy, to get a sub-Doppler lock. Ie the laser
is stabilized to a couple of 100Hz to a few kHz, at most.
(An alternative, that nobody seems to use would be to use DVALL,
which uses the the Zemann splitting to get a narrow line width)

Using that, you get a laser that is very close to the the real
absorption maximum of the vapor cell used, hence reducing light
shift variation due to detuning/wander of the laser wavelength.

As for intensity noise, yes, it's not glorious with lasers, but
most papers I've read have a stabilization for that as well, so
it gets attenuated a bit.

        Attila Kinali

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[time-nuts] What does determine the short term stability of an Rb vapor cell standard?

[Attila Kinali]

Moikka moi,

In the past, it has been again and again claimed that the HP 5065 has
such an outstanding short term stability because of its large vapor cell.
But the more I read, the less I believe this. E.g. if you look at the
papers by the group around Gaetano Mileti and Christoph Affolderbach
from University of Neuchatel, you'll see that they get an ADEV well
below 1e-12 with a vapor cell that is just 3x3cm (actually smaller
than that... but details). Yes, they use a laser instead of an Rb lamp,
which increases SNR. But that would mean it's not the cell size per se
that limits the short term stability, but the pumping of the atoms
and the light noise on the photo cell. Hence it should be, theoretically
at least, be possible, to take one of the telecom Rubidium standards,
replace the lamp with something better, and come close to the performance
of an 5065 So, what part of this is wrong and what am I missing?


Attila Kinali

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Re: [time-nuts] ULN regulator with more current capability than LT3042?

[Attila Kinali]

Hoi Gerhard,

On Sun, 18 Mar 2018 21:41:28 +0100
Gerhard Hoffmann <dk...@arcor.de> wrote:

> Use the LT3042 with an external power transistor, such as D44VH10G:
> 
> < 
> https://www.flickr.com/photos/137684711@N07/29197476530/in/album-72157662535945536/
>  
>  >
> 
> Performance is about the same as the LT3042 alone. That is exactly the 
> circuit from the data sheet

Have you measured it's dynamic performance?
I did some spice simulations some time ago and noticed that there are
some load conditions where this circuit is very close to oscillation
(ie load changes lead to heavy ringing)of course, this is under
the assumption that the spice model of the LT3042 is accurate in that
regard.

Attila Kinali

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Re: [time-nuts] Recommendations for Mains Power Monitor / Logger

[Attila Kinali]

On Sun, 11 Mar 2018 14:41:23 -0500
Dana Whitlow <k8yumdoo...@gmail.com> wrote:

> I'll have to take a look around to see if there isn't something cheap that
> can run
> standalone so I don't have to tie up (or wear out) a whole PC for the
> acquistion
> process.

Blub... I should the whole mailsorry about that.

How about this: get a uC board (e.g. STM32discovery), replace
the crystal with a 10MHz input from your frequency reference.
Use the on-chip 12bit (really just 6bit) ADC to sample the
sine wave from your mains. Do phasor measurement in software.

Probably any sampling frequency between 200Hz and 1kHz should
do the job, Which is slow enough so you can still handle the
samples with the uC alone and don't need any fancy DSP.


        Attila Kinali

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Re: [time-nuts] Recommendations for Mains Power Monitor / Logger

[Attila Kinali]

On Sun, 11 Mar 2018 14:41:23 -0500
Dana Whitlow <k8yumdoo...@gmail.com> wrote:

> Now I'm getting interested in this.  My concept is to take the 60 Hz in, do
> reasonable
> HW filtering to knock off the HF junk that commonly rides on the sinewave,
> then use
> an RC quadrature phase splitter to yield I & Q signals.  Then sample at
> 1PPS with
> my Rb's PPS as the sample trigger,  and capture the result with a 2-channel
> data
> acquisition gadget of some sort.  It's that last item that's holding me
> back.

Just get a USB soundcard. feed the left channel with the 50/60Hz
from your mains, and the right channel with some signal between
about 1kHz and 10kHz that you somehow derived from your frequency
standard, then you can do the rest in software on your PC. If you
do not want to code, you can use GnuRadio and use their Labview
like point-and-click interface (yes, GnuRadio can be used for more
than just to look for long lost satellites with oversized antennas ;-).
This way you don't even need a 90° hybrid or anything similarly
temperature sensitive.

Attila Kinali

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Re: [time-nuts] Recommendations for Mains Power Monitor / Logger

[Attila Kinali]

Hi,

I'd like to add two things:

On Sat, 10 Mar 2018 20:46:16 -0800
"Tom Van Baak" <t...@leapsecond.com> wrote:

> 1) Safety. I usually use a low voltage step-down transformer. This gives 
> isolation and safety. Anything from 3 VAC to 24 VAC is fine.

Please, do not just add a transformer. Make it also impossible to touch
any wire comming from mains or anything that could potentially have
mains voltage on it. In europe, the minimum isolation distance between mains 
and anything on the low voltage side is at least 5mm (IIRC). I recommend
to use at least this much distance in your designs as well, even if a much
smaller distance would be enough to prevent arcing in most cases (the reason
for this large gap is to ensure that dust and humidity do not cause an
isolation fault under normal, household conditions).

 
> 2) Trigger. There are dozens of schematics on the web for capturing the zero-
> crossing of a low-voltage sine wave. You can easily go overboard on this. Or 
> just keep it simple and feed the signal through a resistor directly into a 
> microprocessor input. The internal clamping diodes do their thing. A Schmitt 
> trigger input is helpful but not necessary depending on how your software 
> makes the measurement.

Please do not use the internal clamping diodes of an IC as the main way
to clamp a voltage. These diodes are ment for protection against ESD events.
They are not designed to constantly dissipate energy. If you do it anyways,
the diodes will fail after a while... and slowly at that.
If you need to clamp voltage use two Schottky diodes (BAT54, MBR0502,...)
to Vcc and GND. Also ensure that the current drawn from Vcc at all times
exceedes the current injected into Vcc through the clamping diodes, otherwise
you will have an uncontrolled raise in power supply voltage and might exceed
the rating of your circuit.

Attila Kinali

-- 
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Re: [time-nuts] Ultra low power RTC

[Attila Kinali]

On Thu, 8 Mar 2018 00:33:58 +0100
Mike Cook <michael.c...@sfr.fr> wrote:

> This is interesting. When you talk of self discharge, is there any way
> of harnessing that. Is that what the chip manufactures are doing?

No. It's a chemical reaction inside the cell. The energy is turned
into heat directly and never leaves the cell in a usable form.

    Attila Kinali

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Re: [time-nuts] Frequency deviations in Europe affect clocks

[Attila Kinali]

On Wed, 07 Mar 2018 22:01:25 +0100
Pete Stephenson <p...@heypete.com> wrote:

> Fortunately the Swiss rail system doesn't, as far as I know, use powerline 
> frequency for timekeeping, even at remote stations, so all the railway 
> clocks are still running properly. 

They used to have a central HBG receiver at all train stations,
with a few exceptions where reception was bad (there, they got a
special permission to use DCF77 instead). I have no idea what
they use these days for synchronization.

        Attila Kinali

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Re: [time-nuts] Ultra low power RTC

[Attila Kinali]

On Wed, 7 Mar 2018 12:06:43 -0500
Bob kb8tq <kb...@n1k.org> wrote:

> Ok, so energy harvesting from Lazy Bob in his arm chair makes a button cell 
> look like a giant power source ….. 

Giant is an understatement. For comparison, a single brain cell uses
approximately 0.5nW of power. A human body dissipates something around
100 to 200W of heat, constantly but this is going a bit too OT I guess :-)

    Attila Kinali

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[time-nuts] How to properly simulate PLLs?

[Attila Kinali]

Hi,

I have a small side task, where I need to design a PLL system
As it is a bit non-conventional, I am not confident that my
pen and paper analysis is correct and the usuall tool I use
(Analog's ADPLLsim) doesn't cover it. So my first thought
was to use spice to simulate the loop. But I am not sure
how the non-linear effects of the PLL, the divider chains etc
affect the whole system and whether a spice simulation (which
would use a linear approximation of a few components) would
model the system faithfully. Not to mention that this would
be only valid simulation of the locked state and anything
that involves the PLL being unlocked (initial lock in process,
large phase and frequency jumps that cause unlocks) cannot
be handled at all. Neither would it give me a proper estimate
of the noise propagation through the system.

So, is there any canonical way how to simulate PLLs?
If yes, what should I read? (My google foo didn't return
anything helpful).

Thanks in advance

Attila Kinali

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Re: [time-nuts] Ultra low power RTC

[Attila Kinali]

On Wed, 7 Mar 2018 08:27:00 -0500
Bob kb8tq <kb...@n1k.org> wrote:

> Since we don’t often *need* the smallest cell made *and* we’re probably 
> talking lifetime of the cell….. does 22 na vs 33 na matter?

Not really. It starts to matter when you are space limited and don't
have space for a CR2032.

At this level, though, every tiny bit of leakage matters. Finger prints,
dust, humidity, FR4... Going below 1µA in current consumption is like
going below 10^-12 in frequency stability, suddenly 1M is a low resistance.
 
> Based on the previous data on the chip, I think I would just run the crystal
> all the time. 

The the watches (quartz with analog dials) I have run >5 years
on their batteries, an I am pretty sure they don't have a CR2032.
And at least one of them must have a TCXO.


        Attila Kinali
-- 
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use without that foundation.
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Re: [time-nuts] ADEV data for mechanical clocks

[Attila Kinali]

On Tue, 06 Mar 2018 21:10:00 -0800
Hal Murray <hmur...@megapathdsl.net> wrote:

> Does anybody have any ADEV data for mechanical clocks?  (I didn't find any by 
> google, but there was a lot of noise so maybe I missed something.)

How about Tom's Powers of Ten?
http://www.leapsecond.com/ten/clock-powers-of-ten-tvb.pdf

    Attila Kinali

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Re: [time-nuts] Ultra low power RTC

[Attila Kinali]

On Tue, 6 Mar 2018 21:57:32 -0500
Bob kb8tq <kb...@n1k.org> wrote:

> Assuming you are going to run it off a battery. What’s the self discharge
> rate on a reasonable battery? 

With supply currents below 100nA you can assume that you are likely
to be limited by the self-discharge using coin sized LiMnO2 cells
(e.g. a CR2032 is specced in the order of 100-300nA self-discharge).
For the smaller cells, you have to check which one is larger, but
they are of the same order of magnitude.


    Attila Kinali
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Re: [time-nuts] Ultra low power RTC

[Attila Kinali]

On Tue, 6 Mar 2018 22:59:34 +
Mark Sims <hol...@hotmail.com> wrote:

> Sparkfun is selling an interesting RTC clock chip board. 
> It draws 22 nA.  It has a rather novel clock generator...
> a tuning fork crystal disciplines an RC oscillator every few minutes.
>  They claim 3 minutes per year drift.

*Sigh* There are a couple of things wrong with that description.

1) The part is from Microcrystal, so you can believe the specs
they publish with high confidence. This also means this is probably
the exact same chip you will find in Swiss quartz watches.
(Microcrystal is part of the Swatch group and the main supplier
of 32kHz oscillators and electronics for the Swiss watch industry)

2) The 22nA is the _typical_ consumption in auto-cal mode.
Max (the number you should design with) is 32nA. Keep in
mind this number is for the chip alone, no external connection.
It also includes the implicit condition that all input pins are
at valid voltage levels. If a pull up/down resistor is too weak
(because you tried to safe a few more nA) it will result in
pins being driven by leakage currents, possibly reaching invalid
voltage levels, which in turn will cause shot-through currents
through the input stages, increasing the power consumption 10 fold
at least, 1000 fold easily.

3) The current ratings are at 25°C. Going higher means also
an increase in power consumption. How much, is not specified.

4) The 3minutes per year number comes from the +/-3ppm first year
aging. This is, as usual, at 25°C and is on top of the typ. +/2ppm
time accuracy. So, the real accuracy is more like 5min after the first
year... when running from Xtal all the time!
Which has a typ. 60nA/max 80nA current spec!
Taking temperature into consideration, assuming something in the order
of 10 minutes per year is probably more realistic... if you stay
close to 25°C. The quadratic nature of the temperature dependence
for tuning fork X-cut crystals causes high deviations pretty quickly
(In one of the devices I designed, the 10ppm spec of the crystal
suddenly became 300ppm when taking the whole temperature range at
which it had to operate into consideration)

5) The precision of the auto-cal mode is not specified. It can be
litterally anything. Especially considering that the datasheet
talks about using it "several hours at Backup Supply Voltage," 
i.e. as an emergency measure when the normal power supply is lost.

        Attila Kinali

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Re: [time-nuts] ECS ECOC-2522 (was GPS Talking Clock)

[Attila Kinali]

Hoi Nick,

On Mon, 5 Mar 2018 09:36:01 -0800
Nick Sayer via time-nuts <time-nuts@febo.com> wrote:

> I’ve built two GPSDO units now with this OCXO. For the first one, I fed the 
> DAC (AD5680) from the oscillator’s reference output. This resulted in a very 
> poor (compared to expected) short term ADEV result (1-2 E-11). There was a 
> lot of noise (something like 5 mV P-P) on the reference output. Also, rather 
> oddly, the reference voltage was something like 2.8v. The datasheet doesn’t 
> say what the expected voltage is, but if you were to use that as your DAC 
> reference, you’d be throwing away the top 20% or so of the tuning range.

That sounds weird. Usually the reference voltage is the full scale
of the EFC range. Als, it should be pretty quiet, as it's (again usually)
derived from a internal Zener diode inside the oven. I could understand
a few dozen µV of noise (in a BW of 0.1Hz to 10Hz), but it shouldn't be
more than that. mV level of noise would mean that something is seriously
wrong with the reference.


> For the second unit, I built it with the same circuit I use for the CW 
> OH300, which lacks a reference output. There, instead, I use an NCP51460 
> precision regulator for a reference. There, I achieved a short term ADEV 
> much closer to expectations. It’s just under 6E-12 at tau 1-5s. ECS claims 
> it ought to be closer to 3, but it’s entirely possible that my reference 
> (Thunderbolt) and/or counter (53220A) are contributing error, or that my 
> design has some other noise contribution I haven’t yet found. Still, it’s at 
> least in the ball park. And the oscillator hasn’t even yet been running for 
> 24 hours, so it may get better with some time (I’m a little skeptical about 
> wear-in helping low-tau ADEV though. Doesn’t that usually operate on longer 
> term drift instead?).

For short tau measurements, It is advisable to set the Tbolt into holdover.
If the drift of the Tblot is not negligible, then you can measure its drift
and compensate for it manually after measurement. This will give you more
accurate results for these short tau measurements. 

Also, keep in mind that precision OCXO take a couple of days to settle.
I have a few measurements that a relative high frequency drift up to 
one to three weeks after power up, before the OCXO settles for something
an order of magnitude lower. I don't know the OH300, but they might
exhibit something similar, just at a different timescale. Look at the
datasheet, it should state a number of how many hours/days the OCXO
reaches the stability specs. Another aspect is that you should remove
any apparent phase/frequency drift (and probably other deterministic
effects) before calculating ADEV.



Attila Kinali
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Re: [time-nuts] Need a Watch Recommendation

[Attila Kinali]

On Mon, 5 Mar 2018 07:45:51 -0800
Jerry Hancock <je...@hanler.com> wrote:

> An by the way, I also have a Tissot P-touch as a retirement gift from IBM.  
> Got the watch, as they say.  I can say it is very accurate for a non-
> disciplined watch if you wear it every day.

Even if you do not wear it, it's very accurate. I guess they use
the internal termperature sensor to compensate the crystal. 
How they get to sub-ppm stability over half a year, I have no clue.
And this one is almost 20 years old.

        Attila Kinali
-- 
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the prosperity and technological sophistication in the world is of no 
use without that foundation.
 -- Miss Matheson, The Diamond Age, Neil Stephenson
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Re: [time-nuts] Need a Watch Recommendation

[Attila Kinali]

On Mon, 5 Mar 2018 01:38:06 -0500
Don Murray via time-nuts <time-nuts@febo.com> wrote:


> So it looks as if I am in need of a new wristwatch,
> which will give me some kind of time accuracy.

I've owned several Swatch and Tissot over the past decades,
Growing up in Switzerland does that to you. :-)

I currently have a Tissot P-Touch (first generation) and
a Swatch Irony in active use. Both are accurate enough
that I only set them twice a year (DST switch) and they
are usually off by less than 10s. Which is good enough
for my needs as a wristwatch.

So I guess, go for any modern Swiss quartz watch :-)

    Attila Kinali

-- 
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[time-nuts] lasers (was: Microsemi up for sale?)

[Attila Kinali]

a tiny little package. More information on its
construction and performance can be found in [6] (note: their calculation
of linewidth is wrong, it should be 36kHz/sqrt(2) = 25kHz).

The price was, when I looked at it 2 years ago, at 2500€.


Attila Kinali


[1] https://en.wikipedia.org/wiki/Diffraction_grating

[2] https://www.youtube.com/watch?v=EuWI1WPrZ2I

[3] "Mode stability of external cavity diode lasers", by Saliba,
Junker, Turner, Scholten, 2009
http://dx.doi.org/10.1364/AO.48.006692
https://cpb-ap-southeast-2-juc1ugur1qwqqqo4.stackpathdns.com/blogs.unimelb.edu.au/dist/5/118/files/2015/11/Saliba-et-al.-2009-Applied-Optics-Mode-stability-of-external-cavity-diode-lasers-1buob6t.pdf

[4] "Littrow configuration tunable external cavity diode laser with
fixed direction output", by Hawthorn, Weber, Scholten, 2001
https://doi.org/10.1063/1.1419217
https://www.thevespiary.org/library/Files_Uploaded_by_Users/no1uno/pdf/Instrumentation/Laser.Design/Hawthorn.Weber.Scholten.Littrow.Configuration.Tuneable.External.Cavity.Diode.Laser.with.Fixed.Direction.Output.Beam.pdf

[5] "A narrow-band tunable diode laser system with grating feedback,
and a saturated absorption spectrometer for Cs and Rb", by MacAdam,
Steinbach, Wieman, 1992
https://doi.org/10.1119/1.16955
https://www.thevespiary.org/library/Files_Uploaded_by_Users/no1uno/pdf/Instrumentation/Laser.Design/Laser.Locking/MacAdam.Steinchach.Wieman.A.Narrow.Band.Tunable.Diode.Laser.System.with.Grating.Feedback.and.a.Saturated.Absorption.Spectrometer.for.Cs.and.Rb.pdf


[6] "Compact Bragg Grating Stabilised Ridge Waveguide Laser Module
with a power of 380mW at 780nm", by Rauch and Sacher, 2015
https://doi.org/10.1109/LPT.2015.2438545
https://www.sacher-laser.com/downloads/publications/5r1249_en.pdf


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Re: [time-nuts] FRK

[Attila Kinali]

On Tue, 27 Feb 2018 13:53:36 -0500
ewkehren via time-nuts <time-nuts@febo.com> wrote:

> I have never seen a FRK or M 100 that did not have a screw iin lamp but 
> Attila`s unit looks like nothing I have seen before,  I am not a Corby but 
> over time 20 units have passed through my hands  

My lamp is beneath the base plate, which I didn't take a photograph
of, because you don't see anything but some foam that I didn't want
to remove, out of fear it would just crumble in my hands.
>From what I can tell, the design is close to, but not exactly
as described in the FRK-L manual on Didier's site.


        Attila Kinali
-- 
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use without that foundation.
 -- Miss Matheson, The Diamond Age, Neil Stephenson
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Re: [time-nuts] Assorted replies, and request for info

[Attila Kinali]

On Tue, 27 Feb 2018 06:58:04 -0500
ew via time-nuts <time-nuts@febo.com> wrote:

> Last year we did some work with a Tbolt and M100 using 40 000 seconds
> and 7 E-17 per uV. This was done with the support of Warren that I updated
> regularly. One set of data he responded on with: you are getting 1E-13 but
> what kind of Lab, 0.1 C over two weeks? The answer Juerg,s basement Lab in
> Switzerland while every body was on vacation. All critical tests are run
> over night.

In case you wonder what kind of basement this is, think of a German
style single-family home. Then add at +1 for sturdyness.. maybe even +2
and you are at how Swiss build their homes. Basements in Switzerland
are how other countries build their bunkers: Thick concrete walls.
Together with being underground (or semi-underground as in Jürg's case)
gives a very decent thermal mass and isolation. Having more than 5°C
temperature variation over a year in an (unheated) basement is unusual
and usually means there is something wrong with the building.

> What we now spend extensive time on is AC power. I have not seen much on time-
> nuts on this subject. Latest effort replacing vacuum fluorescents with LED 
> some thing I have not found in the US.

Be carefull with LED flourescent lamp replacements. You will replace
the 50/60Hz buzz with a 10-500kHz buzz that also tends to wander around
with time and temperature.

If you really want to have a quite light source, you have to build your
own LED lights, with properly filtered current sources. Nothing difficult,
but you have to design it properly because you are dealing with mains power.


Attila Kinali
-- 
It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
 -- Miss Matheson, The Diamond Age, Neil Stephenson
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Re: [time-nuts] FRK

[Attila Kinali]

On Tue, 27 Feb 2018 09:01:31 -0500
Bob kb8tq <kb...@n1k.org> wrote:

> Judging from the date codes on some of the parts, I’d guess that 
> your FRL-L is from 1982. I’m only looking at a few parts that came 
> through well enough in the picture to read (and that have what look 
> like rational date codes …).

Sorry, I didn't take much care when taking the pictures.
I can do better ones later.

But yes, the board has definitely an 80s vibe. The whole construction
is different then what I am used to from 80s electronics, though.
But I guess that's because it was designed and manufactured for
hi-rel applications. 

        Attila Kinali

-- 
It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
 -- Miss Matheson, The Diamond Age, Neil Stephenson
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Re: [time-nuts] FRK

[Attila Kinali]

On Mon, 26 Feb 2018 20:04:56 -0800
"Tom Van Baak" <t...@leapsecond.com> wrote:

> Bert's M100 Rb teardown photos are now here:
> 
> http://leapsecond.com/bert/m100.htm

For those, who would like to see the rest of M100/FRK,
I just took pictures of my FRK-L that was sitting on my
desk for way too long:

http://time.kinali.ch/Efratom_FRK-L/

Yes, there are only the pictures of the four PCBs from outside.
I didn't want to take the FRK further appart, as that would
require a soldering iron, and I really should be doing something
else.

    Attila Kinali

-- 
It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
 -- Miss Matheson, The Diamond Age, Neil Stephenson
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Re: [time-nuts] Replacement A9 boards for the HP 5065A

[Attila Kinali]

On Sat, 24 Feb 2018 23:44:16 -0500
Charles Steinmetz <csteinm...@yandex.com> wrote:

> Given the relatively low resistances at the op-amp inputs (10k ohms), 
> the ultra-low input "bias" (leakage) current of the 6240 is simply 
> unnecessary.  Any offset due to the input currents (within the general 
> range of any of these op-amps) is insignificant compared to the op-amp's 
> offset voltage.  Thus, offset voltage, offset voltage tempco, and offset 
> voltage long-tem drift are the critical parameters (as Poul-Henning 
> pointed out).  And here, the 1012 is clearly the best of the three.  In 
> addition to having the lowest input offset spec, the 1012 has guaranteed 
> maximum specifications for these important parameters.  The 6240 (for 
> good reason) is *not even rated* for long-term stability (drift). 
> (Long-term offset stability is a particular weakness of CMOS op-amps.)

Oh.. right, I didn't think about long term behaviour. Thanks for the correction!

BTW: How about using an LTC2057 then? Its input bias current  and
GBW spec is similar to the LT1012, but its offset voltage and drift
are far superior. Or would its charge injection noise be too large
for this application?

Attila Kinali



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Re: [time-nuts] Allan variance by sine-wave fitting

[Attila Kinali]

On Mon, 26 Feb 2018 02:43:04 -0800
"Tom Van Baak" <t...@leapsecond.com> wrote:

> This note is a follow-up to Ralph Devoe's ADEV posting earlier this month.
> 
> It's a long story but last week I was in the Bay Area with a car full of 
> batteries, BVA and cesium references, hp counters, and a TimePod. I was able 
> to double check Ralph's Digilent-based ADEV device [1] and also to 
> independently measure various frequency standards, including the actual 5065A 
> and 5071A that he used in his experiment.
> 
> For the range of tau where we overlap, his ADEV measurements closely match my 
> ADEV measurements. So that's very good news. His Digilent plot [2] and my 
> TimePod / TimeLab plot are attached.

Nice. Thank you!

BTW: Do you know the cause of the oscillations in the 5065 vs BVA plot?

> I'm sure more will come of his project over time and I hope to make 
> additional measurements using a wider variety of stable / unstable sources, 
> either down there in CA with another clock trip or up here in WA with a clone 
> of his prototype. It would be nice to further validate this wave fitting 
> technique, perhaps uncover and quantify subtle biases that depend on power 
> law noise (or ADC resolution, or sample rate, or sample size, etc.), and also 
> to explore environmental stability of the instrument.

For this, we would need a better understanding of what noise is 
mathematically and how it is affected by various components in
the signal path. But our mathematical description is lacking
at best (we only can descirbe white and 1/f^2 noise properly).


Attila Kinali
-- 
It is upon moral qualities that a society is ultimately founded. All 
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use without that foundation.
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Re: [time-nuts] Selling Time and Frequency Equipment

[Attila Kinali]

On Sat, 24 Feb 2018 16:19:04 +
MIKE ELDRIGE <mike.eldr...@msn.com> wrote:

> The starting price is going to be $4000.00 not a penny less.

https://www.ebay.com/itm/DATUM-Symmetricom-4040A-RS-11696-501-Cesium-Frequency-Standard-Atomic-Clock/112784315644

https://www.ebay.com/itm/DATUM-Symmetricom-4040B-077-003-08832-129-Cesium-Frequency-Standard-Atomic-Clock/112745451687


Just saying...

        Attila Kinali


-- 
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Re: [time-nuts] HP 5065A super

[Attila Kinali]

Hoi Bob,

On Thu, 22 Feb 2018 21:58:09 -0500
Bob kb8tq <kb...@n1k.org> wrote:

> The same nickel plating effect gets into a lot of things. If you are shopping 
> for very 
> low IMD connectors, nickel plating is out. Things get non-linear (to a very 
> slight 
> degree) when it is present. If -180 db is the goal for those spurs, you might 
> only
> hit -120 db with the nickel connectors …..

Interesting. About what frequency range are you talking?

        Attila Kinali

-- 
It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
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Re: [time-nuts] HP 5065A super

[Attila Kinali]

On Thu, 22 Feb 2018 15:33:50 +
"Poul-Henning Kamp" <p...@phk.freebsd.dk> wrote:

> >Then i would go for the LTC6240HV with a +/-5V power supply.
> 
> Offset voltage (stability) is a, if not the, *very* important
> parameter for the integrator.

That's another reason to choose the LTC6240 over the LT1793.
Beside the smaller 1/f noise (0.55µVpp vs 2.4µVpp), the LTC6240
has a much lower temperature coefficient (0.7µV/°C vs 8µV/°C).

The biggest drawback of the LT6240HV is its limited input range
of -5V to +3V (for a +/-5V supply). But in an integrator application,
this shouldn't be a problem (phase reversal is prevented by the 10k
input resistor). 


    Attila Kinali

-- 
It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
 -- Miss Matheson, The Diamond Age, Neil Stephenson
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Re: [time-nuts] HP 5065A super

[Attila Kinali]

On Thu, 22 Feb 2018 09:24:53 -0500
ew via time-nuts <time-nuts@febo.com> wrote:

> Attached the schematic of the A9 my file of the picture is to large it is the
> integrator. 

Ah.. this looks significantly different than my 5065 service manual shows.

So, I guess you want to build a new board that replaces this?

Then i would go for the LTC6240HV with a +/-5V power supply.
I agree with Charles that you want to have low noise power supplies,
though I think using a much cheaper and easier to solder TPS7A49
together with an TPS7A3001 should be more than enough, considering
that the LTC6240HV has a PSRR of >80dB.

If you need more than +/-5V range for the EFC, I'd add an
LTC2057 or LT6018 as amplifier stage after the integrator,
powered from +/-15V.

An alternative design would be to use a discrete JFET/MOSFET
input stage together with an LT6018. But you'd need to select
your FET carefully, as it then would limit your 1/f noise and
determine your leakage current.

        Attila Kinali
-- 
It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
 -- Miss Matheson, The Diamond Age, Neil Stephenson
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Re: [time-nuts] HP 5065A super

[Attila Kinali]

On Thu, 22 Feb 2018 07:00:54 -0500
ew via time-nuts <time-nuts@febo.com> wrote:

> Now a step by step work over, including HP mods for later  units like 
> replacing the 74196’s in the synthesizer module with 74LS196. May have been 
> end of life of the 74196.

With some slight change of the circuit, you should be able to replace
the 74196 by an 74163 which is available as LVC and thus should be
around for the next 10-20 years at least.

> Now to the purpose of this post. The A9 module is after 88 a significant 
> change and Corby sees an improvement against his Maser. We are doing a board 
> and maybe some other will be interested.

What does the A9 module do, for those of us who have not learned the inner
workings of the 5065 by heart? "Integrator Assembly" doesn't say too much

> Here are the issues
> A    is the LT1793 the best choice the time constant is 0.05 seconds with a 
> 10 K resistor and 5 uF Capacitor

What are your constraints? For every single parameter, there is an opamp
that beats the LT1793.
Do you just want to replace the opamp on A9 or build a new A9 from scratch?
If you can live with a power supply <12V, then I'd go for the LTC6240HV.

> B    should we add resistors and decoupling on the + - 15 volt op amp supplies

Depends on the noise of the power supply. My experience is, that resistors
in the power path causes more trouble than not having them. Though, I highly
suspect those were mostly caused by improper design. If you have problem with
noise on the power supply, I would rather suggest to use some low noise
LDOs instead. The TPS7Axx family from TI has quite a few offerings of
suitable LDOs. They are not on par with the LT3042, but they beat anything
you will have in 5065. And they are easier to solder :-)


> C    Gold plating the edge connecter,  does any one know a reasonable source, 
> or is doing it at home an option and if yes, how best way to do so.

There are gold plating solutions available, if you want to do it at home.
Though I would suggest to choose a PCB manufacturer that offers it.
In europe, i'd recommend Eurocircuits, but i'm pretty sure you have a
similarly cheap shop in the US. There are probably some shops in China
that offer that as well. Mind you, gold plating will increase the PCB
cost considerably, as it's a non-standard process. Not to mention that
you need hard gold for connector contacts, which is different from the
standard gold plating you will get as surface finish.


Attila Kinali
-- 
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the prosperity and technological sophistication in the world is of no 
use without that foundation.
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Re: [time-nuts] LED instead of discharge lamp for Rb vapor cell standards

[Attila Kinali]

On Wed, 21 Feb 2018 18:10:17 +
"Poul-Henning Kamp" <p...@phk.freebsd.dk> wrote:

> >So the Rb85 "notch" filter might not get rid of all the unwanted light
> >and some of this might depopulate the excited state of the Rb87
> >that are in the RF cavity.
> 
> I have a hard time seeing how you can not get worse S/N that way.


Well, the question is how much? Keep in mind that an Rb lamp is
anything but a clean light source. 

> If you want to do it with a LED, I think it needs to be a stabilized
> LED-Laser.

The problem with a Laser is that you need to lock it to the
right line. This requires either some significant change to the
electronics of the Rb standard, or an additional vapor cell and
some optics to lock it to that cell. Neither is trivial (apparently,
according to the papers I've read, not difficult, but I don't trust
that until I have tried myself).

Attila Kinali

-- 
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[time-nuts] LED instead of discharge lamp for Rb vapor cell standards

[Attila Kinali]

Moin,

Has anyone ever tried using a LED instead of a discharge lamp for Rb standards?
There are quite a few and very cheap 780nm IR LEDs available. They usually
have a line width in the order of 20nm to 50nm (FWHM). This means that they
still need the Rb85 filter, but they would not produce all those spectral lines
that the discharge lamp has, thus one could get rid of the (not so cheap)
optical filter that Corby uses for the super-5065. 

The one thing I am not sure about is the filter efficiency of Rb85.
Because now the light isn't two discrete lines from the Rb87 lamb
of which one needs to be masked, but a continuous and wide spectrum.
So the Rb85 "notch" filter might not get rid of all the unwanted light
and some of this might depopulate the excited state of the Rb87
that are in the RF cavity.

As a side-effect, you also get easier regulation of the light intensity
of the LED, thus potentially less instability due to light-shift variation.
Beside the LED operation being much simpler than that of a discharge lamp
and overall less heat dissipation.

        Attila Kinali

-- 
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use without that foundation.
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Re: [time-nuts] The "NAKED" 5065A optical unit

[Attila Kinali]

On Wed, 21 Feb 2018 15:37:53 +
"Poul-Henning Kamp" <p...@phk.freebsd.dk> wrote:

> I was talking about driving the single-transistor UHF generator which
> ionizes the Rb in the lamp, so far I have not even established if
> this voltage affects the HP5065 performance in the first place.

Oops... sorry, I missed that piece of context.
Yes, it is very unlikely that the noise of lamp power supply
would affect anything. At most, I could imagine that the frequency
drift of the lamp oscillator could maybe have some effects, but
even that is rather unlikely or swamped by other disturbances.

        Attila Kinali

-- 
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use without that foundation.
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Re: [time-nuts] The "NAKED" 5065A optical unit

[Attila Kinali]

On Tue, 20 Feb 2018 09:36:49 -0700
Mark Goldberg <marklgoldb...@gmail.com> wrote:

> I don't know anything about these devices, but for TCXOs, the power supply
> noise significantly affects the phase noise of the output. An LM317 is not
> well specified for noise and I expect is is orders of magnitude worse than
> something like an LT3042 low noise regulator.

It's >30dB for broadband noise, according to Gerhard Hoffmann's measurement:
https://www.flickr.com/photos/137684711@N07/24070698809/in/album-72157662535945536/

        Attila Kinali

-- 
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Re: [time-nuts] The "NAKED" 5065A optical unit

[Attila Kinali]

On Tue, 20 Feb 2018 10:03:20 -0800
<cdel...@juno.com> wrote:

> You do NOT want to take one apart to this level!
> 
> It's never going to operate again.

Why not? Is there something you had to break to open it up this far?

        Attila Kinali
-- 
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 -- Miss Matheson, The Diamond Age, Neil Stephenson
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Re: [time-nuts] eBay GPS antenna.

[Attila Kinali]

On Tue, 6 Feb 2018 07:08:42 -0600
John Green <wpxs...@gmail.com> wrote:

> Thanks for the responses. It looks similar to but not exactly like the two
> antennas referenced. They say the preamp is 3 to 5.5 volts, whereas the
> eBay antenna says its preamp is good from 3.3 to 18 volts, indicating I can
> run it off 12 volts.

I am pretty sure that this is either a mistake or a deliberate
deceit. Most LNA's I am aware of work between 3.3V and 5V. The
cheap ones are definitely all in that range. Some of those might
work for a short time with higher voltage, depending on the actual
semiconductor process used for production. But that means using
those chips outside their specs and putting a high straign on the
semiconductor, which will lead to an early death. It also cannot
be an LDO inside the antenna, as 3.3V is pretty much the lowest
voltage you can get an LNA for. There are some that work at 3.0V
still, but that would leave only 0.3V for the LDO, which requires
a more expensive LDO. I am pretty sure there are some LNAs that work
at 2.5V or even lower, but those would be definitely in the
way-too-expensive category.

So, my guess is, they tested the antenna whether it works with 12V,
seen that it does, and just "adjusted" the specs. But in reality,
the LNA still maxes out at 5V if you want a reliable device.


        Attila Kinali
-- 
The bad part of Zurich is where the degenerates
throw DARK chocolate at you.
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Re: [time-nuts] Anyone have experience with this antenna?

[Attila Kinali]

On Tue, 6 Feb 2018 08:54:23 -0500
Bob kb8tq <kb...@n1k.org> wrote:

> One gotcha (if the data sheets are correct) is going to be the supply voltage.
> We normally stay away from 12V antennas because TBolt’s put out 5V. In the
> case of a survey antenna, 12V is what most of the gear puts out. I don’t know
> of any L1 / L2 gear that puts out 5 rather than 12V ….

Well, that's at least a very easy modification. Just open up the connection
between the bias-T and the LNA and insert some LM1117 or better an TPS7A45xx.

        Attila Kinali

-- 
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[time-nuts] Etching of quartz crystals (was: Rakon HSO-14)

[Attila Kinali]

On Sun, 4 Feb 2018 09:21:54 -0500
Bob kb8tq <kb...@n1k.org> wrote:

> > The images on this page gives a good impression about the current
> > skill-level in that area:
> > 
> > https://www.azonano.com/article.aspx?ArticleID=2740 
> > <https://www.azonano.com/article.aspx?ArticleID=2740>
> 
> The gotcha is shown in the pictures. First point is that they are etching 
> *very*
> small features. A 5 MHz 3rd overtone blank is way thicker than what they are 
> playing with. The second issue is that even at small scale the walls are 
> going 
> non-parallel.

That's exactly the issue here. While SAW resonators benefit quite a lot
from the processing skills learned from semiconductor fabrication, these
skills do not translate into BAW manufacturing. SAW resonators are built
etching or depositing small features ontop of a SiO2 wafer that is supposed
to be as flat as possible. On the other hand BAW oscillators are 3D structures
by themselves. They are lens shaped (thus not flat) to keep the oscillation
energy trapped in the center of the slap, thus allowing the edges to be used
for mounting/contacting, with minimal damping of the oscillation.

Yes, the shapes are simple. But not only because that's the only shapes
we know how to build, but also because these shapes allow us to calculate
how the crystal will oscialate and because the simpler the structure the
easier it is to build it with high precision and accuracy.

It would be possible to use edging of surface structures into the
crystal to form a Bragg reflector (instead of the lense shape).
But I have no idea how well it works. Considering that it is easier
to build a slap that is flat and then etching structures on it, than
to form a 3D structure, I wonder why I have not read about anyone
doing exactly that (beside for SAW structures). 



Attila Kinali
-- 
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the prosperity and technological sophistication in the world is of no 
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Re: [time-nuts] Rakon HSO-14

[Attila Kinali]

On Fri, 2 Feb 2018 11:02:27 -0800
<cdel...@juno.com> wrote:

> Anyone priced a Rakon HSO-14 option 8.
> 
> It's the Oscilloquartz 8607 option 8 replacement.
> 
> I'm almost afraid to ask!

I do not know the HSO-14, but when I asked what the 8607 costs new, I
got ~5000 CHF for the "lowest" grade and over 14k CHF for the highest
grade. Of course this was a couple of years ago. I do not know how
the prices changed in the meantime. Considering that Rakon does not
build a true BVA, but instead puts the electrodes directly on the
resonator, I would expect them to be quite a bit cheaper (because
it doesn't require the couple of µm precision between the resonator
and the holder/elctrodes the BVA has).

    Attila Kinali

-- 
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use without that foundation.
 -- Miss Matheson, The Diamond Age, Neil Stephenson
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Re: [time-nuts] More on SiLabs 5340

[Attila Kinali]

Moin,

On Mon, 29 Jan 2018 15:38:33 -0500
John Ackermann N8UR <j...@febo.com> wrote:

> Today I tried replacing the crystal with a 10 MHz input, and found that 
> the evaluation board requires surgery to support that.  What I was able 
> to do, though, was feed 10 MHz into the "Input 0" port which apparently 
> disciplines the free-running crystal.  I used a 10811A fed into a 
> T2-Mini with divider removed, so all it does is provide the Wenzel 
> squaring circuit.  Results attached, added to the plots from yesterday. 
> Also attached is an ADEV plot proving that the 10 MHz is in control.

There is a small detail that puzzles me: the ADEV for the internal
reference 10MHz and 30MHz bends upwards at tau greater than 0.1s.
Shouldn't that be visible by a change in slope in the phase noise
plot at ~10Hz as well?

Attila Kinali

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use without that foundation.
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Re: [time-nuts] Slightly OT: interest in a four-output, ultra-low jitter, synthesizer block?

[Attila Kinali]

On Thu, 25 Jan 2018 09:32:56 -0500
John Ackermann N8UR <j...@febo.com> wrote:

 
> http://www.silabs.com/documents/public/data-sheets/Si5341-40-D-DataSheet.pdf
> 
> The challenge is that the chip is a 7x7 mm 44-QFN package and really 
> wants to be put on a six-layer circuit board.  That's doable, but 
> challenging, for home assembly.

Solderpaste stencil and a temp controlled frying pan helps :)
 
> Rather than designing the chip into a larger circuit board, I'm thinking 
> of doing a small "carrier" board that would include just the chip and 
> critical bypass caps and have headers to plug into the main board. 
> Then, you could just drop the carrier into a project-specific board and 
> not have to worry about the complex layout and mounting.  I have a 
> contract manufacturer who can build these up, if there's enough quantity 
> to justify the setup cost.

I'd be carefull with header pins at these frequencies. The slew-rate
of the chip is high enough that you get frequency components well into
the 10GHz range. I think a better idea would be just have castellation
at the PCB edge, with the right distances to meet impedance requriements,
and solder the PCB directly onto the main PCB without any connector inbetween. 

Also be aware that these kind of chips are quite peculiar about
the quality of their power supply. You need to design it for the
internal VCO, such that it has good regulation well into the MHz range
and high quality blocking capacitors rated for GHz use. Using 3-terminal
pass through capacitors like the Murata EMIFIL[1] goes a long way
for these kind of applications (at only a slightly higher price than
normal capacitors).


Attila Kinali



[1] https://www.murata.com/en-global/products/emc/emifil/chip




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Re: [time-nuts] Suggestion for a timing GPS receiver (Trimble / Ublox /other?)

[Attila Kinali]

On Tue, 23 Jan 2018 13:33:08 -0500
ewkehren via time-nuts <time-nuts@febo.com> wrote:

> The cheapest is not a 5T there are many 6 and 7 for $ 10. T gives you 
> nothing unless you  have saw tooth correction

It also gives additional performance when your skyview is very bad.
If you see only a small portion of the sky and only have 1-2 satellites
most of the time, then the position hold mode is the difference between
>1µs jitter and <100ns jitter, as Said Jackson noted a few years ago.

        Attila Kinali

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Re: [time-nuts] Symmetricom TimeSource 2500

[Attila Kinali]

On Tue, 23 Jan 2018 12:28:45 -0500
Bruce Hunter via time-nuts <time-nuts@febo.com> wrote:

> A key point is that no provision is made to control the frequency of the 
> PRS-10; it is simply monitored and the offset from GPS continually 
> recorded.  In other words, the PRS-10 does not influence the accuracy or 
> noise of the 10 MHz output unless the GPS reference is lost. 

And it's exactly that hold-over performance that you need for a
communication system. UMTS demands IIRC to keep sync between adjacent
base-stations better than 10µs at any time. LTE can be as low as 1.5µs.
The lawmaker used to demand 24h hold-over and most countries seem to
have switched to 72h in recent years. 1.5µs over 72h requires
frequency stability at the level of 5e-12. Even if you have a
well characterized high-quality OCXO getting bellow 1e-10 at these
time scales needs a bit of fiddling and going below 1e-11 is not easy.
(unless you apply techniques that can cancel out flicker noise,
but as far as I am aware of, nobody does that and I have no
experimental numbers on that, just simulations)


As for GPS operation, the advantage of an Rb vs a good OCXO is not
that big. There is a range between a few 100s and 10-20ks where a
GPSDO with an Rb reference can perform better than one with just an
OCXO. But it's not going to be more than a factor of 10. Beyond..uhmm..
let me guestimate 50ks the GPS will dominate the frequency stability.

I hope that clarifies the need for an Rb in such a unit.

        Attila Kinali
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Re: [time-nuts] Symmetricom TimeSource 2500

[Attila Kinali]

On Mon, 22 Jan 2018 13:17:40 -0500
Bruce Hunter via time-nuts <time-nuts@febo.com> wrote:

> A disappointment of the 2500's architecture is that it burns an SRI PRS-10 in 
> the background as a backup in case of the loss of GPS.  This seems wasteful 
> to me as the operating life of the PRS-10 units is not unlimited.  I suppose 
> the PRS-10 could be disabled, but this would require some simulation 
> circuitry as the 2500 monitors the PRS-10 and goes into a fault condition if 
> the expected PRS-10 presence is absent.  Certainly others have utilized these 
> units for such  use.  Has anyone performed a detailed evaluation of the 2500 
> units in intermittent service?

The PRS-10 is in there because someone needed the additional stability
performance. And to achieve that you need to run it continuously,
because you need to measure its frequency and correct it as it slowly
drifts. As with crystal oscillators, Rb have a retrace as well, so
just measuring the frequency and shutting it off, will not do.
So, what you want is bascially switching off the main component
of the system.

Besides, switching an Rb on and off is not a good thing for its lifespan.
It's like a incandescent light bulb: They can run for decades
if continuously under power, but if you switch them on and off once
a day, they die within a few months.

Also, Rb are spec'ed for a lifespan in the order of 20 years
(the PRS10 has a lifespan of 27 years). Nobody complains if a piece
of equipment needs to be replaced/repaired every 20 to 30 years.
Most likely the power supply will die well before you get even to
the Rb failing.

    Attila Kinali

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Re: [time-nuts] SI5328

[Attila Kinali]

On Mon, 22 Jan 2018 08:18:29 -0600
"Chris Caudle" <ch...@chriscaudle.org> wrote:

> The DSP loop filter gives a really wide range of loop bandwidth, down to
> fractional Hz for some parts.  Using a DDS for the VCO gives a lot of
> flexibility in output frequency selection, but means that there can be
> problems with  spurs.  Part of the SiLabs secret sauce is supposed to
> reduce spurs compared to a simpler NCO implementation, but I don't think
> you can eliminate spurs entirely with any kind of DDS based design.

The secret sauce is not so secret, actually. It's just how you
build a higher order delta-sigma modulator. Most PLL implementations
still use a 1st-order modulator, with the well known spur problem
(they arise from the "idle-tone" problem in delta-sigma modulators)
The "low-spur" fractional PLLs use a 2nd or 3rd order modulator.
There has been some research in the last decade or so on how to
reduce those spurs further (mostly using even higher order and some
times using tricks like actively introducing errors to spread the
spurs) and most of it can be found online on IEEE and the like.

For a gentle introduction, have a look at Schreier, Pavan and Teme's
book "Understanding Delta Sigma Data Converters." 

I find the idea of using two cascaded control loops neat. It helps
to control erros (aka noise) contributed by the second (inner) loop.
However, how this reduces suceptibility to vibration, I am not entirely sure.
The reason why most people do not do this is easily explained: it's more
difficult to get a stable system with nested loops, as the conditions
for stability becomes more complex than with just a standard, straight
forward PID loop.

Attila Kinali


-- 
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Re: [time-nuts] Suggestion for a timing GPS receiver (Trimble / Ublox / other?)

[Attila Kinali]

On Mon, 22 Jan 2018 16:38:01 +0100
Paride Legovini via time-nuts <time-nuts@febo.com> wrote:

> I plan to build a decent GPS/GNSS-based Stratum 1 NTP server, and I'm
> looking for a good and possibly affordable timing GPS receiver.
> 
> As far as I can tell there are a few common options. One is the Trimble
> Resolution T (or SMT), that should be good and proven. The major
> annoyance is converting the 3.3V TTL serial logic-level to RS232, but
> should be doable with a MAX3232 and a few capacitors.
> 
> Another option is this UBLOX LEA-5T:
> 
> https://www.ebay.it/itm/291769145465
> 
> The seller advertises an RS232 output pin, but I'm not sure it's
> actually available, and I'd need at least lines, one for the NMEA
> strings and one for the 1PPS signal. So, even if a RS232 TX pin is
> actually there, it is probably not enough to build a good reference
> clock, and I'd still need to convert some TTL levels to RS232...
> 
> Does anybody have experience with this receiver?
> How does it compare to the Resolution T/SMT?

For raw GPS PPS output, your performance is limited by multi-path
and how much of the sky you see. If you have perfect conditions,
I expect both to perform at the same level. Under not so perfect
conditions, go for the LEA. I have here a Trimble UCCM and 
Oscilloquartz Star4 GPSDO (using a LEA-5T). Compared to the Star4,
the UCCM is basically deaf. And mind you, the LEA-5 family came out
somewhen around 2006, ie is already a more than 10 year old design
and probably of the same age as the UCCM. The modern LEA's got a few
dB better yet.

For an NTP server, where you wont need anything better than 1µs
resolution, I think one of the many 10-bucks ublox LEA/NEO boards
that you can find on ebay are good enough (standard navigation
receivers give you better than 100ns accuracy). If you still want
to have a timing receiver, then go for one of the NEO-M8T, LEA-M8T or
LEA-6T based boards. Be aware that the NEO modules do not have the
circuit to provide power to the antenna, so it must be either
passive or you need an external bias-T. The LEA's can provide up
to 50mA (so no Zephyr!). 

If you want to step up your game and get even better stability,
take one of the LEA based GPSDOs (like the Star4 mentioned above).


Attila Kinali


-- 
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use without that foundation.
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Re: [time-nuts] SI5328

[Attila Kinali]

Hoi Bert,

On Mon, 22 Jan 2018 06:34:42 -0500
ew via time-nuts <time-nuts@febo.com> wrote:

> In my opinion the SI 5328 is worth looking at for time nut application, like 
> offset frequency. My problem is solder ability. Does any one know a source
> for an evaluation board or as an alternative a source that would do a small
> volume assembly?

As others have written, an eval board is available.

There are many small volume assmebly houses available. But the problem
is that you will have setup costs in the order of at least 100-300€,
even if you go to China. So, producing lots of less than 10 is not economical,
probably should aim for 100.

        Attila Kinali

-- 
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Re: [time-nuts] trimble Thunderbolt, how to get 25 or 27 mHz from it??

[Attila Kinali]

On Mon, 8 Jan 2018 13:14:16 +
Chris Wilson <ch...@chriswilson.tv> wrote:

> Thanks for the very fast reply! Would it be possible to use one of
> these frequency multiplier IC's? Sounds simpler, but maybe there are
> down sides?
> 
> http://uk.farnell.com/on-semiconductor/nb3n502dg/pll-clock-multiplier-8soic/dp/2101849

Bruce's idea is much lower noise. The NB3N502 datasheet states
an typical output jitter of 15ps. That's HUGE for a normal VCXO
output that is usually below 1ps. The low-noise OCXOs have something
in the order of 100fs. Alternatively, you can use something like
an ADF4002 and an VCXO with 25/27MHz. That should give you a much
better performance, mostly limited by the VCXO. But you will need
to have a sine-to-square conversion of the 10MHz output of the
Thunderbolt first, as the ADF4002 has a slew-rate limit on its
reference input.

BTW: stay away from any VCXO that mentiones "programable" in its datasheet.
These are XO + fractional PLL combinations where the PLL allows quick
and cheap realization of odd frequencies. But their spurs and noise floor
is much worse than normal XOs.

    Attila Kinali

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Re: [time-nuts] AM vs PM noise of signal sources

[Attila Kinali]

cles on how to build low-noise oscillators that are
only limited by the thermal noise in the 50Ω source resistance, Ie oscillators
that have a white noise floor at almost -174dBm (note: dBm not dBc).

It is "known" how to build such oscillators, but it doesn't mean it's easy :-)

Attila Kinali


[1] "A General Theory of Phase Noise in Electrical Oscillators",
Hajimiri and Lee, 1998

[2] "How Low Can They Go?", by Poddar, Rohde, Apte, 2013
http://time.kinali.ch/rohde/noise/how_low_can_they_go-2013-poddar_rohde_apte.pdf
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Re: [time-nuts] AM vs PM noise of signal sources

[Attila Kinali]

On Tue, 2 Jan 2018 23:34:18 +0100
Magnus Danielson <mag...@rubidium.dyndns.org> wrote:

[About AM noise being of equal power as PM noise]

> Now, for actual sources this is no longer true. The AM noise can be much
> higher, which is why it can be a real danger to the PM noise if there is
> a AM to PM noise conversion. One source of such conversion can be the
> amplification stage, but another could be a mistuned filter, which have
> different amplitudes of the side-bands, which can create conversion as
> the balance does not balance the same way anymore.

Yes, exactly. I am currently trying to understand how noise affects
circuits an how input and circuit noise get converted to output noise.
First assumption that needs to be dropped is that the noise processes
is purely additive and independent of the signal. This means that a
noise process does not anymore produce equal AM and PM power.

I think I have a 90% solution of the noise processes and conversions
in a sine-to-square converter (aka zero-crossing detector, aka comparator).
But there is one process that keeps puzzling me. I think I know where in
the circuit it must come from, but I have no explanation as to how it happens.


        Attila Kinali
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[time-nuts] AM vs PM noise of signal sources

[Attila Kinali]

Hi,

I am currently looking at noise calculations that deal with AM and PM noise.
To check whether the calculations make sense, I am looking for some numbers
of the white noise floor AM and PM noise levels of signal sources.
Unfortunately, almost everyone only deals with PM noise and hardly
anyone mentiones AM noise levels. The best I could find sofar is [1]
which supports the notion that AM noise is so far below PM noise, that
it is insignificant. Does someone else have more data and would be willing
to share?

Attila Kinali


[1] http://www.wenzel.com/documents/amnoise.htm

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Re: [time-nuts] Down-conversion to IF and sampling

[Attila Kinali]

On Sat, 23 Dec 2017 21:00:39 +
Stephan Sandenbergh <ssandenbe...@gmail.com> wrote:

> I guess I'm just worried that I might be missing something obvious here?
> And I know there is no better place to ask such a question other than on
> time-nuts :)

No, your derivation is correct. Though conventionally, it would be
written as: V_{IF}(t) = sin[(ω_{RF} - ω_{LO})t - Δφ_{RF-LO}(t)]
Hence, the sampled signal becomes:
V_{IF}[nT_s] = sin[(ω_{RF}*(nT_s) - ω_{LO}*(nT_s) - Δφ_{RF-LO}[nTS]]

In this notation, it is a bit more obvious what's going on. Assuming
both RF and LO frequency are constant, then the sampled voltage only
depends on the difference of the frequencies, and the initial phase offset
at time t = 0*T_s. Be aware that this only holds true if you either
use a low pass filter after the mixer or use complex down conversion.
In all other cases you have to account for the (ω_{RF} + ω_{LO}) component
as well.

Using x(t) = x_0 + y_0*t confuses things a bit, as this means
that you are modulating the phase with a frequency of y_0, which you
probably do not intend.

Any phase noise you have in the system, you can fold into φ_{RF-LO}(t).

Please note, the above has the implicit assumption, that:
ω_{IF} is < 0.5 * ω_{LO}, ie that the IF signal is in the first
Nyquist zone. Otherwise you have to treat the ADC as another mixer stage,
with it's own ω_{LO_{ADC}} and φ_{LO_{ADC}}.

As Tim Shoppa mentioned, you do not want to have a ratio with small integers
between the LO frequency and the sampling frequency, as any feedthrough of
the LO and its harmonics will lead to a DC offset and spurs. The amplitude
of both will depend on the exact phase relation between the LO frequency
and the sampling frequency, which is usually stable, but not time-nuts stable.


        Attila Kinali
-- 
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Re: [time-nuts] Oscilloquartz 8600-3 Disassembly pictures...

[Attila Kinali]

On Sat, 16 Dec 2017 15:14:25 -0800
"Tom Van Baak" <t...@leapsecond.com> wrote:

> Ed Palmer text and photos:
> http://leapsecond.com/museum/osa8601/
> http://leapsecond.com/museum/osa8601/view.htm

The 7.04.82 in the 11th picture is likely to be a date code.
But it's in European notation, meaning day.month.year.
Ie it's 7th Arpil, 1983

Rule of thumb: if it's "/" then it's MM/DD/YY or YY/MM/DD (depending
whether it's USian or Japanese). If it's "." then it's DD.MM.YY
(most common European notation). If it's "-" it was supposed
to be -MM-DD by ISO8601, but too many people confused it as
being the "new way" to write dates, so it can be literally anything.


Thanks for the pictures!

Attila Kinali

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Re: [time-nuts] Determining Allan Deviation From Interpolated Peak Frequency Readings

[Attila Kinali]

On Fri, 15 Dec 2017 10:08:29 -0700
Mark Goldberg <marklgoldb...@gmail.com> wrote:

> > The approach using FFT works, but just using the peak frequency, you throw
> > away half of the data (the phase) and also limit yourself in precision
> > to the bin width. It's not 100% clear that estimating the frequency
> > using an FFT is unbiased in this case, thus you might get worse (or better)
> > results than what the oscillator actually does.
> >
> 
> Since I do not know the exact algorithm used to interpolate peak frequency,
> I don't know the effect on precision. They do claim that the peak frequency
> determination precision is much smaller than the bin width, which seems to
> be shown by the data.
> 
> The results are good enough to discern between "bad" and "good" units under
> test, but I have no way to compare my results to any other method of
> measurement. This is all I have access to.

If all you want is to discern good and bad units, this is good enough.
 
> > [1] "Oscillator metrology with software defined radio",
> > by Sherman and Jördens, 2016
> > https://arxiv.org/abs/1605.03505
> >
> 
> I have seen this paper before. Unfortunately, it is a lot more work to
> implement than what I have already done. I am really a hardware engineer,
> with decades old education in control systems that has not been used in a
> long time. It would take getting my brain back in gear and re-studying, not
> a bad thing actually!
> 
> The other issue is the Perseus drivers have issues under Windows 10 that
> may or may not be solved. I was able to get it to work with Spectrum Lab,
> but it does not work with many other tools that would be able to implement
> this algorithm.
> 
> That said, I may look into it further in the future.

Apparently the Perseus is supported by GnuRadio[1]. Which means you can
just click your control system together (similar to LabView). According
to [2] the driver uses libusb and works on windows as well.

If you want to use GnuRadio, I suggest you go to one of the many Hackfests[3]
they have and let them jump-start you (I started this way years ago).


Attila Kinali


[1] https://gnuradio.org/
[2] https://github.com/Microtelecom/libperseus-sdr
[3] https://www.gnuradio.org/event-type/hackfest/


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Re: [time-nuts] IEEE Spectrum - Dec 2017 - article on chip-scale atomic frequency reference

[Attila Kinali]

On Fri, 15 Dec 2017 17:17:31 +0100
Mike Cook <michael.c...@sfr.fr> wrote:

> > The original paper in question is [1]. As with the nitrogen vacancy
> > clocks, which also trap nitrogen within a Carbon lattice, these have the
> > drawback of quite high temperature coefficients, Harding et al measured 
> > 89ppm/K.
> 
> I wonder if Cs-133 can be inserted into C-60 fullerene? If it could,
> then a primary reference on a chip might be possible.

No, it wouldn't. It isn't the species of atom being used that defines
whether it is a primary standard or not, but rather that it is possible
to exactly calculate the frequency of the output given all disturbances.
It is possible to achieve this with Cs, Rb, Hg, Yb, Sr, ... it just depends
on how you do it.

The problem with the atom-in-fullerene is that the atom is not in 
(a good approximation of) vacuum, as it is surrounded by a molecule
in close proximity. This means the surrounding atoms disturb the electrons
of the probed atom. This is what causes the large temperature dependence.

Attila Kinali
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It is upon moral qualities that a society is ultimately founded. All 
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Re: [time-nuts] IEEE Spectrum - Dec 2017 - article on chip-scale atomic frequency reference

[Attila Kinali]

On Fri, 8 Dec 2017 09:40:29 -0800
Tom McDermott <tom.n...@gmail.com> wrote:

> Researchers at Oxford U. have fabricated an atomic reference based on
> a single nitrogen molecule inside a 60-atom carbon sphere ("Fullerene").
> The cage of carbon isolates the nitrogen from external electric fields,
> and they've developed a method to also isolate it from external magnetic
> fields.

The original paper in question is [1]. As with the nitrogen vacancy
clocks, which also trap nitrogen within a Carbon lattice, these have the
drawback of quite high temperature coefficients, Harding et al measured 89ppm/K.

    Attila Kinali


[1] "Spin Resonance Clock Transition of the Endohedral Fullerene 15N@C60",
by Harding, Zhou, Zhou, Myers, Ardavan, Briggs, Porfyrakis, Laird, 2017
https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.119.140801
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Re: [time-nuts] Determining Allan Deviation From Interpolated Peak Frequency Readings

[Attila Kinali]

Hey Mark

On Wed, 6 Dec 2017 15:43:49 -0700
Mark Goldberg <marklgoldb...@gmail.com> wrote:

> https://sites.google.com/site/perseusmods/
> and
> https://sites.google.com/site/spectrumlabtesting/
> 
> using wide FFT bins and Spectrum Lab's peak frequency interpolation
> function. I would appreciate comments as to the effectiveness of this
> approach. I have a thick skin, so any criticism is welcome if it improves
> the process.

The approach using FFT works, but just using the peak frequency, you throw
away half of the data (the phase) and also limit yourself in precision
to the bin width. It's not 100% clear that estimating the frequency
using an FFT is unbiased in this case, thus you might get worse (or better)
results than what the oscillator actually does.

What you are trying to do is spectral estimation from a limited number of
samples. You want to have some kind of continuity, that might allow you to
track minute changes from block you are processing to the next block.
The easiest way to do this would be to downconvert the signal on the PC
to zero Hz and take the phase information (simplest way: use a NCO as a 
reference, then pass the reference and signal into a CORDIC to get the phase
difference). Recording this phase difference should give you a lower floor
for *DEV than your FFT method. It will also alow you to track small phase
changes (aka small frequency fluctuations) that happen over long periods.
Sherman and Jördens[1] describe the approach in more detail.

Other than that, the general approach looks ok.


    Attila Kinali


[1] "Oscillator metrology with software defined radio",
by Sherman and Jördens, 2016
https://arxiv.org/abs/1605.03505
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Re: [time-nuts] Fluke/Pendulum PM6680/CNT-80 measurement instability/outliers

[Attila Kinali]

On Thu, 14 Dec 2017 22:08:01 -0600
Bill Byrom <t...@radio.sent.com> wrote:

> I have a few questions about your setup:
> (1) What is the waveform shape you are measuring? Are you measuring a
> square wave (or some other duty cycle waveform with fast rise and
> falling edges)? Or is it a sinewave with low harmonic content?

Sine, +7dBm

> (2) How is the counter voltage threshold set with respect to the peak
> excursions? Is it set to the 50% point or near the bottom or top of the
> waveform?

Auto-set to mid-range.

> (3) How are you connecting the source to the counter input? Is it a 50
> ohm RG-58 cable with BNC connectors? Are there any TEE connectors or
> feed-through terminations? What is the cable impedance? You can easily
> find 75 ohm cables with 75 ohm BNC connectors which will mate (with a
> bit of difficulty in some cases) with 50 ohm female connectors. If you
> have a 50 ohm counter impedance, a 75 ohm cable can cause difficulty.

Short (15cm) piece of RG-172 (IIRC) with SMA connector, all 50 Ohm

> (4) What is the output impedance of the source you are measuring?

50Ohm

> (5) What is the input impedance of the counter (as it is set up for your
> test)?

50Ohm

But you are right. I should have suspected the oscillator side instead of
the instrument or its reference. I just checked the time-stamps of the outliers.
All of them are during times someone was in the office. None during nights
or weekends. So it's likely that there is a bad contact somewhere and
I or someone else caused that to jump from time to time.

Thanks for your time and help!

Attila Kinali

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Re: [time-nuts] Performance verification for time counters

[Attila Kinali]

On Fri, 1 Dec 2017 21:10:55 +
Leo Bodnar <l...@leobodnar.com> wrote:

> As promised, I started setting up dual asynchronous sources experiment
> and performed a quick sanity check.  What I have [unsurprisingly] found
> is that at this level controlled environment is a problem in itself. 
> For example, undoing input signal SMA connector by one turn shifted my
> results by around 3.5ps - close to expected figure but still inconvenient.
> I'll have to plan the setup before I build and validate it, otherwise the 
> results are not trustworthy.

3.5ps is pretty much what I'd expect in additional delay, when undoing an
SMA connector by one turn. One turn is about 0.7mm, assuming a VF of 0.6
you get to ~3.5ps.
I am quite impressed that you could measure it this accurately.
What measurement technique do you use?


        Attila Kinali

-- 
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Re: [time-nuts] Trimble Mini-T Timing Glitches

[Attila Kinali]

On Thu, 30 Nov 2017 21:31:54 +
Leo Bodnar <l...@leobodnar.com> wrote:

> From: Bob kb8tq <kb...@n1k.org>
> > GPS extracts time and location by locking on to various codes in the 
> > transmissions. 
> > One of them happens to run at about a 1 KHz clock rate. A slip on that part 
> > of the 
> > process gives you a (modulo) 1 ms clock jump. Certain types of interference 
> > may
> > “help” the receiver make these sorts of mistakes.

> Bob, this is quite an unorthodox description of how GPS works.
> You probably want to rephrase that before it gets ripped to shreds.

Actually, that's a pretty accurate, two sentence description.
It wouldnt be possible to build a GPS receiver using this, but
it's ok for the purpose.

On Thu, 30 Nov 2017 23:05:55 +
Leo Bodnar <l...@leobodnar.com> wrote:

> I can't see how randomly selected 1ms of data can contain unambiguously 
> detectable start of C/A code.
> If NAV data bit phase flip occurred within this 1ms of data then correlation 
> search will most probably fail.
> Yes, the probability of this is only 5% (assuming equal number of 1s and 0s 
> in NAV message) but still not zero.
> Perhaps the quote should have added "carefully chosen 1ms of data"


The C/A code repeates every 1ms. The decoder cannot tell the repetitions
themselves appart at all. To solve this ambiguity, the decoder has to wait
for the flip caused by the tranmitted data, that happens exactly at those
1ms boundaries. As you noted, they happen only every 20ms (50baud data).
So, if you take these bit flips into account, there is now a 20ms ambiguity.
To resolve this, one has to wait for a start of frame (Preamble of the TLM
in GPS-speak), which then gives an 6s amibiguitiy, but as the data frame
contains the current time, the ambiguity can be completely resolved.

Now, depending on how the decoder is organized, it is totally possible,
that the decoder jumps by 1ms. Why doesn't this cause a loss of correltation?
Because most modern receivers use multiple C/A code-blocks for corrlation.
Correlation times of 10ms or 20ms are pretty normal, 100ms are not unheard of.
Thus, when using such long correlation times, slipping by 1ms will only cause
a slight degradation of C/N0 but it will still sufficiently high.
And also the data will decode correctly, because it's just a 5% (or -1.45dB) 
loss of signal assuming 20ms correlation time[1].

I've encountered modern receivers (aka not older than 5 years), that slip 
by 1ms under certain conditions.


> At the minimum, one would typically select 2ms of sampled data when they are 
> doing a correlation search and then
> they are guaranteed a full PRN sequence somewhere in there.

2ms is actually a pretty bad choice. If the bit flip happens within
those 2ms, then the correlation output, if perfectly matched, will 
be exactly zero (assuming no noise). You have to use either 1ms
correlation times, for aquisition, or a more sophisticated method.
Section 5.8 "signal acquisition" in Kaplan and Hegarty's book[2]
contains a few common techniques with good explanations.


Attila Kinali

[1] ok, it's actually more like 10%/1.91dB loss, because the
signal during that flipped 1ms is multiplied by -1 instead of +1, so it
causes twice the amount of signal los than uncorrelated signal

[2] "Understanding GPS - Principles and Applications", 2nd ed
by Kaplan and Hegarthy, 2006

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Re: [time-nuts] Performance verification for time counters

[Attila Kinali]

On Thu, 30 Nov 2017 09:39:59 -0500
Bob kb8tq <kb...@n1k.org> wrote:

>  That last decade ( 0.01 Hz period to 0.001 Hz)

What puzzles me here is, the reason why someone would care
about sub-1Hz frequencies in a telephone system? IIRC POTS
did cut off somewhere areound 100-300Hz anyways.

        Attila Kinali
-- 
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the prosperity and technological sophistication in the world is of no 
use without that foundation.
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[time-nuts] ergodicity vs 1/f (was: Allan variance by sine-wave fitting)

[Attila Kinali]

On Thu, 30 Nov 2017 12:44:13 +0100
Mattia Rizzi <mattia.ri...@gmail.com> wrote:

> Let me emphasize your sentence:  "you will have a statistically significant
> number of samples of *one* realization of the random variable.".
> This sentence is the meaning of ergodic process [
> https://en.wikipedia.org/wiki/Ergodic_process]
> If it's ergodic, you can characterize the stochastic process using only one
> realization.
> If it's not, your measurement is worthless, because there's no guarantee
> that it contains all the statistical information.

You are mixing up ergodicity and reproducability.

Also, you are moving the goalpost. 
We usually want to characterize a single clock or oscillator.
Not a production lot. As such the we only care about the statistical
properties of that single instance. If you want to verify that your
production lot has consistent performance metrics, then this is a
completely different goal and requires a different methodology. But 
in the end it will boil down to measuring each clock/oscillator
individualy to make sure it fullfils the specs.


> >A flat signal cannot be the realization of a random variable with
> a PSD ~ 1/f. At least not for a statisticially significant number
> of time-samples
> 
> Without ergodicity you cannot claim it. You have to suppose ergodicity.

If you demand ergodicity, you cannot have 1/f.
You can have only one or the other. Not both.
And if you choose ergodicity, you will not faithfully model a clock.
 
> If it's not stationary, it can change over time, therefore you are not
> authorized to use a SA. It's like measuring the transfer function of a
> time-varying filter (e.g. LTV system), the estimate doesn't converge.

Please take one of the SA's you have at CERN, measure an oscillator
for a long time and note down the center frequency with each measurement.
I promise you, you will be astonished.


Attila Kinali
-- 
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the prosperity and technological sophistication in the world is of no 
use without that foundation.
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Re: [time-nuts] Allan variance by sine-wave fitting

[Attila Kinali]

On Tue, 28 Nov 2017 09:52:37 +0100
Mattia Rizzi <mattia.ri...@gmail.com> wrote:

> >Well, any measurement is an estimate.
> 
> It's not so simple. If you don't assume ergodicity, your spectrum analyzer
> does not work, because:
> 1) The spectrum analyzer takes several snapshots of your realization to
> estimate the PSD. If it's not stationary, the estimate does not converge.

I do not see how ergocidity has anything to do with a spectrum analyzer.
You are measuring one single instance. Not multiple.
And no, you do not need stationarity either. The spectrum analyzer has
a lower cut of frequency, which is given by its update rate and the
inner workings of the SA. 

> 2) It's just a single realization, therefore also a flat signal can be a
> realization of 1/f flicker noise. Your measurement has *zero* statistical
> significance.

A flat signal cannot be the realization of a random variable with
a PSD ~ 1/f. At least not for a statisticially significant number
of time-samples. If it would be, then the random variable would not
have a PSD of 1/f. If you go back to the definition of the PSD of
a random variable X(ω,t), you will see it is independent of ω. 

And about statistical significance: yes, you will have zero statistical
significance about the behaviour of the population of random variables,
but you will have a statistically significant number of samples of *one*
realization of the random variable. And that's what you work with.


    Attila Kinali
-- 
It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
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 -- Miss Matheson, The Diamond Age, Neil Stephenson
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Re: [time-nuts] Allan variance by sine-wave fitting

[Attila Kinali]

On Mon, 27 Nov 2017 23:50:22 +0100
Attila Kinali <att...@kinali.ch> wrote:

> > Every experimentalist suppose ergodicity on this kind of noise, otherwise
> > you get nowhere.
> 
> Err.. no. Even if you assume that the spectrum tops off at some very
> low frequency and does not increase anymore, ie that there is a finite
> limit to noise power, even then ergodicity is not given.
> Ergodicity breaks because the noise process is not stationary.
> And assuming so for any kind of 1/f noise would be wrong.

Addendum: the reason why this is wrong is because assuming noise
is ergodic means it is stationary. But the reason why we have to
treat 1/f noise specially is exactly because it is not stationary.
I.e. we lose the one property in our model that we need to make
the model realistic.

    Attila Kinali

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Re: [time-nuts] Allan variance by sine-wave fitting

[Attila Kinali]

Hoi Mattia,

On Mon, 27 Nov 2017 23:04:56 +0100
Mattia Rizzi <mattia.ri...@gmail.com> wrote:

> >To make the point a bit more clear. The above means that noise with
> > a PSD of the form 1/f^a for a>=1 (ie flicker phase, white frequency
> > and flicker frequency noise), the noise (aka random variable) is:
> > 1) Not independently distributed
> > 2) Not stationary
> > 3) Not ergodic
> 
> I think you got too much in theory. If you follow striclty the statistics
> theory, you get nowhere.
> You can't even talk about 1/f PSD, because Fourier doesn't converge over
> infinite power signals.

This is true. But then the Fourier transformation integrates time from
minus infinity to plus infinity. Which isn't exactly realistic either.
The power in 1/f noise is actually limited by the age of the universe.
And quite strictly so. The power you have in 1/f is the same for every
decade in frequency (or time) you go. The age of the universe is about
1e10 years, that's roughly 3e17 seconds, ie 17 decades of possible noise.
If we assume something like a 1k carbon resistor you get something around
of 1e-17W/decade of noise power (guestimate, not an exact calculation).
That means that resistor, had it been around ever since the universe was
created, then it would have converted 17*1e-17 = 2e-16W of heat into
electrical energy, on average, over the whole liftime of the universe.
That's not much :-)

> In fact, you are not allowed to take a realization, make several fft and
> claim that that's the PSD of the process. But that's what the spectrum
> analyzer does, because it's not a multiverse instrument.

Well, any measurement is an estimate.

> Every experimentalist suppose ergodicity on this kind of noise, otherwise
> you get nowhere.

Err.. no. Even if you assume that the spectrum tops off at some very
low frequency and does not increase anymore, ie that there is a finite
limit to noise power, even then ergodicity is not given.
Ergodicity breaks because the noise process is not stationary.
And assuming so for any kind of 1/f noise would be wrong.


Attila Kinali
-- 
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Re: [time-nuts] Allan variance by sine-wave fitting

[Attila Kinali]

On Mon, 27 Nov 2017 19:37:11 +0100
Attila Kinali <att...@kinali.ch> wrote:

> X(t): Random variable, Gauss distributed, zero mean, i.i.d (ie PSD = const)
> Y(t): Random variable, Gauss distributed, zero mean, PSD ~ 1/f
> Two time points: t_0 and t, where t > t_0
> 
> Then:
> 
> E[X(t) | X(t_0)] = 0
> E[Y(t) | Y(t_0)] = Y(t_0)
> 
> Ie. the expectation of X will be zero, no matter whether you know any sample
> of the random variable. But for Y, the expectation is biased to the last
> sample you have seen, ie it is NOT zero for anything where t>0.
> A consequence of this is, that if you take a number of samples, the average
> will not approach zero for the limit of the number of samples going to 
> infinity.
> (For details see the theory of fractional Brownian motion, especially
> the papers by Mandelbrot and his colleagues)

To make the point a bit more clear. The above means that noise with
a PSD of the form 1/f^a for a>=1 (ie flicker phase, white frequency
and flicker frequency noise), the noise (aka random variable) is:

1) Not independently distributed
2) Not stationary
3) Not ergodic 


Where 1) means there is a correlation between samples, ie if you know a
sample, you can predict what the next one will be. 2) means that the
properties of the random variable change over time. Note this is a
stronger non-stationary than the cyclostationarity that people in
signal theory and communication systems often assume, when they go
for non-stationary system characteristics. And 3) means that
if you take lots of samples from one random process, you will get a
different distribution than when you take lots of random processes
and take one sample each. Ergodicity is often implicitly assumed
in a lot of analysis, without people being aware of it. It is one
of the things that a lot of random processes in nature adhere to
and thus is ingrained in our understanding of the world. But noise
process in electronics, atomic clocks, fluid dynamics etc are not
ergodic in general.

As sidenote:

1) holds true for a > 0 (ie anything but white noise).
I am not yet sure when stationarity or ergodicity break, but my guess would
be, that both break with a=1 (ie flicker noise). But that's only an assumption
I have come to. I cannot prove or disprove this.

For 1 <= a < 3 (between flicker phase and flicker frequency, including flicker
phase, not including flicker frequency), the increments (ie the difference
between X(t) and X(t+1)) are stationary.

Attila Kinali


-- 
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Re: [time-nuts] Allan variance by sine-wave fitting

[Attila Kinali]

hase noise, so it's not possible to see in your plots where
flicker noise becomes relevant (that's why we have MDEV).

Or TL;DR: for measurements in our field, you cannot assume that the
noise you have is uncorrlated or has zero mean. If you do simulations,
you have to account for that properly (which is not an easy task).
Thus you can also not assume that your estimator has no bias, because
the underlying assumptions in this deduction is that the noise has
zero mean and averages out if you take a large number of samples.

And we have not yet touched the topic of higher order noises, with a PSD
that's proportional to 1/f^a with a>1.

> Attila says that I exaggerate the difficulty of programming an FPGA. Not
> so. At work we give experts 1-6 months for a new FPGA design. We recently
> ported some code from a Spartan 3 to a Spartan 6. Months of debugging
> followed.

This argument means that either your design was very complex, or it
used features of the Spartan3 that are not present in Spartan6 anymore.
The argument does not say anything about the difficulty of writing
a down-mixer and sub-sampling code (which takes less than a month,
including all validation, if you have no prior experience in signal
processing). Yes, it's still more complicated than calling a python
function. But if you'd have to write that python function yourself
(to make the comparison fair), then it would take you considerably
longer to make sure the fitting function worked correctly.
Using python for the curve fitting is like you would get the VHDL code
for the whole signal processing part from someone. That's easy to handle.
Done in an afternoon. At most.

And just to further underline my point here: I have both written
VHDL code for FPGAs to down mix and subsample and done sine fitting
using the very same python function you have used. I know the complexity
of both. As I know their pitfalls.

> FPGA's will always be faster and more computationally efficient
> than Python, but Python is fast enough. The motivation for this experiment
> was to use a high-level language (Python) and preexisting firmware and
> software (Digilent) so that the device could be set up and reconfigured
> easily, leaving more time to think about the important issues.

Sure. This is fine. But please do not bash other techniques, just because
you are not good at handling them. Especially if you hide the complexity
of your approach completely in a sidermark. (Yes, that ticked me off)

> Attila has about a dozen criticisms of the theory section, mostly that it
> is not rigorous enough and there are many assumptions. But it is not
> intended to be rigorous. 

If it is not intended as such, then you should make it clear in
the paper. Or put it in an appendix. Currently the theory is almost 4 of
the 8 pages of your paper. So it looks like an important part.
And you still should make sure it is correct. Which currently it isn't.

> This is primarily an experimental paper and the
> purpose of the theory is to give a simple physical picture of the
> surprizingly good results. It does that, and the experimental results
> support the conjecture above.

Then you should have gone with a simple SNR based formula like S
or referenced one of the many papers out there that do this kind of
calculations and just repeated the formula with a comment that the
derivation is in paper X.

> The limitations of the theory are discussed in detail on p. 6 where it is
> called "... a convenient approximation.." Despite this the theory agrees
> with the Monte Carlo over most of parameter space, and where it does not is
> discussed in the text.

Please! This is bad science! You build a theory on flawed foundations,
use this theory as a foundation in your simulations. And when the
simulations agree with your theory you claim the theory is correct?
Please, do not do this!

Yes, it is ok to approximate. Yes it is ok to make assumptions.
But please be aware what the limits of those approximations and
assumptions are. I have tried to point out the flaws in your
argumentation and how they affect the validity of your paper.
If you just want to do an experimental paper, then the right
thing to do would be to cut out all the theory and concentrate
on the experiments.


I hope it comes accross that I do not critisize your experiments
or the results you got out of them. I critisize the analysis you
have done and that it contains assumptions, which you are not aware
of, that invalidate some of your results. The experiments are fine.
The precision you get is fine. But your analysis is flawed.

Attila Kinali

-- 
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Re: [time-nuts] Next upgrade

[Attila Kinali]

On Thu, 23 Nov 2017 13:18:35 -0500
Bert Kehren via time-nuts <time-nuts@febo.com> wrote:

> There was recently discussion of the use of the LTC1655 which 
> is still my # 1  choice. What was not mentioned on the 1650 is that in needs 
> a external reference  discontinued and double ling the cost.

There is just a tad bit of catch here:
The LTC1655 has an order of magnitude higher noise, a factor 2-3 higher
tempco of an LTC1650+LTC6655, a factor 2 higher DNL and a factor 2 higher INL.
The LTC1650 is the better DAC. That's why it's more expensive.

Whether the increased performance is worth the money or not, depends
on the application.

While we are at it, I'd like to mention the LTC1821. It beats the LTC1650
in most parameters, including price. But it has an increadibly low
spec'ed noise (typ 20nV/sqrt(Hz) at full scale output)

> 18 bits would be nicer but we have not  found one affordable.

It seems that manufacturing gets too costly for anything beyond 16bit
(unless you cut off at 10Hz).

Though, if you have a decent 16bit DAC and want to get to 18bit,
that's fairly simple using delta-sigma modulation... if you can live
with a low pass fillter after the DAC. But the DNL will be the limiting
factor here (unless you use some special techniques) and the (absolute) INL
will not get better, for obvious reasons.

        Attila Kinali


-- 
You know, the very powerful and the very stupid have one thing in common.
They don't alters their views to fit the facts, they alter the facts to
fit the views, which can be uncomfortable if you happen to be one of the
facts that needs altering.  -- The Doctor
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Re: [time-nuts] Allan variance by sine-wave fitting

[Attila Kinali]

On Wed, 22 Nov 2017 15:38:33 -0800
Ralph Devoe <rgde...@gmail.com> wrote:

> To focus on the forest instead of the trees:  The method uses a
> $300 student scope (Digilent Analog discovery- a very fine product), which
> any skilled amateur can modify in a weekend, and produce a device which is
> 10-100 times better than the expensive counters we are used to using.  The
> software contains only 125 lines of Python and  pretty much anyone can
> write their own. In practice this device is much easier to use than my
> 53132a.

That's true. Such a system is increadibly easy to use.
But you can as well go for something like the redpitaya.
Because its architecture is ment for continuous sampling
you can do all the fancy stuff that Sherman and Jördens
did. And thanks to GnuRadio support, you don't even have
to write python for it, but can just click it together using
the graphical interface. How is that for simplicity? :-)
An I know someone from NIST is actually working on making
a full featured phase noise/stability measurement setup
out of a redpitaya.

Oh.. and what I forgot to mention: I know how difficult it is to
do a proper uncertainty and nooise analysis of least-squares of sines.
I tried it last year and failed. There is lots of math involved that
I haven't mastered yet.


        Attila Kinali


-- 
You know, the very powerful and the very stupid have one thing in common.
They don't alters their views to fit the facts, they alter the facts to
fit the views, which can be uncomfortable if you happen to be one of the
facts that needs altering.  -- The Doctor
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Re: [time-nuts] Allan variance by sine-wave fitting

[Attila Kinali]

e whether they hold true.

In general, your method works and does lead to decent results.
But it is not any more computationally efficient than the DMDT or DD
methods. What you do is to hide a lot of the complexity in a scipy
function, which is neither efficient nor fast. Your noise/jitter analysis
lacks lots of mathematical rigor and has a lot of implicit assumptions that
are neither clearly stated nor generally true. Panek did a noise to jitter
analysis in [4] in a setting that is not unlike yours. Even though  his
analysis has problems as well (e.g. he does not account for the numer of
samples taken), he is much closer to the what is going on.
If you adapt his analysis to your case, you would get a much better result.


And a final nitpick: Please use s for seconds instead of sec.
Also, please note that the s is in lower case, i.e. it's ns and µs
not nS or µS. All SI units that are not derived from names are written
in lower case [5].


Attila Kinali


[1] "The CORDIC Trigonometric Computing Technique*", by Jack E. Volder, 1959

[2] "Oscillator metrology with software defined radio", by Sherman and Jördens,
2016

[3] https://en.wikipedia.org/wiki/Big_O_notation

[4] "Random Errors in Time Interval Measurement Based on SAW Filter
Excitation", by Petr Panek, 2008

[5] https://en.wikipedia.org/wiki/International_System_of_Units#General_rules

-- 
You know, the very powerful and the very stupid have one thing in common.
They don't alters their views to fit the facts, they alter the facts to
fit the views, which can be uncomfortable if you happen to be one of the
facts that needs altering.  -- The Doctor
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Re: [time-nuts] H-Maser drift (was: Why discipline Rubidium oscillator?)

[Attila Kinali]

On Tue, 21 Nov 2017 14:50:48 +0100
Attila Kinali <att...@kinali.ch> wrote:

> The source for the Hydrogen atoms is usually a heated platinum
> valve (a heated plate of platinum that is thin enough that the
> Hydrogen will leak through). 

Several people pointed out that the valve is made of paladium
and not of platinum. Sorry about that. And thanks to everyone
who corrected me.


        Attila Kinali

-- 
It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
 -- Miss Matheson, The Diamond Age, Neil Stephenson
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Re: [time-nuts] H-Maser drift (was: Why discipline Rubidium oscillator?)

[Attila Kinali]

On Tue, 21 Nov 2017 15:31:25 +0100
Ole Petter Ronningen <opronnin...@gmail.com> wrote:

> > Hehe.. Yes. It's "small" compared to the cavity. Depending on the
> > exact cavity construction, the storage space can be as small as
> > a tenth of the total cavity volume.
> 
> Thats interesting, I would think a small volume would result in increased
> spin exchange - do you have any papers detailing the tradeoffs with
> big/small storage bulbs?

I would have to go through my collection to find those that mention
anything on it.

The tradeoff is bascially, that you want to have an as large volume
as possible to minimize wall and atom-atom collisions. But there is
only a certain volume within the cavity, where the field has the
right orientation. The higher the mode of the cavity, the smaller
the volume (relative to the cavity size). Higher cavity modes are
used to shrink the overall cavity size, without the need of loading,
which introduces losses. 

Attila Kinali

-- 
It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
 -- Miss Matheson, The Diamond Age, Neil Stephenson
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Re: [time-nuts] H-Maser drift (was: Why discipline Rubidium oscillator?)

[Attila Kinali]

On Tue, 21 Nov 2017 15:14:59 +0100
Ole Petter Ronningen <opronnin...@gmail.com> wrote:

> > [...] The advantage of the platinum valve
> > system is that it "generates" single atom Hydrogen, as required
> > by the maser.
> 
> Picking nits here.. It was my understanding that the splitting of molecular
> hydrogen into atomic hydrogen happens using RF in the dissociator - not in
> the platinum leak valve. Is my understanding incorrect?

Good question. I don't know. I've only read a dozen or so papers on
maser construction. I have never owned or operated one. Much less
taken appart and studied its construction.

> > Within the cavity there is a small glass bulb that keeps the atoms
> > in the right position of the cavity field.
> 
> 4.5 liters in EFOS type masers - so not *that* small. I believe other
> masers are the same order of magnitude.

Hehe.. Yes. It's "small" compared to the cavity. Depending on the
exact cavity construction, the storage space can be as small as
a tenth of the total cavity volume.


Attila Kinali

-- 
It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
 -- Miss Matheson, The Diamond Age, Neil Stephenson
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[time-nuts] H-Maser drift (was: Why discipline Rubidium oscillator?)

[Attila Kinali]

On Tue, 21 Nov 2017 04:24:51 -0600
Dana Whitlow <k8yumdoo...@gmail.com> wrote:

> This is an active maser, meaning a self-sustaining oscillator whose gain
> medium
> was a volume of hydrogen atoms (at low pressure) maintained in a population-
> inverted state by squirting a thin stream of state-selected H atoms into a
> glass bulb,

They are not maintained in this state. Rather the Hydrogen atoms are
"used up" by emiting a photon at 1.4GHz. They are then "removed"
by leaking out of the opening of the bulb and pumped away.
The source for the Hydrogen atoms is usually a heated platinum
valve (a heated plate of platinum that is thin enough that the
Hydrogen will leak through). The advantage of the platinum valve
system is that it "generates" single atom Hydrogen, as required
by the maser. These atoms go through a specially formed magnet
that deflects the atoms that are in the wrong state (c.f. Stern-Gerlach
experiment). Those in the right state make it into the cavity.
Within the cavity there is a small glass bulb that keeps the atoms
in the right position of the cavity field. In order not to perturbe
the atoms too much, the bulb walls are coated with Teflon.

> The inside of the bulb was treated so that the collisions with the surface did
> not usually cause a quantum state change of the H atom involved.  I've read 
> that
> the average excited atom typically "survived" a large number of such wall
> collisions before being "consumed" by contributing a quantum of energy to
> the oscillating mode; this has always amazed me.

Yes, IIRC normal numbers are several 10s to 100s of wall collisions
before the atom loses its state due to wall colisions and without
contributing to the signal.

> So the primary frequency-determining mechanism is the collision-broadened
> line width of the gain mechanism. However, the cavity resonance exhibits a
> noticeable frequency-pulling effect, and our maser has a feedback loop that
> strives to keep the cavity tuned to the center of the medium's gain
> profile.
> But I think this loop is not a tight loop, ergo not completely successful.

The loop is quite tight. But there are multiple effects that prevent
perfect operation. Major problems are the low signal levels and the
shifts due wall colisions and cavity pulling.

> I've long wondered what causes the slow frequency drift, typically amounting
> to about 3E-14 over a time span of several months.

Mostly changes in the wall coating leading to a different wall collision
shift and mechanical changes of the cavity dimension (think air pressure
and creep) leading to a different cavity pulling. To a lesser extend
it's the changes in the quality of the vacuum and number of Hydrogen atoms
in the cavity.


Attila Kinali

-- 
It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
 -- Miss Matheson, The Diamond Age, Neil Stephenson
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[time-nuts] GNSS signals (was: Why discipline Rubidium oscillator?)

[Attila Kinali]

On Mon, 20 Nov 2017 20:50:17 -0800
Jerry Hancock <je...@hanler.com> wrote:

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

for your rainy Sunday reading:

http://www.navipedia.net/index.php/GPS_Signal_Plan
http://www.navipedia.net/index.php/Galileo_Signal_Plan
http://www.navipedia.net/index.php/GLONASS_Signal_Plan
http://www.navipedia.net/index.php/BeiDou_Signal_Plan

And because everyone likes large, colorful graphs:
http://www.insidegnss.com/auto/popupimage/GLONASS%20spectrum%200408.jpg

Yes, it's getting crowded.

        Attila Kinali

-- 
It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
 -- Miss Matheson, The Diamond Age, Neil Stephenson
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[time-nuts] Disciplining a Cs beam standard (was: Why discipline Rubidium oscillator?)

[Attila Kinali]

On Mon, 20 Nov 2017 20:18:18 -0500
Bob kb8tq <kb...@n1k.org> wrote:

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

It is actually quite easy. You measure the satellite carrier and code
phases relative to the output signal of the Cs, collect all the data,
wait a couple of weeks until the IGS final product becomes available,
then you calculate the frequency and phase difference and steer the
Cs accordingly using a control loop with a tau in the order of 3 weeks
at minimum (due to the delay in IGS data), rather 10 to 50 weeks.

Simple, right? :-)

    Attila Kinali
-- 
It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
 -- Miss Matheson, The Diamond Age, Neil Stephenson
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Re: [time-nuts] Input filter for data logger

[Attila Kinali]

On Sun, 19 Nov 2017 22:56:41 +
Angus <not.ag...@btinternet.com> wrote:

> >> The MV89 is a beast of an OCXO and uses more power at warm-up than any 
> >> other
> >> I know of. But it is spec'ed ~1W for steady state. Which means the
> >> outside of the OCXO should be about hand-warm. If it's too hot, then
> >> the heater circuit is probably broken and running at full-throttle.
> >
> >If so, I think something is not OK with my MV89. It is probably 110 
> >degrees or so.
> 
> They do run hot, so if that's 110 DegF and not DegC it's OK (depending
> on ambient...) The data sheet says 4.2W at 25 DegC.

Oops.. I miscalculated the power consumption of the MV89..
Sorry about.

Today doesn't seem to be a good day for me to answer questions it seems.

Attila Kinali

-- 
You know, the very powerful and the very stupid have one thing in common.
They don't alters their views to fit the facts, they alter the facts to
fit the views, which can be uncomfortable if you happen to be one of the
facts that needs altering.  -- The Doctor
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Re: [time-nuts] Input filter for data logger

[Attila Kinali]

On Mon, 20 Nov 2017 11:47:09 +1300 (NZDT)
Bruce Griffiths <bruce.griffi...@xtra.co.nz> wrote:

> That's a fairly standard JFET BJT negative feedback amp that's not usually 
> unstable.

Uh.. uhmm.. sorry about that... I'm electronically challenged, it seems.

    Attila Kinali

-- 
You know, the very powerful and the very stupid have one thing in common.
They don't alters their views to fit the facts, they alter the facts to
fit the views, which can be uncomfortable if you happen to be one of the
facts that needs altering.  -- The Doctor
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Re: [time-nuts] Input filter for data logger

[Attila Kinali]

On Sun, 19 Nov 2017 16:10:54 -0500
Vlad <t...@patoka.org> wrote:

> Here is my schematic:
> 
> http://www.patoka.ca/OCXO/LOGGER/IMG_20171119_155907272.jpg

Ok.. I am surprised, this doesn't oscillate.

You have a two stage amplifier, where the second stage
has a negative feedback path into the first stage.

When a pulse comes in, the jfet will turn on and conduct
current through its drain and source resistors. When the
current reaches something around 6-8mA the pnp will start
conducting. But the collector current of the pnp goes into
the source resistor of the jfet. This will increase the
voltage on the source, thus decreasing the gate-source
voltage, thus turn the jfet off, which in turn will turn
the pnp off, which in then will stop conducting, thus
no current into the source resistor, thus the jfet will
start conducting again... I guess you get it.
 
> I did some simple tests for this. In it seems it was OK up to 10Mhz.
> 
> > But guessing from what you showed, I would say that your amplifier
> > circuit isn't stable and has some gain peaking at around 10MHz.
> > There are two ways to proceed: Either optimize your circuit or
> > simplify it using modern components to the input signal you expect.
> 
> The main purpose for this circuit is to protect the MCU input and make 
> some sine to square conversion.

Use a biased 74AC04. That's the easiest. And you will have very
little noise degradation.

I would think that the MCU can probably take more abuse than the
74AC. Modern ASICs have quite a bit of protection circuits on
their inputs. I am not sure whether the 74-families have seen
upgrades on their protection circuits in the last 30-40 years.

Attila Kinali


-- 
You know, the very powerful and the very stupid have one thing in common.
They don't alters their views to fit the facts, they alter the facts to
fit the views, which can be uncomfortable if you happen to be one of the
facts that needs altering.  -- The Doctor
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Re: [time-nuts] Input filter for data logger

[Attila Kinali]

On Sun, 19 Nov 2017 11:40:27 -0500
Vlad  wrote:

> I am doing another fun project. It is data logger at this time. The 
> "heart" is MV89A OCXO and the "brain" is STM32.
> "The box" has 1PPS input to control DAC which will control OCXO. BTW, 
> this M89A is pretty hot to touch. My other OCXO's not that much warmed. 
> Is it normal for this Morion model ?

The MV89 is a beast of an OCXO and uses more power at warm-up than any other
I know of. But it is spec'ed ~1W for steady state. Which means the
outside of the OCXO should be about hand-warm. If it's too hot, then
the heater circuit is probably broken and running at full-throttle.

> I woul ask an advise regarding following issue. I have signal generator 
> which produce the square wave. The freq. is 192Hz.
> 
> http://www.patoka.org/OCXO/LOGGER/IMG_20171119_104659813.jpg
> 
> However, the logger measure it TWICE ! I think its because of that 
> signal form. Here is the output (in microseconds):
> 
> http://www.patoka.org/OCXO/LOGGER/IMG_20171119_104838190.jpg
> 
> In average delta is .0026041 s, which is almost equal to 384 Hz (192x2)
> 
> For the input I am using the schema similar as HP was using in one of 
> their counters:
> 
> http://www.patoka.org/OCXO/LOGGER/IMG_20171110_123201987.jpg

Can you show us what _your_ circuit looks like instead of some bad
(literal) screenshot?

But guessing from what you showed, I would say that your amplifier
circuit isn't stable and has some gain peaking at around 10MHz.
There are two ways to proceed: Either optimize your circuit or
simplify it using modern components to the input signal you expect.

I personally, would go for simplification, unless you want something
special.

If you only want to time-stamp input pulses and you can ensure
that those pulses are between 0 and 5V, then I'd use a 74LVC1G34
or 74LVC1G04, depending on whether you want inversion or not
(do not use the 74LVC1G14 as the hysteresis will increase the noise level)

If you want to measure sine input as well, then you have to AC
couple and add some bias voltage when using an LVC gate.

-- 
It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
 -- Miss Matheson, The Diamond Age, Neil Stephenson
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[time-nuts] Recommendation for cheap GBIP adapter for Linux

[Attila Kinali]

Hi,

I have a need for a GBIP adapter that I can use with Linux.
It shouldn't be too expensive, but I rather spend a few bucks
more for ease of use. Where "ease of use" means I don't have
problems with weird drivers on Linux (Windows doesn't matter at all).
I do not mind writing my own read-out software (that's quickly and
easily done). What would people here recommend?


        Attila Kinali
-- 
It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
 -- Miss Matheson, The Diamond Age, Neil Stephenson
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