Re: [time-nuts] Physics !

[cook michael]

Le 11/03/2011 01:24, J. Forster a écrit :

One Watt per square meter:



===

The ‘scandal’ of the kilogram



First, it’s vital for us as consumers to be confident about what we buy –
we don’t want to be ripped off at the checkout with an underweight bag
of carrots or, more seriously, be given the wrong dose during
radiotherapy for cancer treatment.

Hmm. At the moment I do know that the mass of my carrots can be compared 
in a very legal way to a lump of platinum held at the BIPM. I suspect 
that I will be long dead before lawyers are comparing carrots with planks?



-John

===



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Re: [time-nuts] time interval with 10 ps resolution using cheap FPGA ?

[Tristan Steele]

I can't really add much to the questions - but I am very interested in the
answer!

Tristan

On 11 March 2011 16:33, beale  wrote:

> I was interested to see this 2009 Fermilab paper which claims a 10 ps (RMS)
> timing resolution in a TDC (time to digital converter) implented in the
> Altera Cyclone II FPGA, which of course has a much slower clock than that.
>  They call their technique a "wave union TDC", involving multiple readouts
> of an internal ring oscillator triggered by the input signal, permitting
> calibration of the relatively coarse and uneven delay elements in the FPGA.
> http://lss.fnal.gov/archive/2009/conf/fermilab-conf-09-275-e.pdf
>
> I have not worked with them yet, but there are some pretty cheap FPGA
> development boards now-, for example, at the $50 price point for a fully
> assembled "Papilio One" board (hosting a Xilinx Spartan 3e) from Gadget
> Factory.  Has anyone tried to make such an extended-resolution TDC using
> this type of FPGA platform? Any opinions on whether it can be done?
>
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[time-nuts] time interval with 10 ps resolution using cheap FPGA ?

[beale]

I was interested to see this 2009 Fermilab paper which claims a 10 ps (RMS) 
timing resolution in a TDC (time to digital converter) implented in the Altera 
Cyclone II FPGA, which of course has a much slower clock than that.  They call 
their technique a "wave union TDC", involving multiple readouts of an internal 
ring oscillator triggered by the input signal, permitting calibration of the 
relatively coarse and uneven delay elements in the FPGA. 
http://lss.fnal.gov/archive/2009/conf/fermilab-conf-09-275-e.pdf

I have not worked with them yet, but there are some pretty cheap FPGA 
development boards now-, for example, at the $50 price point for a fully 
assembled "Papilio One" board (hosting a Xilinx Spartan 3e) from Gadget 
Factory.  Has anyone tried to make such an extended-resolution TDC using this 
type of FPGA platform? Any opinions on whether it can be done?

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[time-nuts] Physics !

[J. Forster]

One Watt per square meter:



===

The ‘scandal’ of the kilogram


http://physicsworld.com/blog/2011/01/by_matin_durrani_with_tunisia.html

By Matin Durrani

With Tunisia in political turmoil, parts of Australia under water and
dozens dead in a Moscow bomb blast, a meeting on SI units in the confines
of the Royal Society in London might seem absolutely right at the bottom
of anyone’s news agenda. Surely the conservative world of metrology, where
physicists spend years sharpening up their measurements of the seven
fundamental base units, is unlikely to cause much of a stir?

But the two-day meeting, which ended yesterday, did attract a dozen or so
journalists, that led to reports in the Wall Street Journal, the Guardian,
New Scientist and the BBC.

They were no doubt attracted in part by the presence of the world’s top
metrologists, but also by the meeting’s focus: to discuss whether to
revamp the SI system of units so that it is based purely on the
fundamental constants of physics.

The importance of the meeting was underlined by the fact that the
organizers had managed to snare the UK’s minister for universities and
science David Willetts, who in his opening remarks gave a good impression
of at least seeming to understand what metrology is all about; he isn’t
nicknamed “two brains” for nothing.

As Willetts pointed out (thanks no doubt to his speechwriters),
metrology and the measurement system are important on three counts.

First, it’s vital for us as consumers to be confident about what we buy –
we don’t want to be ripped off at the checkout with an underweight bag
of carrots or, more seriously, be given the wrong dose during
radiotherapy for cancer treatment.

Second, metrology is key for advanced technology – accurate timekeeping
via atomic clocks has proved essential for GPS, for example. Third, and
this is what the meeting was about, the work is essential if we are to
define our measurement system entirely in terms of fundamental
constants.

That’s the name of the game in metrology these days – finding a way
of defining mass without just resorting embarrassingly, as we do now, to
a lump of metal in the basement of the International Bureau of Weights
and Measures (BIPM) outside Paris and saying “that’s a kilogram”. After
all, periodic inspections of the lump have shown it’s been changing its
mass slowly over time. As laser physicist Bill Phillips
from the National Institute of Standards and Technology (NIST) told
delegates during one question-and-answer session on Monday, “It’s a
scandal that we’ve got this kilogram hanging around that’s changing its
mass”.

In among the audience at the meeting was Physics World columnist Robert
Crease from Stony Brook University in New York, who in December wrote
about visiting the BIPM last autumn for what could be one of the last ever
annual inspections of the kilogram.

Crease was on hand to get the latest goings-on among the world’s
metrology community for a feature on the redefinition of the kilogram in
the March issue of Physics World magazine – so keep an eye out for that.

But redefining the kilogram is not that easy. One option is to take a
 large, nearly perfect silicon sphere, count how many atoms are in it
(which determines Avogadro’s constant) and then multiply that number by
the mass of each atom. If you’re interested, a new paper in Physical
 Review Letters provides the most accurate value for the Avogadro constant
to within 30 parts in a billion – the result of a collaboration between
eight different national metrology institutes around the world.

The other is to use a “Watt balance”, which does not require big
 collaborations, but is conceptually harder to understand. It involves
 balancing the force through a coil with the mass of an object, and then
 doing another bit of jiggery pokery involving the quantum-Hall effect
 (to measure resistance) and the Josephson junction (to measure voltage).


 The plan is for the world’s metrology community – represented by the CIPM
 –  to put forward a proposal at its meeting next October that the SI
 system should be revamped. That proposal will go to the organization to
 which the CIPM reports – the General
 Conference on Weights and Measures (CGPM) – which is basically a bunch
 of diplomats in a smoke-filled room (without the smoke). If they give it
  the nod, well then it’s time to rewrite the physics textbooks.

 In the current system, the kilogram, ampere, kelvin and the mole are
 all linked to exact numerical values of the mass of the international
 prototype kilogram in Paris, the permeability of the vacuum, the
 triple-point temperature of water, and to the molar-mass of carbon-12
 respectively. The plan is to change all that so that these four units
 are linked to exact numerical values of the Planck constant, the charge
 of the electron, the Boltzmann constant and to the Avogadro constant
 respectively.

 It’s likely that the CIPM proposal will
 seek t

Re: [time-nuts] 50/60 Hz clocks

[Mike S]

At 04:54 PM 3/10/2011, Cezary Rozluski wrote...
Let us suppose I have Thunderbolt (I really have one)  as a 
time/frequency source, but any other time-nuts recognized frequency 
source should by sufficient for the fun to drive old 50/60Hz stuff 
with the highest precision available (and for fun, comparable to 
www.leapsecond.com  solution, modulo cesium/hydrogen clock).  It would 
be very nice to see correction for leap seconds as well :-) :-)


Perhaps a cheap DC/AC inverter (like they make to run AC electronics in 
cars or recreational vehicles). I suspect most are crystal controlled 
for the frequency. Divide down your 10 MHz to match the crystal, and 
inject your more precise frequency. 50 Hz is likely to be easier than 
60 Hz, because it is an integer division from 10 MHz.


Then again, even if they're crystal controlled, they may cheat and just 
be "close enough." i.e. 32768 Hz crystal, /656 for ~49.95 Hz, /546 for 
~60.01 Hz. 



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Re: [time-nuts] 50/60 Hz clocks

[Robert LaJeunesse]

Poor man's solution: Use an Arduino to read the Thunderbolt 1PPS and lock a 
50Hz 
(or 60Hz) square wave to the 1PPS. Any resulting jitter can likely be kept in 
the tens of microsecond range, easily filtered out by the clock mechanics. 
Filter the square wave a bit and feed it into an audio amplifier (or two) of 
sufficient power to run the clock. (Possibly a 12V powered bridge amplifier at 
~14W would be adequate?)  Use some sort of audio output or filament transformer 
backwards to create the proper line voltage to run the clock. Maybe run the 
whole thing off a 12V battery with float charger for uninterruptible timing.

good luck

Bob L.



From: Cezary Rozluski 
To: time-nuts@febo.com
Sent: Thu, March 10, 2011 4:54:37 PM
Subject: [time-nuts] 50/60 Hz clocks

...
Let us suppose I have Thunderbolt (I really have one)  as a time/frequency 
source, but any other time-nuts recognized frequency source should by 
sufficient 
for the fun to drive old 50/60Hz stuff with the highest precision available 
(and 
for fun, comparable to www.leapsecond.com  solution, modulo cesium/hydrogen 
clock).  It would be very nice to see correction for leap seconds as well :-) 
:-)

Regards,

Cezary
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Re: [time-nuts] 50/60 Hz clocks

[paul swed]

Be it 50 or 60 Hertz clocks if you do not want to alter it you need to use a
DC to AC converter. Generally these things are inexpensive and used for cars
or computer UPS systems. Though some of these actually have a square wave
out. Not great for the little motors.
Internally you would need to get into the thing that controls the 60 Hz
frequency and add your control in from the Tbolt by any number of
approaches. The other thing you need is a way to slew the clock forward or
back to synchronize it.
This is all fairly inexpensive I see APC UPS's at fleamarkets for very
little cost. Especially if the batteries are dead.
That would be my non HP approach to the problem.
Regards
Paul
WB8TSL

On Thu, Mar 10, 2011 at 5:21 PM, ehydra  wrote:

> The exclusive solution feasible is:
> http://shop-emea.u-blox.com/abashop?s=274&p=productdetail&sku=553
> Nice, as you can program it for PPS at 10KHz or some other frequency.
>
> More cheap, not so spectacular:
> Cirrus CS2000 PLL
> Locks on 50Hz or more
>
>
> - Henry
>
> --
> ehydra.dyndns.info
>
>
> Cezary Rozluski schrieb:
>
>  Let us suppose I have Thunderbolt (I really have one)  as a time/frequency
>> source, but any other time-nuts recognized frequency source should by
>> sufficient for the fun to drive old 50/60Hz stuff with the highest precision
>> available (and for fun, comparable to www.leapsecond.com  solution,
>> modulo cesium/hydrogen clock).  It would be very nice to see correction for
>> leap seconds as well :-) :-)
>>
>> Regards,
>>
>> Cezary
>>
>
>
>
> ___
> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
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>
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Re: [time-nuts] 50/60 Hz clocks

[ehydra]

The exclusive solution feasible is:
http://shop-emea.u-blox.com/abashop?s=274&p=productdetail&sku=553
Nice, as you can program it for PPS at 10KHz or some other frequency.

More cheap, not so spectacular:
Cirrus CS2000 PLL
Locks on 50Hz or more


- Henry

--
ehydra.dyndns.info


Cezary Rozluski schrieb:
Let us suppose I have Thunderbolt (I really have one)  as a 
time/frequency source, but any other time-nuts recognized frequency 
source should by sufficient for the fun to drive old 50/60Hz stuff with 
the highest precision available (and for fun, comparable to 
www.leapsecond.com  solution, modulo cesium/hydrogen clock).  It would 
be very nice to see correction for leap seconds as well :-) :-)


Regards,

Cezary




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[time-nuts] 50/60 Hz clocks

[Cezary Rozluski]

It perhaps the old story it is difficult for 
non-continental Americans have opportunities to 
buy valuable time-nuts equipment such as e.g. 
‘Hewlett Packard Vintage Digital Clock Model 115BR-HO8’ seen on ebay recently…


To temporary cheer up (?) myself I found (and 
bought) available on local (European) market nice 
COPAL flip-clock with witch is identical to that 
one shown on an ended ebay auction 
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=230590647002+ 
I refer to only for purpose of image of the 
clock, so please forgive me link to auction on ebay.com


As the clock mentioned above has very nice 
seconds dial I revisited outstanding pages: 
http://www.leapsecond.com/pages/atomic-nixie/


Well – it is nice solution presented, but I would 
like ask you what would be from time-nuts 
perspective simple (the simplest ?)  solution to 
drive such 50/60 Hz clocks without to much 
overweighed stuff (and of course without 
modifying the clock itself addig e.g step motor etc, etc).


As an overweight I would consider driving from 
industry function/arbitrary generators and nice 
but pretty rare and expensive on European market  HP 6827A.


Let us suppose I have Thunderbolt (I really have 
one)  as a time/frequency source, but any other 
time-nuts recognized frequency source should by 
sufficient for the fun to drive old 50/60Hz stuff 
with the highest precision available (and for 
fun, comparable to www.leapsecond.com  solution, 
modulo cesium/hydrogen clock).  It would be very 
nice to see correction for leap seconds as well :-) :-)


Regards,

Cezary


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Re: [time-nuts] Timecode clock for acution in UK

[Peter Vince]

Thanks for pointing this out David.  I already have a couple, and they
are very nice - even keeping good time (domestically speaking - a
couple of seconds per month!) without the EBU/SMPTE time code
reference.  (Locking to mains frequency (50 or 60Hz) is possible from
a DIL switch on the back panel.

 Peter


On 9 March 2011 10:43, David C. Partridge  wrote:
> 
>
> David Partridge

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Re: [time-nuts] MAR-5?

[Chris Albertson]

On Thu, Mar 10, 2011 at 10:01 AM, Jean-Louis Oneto
 wrote:
> Hello,
> In fact there was once (in the '80s I think) a MAR-5, but last time I had to
> replace one, I was unable to find the datasheet either, and I replaced it by

Data sheet for MAR-5 is available here
http://www.datasheetarchive.com/pdf-datasheets/Datasheets-115/DSAP002285.html


-- 
=
Chris Albertson
Redondo Beach, California

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Re: [time-nuts] Plot phase noise spectrum from DMTD measurement?

[ehydra]

S/N drops spectacular!

Any probs to cut the noise-floor here? The text looks like art.


- Henry


--
ehydra.dyndns.info



Bruce Griffiths schrieb:

Stephan Sandenbergh wrote:

Thanks,

I'm familiar with the designs you posted to measure voltage noise ect. on
you home page. These, with some modification, mainly removing the 
blocking

caps, seems that it would do the trick.

Cheers,

Stephan.

On 10 March 2011 10:50, Bruce Griffiths  
wrote:


  
For conventional phase noise measurements at offsets in the (10Hz, 
20kHz)

range one can use a sound card with a low noise preaamp.
Suitable sound card preamps with lower noise floors than Enrico's or
Wenzel's designs can be built using readily available components.
Wider bandwidths ( up to 1MHz or so) are not difficult to achieve.

Bruce


Stephan Sandenbergh wrote:



Hi,

Cross-correlation a very clever idea! Thanks for the reference - 
Rubiola

got
some good sources of reference on his home page.

One thing though - for a phase-noise kit one will probably need to 
replace
the ZCD with a low-noise amplification stage of around 80dB to be to 
allow

sampling at ADC voltage levels?

Cheers,

Stephan.

On 8 March 2011 22:28, Magnus Danielson
  wrote:



  

On 03/08/2011 07:46 PM, Stephan Sandenbergh wrote:





Hi,

I recently noticed something interesting: The DMTD measurement 
gives a

set
of phase values x(t). From which fractional frequency y(t) is
calculable.
So
now it seems viable to plot the spectrum, Sy(f) and if you scale it
properly
you arrive at Sphi(f). If I'm  not making a gross error somewhere the
math
seems to check out. But, I'm wondering is there a physical reason why
this
isn't valid?

I have not seen this being done anywhere - so I assume there is.
However,
it
seems possible to plot Sphi(f) for 1Hz

Re: [time-nuts] Plot phase noise spectrum from DMTD measurement?

[Bruce Griffiths]

Without nulling the carrier the dynamic range of your ADC will limit the 
measurement system phase noise fllor.


With a 300KHz beat frequency the post mixer preamp response need not 
extend to dc.


Bruce

Stephan Sandenbergh wrote:

Thanks,

I'm familiar with the designs you posted to measure voltage noise ect. on
you home page. These, with some modification, mainly removing the blocking
caps, seems that it would do the trick.

Cheers,

Stephan.

On 10 March 2011 10:50, Bruce Griffiths  wrote:

   

For conventional phase noise measurements at offsets in the (10Hz, 20kHz)
range one can use a sound card with a low noise preaamp.
Suitable sound card preamps with lower noise floors than Enrico's or
Wenzel's designs can be built using readily available components.
Wider bandwidths ( up to 1MHz or so) are not difficult to achieve.

Bruce


Stephan Sandenbergh wrote:

 

Hi,

Cross-correlation a very clever idea! Thanks for the reference - Rubiola
got
some good sources of reference on his home page.

One thing though - for a phase-noise kit one will probably need to replace
the ZCD with a low-noise amplification stage of around 80dB to be to allow
sampling at ADC voltage levels?

Cheers,

Stephan.

On 8 March 2011 22:28, Magnus Danielson
  wrote:



   

On 03/08/2011 07:46 PM, Stephan Sandenbergh wrote:



 

Hi,

I recently noticed something interesting: The DMTD measurement gives a
set
of phase values x(t). From which fractional frequency y(t) is
calculable.
So
now it seems viable to plot the spectrum, Sy(f) and if you scale it
properly
you arrive at Sphi(f). If I'm  not making a gross error somewhere the
math
seems to check out. But, I'm wondering is there a physical reason why
this
isn't valid?

I have not seen this being done anywhere - so I assume there is.
However,
it
seems possible to plot Sphi(f) for 1Hz

Re: [time-nuts] Plot phase noise spectrum from DMTD measurement?

[Bruce Griffiths]

Stephan Sandenbergh wrote:

Thanks,

I'm familiar with the designs you posted to measure voltage noise ect. on
you home page. These, with some modification, mainly removing the blocking
caps, seems that it would do the trick.

Cheers,

Stephan.

On 10 March 2011 10:50, Bruce Griffiths  wrote:

   

For conventional phase noise measurements at offsets in the (10Hz, 20kHz)
range one can use a sound card with a low noise preaamp.
Suitable sound card preamps with lower noise floors than Enrico's or
Wenzel's designs can be built using readily available components.
Wider bandwidths ( up to 1MHz or so) are not difficult to achieve.

Bruce


Stephan Sandenbergh wrote:

 

Hi,

Cross-correlation a very clever idea! Thanks for the reference - Rubiola
got
some good sources of reference on his home page.

One thing though - for a phase-noise kit one will probably need to replace
the ZCD with a low-noise amplification stage of around 80dB to be to allow
sampling at ADC voltage levels?

Cheers,

Stephan.

On 8 March 2011 22:28, Magnus Danielson
  wrote:



   

On 03/08/2011 07:46 PM, Stephan Sandenbergh wrote:



 

Hi,

I recently noticed something interesting: The DMTD measurement gives a
set
of phase values x(t). From which fractional frequency y(t) is
calculable.
So
now it seems viable to plot the spectrum, Sy(f) and if you scale it
properly
you arrive at Sphi(f). If I'm  not making a gross error somewhere the
math
seems to check out. But, I'm wondering is there a physical reason why
this
isn't valid?

I have not seen this being done anywhere - so I assume there is.
However,
it
seems possible to plot Sphi(f) for 1Hz

Re: [time-nuts] Plot phase noise spectrum from DMTD measurement?

[Bruce Griffiths]

Stephan Sandenbergh wrote:

Hi,

Thanks this is good advice.

Pointing the spectrum analyzer to fc + delta seems to be similar
than deducing phase noise from the ZCD output since this would be with
reference to (fc + delta) in any how? Provided the aliasing issue can be
sorted.

Regarding the aliasing issue - in order to plot phase noise up to 100kHz I
would use a 300kHz beat sampled at 100MHz (which is the sampling system I
got available). Obviously, making sure I have sufficient bandwidth in all
areas.
   
The definition requires that both the noise at fc + delta and the noise 
at fc-delta be added to obtain the phase noise at an offset of delta.

This is easy to do either in an FPGA or in post processing.

If you are sampling at 100MHz then the post mixer filter only need limit 
the bandwidth sufficiently to eliminate the mixer sum product and keep 
the noise signal within the bandwidth of the following amplifier. 
Additional filtering if required can be implemented as digital filters.


Note with a 300kHz beat frequency phase noise components at offsets 
greater than fcarrier + 300KHz will be folded into the mixer output 
spectrum so using a carrier  bandpass filter with a bandwidth smaller 
than the beat frequency may be advisable.

Cheers.

Stephan.
   

Bruce


On 10 March 2011 10:50, Bruce Griffiths  wrote:

   

For conventional phase noise measurements at offsets in the (10Hz, 20kHz)
range one can use a sound card with a low noise preaamp.
Suitable sound card preamps with lower noise floors than Enrico's or
Wenzel's designs can be built using readily available components.
Wider bandwidths ( up to 1MHz or so) are not difficult to achieve.

Bruce


Stephan Sandenbergh wrote:

 

Hi,

Cross-correlation a very clever idea! Thanks for the reference - Rubiola
got
some good sources of reference on his home page.

One thing though - for a phase-noise kit one will probably need to replace
the ZCD with a low-noise amplification stage of around 80dB to be to allow
sampling at ADC voltage levels?

Cheers,

Stephan.

On 8 March 2011 22:28, Magnus Danielson
  wrote:



   

On 03/08/2011 07:46 PM, Stephan Sandenbergh wrote:



 

Hi,

I recently noticed something interesting: The DMTD measurement gives a
set
of phase values x(t). From which fractional frequency y(t) is
calculable.
So
now it seems viable to plot the spectrum, Sy(f) and if you scale it
properly
you arrive at Sphi(f). If I'm  not making a gross error somewhere the
math
seems to check out. But, I'm wondering is there a physical reason why
this
isn't valid?

I have not seen this being done anywhere - so I assume there is.
However,
it
seems possible to plot Sphi(f) for 1Hz

Re: [time-nuts] MAR-5?

[Jean-Louis Oneto]

Hello,
In fact there was once (in the '80s I think) a MAR-5, but last time I had to 
replace one, I was unable to find the datasheet either, and I replaced it by 
an ERA-5SM+ which was fine.

Best regardzs,
Jean-Louis Oneto

- Original Message - 
From: "John Green" 

To: 
Sent: Thursday, March 10, 2011 5:49 PM
Subject: Re: [time-nuts] MAR-5?



Doh! Never mind. It was the ERA-5SM I was thinking of. Boy, my age is
beginning to show. Apologies.
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Re: [time-nuts] MAR-5?

[John Green]

Doh! Never mind. It was the ERA-5SM I was thinking of. Boy, my age is
beginning to show. Apologies.
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[time-nuts] OT question Mini Circuits MAR-5?

[John Green]

Please excuse the off topic nature of this question, but I knew you guys
would know. Is there, or was there a MAR-5 mmic? I thought I had some but
when I look for specs, everything I am finding seems to skip over the MAR-5.
If not, I'll have to dig into my mmic repository to see just what I do have.
If I remember, it has pretty good S11, S22 plus a decent noise figure and a
+17 DBM 1 Db compression point. I was looking for something to drive the
L.O. port of a 17 level mixer at about a +13DBM level.
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Re: [time-nuts] Spacecraft Timekeeping

[Javier Herrero]

El 10/03/2011 15:35, jimlux escribió:


Heck, every time I buy parts at home, it seems the packing slip always 
has some sort of generic "these parts may be subject to export 
controls" notice on it.  Yep.. those 10Meg resistors just might be a 
vital piece of an armament...


This remembers me when I bought a connnector and was informed that it 
was ITAR classiffied - first that I thought was that it was not soo 
heavy nor contundent to make too much harm if I throw it to the enemy's 
head... at the end, it was an error - it was not ITAR :)


Regards,

Javier

--

Javier HerreroEMAIL: jherr...@hvsistemas.com
Chief Technology Officer
HV Sistemas S.L.  PHONE: +34 949 336 806
Los Charcones, 17 FAX:   +34 949 336 792
19170 El Casar - Guadalajara - Spain  WEB: http://www.hvsistemas.com


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Re: [time-nuts] Spacecraft Timekeeping

[jimlux]

It is more a matter about that the involved technology could be ITAR
classified or with other export restrictions. Ask Hughes and Boeing
about the fine for export control violations in Intelsat 708 :)
http://en.wikipedia.org/wiki/Intelsat_708


I think most people who work with rockets with guidance systems (aka 
defense articles) are pretty well versed in export controls.  As are 
people who sell equipment that winds up on such rockets.


Doesn't mean there are spectacular lapses, but it's pretty tough these 
days to claim "I didn't know".


And there's always some hair splitting at the edges: pulsed vs CW TWTAs, 
for instance, or atomic clocks vs "Space Qualified" atomic clocks, or 
"radiation hard" (There's a remarkable number of ICs which are described 
as radiation tolerant to 100-300kRad, made on processes that should be 
hard to MegaRads.)


Heck, every time I buy parts at home, it seems the packing slip always 
has some sort of generic "these parts may be subject to export controls" 
notice on it.  Yep.. those 10Meg resistors just might be a vital piece 
of an armament...


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Re: [time-nuts] Plot phase noise spectrum from DMTD measurement?

[Stephan Sandenbergh]

Thanks,

I'm familiar with the designs you posted to measure voltage noise ect. on
you home page. These, with some modification, mainly removing the blocking
caps, seems that it would do the trick.

Cheers,

Stephan.

On 10 March 2011 10:50, Bruce Griffiths  wrote:

> For conventional phase noise measurements at offsets in the (10Hz, 20kHz)
> range one can use a sound card with a low noise preaamp.
> Suitable sound card preamps with lower noise floors than Enrico's or
> Wenzel's designs can be built using readily available components.
> Wider bandwidths ( up to 1MHz or so) are not difficult to achieve.
>
> Bruce
>
>
> Stephan Sandenbergh wrote:
>
>> Hi,
>>
>> Cross-correlation a very clever idea! Thanks for the reference - Rubiola
>> got
>> some good sources of reference on his home page.
>>
>> One thing though - for a phase-noise kit one will probably need to replace
>> the ZCD with a low-noise amplification stage of around 80dB to be to allow
>> sampling at ADC voltage levels?
>>
>> Cheers,
>>
>> Stephan.
>>
>> On 8 March 2011 22:28, Magnus Danielson
>>  wrote:
>>
>>
>>
>>> On 03/08/2011 07:46 PM, Stephan Sandenbergh wrote:
>>>
>>>
>>>
 Hi,

 I recently noticed something interesting: The DMTD measurement gives a
 set
 of phase values x(t). From which fractional frequency y(t) is
 calculable.
 So
 now it seems viable to plot the spectrum, Sy(f) and if you scale it
 properly
 you arrive at Sphi(f). If I'm  not making a gross error somewhere the
 math
 seems to check out. But, I'm wondering is there a physical reason why
 this
 isn't valid?

 I have not seen this being done anywhere - so I assume there is.
 However,
 it
 seems possible to plot Sphi(f) for 1Hz<   f<100kHz when having a vbeat =
 100kHz sampled for 1 second.

 I'm familiar with the loose and tight phase-locked methods of measuring
 phase noise, but am quite curious to know if phase noise from a DMTD
 measurement is a valid assumption.

 I would guess that if the frequency domain phase noise measurement
 requires
 phase-lock then the time-domain measurement requires as well. However,
 here
 in lies my real interest - two GPSDOs are phase-locked (not to 1Hz,
 something far less I know) so can it be possible to measure GPSDO Adev
 and
 phase-noise using a single DMTD run? Am I making a wrong assumption
 somewhere?



>>> An architecture not completely different to the DMTD architecture is used
>>> in phase-noise kits. Instead of having two sources and one intermediary
>>> oscillator is instead there one source and two intermediary oscillators.
>>> The
>>> oscillators is locked to the carrier frequency rather than an offset. The
>>> mixed down signal is then cross-correlated to get the spectrum.
>>> Increasing
>>> the averaging factor and the spectrum can be suppressed below that of the
>>> intermediary oscillators. Since the two intermediary oscillators have
>>> uncorrelated noise, the external noise is what correlates over time. This
>>> technique is simply called cross-correlation. Such a cross-correlation
>>> setup
>>> can run very close to the carrier in terms of offsets.
>>>
>>> In contrast will a DMTD with it's offset frequency be problematic at low
>>> offsets since the positive and negative offsets noise will not occur at
>>> the
>>> same frequency in a DMTD setup. Consider a a DMTD with a 10 Hz offset,
>>> pointing a spectrum analyzer on 100 Hz will measure the down-converted
>>> average of carrier+(100-10) Hz and carrier-(100+10) Hz, thus carrier+90
>>> Hz
>>> and carrier-110 Hz.
>>>
>>> Creating a mixed-mode setup for phase-noise/DMTD will however be
>>> possible.
>>>
>>> So, DMTD as such is relatively limited, but add an RF switch and another
>>> oscillator and you get a cross-correlation phase-noise kit.
>>>
>>> To turbo-charge the phase-noise kit use a quadrature combiner and
>>> amplitude
>>> adjustment to create a interferometric mixdown, working around part of
>>> the
>>> mixer limitations. Enrico Rubiola has writen about this approach.
>>>
>>> Cheers,
>>> Magnus
>>>
>>>
>>> ___
>>> time-nuts mailing list -- time-nuts@febo.com
>>> To unsubscribe, go to
>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>> and follow the instructions there.
>>>
>>>
>>>
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>
>
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Re: [time-nuts] Plot phase noise spectrum from DMTD measurement?

[Stephan Sandenbergh]

Hi,

Thanks this is good advice.

Pointing the spectrum analyzer to fc + delta seems to be similar
than deducing phase noise from the ZCD output since this would be with
reference to (fc + delta) in any how? Provided the aliasing issue can be
sorted.

Regarding the aliasing issue - in order to plot phase noise up to 100kHz I
would use a 300kHz beat sampled at 100MHz (which is the sampling system I
got available). Obviously, making sure I have sufficient bandwidth in all
areas.

Cheers.

Stephan.

On 10 March 2011 10:50, Bruce Griffiths  wrote:

> For conventional phase noise measurements at offsets in the (10Hz, 20kHz)
> range one can use a sound card with a low noise preaamp.
> Suitable sound card preamps with lower noise floors than Enrico's or
> Wenzel's designs can be built using readily available components.
> Wider bandwidths ( up to 1MHz or so) are not difficult to achieve.
>
> Bruce
>
>
> Stephan Sandenbergh wrote:
>
>> Hi,
>>
>> Cross-correlation a very clever idea! Thanks for the reference - Rubiola
>> got
>> some good sources of reference on his home page.
>>
>> One thing though - for a phase-noise kit one will probably need to replace
>> the ZCD with a low-noise amplification stage of around 80dB to be to allow
>> sampling at ADC voltage levels?
>>
>> Cheers,
>>
>> Stephan.
>>
>> On 8 March 2011 22:28, Magnus Danielson
>>  wrote:
>>
>>
>>
>>> On 03/08/2011 07:46 PM, Stephan Sandenbergh wrote:
>>>
>>>
>>>
 Hi,

 I recently noticed something interesting: The DMTD measurement gives a
 set
 of phase values x(t). From which fractional frequency y(t) is
 calculable.
 So
 now it seems viable to plot the spectrum, Sy(f) and if you scale it
 properly
 you arrive at Sphi(f). If I'm  not making a gross error somewhere the
 math
 seems to check out. But, I'm wondering is there a physical reason why
 this
 isn't valid?

 I have not seen this being done anywhere - so I assume there is.
 However,
 it
 seems possible to plot Sphi(f) for 1Hz<   f<100kHz when having a vbeat =
 100kHz sampled for 1 second.

 I'm familiar with the loose and tight phase-locked methods of measuring
 phase noise, but am quite curious to know if phase noise from a DMTD
 measurement is a valid assumption.

 I would guess that if the frequency domain phase noise measurement
 requires
 phase-lock then the time-domain measurement requires as well. However,
 here
 in lies my real interest - two GPSDOs are phase-locked (not to 1Hz,
 something far less I know) so can it be possible to measure GPSDO Adev
 and
 phase-noise using a single DMTD run? Am I making a wrong assumption
 somewhere?



>>> An architecture not completely different to the DMTD architecture is used
>>> in phase-noise kits. Instead of having two sources and one intermediary
>>> oscillator is instead there one source and two intermediary oscillators.
>>> The
>>> oscillators is locked to the carrier frequency rather than an offset. The
>>> mixed down signal is then cross-correlated to get the spectrum.
>>> Increasing
>>> the averaging factor and the spectrum can be suppressed below that of the
>>> intermediary oscillators. Since the two intermediary oscillators have
>>> uncorrelated noise, the external noise is what correlates over time. This
>>> technique is simply called cross-correlation. Such a cross-correlation
>>> setup
>>> can run very close to the carrier in terms of offsets.
>>>
>>> In contrast will a DMTD with it's offset frequency be problematic at low
>>> offsets since the positive and negative offsets noise will not occur at
>>> the
>>> same frequency in a DMTD setup. Consider a a DMTD with a 10 Hz offset,
>>> pointing a spectrum analyzer on 100 Hz will measure the down-converted
>>> average of carrier+(100-10) Hz and carrier-(100+10) Hz, thus carrier+90
>>> Hz
>>> and carrier-110 Hz.
>>>
>>> Creating a mixed-mode setup for phase-noise/DMTD will however be
>>> possible.
>>>
>>> So, DMTD as such is relatively limited, but add an RF switch and another
>>> oscillator and you get a cross-correlation phase-noise kit.
>>>
>>> To turbo-charge the phase-noise kit use a quadrature combiner and
>>> amplitude
>>> adjustment to create a interferometric mixdown, working around part of
>>> the
>>> mixer limitations. Enrico Rubiola has writen about this approach.
>>>
>>> Cheers,
>>> Magnus
>>>
>>>
>>> ___
>>> time-nuts mailing list -- time-nuts@febo.com
>>> To unsubscribe, go to
>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>> and follow the instructions there.
>>>
>>>
>>>
>> ___
>> time-nuts mailing list -- time-nuts@febo.com
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>> and follow the instructions there.
>>
>>
>>
>
>
>
> ___
> time-nuts mailing l

Re: [time-nuts] Plot phase noise spectrum from DMTD measurement?

[Bruce Griffiths]

For conventional phase noise measurements at offsets in the (10Hz, 
20kHz) range one can use a sound card with a low noise preaamp.
Suitable sound card preamps with lower noise floors than Enrico's or 
Wenzel's designs can be built using readily available components.

Wider bandwidths ( up to 1MHz or so) are not difficult to achieve.

Bruce

Stephan Sandenbergh wrote:

Hi,

Cross-correlation a very clever idea! Thanks for the reference - Rubiola got
some good sources of reference on his home page.

One thing though - for a phase-noise kit one will probably need to replace
the ZCD with a low-noise amplification stage of around 80dB to be to allow
sampling at ADC voltage levels?

Cheers,

Stephan.

On 8 March 2011 22:28, Magnus Danielson  wrote:

   

On 03/08/2011 07:46 PM, Stephan Sandenbergh wrote:

 

Hi,

I recently noticed something interesting: The DMTD measurement gives a set
of phase values x(t). From which fractional frequency y(t) is calculable.
So
now it seems viable to plot the spectrum, Sy(f) and if you scale it
properly
you arrive at Sphi(f). If I'm  not making a gross error somewhere the math
seems to check out. But, I'm wondering is there a physical reason why this
isn't valid?

I have not seen this being done anywhere - so I assume there is. However,
it
seems possible to plot Sphi(f) for 1Hz<   f<100kHz when having a vbeat =
100kHz sampled for 1 second.

I'm familiar with the loose and tight phase-locked methods of measuring
phase noise, but am quite curious to know if phase noise from a DMTD
measurement is a valid assumption.

I would guess that if the frequency domain phase noise measurement
requires
phase-lock then the time-domain measurement requires as well. However,
here
in lies my real interest - two GPSDOs are phase-locked (not to 1Hz,
something far less I know) so can it be possible to measure GPSDO Adev and
phase-noise using a single DMTD run? Am I making a wrong assumption
somewhere?

   

An architecture not completely different to the DMTD architecture is used
in phase-noise kits. Instead of having two sources and one intermediary
oscillator is instead there one source and two intermediary oscillators. The
oscillators is locked to the carrier frequency rather than an offset. The
mixed down signal is then cross-correlated to get the spectrum. Increasing
the averaging factor and the spectrum can be suppressed below that of the
intermediary oscillators. Since the two intermediary oscillators have
uncorrelated noise, the external noise is what correlates over time. This
technique is simply called cross-correlation. Such a cross-correlation setup
can run very close to the carrier in terms of offsets.

In contrast will a DMTD with it's offset frequency be problematic at low
offsets since the positive and negative offsets noise will not occur at the
same frequency in a DMTD setup. Consider a a DMTD with a 10 Hz offset,
pointing a spectrum analyzer on 100 Hz will measure the down-converted
average of carrier+(100-10) Hz and carrier-(100+10) Hz, thus carrier+90 Hz
and carrier-110 Hz.

Creating a mixed-mode setup for phase-noise/DMTD will however be possible.

So, DMTD as such is relatively limited, but add an RF switch and another
oscillator and you get a cross-correlation phase-noise kit.

To turbo-charge the phase-noise kit use a quadrature combiner and amplitude
adjustment to create a interferometric mixdown, working around part of the
mixer limitations. Enrico Rubiola has writen about this approach.

Cheers,
Magnus


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Re: [time-nuts] Plot phase noise spectrum from DMTD measurement?

[Bruce Griffiths]

If you can solve the aliasing problem then its easy to average the noise 
at frequencies fbeat-foffset and fbeat+foffset to synthesize the 
measured phase noise values with a beat frequency of 0 Hz as would be 
measured by a conventional phase measurement setup.


Bruce

Stephan Sandenbergh wrote:

Hi,

This makes sense.

Thanks,

Stephan.

On 8 March 2011 21:08, Bruce Griffiths  wrote:

   

Stephan Sandenbergh wrote:

 

Hi,

I recently noticed something interesting: The DMTD measurement gives a set
of phase values x(t). From which fractional frequency y(t) is calculable.
So
now it seems viable to plot the spectrum, Sy(f) and if you scale it
properly
you arrive at Sphi(f). If I'm  not making a gross error somewhere the math
seems to check out. But, I'm wondering is there a physical reason why this
isn't valid?

I have not seen this being done anywhere - so I assume there is. However,
it
seems possible to plot Sphi(f) for 1Hz<   f<100kHz when having a vbeat =
100kHz sampled for 1 second.

I'm familiar with the loose and tight phase-locked methods of measuring
phase noise, but am quite curious to know if phase noise from a DMTD
measurement is a valid assumption.

I would guess that if the frequency domain phase noise measurement
requires
phase-lock then the time-domain measurement requires as well. However,
here
in lies my real interest - two GPSDOs are phase-locked (not to 1Hz,
something far less I know) so can it be possible to measure GPSDO Adev and
phase-noise using a single DMTD run? Am I making a wrong assumption
somewhere?

Cheers,

Stephan.


   

Aside from the aliasing problem inherent when using a DMTD (The sampling
rate is equal to the beat frequency but the the bandwidth is necessarily
greater than the nyquist limit to permit the DMTD ZCD to work unless of
course one uses a front end bandpass filter - however the associated phase
shift tempco usually precludes this ) the output phase difference measures
also include contributions from the reference source and the offset source.
The contribution from the offset source depends on the phase difference
between the 2 sources being compared. Using a low noise reference and phase
locking the offset to the reference source will help somewhat as will
minimising the phase difference between the reference and the source under
test.

Bruce


 




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Re: [time-nuts] Plot phase noise spectrum from DMTD measurement?

[Stephan Sandenbergh]

Hi,

Cross-correlation a very clever idea! Thanks for the reference - Rubiola got
some good sources of reference on his home page.

One thing though - for a phase-noise kit one will probably need to replace
the ZCD with a low-noise amplification stage of around 80dB to be to allow
sampling at ADC voltage levels?

Cheers,

Stephan.

On 8 March 2011 22:28, Magnus Danielson  wrote:

> On 03/08/2011 07:46 PM, Stephan Sandenbergh wrote:
>
>> Hi,
>>
>> I recently noticed something interesting: The DMTD measurement gives a set
>> of phase values x(t). From which fractional frequency y(t) is calculable.
>> So
>> now it seems viable to plot the spectrum, Sy(f) and if you scale it
>> properly
>> you arrive at Sphi(f). If I'm  not making a gross error somewhere the math
>> seems to check out. But, I'm wondering is there a physical reason why this
>> isn't valid?
>>
>> I have not seen this being done anywhere - so I assume there is. However,
>> it
>> seems possible to plot Sphi(f) for 1Hz<  f<100kHz when having a vbeat =
>> 100kHz sampled for 1 second.
>>
>> I'm familiar with the loose and tight phase-locked methods of measuring
>> phase noise, but am quite curious to know if phase noise from a DMTD
>> measurement is a valid assumption.
>>
>> I would guess that if the frequency domain phase noise measurement
>> requires
>> phase-lock then the time-domain measurement requires as well. However,
>> here
>> in lies my real interest - two GPSDOs are phase-locked (not to 1Hz,
>> something far less I know) so can it be possible to measure GPSDO Adev and
>> phase-noise using a single DMTD run? Am I making a wrong assumption
>> somewhere?
>>
>
> An architecture not completely different to the DMTD architecture is used
> in phase-noise kits. Instead of having two sources and one intermediary
> oscillator is instead there one source and two intermediary oscillators. The
> oscillators is locked to the carrier frequency rather than an offset. The
> mixed down signal is then cross-correlated to get the spectrum. Increasing
> the averaging factor and the spectrum can be suppressed below that of the
> intermediary oscillators. Since the two intermediary oscillators have
> uncorrelated noise, the external noise is what correlates over time. This
> technique is simply called cross-correlation. Such a cross-correlation setup
> can run very close to the carrier in terms of offsets.
>
> In contrast will a DMTD with it's offset frequency be problematic at low
> offsets since the positive and negative offsets noise will not occur at the
> same frequency in a DMTD setup. Consider a a DMTD with a 10 Hz offset,
> pointing a spectrum analyzer on 100 Hz will measure the down-converted
> average of carrier+(100-10) Hz and carrier-(100+10) Hz, thus carrier+90 Hz
> and carrier-110 Hz.
>
> Creating a mixed-mode setup for phase-noise/DMTD will however be possible.
>
> So, DMTD as such is relatively limited, but add an RF switch and another
> oscillator and you get a cross-correlation phase-noise kit.
>
> To turbo-charge the phase-noise kit use a quadrature combiner and amplitude
> adjustment to create a interferometric mixdown, working around part of the
> mixer limitations. Enrico Rubiola has writen about this approach.
>
> Cheers,
> Magnus
>
>
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Re: [time-nuts] Plot phase noise spectrum from DMTD measurement?

[Stephan Sandenbergh]

Hi,

This makes sense.

Thanks,

Stephan.

On 8 March 2011 21:08, Bruce Griffiths  wrote:

> Stephan Sandenbergh wrote:
>
>> Hi,
>>
>> I recently noticed something interesting: The DMTD measurement gives a set
>> of phase values x(t). From which fractional frequency y(t) is calculable.
>> So
>> now it seems viable to plot the spectrum, Sy(f) and if you scale it
>> properly
>> you arrive at Sphi(f). If I'm  not making a gross error somewhere the math
>> seems to check out. But, I'm wondering is there a physical reason why this
>> isn't valid?
>>
>> I have not seen this being done anywhere - so I assume there is. However,
>> it
>> seems possible to plot Sphi(f) for 1Hz<  f<100kHz when having a vbeat =
>> 100kHz sampled for 1 second.
>>
>> I'm familiar with the loose and tight phase-locked methods of measuring
>> phase noise, but am quite curious to know if phase noise from a DMTD
>> measurement is a valid assumption.
>>
>> I would guess that if the frequency domain phase noise measurement
>> requires
>> phase-lock then the time-domain measurement requires as well. However,
>> here
>> in lies my real interest - two GPSDOs are phase-locked (not to 1Hz,
>> something far less I know) so can it be possible to measure GPSDO Adev and
>> phase-noise using a single DMTD run? Am I making a wrong assumption
>> somewhere?
>>
>> Cheers,
>>
>> Stephan.
>>
>>
> Aside from the aliasing problem inherent when using a DMTD (The sampling
> rate is equal to the beat frequency but the the bandwidth is necessarily
> greater than the nyquist limit to permit the DMTD ZCD to work unless of
> course one uses a front end bandpass filter - however the associated phase
> shift tempco usually precludes this ) the output phase difference measures
> also include contributions from the reference source and the offset source.
> The contribution from the offset source depends on the phase difference
> between the 2 sources being compared. Using a low noise reference and phase
> locking the offset to the reference source will help somewhat as will
> minimising the phase difference between the reference and the source under
> test.
>
> Bruce
>
>
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