Re: [time-nuts] OXCO Spurious Output at Line Frequencies

[Stéphane Rey]

Hi Martyn,

For such measurement you may shield your DUT and instruments. Ever using 
a shielded room which might not be easy for everyone or using shielded 
tents. You can find them made custom for 600-1000€ depending on the 
size. I've just ordered two of them from a company in netherlands


For main line frequencies, you may differentiate what is conducted from 
what is radiated. For EMI, I'm using now active low pass filter at very 
low frequency to follow my low noise regulators and I get very good 
result, but honestly not tested as low as -130dBc... But on low noise 
PLL or oscillators I can get rid of any spurious from PSU but at 50Hz, 
my noise floor has never reached -130dBc...  I'm working on a very low 
noise generator (20fs jitter 10Hz-1Mhz) at the moment and at 50 Hz, the 
phase noise is  -80dBc/Hz which is already not bat at 6 GHz


I've measured last week a Wentzel VCXO giving -150dBc/Hz @ 50 Hz and I 
could measure the 50 Hz at -130dBc/Hz but this had not the active filter 
on it. I test it again using the shielded tent exactly to know what is 
radiated from conducted. If still there under the tent I will try using 
my active filter to see if this makes a difference.



Cheers
Stephane

-- Message d'origine --
De : "Martyn Smith" 
À : time-nuts@febo.com
Envoyé 12/07/2016 12:44:31
Objet : [time-nuts] OXCO Spurious Output at Line Frequencies


Hello,

I have a customer who is measuring the phase noise of my 10 MHz 
ultra-low phase noise frequency standard.


He is seeing spurious signals at line frequencies (50 and 100 Hz as we 
are in Europe) at a level around -130 dBc.


My opinion is that it's impossible to get much better than that.  Even 
running on batteries make little difference, since the equipment is in 
a test rack with AC signals everywhere.


Even the £50k R test set he is using only quotes a spurious spec of 
-90 dBc.


What experience does anyone have here?

Best Regards

Martyn


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[time-nuts] DMTD downmixer question

[Stéphane Rey]

Hi there,

I will receive my SR620 soon and want of course to use it as well for 
stability measurement using the DMTD method.


I've read many things on how to design the downmixer. There will be a 
DDS or low noise generator as LO, the two mixers, and the squarer. There 
are apparently many ways to do the squarer. Some of the ways I've seen 
are using fast comparator, logic gate, fast amplifiers...
Finally is there a way which looks better than the others ? I was 
hesitating between a fast comparator and an ECL logic gate for instance.


Thanks & cheers
Stephane

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Re: [time-nuts] buying a time interval counter

[Stéphane Rey]

Ji Jerry,
The Fluke exhibit a 100ps resolution whereas the SR620 has 25ps.
This is the main difference I see from datasheets.

cheers
Stephane

-- Message d'origine --
De : "Jerry" <jster...@att.net>
À : "'Stéphane Rey'" <steph@wanadoo.fr>; "'Discussion of precise 
time and frequency measurement'" <time-nuts@febo.com>; "'Brooke Clarke'" 
<bro...@pacific.net>

Envoyé 30/06/2016 17:01:50
Objet : RE: [time-nuts] buying a time interval counter

How does the Fluke PM6690 (same as Pendulum CNT-90) compare to the 
SR620?  A neighbor is selling one in perfect condition (per him) for 
$900


Jerry
NY2KW

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of 
Stéphane Rey

Sent: Thursday, June 30, 2016 10:07 AM
To: Brooke Clarke; Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] buying a time interval counter

Hi,
I've ordered a SR620 with the option 01 (higher stability standard) 
Should be there  in August Thanks Stephane


-- Message d'origine --
De : "Brooke Clarke" <bro...@pacific.net> À : "Stéphane Rey" 
<steph@wanadoo.fr>; "Discussion of precise time and frequency 
measurement" <time-nuts@febo.com> Envoyé 29/06/2016 19:20:22 Objet : 
Re: [time-nuts] buying a time interval counter



Hi Stephane:

I traded my HP 53132A counter for an SR 620.  The 53132 has what I'd
call a user hostile interface, so if you are manually controlling the
counter the SR 620 has a huge advantage.
I also like the long display on the 620 which can be read from across
the room.

PS Stanford Research is a company founded by physicists and makes some
really high quality stuff.  In fact some of the products
HP/Agilent/Keysight sells are repackaged SR instruments.
http://www.prc68.com/I/TandFTE.shtml#SR620

The claim to fame for the HP 53132A is that it can make a frequency
(not time interval) measurement to 1E12 in a second.  Here's how to 
get

that same result with the SR620:
http://www.prc68.com/I/FTS4060.shtml#SR620Fast

On the down side the printing functions on the 620 require an Epsom
printer.  Does anyone have a solution for that?

PS SR also makes a 10 MHz crystal oscillator that has options trading
stability for aging as well as the EFC tuning polarity and range so as
to match other OCXOs.
http://prc68.com/I/TandFTE.shtml#SC10

At one point they were looking into making a GPS time receiver where
the cable length calibration would be built-in.

-- Have Fun,

Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernment.com/2012Issues.html
The lesser of evils is still evil.

 Original Message 

Hello there,

I'm planning to buy a such instrument in order to do some frequency
stability measurement at work. The SR620 seems to be discontinued.
What model still distributed would you think is good for that at the
moment ?

Thanks & cheers
Stephane
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Re: [time-nuts] buying a time interval counter

[Stéphane Rey]

Hi,
I've ordered a SR620 with the option 01 (higher stability standard)
Should be there  in August
Thanks
Stephane

-- Message d'origine --
De : "Brooke Clarke" <bro...@pacific.net>
À : "Stéphane Rey" <steph@wanadoo.fr>; "Discussion of precise time 
and frequency measurement" <time-nuts@febo.com>

Envoyé 29/06/2016 19:20:22
Objet : Re: [time-nuts] buying a time interval counter


Hi Stephane:

I traded my HP 53132A counter for an SR 620.  The 53132 has what I'd 
call a user hostile interface, so if you are manually controlling the 
counter the SR 620 has a huge advantage.
I also like the long display on the 620 which can be read from across 
the room.


PS Stanford Research is a company founded by physicists and makes some 
really high quality stuff.  In fact some of the products 
HP/Agilent/Keysight sells are repackaged SR instruments.

http://www.prc68.com/I/TandFTE.shtml#SR620

The claim to fame for the HP 53132A is that it can make a frequency 
(not time interval) measurement to 1E12 in a second.  Here's how to get 
that same result with the SR620:

http://www.prc68.com/I/FTS4060.shtml#SR620Fast

On the down side the printing functions on the 620 require an Epsom 
printer.  Does anyone have a solution for that?


PS SR also makes a 10 MHz crystal oscillator that has options trading 
stability for aging as well as the EFC tuning polarity and range so as 
to match other OCXOs.

http://prc68.com/I/TandFTE.shtml#SC10

At one point they were looking into making a GPS time receiver where 
the cable length calibration would be built-in.


-- Have Fun,

Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernment.com/2012Issues.html
The lesser of evils is still evil.

 Original Message 

Hello there,

I'm planning to buy a such instrument in order to do some frequency 
stability measurement at work. The SR620 seems to be discontinued. 
What model still distributed would you think is good for that at the 
moment ?


Thanks & cheers
Stephane
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Re: [time-nuts] buying a time interval counter

[Stéphane Rey]

I will try to buy one of these SR620. I've some Standford & Research 
products like the 535 or the 30 MHz DDS generator. I do admit I'm not 
fan of the front panel interface as well but this is ok and usable. The 
SR620 would probably be PC controlled anyway to automate some 
measurements.
The 10 MHz reference will come from a GPSDO which is broadcasted over 
optical fibers. However the optical SFPs have been tested to have 500fs 
RMS jitter which mich be pretty high for that.
I've a Thunderbolt GPSDO sleeping in a box that will do the job 
otherwise. I plan to buy a Rb oscillator for reference for DTMD method 
and design a small circuit for the downmixing.

To be continued.
Thanks for the comments
Stephane


-- Message d'origine --
De : "Brooke Clarke" <bro...@pacific.net>
À : "Stéphane Rey" <steph@wanadoo.fr>; "Discussion of precise time 
and frequency measurement" <time-nuts@febo.com>

Envoyé 29/06/2016 19:20:22
Objet : Re: [time-nuts] buying a time interval counter


Hi Stephane:

I traded my HP 53132A counter for an SR 620.  The 53132 has what I'd 
call a user hostile interface, so if you are manually controlling the 
counter the SR 620 has a huge advantage.
I also like the long display on the 620 which can be read from across 
the room.


PS Stanford Research is a company founded by physicists and makes some 
really high quality stuff.  In fact some of the products 
HP/Agilent/Keysight sells are repackaged SR instruments.

http://www.prc68.com/I/TandFTE.shtml#SR620

The claim to fame for the HP 53132A is that it can make a frequency 
(not time interval) measurement to 1E12 in a second.  Here's how to get 
that same result with the SR620:

http://www.prc68.com/I/FTS4060.shtml#SR620Fast

On the down side the printing functions on the 620 require an Epsom 
printer.  Does anyone have a solution for that?


PS SR also makes a 10 MHz crystal oscillator that has options trading 
stability for aging as well as the EFC tuning polarity and range so as 
to match other OCXOs.

http://prc68.com/I/TandFTE.shtml#SC10

At one point they were looking into making a GPS time receiver where 
the cable length calibration would be built-in.


-- Have Fun,

Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernment.com/2012Issues.html
The lesser of evils is still evil.

 Original Message 

Hello there,

I'm planning to buy a such instrument in order to do some frequency 
stability measurement at work. The SR620 seems to be discontinued. 
What model still distributed would you think is good for that at the 
moment ?


Thanks & cheers
Stephane
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Re: [time-nuts] buying a time interval counter

[Stéphane Rey]

Hi Dave,

Yep it looks like it's still available. I've seen discontinued on a 
distributor website which made me thinking the product wasn't available 
anymore.

I'll look what is the price for the HP53230A for comparison.

Cheers
Stephane



-- Message d'origine --
De : "Dr. David Kirkby (Kirkby Microwave Ltd)" 
<drkir...@kirkbymicrowave.co.uk>
À : "Discussion of precise time and frequency measurement" 
<time-nuts@febo.com>; "Stéphane Rey" <steph@wanadoo.fr>

Envoyé 29/06/2016 18:22:50
Objet : Re: [time-nuts] buying a time interval counter



On 29 Jun 2016 17:02, "Stéphane Rey" <steph@wanadoo.fr> wrote:
>
> Hello there,
>
> I'm planning to buy a such instrument in order to do some frequency 
stability measurement at work. The SR620 seems to be discontinued.


It still looks available to me
http://www.thinksrs.com/products/SR620.htm

There is also a Keysight 53230A with a slightly better (20 ps vs 25 ps) 
single shot resolution.  It looks more modern,  but I don't know how 
well they compare.


Dave.


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[time-nuts] buying a time interval counter

[Stéphane Rey]

Hello there,

I'm planning to buy a such instrument in order to do some frequency 
stability measurement at work. The SR620 seems to be discontinued. What 
model still distributed would you think is  good for that at the moment 
?


Thanks & cheers
Stephane
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[time-nuts] Mike Monet, please contact me

[Stéphane Rey]

Sorry for flooding the list but can't find a working email to contact 
you Mike.


Thanks and cheers
Stephane
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Re: [time-nuts] software for HP58503 ?

[Stéphane Rey]

Well, it works better with correct RS232 wiring   :-/
Now I can connect with SatStat ang get my status. I've seen there is 
GPScon which sounds nice. Any other software suggested ?

Cheers
Stephane

-- Message d'origine --
De : "Stéphane Rey" <steph@wanadoo.fr>
À : "Discussion of precise time and frequency measurement" 
<time-nuts@febo.com>

Envoyé 19/03/2016 23:09:00
Objet : [time-nuts] software for HP58503 ?


Hi,
I'd like to connect my HP58503 to a pc running windosw 7 Enterprise.
I do not have com port, I'm using an USB FTDI converter.
Which software could I use ?
I've tried the Symetricon SatSat but can't connect to my GPSDO
any suggestion ?
Cheers
Stephane

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[time-nuts] software for HP58503 ?

[Stéphane Rey]

Hi,
I'd like to connect my HP58503 to a pc running windosw 7 Enterprise.
I do not have com port, I'm using an USB FTDI converter.
Which software could I use ?
I've tried the Symetricon SatSat but can't connect to my GPSDO
any suggestion ?
Cheers
Stephane

---
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Re: [time-nuts] PLL book 3rd edition

[Stéphane Rey]

Here at CERN in particle accelerators we're not looking at the same 
properties for PLLs than one would require for radiocom.
Two features usually requested are very low short term phase jitters 
(100fs-1ps) which directly leads into particule beam stability, as well 
as being able to synchronously reset the dividers for phase sync. which 
is usually not possible with integrated PLL ICs like NXP/AD/Hittite 
ones.
This is also an unsual application which is not representative of mass 
usage of PLLs. RF Phase stability and synchronization is a key for 
accelerators performance and thus the approach is different than for 
PLLs I'm designing for radiocom...


Stephane, F1TJJ

-- Message d'origine --
De : "jimlux" <jim...@earthlink.net>
À : time-nuts@febo.com
Envoyé 08/03/2016 14:30:51
Objet : Re: [time-nuts] PLL book 3rd edition


On 3/8/16 12:19 AM, Stéphane Rey wrote:

Hi Rick,

There are hopefully many applications where monolythics PLL can't
achieve the requested functionalitities or performances so that there 
is

still room to build block PLLs. I'm still desiging such things for my
job for instance.



As do we at JPL.  In fact, I'd say that given the advent of more 
"software driven" radios, with things like PLLs with DDS or NCO in the 
loop, having a text that covers performance on an analytical basis is 
useful.


However, it's a pretty darn small market. (Considering we do a "new 
design" every 5-10 years)


And, we use the data sheets and ap notes as a much as we'd use the 
textbook.


What is really hard to find is good data on the noise properties of the 
other components.  Everyone makes noise plots for the oscillators and 
amplifiers and publishes them.  For instance, what about the noise 
added by the Phase Frequency Detector - that's not a spec that shows up 
on the data sheet. (but does get discussed here on time-nuts)


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Re: [time-nuts] PLL book 3rd edition

[Stéphane Rey]

Hi Rick,

There are hopefully many applications where monolythics PLL can't 
achieve the requested functionalitities or performances so that there is 
still room to build block PLLs. I'm still desiging such things for my 
job for instance.


Regards
Stephane F1TJJ

-- Message d'origine --
De : "Richard (Rick) Karlquist" 
À : ka2...@aol.com; "Discussion of precise time and frequency 
measurement" 

Cc: enrico.rubi...@gmail.com
Envoyé 08/03/2016 04:33:24
Objet : Re: [time-nuts] PLL book 3rd edition


I know for me, I mainly use the "synthesizer on a chip" IC's
from Analog Devices/Hittite and National.  Their data sheets
and ap notes serve as the "textbook".  I'm not sure there
will be much call going forward for a book on fundamentals
that explains how to design synthesizers from first
principles using basic building blocks.  Having designed
PLL's for over 40 years, I know all about how to do this,
yet is now a nearly useless skill with the IC's now available.
Only the IC designers themselves need these skills.
Occasionally I find myself mentoring these guys in the
hope of getting better chips to buy :-)  (I have a
patent on a phase detector design that was made into
a chip, but the chip is built by Keysight's captive
foundry which doesn't sell much to the merchant market.)

No criticism of the book; it's just a market issue.

Rick N6RK

On 3/7/2016 4:52 PM, KA2WEU--- via time-nuts wrote:

To all :

I have published the following book

" Microwave and Wireless Synthesizers: Theory and Design, Ulrich L.  
Rohde,

John Wiley & Sons, August 1997, ISBN  0-471-52019-5."

and  have since kind of drifted into the VCO und high stability
oscillators.
The  first edition

"Digital PLL Frequency Synthesizers - Theory and Design, Ulrich L.  
Rohde,

Prentice-Hall, Inc., Englewood Cliffs, NJ, January 1983  "

has sold more then 10 000 copies. Is there any of you out  there who 
would
like to take over a needed update and take over the resulting  
revenues and

unfortunately also the work and glory and who feels qualified to so  ?

As I am more or less now in microwave technology and less in  PLL 
IC's, I
hate to see this standard textbook disappear Who can help or  want 
to

take over?

Ulrich






In a message dated 3/2/2016 12:04:00 P.M. Eastern Standard Time,
time-nuts@febo.com writes:




In a message dated 2/16/2016 9:03:59 A.M. Eastern  Standard Time,
time-nuts@febo.com  writes:.

http://www.synergymwave.com/articles/2016/calculation-of-fm-and-am.pdf
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Re: [time-nuts] Aeroflex IFR 3413

[Stéphane Rey]

Hi Clint,

I do not know this instrument, however let me share my current 
experience with my IFR2945.
I've found a faulty board to be part of the main PLL. The failled 
component was an old CPLD. I've requested a quotation from both the CPLD 
and the full board.
The CPLD was 90 euros with 9 months of leadtime (!) and the full board 
460€ with 1 month. I've bought the full board.

The company is actually Cobham Wireless who owns Marconi Aeroflex now.
After 3 months nothing yet received. I had to complain.
I finally got the board after 3.5 months. Put in the instrument and 
still not working. New release of the board with FPGA instead of CPLD. 
The FPGA outputs are not doing anything. Ask to the support again and it 
appears the board has not been programmed/tested... but they don't want 
to send me the code for programming (I've the tools at work). I have to 
send back my board
After 3 weeks they tell me I should have ordered the slash T version 
(which costs 30% more)  Well guys.. you made the quotation for that 
board... What could I do with a non programmed board 
Meanwhile my support guy tells me the facility he works in France... is 
going to be closed suddenly. By the way they're all fired.
Cobham Wireless is under restructuration and they're closing some sites. 
My board has been lost !
Finally apparently they've sent me a new board, I hope programmed this 
time and I'm waiting for it...


According to the very nice french support guy I was in contact with, in 
IFR2945/2965 there are very few components like that which are 
programmable for which this is no option other than Cobham support but 
at the moment it looks like an incredible mess there.


Good luck
Cheers
Stephane

-- Message d'origine --
De : "Clint Jay" 
À : time-nuts@febo.com
Envoyé 09/02/2016 20:58:08
Objet : [time-nuts] Aeroflex IFR 3413

I've acquired from eBay a 'faulty' Aeroflex IFR 3413 signal generator 
with
Option 001 (no attenuator) and an error 509 which I think would 
indicate

it's had power applied to the output port.

Does anyone have service information for these generators?

I'm also looking for firmware upgrades and any experience of adding
'options' I.E. is it possible to add the mechanical or electronic
attenuator options ?

--
Clint.

*No trees were harmed in the sending of this mail. However, a large 
number

of electrons were greatly inconvenienced.*
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[time-nuts] looking for rakable GPSDO

[Stéphane Rey]

Hello,

I'm looking for a 10 MHz output GPSDO with external antenna which would 
be rackable. Symmetricon doesn't seem to propose some neither Keysight.

Found some stuff  in Oscilloquartz. Any other brand to suggest ?

Thanks & cheers
Stephane

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Re: [time-nuts] question Alan deviation measured with Timelab and counters

[Stéphane Rey]

I do understand. 
Has anyone already compared the performances of squaring the 10 MHz vs squaring 
the IF ? 

Stephane

-Message d'origine-
De : time-nuts [mailto:time-nuts-boun...@febo.com] De la part de Bob Camp
Envoyé : dimanche 25 janvier 2015 19:01
À : Discussion of precise time and frequency measurement
Objet : Re: [time-nuts] question Alan deviation measured with Timelab and 
counters

Hi

The approach in the original NIST paper below was sort of a “best guess” about 
how to do the limiting and filtering. When the paper was presented, a number of 
us questioned how that part of the circuit was arrived at. The conversation 
more or less ended up with “that’s something we can investigate further”. The 
Collins paper (and Bruce’s work based on it) is a much better way to look at 
the 10 Hz squaring process. At 10 MHz, that stuff is not needed.

Bob

 On Jan 25, 2015, at 10:44 AM, Stéphane Rey steph@wanadoo.fr wrote:
 
 Hi everyone.
 
 Many thanks for your very useful comments.
 I had already seen most of the documents you were pointing but not on 
 the collins and Bruce discussion around the multistage filter. However 
 I've already seen this approach in the document from Allan
 (http://tf.nist.gov/timefreq/general/pdf/84.pdf)
 
 At first I had in mind to square the 10 MHz but this is the aim of the 
 evaluation board to evaluate various architectures. So I will 
 implement several squarers including the Collins Approach both at 10 
 MHz and 100 Hz and all the blocks will have input and output 
 connectors so that I will be able to test several layouts.
 
 I will show you the final design.
 
 Cheers
 Stephane
 
 
 -Message d'origine-
 De : time-nuts [mailto:time-nuts-boun...@febo.com] De la part de 
 Charles Steinmetz Envoyé : dimanche 25 janvier 2015 08:08 À : 
 Discussion of precise time and frequency measurement Objet : Re: 
 [time-nuts] question Alan deviation measured with Timelab and counters
 
 Stephane wrote:
 
 I'm now trying to evaluate various architectures of 2-channels 
 squarers and a DMDT. For that I'm designing a PCB with 4 squarers :
 simple 74ac04 gate biased at VCC/2, a LT1016 comparator, the 
 transistor based differential amplifier from Winzel and the one from Charles.
 
 Note that squaring a 10MHz sine wave and squaring a 10 or 100Hz mixer 
 output are two very different tasks.  If you start at baseband, a 
 Collins-style multi-stage limiting amp is a great benefit.  That is 
 generally not necessary if you start at 10MHz (or if you do use a 
 Collins-style limiter it needs far fewer stages).  All of the squarers 
 you mention work well at 10MHz, but not as well at baseband.
 
 The LT1719 is easier to apply and faster than the LT1016.  You may 
 want to use that instead of the 1016.  The LT1719 and LT1715 
 datasheets show the simplest possible implementation (see below).
 
 The MPSH81 devices in my version are available in surface-mount
 (MMBTH81) if that is more convenient.  Other fast transistors will 
 also work (BFT92, BFT93, BFG31).
 
 Best regards,
 
 Charles
 
 
 
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Re: [time-nuts] question Alan deviation measured with Timelab and counters

[Stéphane Rey]

Hi everyone.

Many thanks for your very useful comments.
I had already seen most of the documents you were pointing but not on the
collins and Bruce discussion around the multistage filter. However I've
already seen this approach in the document from Allan
(http://tf.nist.gov/timefreq/general/pdf/84.pdf)

At first I had in mind to square the 10 MHz but this is the aim of the
evaluation board to evaluate various architectures. So I will implement
several squarers including the Collins Approach both at 10 MHz and 100 Hz
and all the blocks will have input and output connectors so that I will be
able to test several layouts.

I will show you the final design.

Cheers
Stephane


-Message d'origine-
De : time-nuts [mailto:time-nuts-boun...@febo.com] De la part de Charles
Steinmetz
Envoyé : dimanche 25 janvier 2015 08:08
À : Discussion of precise time and frequency measurement
Objet : Re: [time-nuts] question Alan deviation measured with Timelab and
counters

Stephane wrote:

I'm now trying to evaluate various architectures of 2-channels squarers 
and a DMDT. For that I'm designing a PCB with 4 squarers :
simple 74ac04 gate biased at VCC/2, a LT1016 comparator, the transistor 
based differential amplifier from Winzel and the one from Charles.

Note that squaring a 10MHz sine wave and squaring a 10 or 100Hz mixer output
are two very different tasks.  If you start at baseband, a Collins-style
multi-stage limiting amp is a great benefit.  That is generally not
necessary if you start at 10MHz (or if you do use a Collins-style limiter it
needs far fewer stages).  All of the squarers you mention work well at
10MHz, but not as well at baseband.

The LT1719 is easier to apply and faster than the LT1016.  You may want to
use that instead of the 1016.  The LT1719 and LT1715 datasheets show the
simplest possible implementation (see below).

The MPSH81 devices in my version are available in surface-mount
(MMBTH81) if that is more convenient.  Other fast transistors will also work
(BFT92, BFT93, BFG31).

Best regards,

Charles



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Re: [time-nuts] question Alan deviation measured with Timelab and counters

[Stéphane Rey]

Hi guys.

After several experiments I could discover that the bad ADEV from the two 
GPSDO DUT are due to GPS lock losses. This is probably because the antenna is 
outside the windows but half the sky is hidden. We can see the on the frequency 
plot the sharp change of 0.5Hz and the locking. Good point.

I'm now trying to evaluate various architectures of 2-channels squarers and a 
DMDT. For that I'm designing a PCB with 4 squarers : simple 74ac04 gate biased 
at VCC/2, a LT1016 comparator, the transistor based differential amplifier from 
Winzel and the one from Charles. I will add two balanced mixers (minicircuits), 
IF filters and amplifiers. 
Does anyone has an idea of what I could add for this evaluation ? 

Cheers
Stephane


-Message d'origine-
De : time-nuts [mailto:time-nuts-boun...@febo.com] De la part de Stéphane Rey
Envoyé : mardi 20 janvier 2015 23:15
À : 'Discussion of precise time and frequency measurement'
Objet : Re: [time-nuts] question Alan deviation measured with Timelab and 
counters

Hi,

Following the tests results in the previous email, today I've performed 
additional measurements showing that the repeatability of the GPSDO DUT is not 
great but is coming from the design. I've tested several over sources and 
repeatability is correct.

I can already make some measurement. Good ! 

Now I'd like to improve. First I'm going to implement a squarer and then I will 
work on the DMTD... I'm thinking to make a setup on the table, and possibly 
make a small PCB then.

Any comment for the tests results of yesterday here under ? 

Cheers
Stephane


-Message d'origine-
De : time-nuts [mailto:time-nuts-boun...@febo.com] De la part de Stéphane Rey 
Envoyé : lundi 19 janvier 2015 22:32 À : 'Discussion of precise time and 
frequency measurement'
Objet : Re: [time-nuts] question Alan deviation measured with Timelab and 
counters

Hi

Here are the results of today's experiments. plots and TIM files attached to 
this email.


Setup #1 : dark blue
I've done again the floor measurement with same conditions : HP58503 for 10 MHz 
Standard, 1PPS for the EXT gating and the Rb on channel A. Same result 
(hopefully)

Setup #2 : Pink
Then I've made what Magnus has suggested, i.e. using the 1 PPS on Channel A, 
the Rb on channel B and internal gating The ADEV has increased by more than 
1 order of magnitude. I guess this confirms the 1PPS stability is lower than 
the 10 MHz

Setup #3-6 : Dark Green, Red, Light blue and Dark yellow.
I've measured several times the GPSDO DUT with SEParate inputs. 1PPS on EXT, Rb 
on channel A and DUT on channel B. This gives 4 different plots... When 
starting the measurement the plots starts directly at different values... Mmmm 
very strange. Is it coming for the setup of the GPSDO ? To be investigated 
further with other sources. This is the plan for tomorrow. However the overal 
shape of the plot sounds relevant to me.

Setup #7-8 + #9 not showed here
I've tested the suggested splitted same signal on both inputs with 1m coax for 
channel B. I've discovered that when swaping the GPSDO on the standard input 
and the Rb on the channel A I have a slight difference. In order to confirm 
I've made two time each measurement and this confirms that having the Rb on 
channel A and GPSDO on the standard input gives the lowest ADEV. The setup #9 
which is the same than the light green gives the superimposed plot on that 
one... So what does it mean ? One of the two sources is better than the other, 
but which one ? 


Some other comments :
- Swaping signals between channel A and B gives the same ADEV (setup #4 and 5, 
light blue and red)
- On some measurement on the GPSDO DUT, (not displayed here), I could see 
during the measurement suddenly an increase of one order of magnitude. The 
HP5370A do not show any difference (the time interval value continues to move 
with a beat but visually impossible to quantify if the value between two values 
has increased. No explanation for that. I'll redo the test with some other 
sources to check if it comes for the measurement system or the GPSDO DUT

In conclusion,
1. swaping the Rb and HP58503 doesn't give the same result. The GPSDO has 
standard seems the best (or the Rb measured) 2. the measurement on the GPSDO 
DUT gives different results with nearly one order of magnitude difference but 
shape is still the same.
3. the 1PPS must be connected on the EXT gating input

What do you think ? 

Cheers
Stephane


-Message d'origine-
De : time-nuts [mailto:time-nuts-boun...@febo.com] De la part de steph.rey 
Envoyé : lundi 19 janvier 2015 16:44 À : Discussion of precise time and 
frequency measurement Objet : Re: [time-nuts] question Alan deviation measured 
with Timelab and counters

 Actually I'm working in the RF department of a big lab, designing RF  
electronics mainly in microwaves range. I'm luckilly having some tools  around 
to play with and a lot of components like  
mixers/amplifiers/couplers/splitters/attenuators

Re: [time-nuts] question Alan deviation measured with Timelab and counters

[Stéphane Rey]

Hi,

Just a stupid question on Timelab.
Why do I have the plot with 1/4 for the time actually used for the measurement 
? I can see that the plot is updated every 4 samples but the scale is not 
relevant. The sample interval is correctly set (1s) 

Cheers
Stephane

-Message d'origine-
De : time-nuts [mailto:time-nuts-boun...@febo.com] De la part de Stéphane Rey
Envoyé : mardi 20 janvier 2015 23:15
À : 'Discussion of precise time and frequency measurement'
Objet : Re: [time-nuts] question Alan deviation measured with Timelab and 
counters

Hi,

Following the tests results in the previous email, today I've performed 
additional measurements showing that the repeatability of the GPSDO DUT is not 
great but is coming from the design. I've tested several over sources and 
repeatability is correct.

I can already make some measurement. Good ! 

Now I'd like to improve. First I'm going to implement a squarer and then I will 
work on the DMTD... I'm thinking to make a setup on the table, and possibly 
make a small PCB then.

Any comment for the tests results of yesterday here under ? 

Cheers
Stephane


-Message d'origine-
De : time-nuts [mailto:time-nuts-boun...@febo.com] De la part de Stéphane Rey 
Envoyé : lundi 19 janvier 2015 22:32 À : 'Discussion of precise time and 
frequency measurement'
Objet : Re: [time-nuts] question Alan deviation measured with Timelab and 
counters

Hi

Here are the results of today's experiments. plots and TIM files attached to 
this email.


Setup #1 : dark blue
I've done again the floor measurement with same conditions : HP58503 for 10 MHz 
Standard, 1PPS for the EXT gating and the Rb on channel A. Same result 
(hopefully)

Setup #2 : Pink
Then I've made what Magnus has suggested, i.e. using the 1 PPS on Channel A, 
the Rb on channel B and internal gating The ADEV has increased by more than 
1 order of magnitude. I guess this confirms the 1PPS stability is lower than 
the 10 MHz

Setup #3-6 : Dark Green, Red, Light blue and Dark yellow.
I've measured several times the GPSDO DUT with SEParate inputs. 1PPS on EXT, Rb 
on channel A and DUT on channel B. This gives 4 different plots... When 
starting the measurement the plots starts directly at different values... Mmmm 
very strange. Is it coming for the setup of the GPSDO ? To be investigated 
further with other sources. This is the plan for tomorrow. However the overal 
shape of the plot sounds relevant to me.

Setup #7-8 + #9 not showed here
I've tested the suggested splitted same signal on both inputs with 1m coax for 
channel B. I've discovered that when swaping the GPSDO on the standard input 
and the Rb on the channel A I have a slight difference. In order to confirm 
I've made two time each measurement and this confirms that having the Rb on 
channel A and GPSDO on the standard input gives the lowest ADEV. The setup #9 
which is the same than the light green gives the superimposed plot on that 
one... So what does it mean ? One of the two sources is better than the other, 
but which one ? 


Some other comments :
- Swaping signals between channel A and B gives the same ADEV (setup #4 and 5, 
light blue and red)
- On some measurement on the GPSDO DUT, (not displayed here), I could see 
during the measurement suddenly an increase of one order of magnitude. The 
HP5370A do not show any difference (the time interval value continues to move 
with a beat but visually impossible to quantify if the value between two values 
has increased. No explanation for that. I'll redo the test with some other 
sources to check if it comes for the measurement system or the GPSDO DUT

In conclusion,
1. swaping the Rb and HP58503 doesn't give the same result. The GPSDO has 
standard seems the best (or the Rb measured) 2. the measurement on the GPSDO 
DUT gives different results with nearly one order of magnitude difference but 
shape is still the same.
3. the 1PPS must be connected on the EXT gating input

What do you think ? 

Cheers
Stephane


-Message d'origine-
De : time-nuts [mailto:time-nuts-boun...@febo.com] De la part de steph.rey 
Envoyé : lundi 19 janvier 2015 16:44 À : Discussion of precise time and 
frequency measurement Objet : Re: [time-nuts] question Alan deviation measured 
with Timelab and counters

 Actually I'm working in the RF department of a big lab, designing RF  
electronics mainly in microwaves range. I'm luckilly having some tools  around 
to play with and a lot of components like  
mixers/amplifiers/couplers/splitters/attenuators, ... almost whatever  the 
frequency is up to several tens of GHz.
 At home since the last 20 years I could as well get nice instruments. 
 The next two measuring tools really missing and for which I'm limited  are the 
phase noise and stability measurement and possibly a good  standard. My 
Effratom FRK Rb is old and probably not the best from a  phase noise and 
stability point of view but until now has never been  characterized. Otherwise 
I've almost everything I

Re: [time-nuts] question Alan deviation measured with Timelab and counters

[Stéphane Rey]

Hi,

Following the tests results in the previous email, today I've performed 
additional measurements showing that the repeatability of the GPSDO DUT is not 
great but is coming from the design. I've tested several over sources and 
repeatability is correct.

I can already make some measurement. Good ! 

Now I'd like to improve. First I'm going to implement a squarer and then I will 
work on the DMTD... I'm thinking to make a setup on the table, and possibly 
make a small PCB then.

Any comment for the tests results of yesterday here under ? 

Cheers
Stephane


-Message d'origine-
De : time-nuts [mailto:time-nuts-boun...@febo.com] De la part de Stéphane Rey
Envoyé : lundi 19 janvier 2015 22:32
À : 'Discussion of precise time and frequency measurement'
Objet : Re: [time-nuts] question Alan deviation measured with Timelab and 
counters

Hi

Here are the results of today's experiments. plots and TIM files attached to 
this email.


Setup #1 : dark blue
I've done again the floor measurement with same conditions : HP58503 for 10 MHz 
Standard, 1PPS for the EXT gating and the Rb on channel A. Same result 
(hopefully)

Setup #2 : Pink
Then I've made what Magnus has suggested, i.e. using the 1 PPS on Channel A, 
the Rb on channel B and internal gating The ADEV has increased by more than 
1 order of magnitude. I guess this confirms the 1PPS stability is lower than 
the 10 MHz

Setup #3-6 : Dark Green, Red, Light blue and Dark yellow.
I've measured several times the GPSDO DUT with SEParate inputs. 1PPS on EXT, Rb 
on channel A and DUT on channel B. This gives 4 different plots... When 
starting the measurement the plots starts directly at different values... Mmmm 
very strange. Is it coming for the setup of the GPSDO ? To be investigated 
further with other sources. This is the plan for tomorrow. However the overal 
shape of the plot sounds relevant to me.

Setup #7-8 + #9 not showed here
I've tested the suggested splitted same signal on both inputs with 1m coax for 
channel B. I've discovered that when swaping the GPSDO on the standard input 
and the Rb on the channel A I have a slight difference. In order to confirm 
I've made two time each measurement and this confirms that having the Rb on 
channel A and GPSDO on the standard input gives the lowest ADEV. The setup #9 
which is the same than the light green gives the superimposed plot on that 
one... So what does it mean ? One of the two sources is better than the other, 
but which one ? 


Some other comments :
- Swaping signals between channel A and B gives the same ADEV (setup #4 and 5, 
light blue and red)
- On some measurement on the GPSDO DUT, (not displayed here), I could see 
during the measurement suddenly an increase of one order of magnitude. The 
HP5370A do not show any difference (the time interval value continues to move 
with a beat but visually impossible to quantify if the value between two values 
has increased. No explanation for that. I'll redo the test with some other 
sources to check if it comes for the measurement system or the GPSDO DUT

In conclusion,
1. swaping the Rb and HP58503 doesn't give the same result. The GPSDO has 
standard seems the best (or the Rb measured) 2. the measurement on the GPSDO 
DUT gives different results with nearly one order of magnitude difference but 
shape is still the same.
3. the 1PPS must be connected on the EXT gating input

What do you think ? 

Cheers
Stephane


-Message d'origine-
De : time-nuts [mailto:time-nuts-boun...@febo.com] De la part de steph.rey 
Envoyé : lundi 19 janvier 2015 16:44 À : Discussion of precise time and 
frequency measurement Objet : Re: [time-nuts] question Alan deviation measured 
with Timelab and counters

 Actually I'm working in the RF department of a big lab, designing RF  
electronics mainly in microwaves range. I'm luckilly having some tools  around 
to play with and a lot of components like  
mixers/amplifiers/couplers/splitters/attenuators, ... almost whatever  the 
frequency is up to several tens of GHz.
 At home since the last 20 years I could as well get nice instruments. 
 The next two measuring tools really missing and for which I'm limited  are the 
phase noise and stability measurement and possibly a good  standard. My 
Effratom FRK Rb is old and probably not the best from a  phase noise and 
stability point of view but until now has never been  characterized. Otherwise 
I've almost everything I need up to 40 GHz I  guess.

 I'm doing further measurement right now which sounds much much more  
consistent. I will share tonight.
 Cheers
 Stephane



 On Mon, 19 Jan 2015 08:59:58 -0500, Bob Camp kb...@n1k.org wrote:
 Hi

 On Jan 18, 2015, at 5:12 PM, Stéphane Rey steph@wanadoo.fr
 wrote:

 Bonsoir Magnus (Are you in Sweeden ?)

 Being able to measure high stability and low phase noise is 
 definitely a need for me as I'm trying to design low noise 
 synthesizers and I'm already reaching the limits of my current tools 
 for phase noise and I

Re: [time-nuts] question Alan deviation measured with Timelab and counters

[Stéphane Rey]

Bonsoir Magnus (Are you in Sweeden ?) 

Being able to measure high stability and low phase noise is definitely a need 
for me as I'm trying to design low noise synthesizers and I'm already reaching 
the limits of my current tools for phase noise and I can't afford an E5052 for 
my own. At work I've one but I will probably not stay after august. And anyway 
I need such tools in my lab at home...
As low-noise and stable synthetizers depends on the standard used, I need as 
well to measure them as well...

Let's start with this simple experiments and once I will understand the ins and 
outs I will try to improve. I know techniques of cross-correlations and you've 
already talked about DMTD that for sure I will have to come to...

Good night
Stephane

-Message d'origine-
De : Magnus Danielson [mailto:mag...@rubidium.se] 
Envoyé : dimanche 18 janvier 2015 22:46
À : Stéphane Rey; 'Discussion of precise time and frequency measurement'
Cc : mag...@rubidium.se
Objet : Re: [time-nuts] question Alan deviation measured with Timelab and 
counters

Bonsoir Stéphane,

On 01/18/2015 10:34 PM, Stéphane Rey wrote:
 Thanks a lot Bob and Magnus for your very helpful comments.

 The HP5370a was indeed in TI mode. By the way what is the difference with 
 +/-TI, the button just aside...

 But I guess I understand where I've missed something : I've tried to put the 
 Rb on channel A and the DUT on channel B but result was always the same but I 
 do understand now that there is indeed a switch to change from COMmon to 
 SEParate and it was always on COM meaning I believe that channel B wasn't 
 used. This explains a lot of things I did not understand. I'm sorry for these 
 so basic issues that might have been solved if I had read carefully the 
 HP5370a manual first.

Good. This confirmation makes sense to be and Bob, now we can relax as the 
mystery is solved.

 So possible conclusions until now are that I have actually measured the ADEV 
 floor of the system rather than my DUT... which is already nice. The second 
 conclusion from these oscillations seen with the GPSDO under test is that 
 there is very likely in this GPSDO design a systemic noise added to the 10 
 MHz output (power supply, PCB coupling, ... I'll make further investigations 
 on it later on).

It's a great opportunity to learn the tools, and once you have the tools, you 
can see if you can't improve things.

 I will experiment all the suggestions you made and will come back. For 
 information the 1PPS from the HP58503b has a positive pulse width that is 
 only few us length.

This only makes it hard to view on a scope, but long enough to reliably trigger 
your counter and scope.

 Now, when considering that the method is to compare the DUT to an other 
 source, I assume then that the other source shall be at least 1 order of 
 magnitude better than the DUT. Otherwise this will be impossible to 
 distinguish who is the instability contributor between the source and DUT, 
 right ?

For a simple setup, yes. But then we are the time-nuts, we have ways of 
handling these things. :) Let's get you started with the basic measurement, it 
will be a good start.

 Then the second question is what kind of very stable source can be used to 
 measure DUT which could be Rb or GPSDO which are already in the range of 
 10E-10 to 10E-12  100s ?

Time-nuts tend to spend their time and money getting even more stable clocks 
and tools. If you have the right tool, you can measure near and
*under* the noise-level of your reference, but not without running into issues. 
One such trick is called cross-correlation, while another is to use 
three-corner hat techniques.

Cheers,
Magnus



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Re: [time-nuts] question Alan deviation measured with Timelab and counters

[Stéphane Rey]

Hello,

First, please do apologize for the confusion answering in the bad email. That's 
things I'm absolutely able to do when replying at 3 am ! Again, sorry for that 
and thanks Magnus for having corrected this.

Back to my setup :

There is indeed nothing on the STOP input of the HP5370a. The standard 10 MHz 
comes from the GPSDO HP-58503B and feeds the HP5370a Standard input. Its ADEV 
is given on page 240 of that document : 
http://www.leapsecond.com/museum/hp58503a/097-58503-13-iss-1.pdf We see that 
the shape is starting at about 2E-12 at 1s, increase to 2E-11 at 100s before 
decreasing again down to E-13 for above 10E3s...

The setup #1 was using the Racal DANA Rb connected on the START input which is 
specified at E-9 / E-10, given on page 16 of the manual : 
http://bee.mif.pg.gda.pl/ciasteczkowypotwor/Racal/9470-9479.pdf
The EXT input receives the 1PPS from the HP58503b. It apparently drives both 
the START and the STOP of the acquisition (the two lights are blinking and the 
time between two measurement is no longer adjustable from the front panel RATE 
potentiometer and the period between two samples is 1.0s (detected by Timelab). 

But yes, the ADEV plot sounds really strange as it goes incredibly low after 
few seconds which is not consistent with the stability of the sources I'm using 
which is why I felt something was wrong

On Setup #2 I've only replaced the Racal Dana Rb with the GPSDO to test. I've 
not made this design and not checked yet anything on it. Could  these 
oscillations be from power supply noise ? To be checked. But how can it follow 
the ADEV plot of the Racal Dana Rb ? mmm Coincidence is not something I 
like too much and I believe something is clearly wrong in my measurement 

But what ???

On the Timelab setup screen before launching the acquisition I've left all the 
parameters as it without touching them. I've just seize 10E6 in the frequency 
field.

Ah, by thay Magnus, for the downmixed test I've forgotten to change this value, 
I will check on monday when back at the office.


Stephane




-Message d'origine-
De : time-nuts [mailto:time-nuts-boun...@febo.com] De la part de Bob Camp
Envoyé : dimanche 18 janvier 2015 14:44
À : Discussion of precise time and frequency measurement
Objet : Re: [time-nuts] question Alan deviation measured with Timelab and 
counters

Hi

Ok, I didn’t think I’d seen the plots before. 

I agree that the plots look like “counter limited” data. That’s a fine 
explanation at the shorter Tau’s. I also agree that some sort of periodic 
“stuff” is getting into one of the signals and creating the ripple. What I’m 
wondering about (and what makes me question the setup) is the fact that the 
data is still “counter limited” at the mid to low parts in 10^-13 level at just 
a bit over 100 seconds. A telecom  Rb is doing pretty well to be at 1x10^-12 at 
100 seconds. Most GPSDO’s are doing well to be mid parts in 10^-12 at that tau. 
Simply put, the data continues to be counter limited to a pretty low point. 

Bob

 On Jan 18, 2015, at 7:13 AM, Magnus Danielson mag...@rubidium.dyndns.org 
 wrote:
 
 Hi Bob,
 
 On 01/18/2015 04:25 AM, Bob Camp wrote:
 Hi
 
 I’m a little concerned about the measurement setup here. Based on the quoted 
 text, there have been a few messages in the thread that have not showed up 
 here.
 
 The messages got accidentally posted in the wrong thread.
 
 =
 
 The “start” input on the counter is defined below. The “stop” input is not 
 defined. Is the counter running in time interval mode or in frequency mode?
 
 IF it’s in time mode - what is the stop hooked to?
 
 IF it’s in frequent mode - what is the gate time set to ?
 
 Is the “standard input” the missing front panel input or is it the external 
 reference input on the back panel?
 
 I was also considering the setup strange in this regard. Common switched in?
 
 =
 
 I’m looking at the data on the link:
 
 http://www.ptp-images.com/affiche-directement-l-image-kccsz71c9a.html
 
 In both cases the slope is roughly 1/tau. Both plots end up in the 3 to 4 x 
 10^-13  range at 100 to 300 seconds. That’s suspiciously good performance 
 for a rubidium or a GPSDO. Which is what makes me wonder about the setup.
 
 The Blue plot (1 pps?) ran for 18 minutes and has 1,114 points in it. The 
 Pink plot ran for about 9 minutes and has a bit over 500 points in it. Both 
 seem reasonable for a 1 pps to 10 MHz sort of setup. That may explain part 
 of my confusion above.
 
 Again - I apologize if this all got explained in a post that went missing 
 here.
 
 Not really. The plots looks to me like measurement setup baseline plots, with 
 some sine noise in them.
 
 Cheers,
 Magnus
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Re: [time-nuts] question Alan deviation measured with Timelab and counters

[Stéphane Rey]

Thanks a lot Bob and Magnus for your very helpful comments.

The HP5370a was indeed in TI mode. By the way what is the difference with 
+/-TI, the button just aside...

But I guess I understand where I've missed something : I've tried to put the Rb 
on channel A and the DUT on channel B but result was always the same but I do 
understand now that there is indeed a switch to change from COMmon to SEParate 
and it was always on COM meaning I believe that channel B wasn't used. This 
explains a lot of things I did not understand. I'm sorry for these so basic 
issues that might have been solved if I had read carefully the HP5370a manual 
first.

So possible conclusions until now are that I have actually measured the ADEV 
floor of the system rather than my DUT... which is already nice. The second 
conclusion from these oscillations seen with the GPSDO under test is that there 
is very likely in this GPSDO design a systemic noise added to the 10 MHz output 
(power supply, PCB coupling, ... I'll make further investigations on it later 
on).

I will experiment all the suggestions you made and will come back. For 
information the 1PPS from the HP58503b has a positive pulse width that is only 
few us length.

Now, when considering that the method is to compare the DUT to an other source, 
I assume then that the other source shall be at least 1 order of magnitude 
better than the DUT. Otherwise this will be impossible to distinguish who is 
the instability contributor between the source and DUT, right ? 

Then the second question is what kind of very stable source can be used to 
measure DUT which could be Rb or GPSDO which are already in the range of 10E-10 
to 10E-12  100s ?


Stephane


-Message d'origine-
De : time-nuts [mailto:time-nuts-boun...@febo.com] De la part de Magnus 
Danielson
Envoyé : dimanche 18 janvier 2015 16:47
À : time-nuts@febo.com
Cc : mag...@rubidium.se
Objet : Re: [time-nuts] question Alan deviation measured with Timelab and 
counters

Bonjour Stéphane,

On 01/18/2015 03:37 PM, Stéphane Rey wrote:
 Hello,

 First, please do apologize for the confusion answering in the bad email. 
 That's things I'm absolutely able to do when replying at 3 am ! Again, sorry 
 for that and thanks Magnus for having corrected this.

Ah well, that's water under the bridge now. I only mentioned it for Bob's 
reference.

 Back to my setup :

 There is indeed nothing on the STOP input of the HP5370a. The standard 10 MHz 
 comes from the GPSDO HP-58503B and feeds the HP5370a Standard input. Its ADEV 
 is given on page 240 of that document : 
 http://www.leapsecond.com/museum/hp58503a/097-58503-13-iss-1.pdf We see that 
 the shape is starting at about 2E-12 at 1s, increase to 2E-11 at 100s before 
 decreasing again down to E-13 for above 10E3s...

 The setup #1 was using the Racal DANA Rb connected on the START input 
 which is specified at E-9 / E-10, given on page 16 of the manual : 
 http://bee.mif.pg.gda.pl/ciasteczkowypotwor/Racal/9470-9479.pdf
 The EXT input receives the 1PPS from the HP58503b. It apparently drives both 
 the START and the STOP of the acquisition (the two lights are blinking and 
 the time between two measurement is no longer adjustable from the front panel 
 RATE potentiometer and the period between two samples is 1.0s (detected by 
 Timelab).

If you run the counter in frequency or period mode, you normally use the STOP 
input, which is then internally split to the START and STOP channels.

If you run the counter in TI mode, then they are usually separate, but you can 
force them the same using the START COMMON switch.

We tend to use the TI mode, with two basic setup:

Stoopid simple: PPS to START and measured clock to STOP. This setup has the 
down-side that the jitter of the PPS (which can be much higher than that of the 
clock) can dominate, if so, the next setup is relevant:

Standard setup: PPS to ARM/EXT input to trigger measurement. DUT to START 
channel and reference clock to STOP channel. Sometime the clocks is 
interchanged, sometimes it is important, somtimes not.

Record the TI data.

 But yes, the ADEV plot sounds really strange as it goes incredibly low 
 after few seconds which is not consistent with the stability of the 
 sources I'm using which is why I felt something was wrong

OK, you made what we call a instrument noise limit measurement. Then you do the 
same thing as a normal measure, but you have start and stop channels see the 
same signal split. It may be good to let the stop channel has a meter or two of 
additional coax to de-correlate the rising edges. This setup will let you 
measure the effect of white noise, slew-rate and counter resolution. It can be 
good for fault analysis and see if the setup gives reasonable noise or if you 
can improve it. 
Adjustment of the trigger points will select a point of optimal slew-rate (and 
sometimes avoid false-trigger noise) and thus finding the optimum trigger noise.

Squaring up the signal may be a nice way

Re: [time-nuts] Current state of optical clocks and the definition of the second

[Stéphane Rey]

Hi,

 

I've took the time to read carefully your long and detailed message Magnus and 
this was very interesting. I've learned many things that have enabled me to 
investigate further. Ah yes, you're right saying that the more you fall into 
these things, the more you discover that you have to learn. Recently I've 
worked a lot on PLLs and I've actually learned a lot on special care to ensure 
low noise Very interesting. By the way I'm still working on this topic to 
improve again the noise (currently on a 3 GHz LO)

 

 

Here are some experiment results : 
http://www.ptp-images.com/affiche-directement-l-image-kccsz71c9a.html

 

1.   Setup #1 (blue plot)

HP5370A

standard input from HP GPSDO

EXT input not connected, internal Arming 0.4s rate

START input from 10 MHz distribution unit RacalDana 9478 Rubidium 

 

2.   Setup #2 (pink plot)

HP5370A 

standard input from HP GPSDO

EXT input not connected, internal Arming 0.4s rate

START input from DUT (10 MHz homemade GPSDO)

 

I'm not sure this is the proper way to connect everything... but this is the 
setup providing the lowest ADEV... which is between 1E-10 and 1E-13. But is the 
truth ?

I feel strange the two plots having the same decreasing path along a linear 
slope (I mean linear on the log-log plot) ... I'm not sure of what I'm 
measuring ? Could this be the system measurement floor ? By the way how to 
measure the ADEV floor of a system other than having a source greater than the 
measurement system ?

What could be these oscillations on the homemade (not by me) GPSDO  ?

 

 

I've tried to downmix the DUT 10 MHz to few kHz using a SR DDS generator and a 
double balanced mixer from minicircuit via a low pass filter tuned at 100 kHz, 
but the level wasn't high enough for the counter (which I found strange as it 
was already nearly 200mV). I hadn't anything in hands to make a squarer quickly 
so I've just added a Minicircuits RF amplifier. The level was good but the ADEV 
has jumped to 1E-6. The signal was noisy already on the oscilloscope which I 
know is for sure the cause. 

I need to make a squarer. I was hesitating between several methods : using a 
CMOS gate, but this will increase the flicker noise from what I've read, using 
an amplifier and clamping diodes or a fast comparator which might create some 
noise around the trigger point... Any recommendation there ? 

I'll try to make this squarer next week to continue my investigations

 

Cheers 

Stephane

 

 

 

-Message d'origine-
De : time-nuts [mailto:time-nuts-boun...@febo.com] De la part de Magnus 
Danielson
Envoyé : mercredi 14 janvier 2015 06:05
À : time-nuts@febo.com
Cc : mag...@rubidium.se
Objet : Re: [time-nuts] Current state of optical clocks and the definition of 
the second

 

 

 

On 01/13/2015 11:41 AM, Attila Kinali wrote:

 On Mon, 12 Jan 2015 20:09:45 +

 Gregory Maxwell  mailto:gmaxw...@gmail.com gmaxw...@gmail.com wrote:

 

 On Mon, Jan 12, 2015 at 12:34 PM, Attila Kinali  mailto:att...@kinali.ch 
 att...@kinali.ch wrote:

 Seems that the state of the art in stabilized lasers has improved a 

 lot lately, e.g. there are commercial available 1550nm devices which 

 have a =3Hz line-width:  http://stablelasers.com/products.html 
 http://stablelasers.com/products.html (well 

 on a short term basis, the medium term performance is not so

 impressive)

 

 Laser stabilization, especially for quantum metrology is still an 

 actively researched field. Current state of the art is IIRC 0.3Hz 

 linewidth (sorry, cannot find the reference at the moment).

 Mid- and long term stability depends highly on the reference used. 

 Current research is fucused mainly on special, low vibration 

 structures made out of low expansion glass or silicon. And these 

 cavities are usually put into a temperature controlled chamber in 

 vacuum.

 

Well, guess what I found standing around in a lab with an optical comb? :)

 

With optical line-widths in sub-Hz range and optical combs you have a nice way 
of comparing the frequency of that free-running and un-steerable but stable 
oscillator. However, as you mix it down the noise of the optical comb will 
dominate, but you can know which multiple of the optical comb and offset it is.

 

 Considering the rarity and extreme cost of H-masers, or just really 

 exceptional quarts oscillators; might it be the case that optical LOs 

 start looking interesting for applications which just need stability 

 (or being steered by other sources; e.g. GPSDL)?

 

 Well, an 8607 costs more than a Rb-standard. Yes, the 8607 has lower 

 close in phase noise and up to several 1000s it rivals the Rb, but 

 handling it is much more difficult than handling an Rb.

 Also, if you want to buy one of those exceptionally low noise/high 

 stable 8607's (those that go down into the 10^-14 range) you'd have to sell 
 your car.

 

 But, if you buy a H-maser from SpectraTime, you get a 8607 for free 

 ;-)

 

That is also the only 

Re: [time-nuts] question Alan deviation measured with Timelab and counters

[Stéphane Rey]

Bonjour Magnus,

Many thanks for your very long and detailed answer. I've read quickly bu will 
go deeper tonight.

Here are the results of today experiments... which are not giving anything 
valuable... I still don't understand the results I get  :-/

With the PM6654C, I've put the HP GPSDO on the standard input, the 1 PPS on 
channel A and the 10 MHz from the DUT (GPSDO as well) on channel B. This gives 
something in the range of 2E-9 which looks like the counter resolution, right ? 
The gating takes 4s and the Time A-B displays a value like 64 E-6
Now if I downmix the channel B to 5 kHz (LO is a DDS Standford  Reseach 
generator), I have a sinus with lower amplitude and no squarer in my hand at 
the moment to shape the signal. Anyway, I do the same operation and I get on 
the display two more digits like xx.xx E-6 but the ADEC is in the range of 
E-7 I do not understand at all this fact. Even if the slew rate is not 
great, I was expecting an improvement.
Note that the values displayed are always changing quite a lot between two 
samples. For instance with the 5 KHz channel B signal, I can read first sample 
at 27.11E-6, in the next one is 31.22E-6... which sounds huge, right ?

I've then found an HP5370A and tried the same operation. Unfortunately the 5 
kHz output is too low for the HP5370A sensitivity. I need an amplifier or 
sqauerer here but had no time to build on today.
Si I could not get anything valuable with the HP5370A at the moment...

Stephane



-Message d'origine-
De : time-nuts [mailto:time-nuts-boun...@febo.com] De la part de Magnus 
Danielson
Envoyé : mercredi 14 janvier 2015 08:04
À : time-nuts@febo.com
Cc : mag...@rubidium.se
Objet : Re: [time-nuts] question Alan deviation measured with Timelab and 
counters

Bonjour Stéphane,

On 01/14/2015 02:16 AM, Stéphane Rey wrote:
 Hi Magnus,

 For some reason I've missed this message and the one from Jim until now ! 
 This answers many of the questions I had. For my defense, I've 3000 messages 
 since the last 3 months on the list !!!

 ah, yes, I'd like to get even better than 1E-12. 1E-14 would be perfect but 
 my best standards for now are a HP GPSDO and an Effratrom FRK Rb which both 
 are around 1E-12 'only'. I may have to invest in something better if prices 
 are acceptable. I guess I won't be able to measure beyond the standard itself.

 The method you describes gives tau=2E-9 ? This is more or less what I could 
 get with the frequency measurement (even a bit lower). So what is the benefit 
 of the time interval measurement here against the frequency measurement ?

I've been sloppy with the scaling factor, so there is a fixed scaling factor 
for the noise that the single-shot resolution produces, and that would be a 
measurement limit that if everything else is ideal would dominate. This 
quantization noise is sqrt(1/12) or about 0.289 if I remember correctly, so 
that is the scale-factor. It will also have a 1/tau slope. So that is how you 
can expect this noise to behave, it will look like white phase noise, but 
isn't, it is highly systematic noise, and if you play nicely with it, you can 
measure below it. However, doing so is non-trivial.

I have one counter that does that. The good old HP5328A with the Option 
040-series of boards will introduce noise to the counting 100 MHz oscillator 
such that averaging gets you down towards 10 ps rather than
10 ns resolution in TI mode. However, it does not help you to get nice 
frequency or stability measures.

I've not taken the time to detail-analyse the ADEV scaling factor thought, I 
should do that, but it follows the general formula of
ADEV(tau) = k*t_res/tau
where t_res is the single-shot resolution and k is a constant.
There is more to this, as counters can show up non-linearities of several 
sorts, and that the trigger conditions of the input has been optimized, which 
can be slew-rate limited for many counters and conditions.

So, anyway, there is a bit of hand-waving in there, but I thought it was better 
to get you to get the basic trend there first, and then we can discuss the 
detailed numbers, as theory is one thing and achieved number can be quite a 
different one.

As for frequency and time-interval measurements, if properly done, they can be 
used interchangeably without much impact. Realize that frequency and 
time-interval measurements will both be based on time-interval measurements as 
the core observation inside the counter, so the single-shot resolution limit 
applies to them both. However, subtle details lies in how the counter works and 
there is ways that the frequency precision can be lost. A good counter is the 
SR620, but the way it does the frequency measure, you need to calibrate the 
internal delay to make it on the mark measure. Using it in time-interval mode 
and you can eliminate that offset, because the start and stop measure of your 
signal under test is done with the same channel, with essentially the same 
delay both trigger-times

Re: [time-nuts] question Alan deviation measured with Timelab and counters

[Stéphane Rey]

Hi John,

I hadn't noticed before you were here as well   ;-)

Thanks for answering. So I do understand I can use Timelab in frequency 
difference even if my counter sends data in TI in nanoseconds. Great.
Ah and thanks for the manual link. I didn't remember this was in the manual of 
the Timepod 
Will investigate further today

-Message d'origine-
De : time-nuts [mailto:time-nuts-boun...@febo.com] De la part de John Miles
Envoyé : mercredi 14 janvier 2015 07:26
À : 'Discussion of precise time and frequency measurement'
Objet : Re: [time-nuts] question Alan deviation measured with Timelab and 
counters

 - Can I use Frequency difference mode from Timelab to monitor time intervals ?
 If no is there a way to use the time interval measurement from the 
 counter with Timelab to plot ADEV ?

If you feed in frequency samples, it will convert them to phase-difference 
samples internally, so the program itself doesn't really care.  The use of 
frequency data has a few drawbacks such as less accurate ADEV plots due to the 
counter's dead time between readings, but it's the easiest way to get started 
and is perfectly usable for many purposes.

In general you should avoid letting the counter do any averaging.  Except in 
very specific circumstances, any apparent improvement in ADEV measurement floor 
will be illusory.   There are exceptions, but this isn't something you want to 
mess with until you're very comfortable with the rest of the measurement 
process.  Your counter's true ADEV measurement floor at t=1s should be assumed 
to be close to its single-shot resolution specification (e.g., 100 ps = about 
1E-10).

 - In case the principle of plotting ADEV from Time Interval, what is 
 the interpretation of the result ? The ADEV shows the relative 
 stability between the two GPSDO... So, practically what does it bring 
 ? And how to use this method if I want to characterize a device ?

An ADEV graph shows frequency stability statistics at different intervals, 
ranging from the rate at which the readings are returned from the counter (tau 
zero, at the left end of the plot) to a maximum interval that's related to how 
long you let the measurement run.  It's much too deep a subject to go into in 
an email; see http://www.ke5fx.com/stability.htm for more pointers.

Again, TimeLab always plots ADEV from time interval/phase data, even if you 
give it frequency readings.  ADEV is fundamentally a frequency stability 
metric, but it can be computed identically from either TI or frequency samples 
(assuming zero dead time).  
 
 - stupid question on Timelab. If I let Timelab in Auto to select the 
 period between two samples (correctly detected), the time scale of the graph 
 is wrong.
 For instance, a 3h plot stops at 2000s (0.5h)... Here again, I miss 
 something but what ?

The TimeLab manual, for one thing. :)  Hit the books (specifically 
http://www.miles.io/TimePod_5330A_user_manual.pdf , page 31).

-- john, KE5FX
Miles Design LLC


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Re: [time-nuts] question Alan deviation measured with Timelab and counters

[Stéphane Rey]

Hi there,

I'm still working on the ADEV measurement and here is what I've experimented 
today and few questions which are arising, that for sure have probably an easy 
answer...

After having measured my 10 MHz GPSDOs with 1Hz and 0.01Hz resolution with 
HP8342A and Phillips PM6654C, I've seen the effect of resolution on the ADEV. 
With the 0.01 Hz resolution I could only achieve 1E-9 at 10 MHz which is very 
likely the floor limitation from the counter resolution. Actually I hope my 
GPSDO is better than that (~1E-12)
The PM6654C can measure Time Intervals with a resolution of 0.01ps and an 
averaging time of 96s. I've then launch a new acquisition from Timelab, 
selecting Frequency difference instead of frequency only. I've not seen a time 
interval mode so I think this measurement gives nothing usable. The counter 
runs upon its own OCXO and I've connected two different GPSDO, one on each 
channel. I've tried both the internal gating as well as external gating with 
the 1PPS from the HP GPSDO with same result. The time interval is about 450ps 
with a variation of about 50ps. I've got an ADEV plot which is now in the range 
of 1E-12 / 1E-13.

However here are my questions :

- Can I use Frequency difference mode from Timelab to monitor time intervals ? 
If no is there a way to use the time interval measurement from the counter with 
Timelab to plot ADEV ?

- In case the principle of plotting ADEV from Time Interval, what is the 
interpretation of the result ? The ADEV shows the relative stability between 
the two GPSDO... So, practically what does it bring ? And how to use this 
method if I want to characterize a device ?

- I've googled for the DMTD and discovered the method. The principle seems 
clear and easy even if I know there might be several pitfails but here again, I 
don't know how to use the method or perform  the result interpretation. In that 
method there is the LO and at leadt two DUTs inputs. I do understand that the 
method gives a relative stability between the two DUT... And what  ? IF I've a 
device to characterize how can I get something useful by comparing with an 
other device that I do not know ? Where am I wrong here ?

- stupid question on Timelab. If I let Timelab in Auto to select the period 
between two samples (correctly detected), the time scale of the graph is wrong. 
For instance, a 3h plot stops at 2000s (0.5h)... Here again, I miss something 
but what ? 

I'm sorry as it's probably weird questions already discussed many times but any 
comment or URL to point to would be a great help.

Many thanks
Stephane


-Message d'origine-
De : time-nuts [mailto:time-nuts-boun...@febo.com] De la part de Bob Camp
Envoyé : vendredi 9 janvier 2015 23:57
À : Discussion of precise time and frequency measurement
Objet : Re: [time-nuts] question Alan deviation measured with Timelab and 
counters

Hi

If your only instrument is a counter.

— and —

You never measure past 1x10^-10 with that counter

— and —

Measurements that bounce around with a standard deviation of the difference 
between readings of 1x10^-10 are ok. 

— then —

No, you don’t need anything better than a 1x10^-10 ADEV. 

Most people would be bothered by a counter that has an typical jump of 1x10^-10 
between every reading, so most would want a standard that’s a bit better than 
that. 

In addition, if you want to guarantee accuracy of a reading, you probably want 
something that’s 5X to 10X better than the level that stops the reading jitter. 

Simply put - ADEV is not standard deviation of frequency. Your frequency 
counter measures frequency. Going from one to the other means you want to have 
better ADEV than you might think. 

Bob

 On Jan 9, 2015, at 10:42 AM, steph.rey steph@wanadoo.fr wrote:
 
 Hi Bob,
 
 Many thanks for your prompt and detailled answer.
 
 My question on applications wasn't on good ADEV where I perfetcly 
 understand the need, but actually what could be the applications of 
 measuring BAD ADEV (10e-7). That was my point asking what king of 
 application can we cover by measuring such high ADEV when you have 
 counters with resolution not greater than 0.01Hz
 
 However you bring to me part of the answer when you talk about the reference 
 and the way to get something cheap and better than 10e-12. I will investigate 
 on DMTD. However, even if you have a beautiful Maser source, will you improve 
 anything above the resolution of your counter. In other words, with my 0.01Hz 
 counter, will I improve my measurement if I replace my GPSDO source with 
 something much better ? I feel the resolution of the counter will anyway 
 limit the ADEV floor, right ? If the last digit of the counter do not move 
 how could we measure something smaller ?
 The counters I'm using are not running on their own reference (OCXO or TCXO) 
 but with the HP58503b which is a GPS disciplined OCXO but with stability in 
 the range of 10e-11 or 10e-12 at best.
 
 I'm working for a big lab where possibly I could have 

Re: [time-nuts] question Alan deviation measured with Timelab and counters

[Stéphane Rey]

Hi Magnus,  

For some reason I've missed this message and the one from Jim until now ! This 
answers many of the questions I had. For my defense, I've 3000 messages since 
the last 3 months on the list !!!

ah, yes, I'd like to get even better than 1E-12. 1E-14 would be perfect but my 
best standards for now are a HP GPSDO and an Effratrom FRK Rb which both are 
around 1E-12 'only'. I may have to invest in something better if prices are 
acceptable. I guess I won't be able to measure beyond the standard itself.

The method you describes gives tau=2E-9 ? This is more or less what I could get 
with the frequency measurement (even a bit lower). So what is the benefit of 
the time interval measurement here against the frequency measurement ?

However if I hear what you says, the GPSDO provides the 10 MHz standard 
reference for the counter, the GPSDO PPS on channel A and channel B receives 
for instance a 10 MHz signal I want to measure. 
So what will be the result of Time A-B then ? I do not understand why you put 
the PPS on channel A instead of something of the same frequency than the DUT ? 
How the time A-B will behave with these two different frequencies...  By 
letting TimeLab know the frequency, it can adjust for any slipped cycles on the 
fly. I guess this is what I've not understood.

Now if I mix down the 10 MHz DUT with a 10.005 reference to increase the 
resolution, I'll get 5 kHz on channel B and still PPS on channel A ? Again I do 
not understand what will happen with these two signals on the time A-B. If I 
push your method a bit more, I could even get a beat frequency of 1 Hz and with 
10-digits I would have increased my resolution by 10E6. Then I will be limited 
by the standard stability but on the principle would it work as well ? 
On that document 
http://www2.nict.go.jp/aeri/sts/2009TrainingProgram/Time%20Keeping/091017_DMTD.pdf
 it says (page 6) the accuracy of measurement is improved by a factor v/vb (the 
DUT and offset LO 1/2.PI.f). So it sounds to me that there is a compromise 
between resolution increase and accuracy. If I chose a beat frequency of 1 Hz 
the accuracy will not be improved but the resolution will be, right ? 

What is the transfer clock you're talking about ? and by the way should the 
offset LO be as stable as the standard reference meaning greater than the DUT ? 

Well, it's far too late here to let my brain working anymore. I will perform 
further experiments tomorrow at the office.

Thanks  cheers
Stephane

-Message d'origine-
De : time-nuts [mailto:time-nuts-boun...@febo.com] De la part de Magnus 
Danielson
Envoyé : samedi 10 janvier 2015 02:05
À : time-nuts@febo.com
Cc : mag...@rubidium.se
Objet : Re: [time-nuts] question Alan deviation measured with Timelab and 
counters

Stephane,

On 01/09/2015 12:53 PM, steph.rey wrote:
 Dear all,

 I'm trying to measure Alan Deviations using Timelab and some frequency 
 counters.
 The device under test is a GPSDO using a TCXO as référence

 I've an HP58503B GPSDO which feeds my counters. I've tried an HP5342A,
 0-18 GHz, 1 Hz resolution and a Philipps PM6654C, 0.01Hz resolution.

 In Timelab, the plot with the HP5342A is around 10e-7 which correspond 
 to 1Hz and with the PM6654C, the plot is around 10e-10.
 I would suspect that this is still the counter which limits the actual 
 response of my device under test.

 My question are :
 - how to measure Alan Deviations with levels below 10e-12/10e-13 ? 
 What can be the application of measurement Alan deviation  10e-10 ? I 
 guess most of the low frequency
 - The HP53503 GPS is given to be 10e-11 / 10e-12. I guess this will 
 limit anyway the measurement floor. I've a Rb source, but it's 
 stability is within the same range. What kind of reference would be 
 more suitable for such measurements ?
 - With the PM6654C on 15h measurement, I can see some frequency jumps 
 of
 800 Hz which are not relevants with the GPSDO undertest. I suspect 
 error in data transmission. This makes the overall measurement totally 
 wrong (10e-5). The counter is in talk only mode. I'd like to get rid 
 of these points maybe 40-50 points out of 1. Is there a way to do 
 that from Timelab or the only option is to export the file and process 
 manually the data ?

I've use the PM6654C with TimeLab. I wire the 10 MHz from the GPSDO and then 
the PPS to Channel A. Channel B has whatever signal I want to measure. By 
letting TimeLab know the frequency, it can adjust for any slipped cycles on the 
fly. This works well. The PM6654C has a single-shot resolution of 2 ns, which 
comes from the internal 500 MHz counting clock. This gives ~ 2E-9/tau (very 
coarse level) measurement limit. If you want to reach the 1E-12 resolution mark 
you need another
2000 of resolution gain, which is what you get if you mix your 10 MHz signal 
with a 10,005 MHz clock or lower. The Dual Mixer Time Difference
(DMTD) is more likely to work well, as it provides some cancellation of the 
transfer clock. Slew-rates 

Re: [time-nuts] GPS-disciplining an ordinary VCXO?

[Stéphane Rey]

 With that VCXO you want to have a 5s to 10s or more loop time constant (0.1Hz 
BW) which typically can only be done in the digital domain..

Hi Said,
Could you point us on something describing that ? What kind of digital 
processing do you think about ?

Cheers
Stephane

-Message d'origine-
De : time-nuts [mailto:time-nuts-boun...@febo.com] De la part de Said Jackson 
via time-nuts
Envoyé : dimanche 28 septembre 2014 07:50
À : Discussion of precise time and frequency measurement
Cc : time-nuts@febo.com
Objet : Re: [time-nuts] GPS-disciplining an ordinary VCXO?

Mark,

In the analog domain you can probably do a PLL with a 1Hz loop BW. Using a PLL 
chip like ADF 4002 or similar. This means all the nasty noise from the NEO will 
taint your PN up to 20Hz or more, very significantly close-in. If you don't 
care about noise (jitter) below 100Hz then this is fine. If you do as it will 
dominate your ADC jitter then you can't use an analog PLL.

With that VCXO you want to have a 5s to 10s or more loop time constant (0.1Hz 
BW) which typically can only be done in the digital domain.. This allows you to 
use the excellent 1Hz to 100Hz PN of that VCXO without tainting it by the noisy 
NEO.

An even better setup would be to lock a very low noise 5 or 10MHz ocxo to the 
GPS with 100s time constant, then use the analog PLL with wider bandwidth (say 
30Hz) to reduce the VCXO PN close-in even further by using the ocxo to supress 
the vcxo PN.

Welcome to our world, if you look at the archives there are 10++ years of 
discussions about exactly doing this...

Bye,
Said



Sent from my iPad

On Sep 27, 2014, at 21:01, Mark A. Haun hau...@keteu.org wrote:

 In my quest to learn Verilog and get my hands dirty with 
 software-defined radio, I'm currently designing a direct-sampling 
 shortwave receiver.  This uses an 80-MSPS ADC, which requires a 
 low-phase-noise oscillator, e.g. Crystek CVHD-950 or Abracon ABLNO.  
 It would be nice to have some provision for locking this oscillator to 
 an external reference, hence my question:
 
 All of the amateur GPSDO designs I've seen are disciplining an OCXO.  
 I understand this is easier because the excellent short-term accuracy 
 of the OCXO means the feedback can run slower, so even a 1 PPS signal 
 can be used.
 
 I am wondering what sort of performance could be achieved by 
 disciplining my VCXO directly with a good GPS module.  I have a NEO-7N
 (Ublox) with configurable timepulse up to 10 MHz.  Someone mentioned 
 that this is derived from 48 MHz, so jitter is reduced if you pick an 
 integer divisor.  That is fine, but I don't have a feel for what other 
 irregularities may be present in the timepulse output, and how they 
 would affect the performance.  I also don't know how to go about 
 designing a PLL loop filter.  I understand the goal is to marry the 
 long-term GPS stability with the short-term VCXO stability but all I 
 have is a phase-noise plot for the VCXO.  How do you know where to 
 split the difference?
 
 It is not essential to the larger project, but what I am ideally going 
 for is 1 ppb frequency match between two ends of a radio link, and 1 
 ppb stability over data symbol times.  That is, carrier stability of ~ 
 1/10 cycle at 10 MHz over one-second symbols.  (Channel coherence 
 imposes this limit.)  I know the experts here can tell me whether this 
 is impossible, totally doable, or somewhere in between!
 
 Thanks,
 
 Mark
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[time-nuts] various question on stability, jitter, PN, ...

[Stéphane Rey]

Hi guys,

 

I told you ! Some questions were to arise...   ;-)

 

At work I'm working on 1.5, 3 and 12 GHz pulsed systems with pulses length
between 0.1 and 5 us. We are especially interested in phase stability pulse
to pulse (repetition rate) and possibly with minor priority on the length of
the phase pulses, pulse to pulse.

 

1. When plotting the phase noise response of a CW signal, one can determine
the RMS jitter in ps or fs. I'm wondering what is corresponding to this
value. As it's RMS I would expect this is the square root of the maximum of
the Gaussian distribution of the frequency jitter. Is it right ? If so this
correspond roughly to 1 sigma deviation, right ? 

 

2. Is there any link between this frequency jitter and the phase jitter ? I
assume no, but...

 

3. What does bring the Allan deviation plot ? This gives stability vs
integration time I know, but how to make an interpretation of this ? Is it a
way to plot the frequency jitter in a more detailed way than just giving the
rms jitter ? 

 In practical use, for a pulsed system does it mean that only the very short
term jitter is of interest ? 

 

4. Is the Allan deviation plot a representation of the jitter vs integration
time, meaning there is a direct relation between the RMS jitter computed at
various offsets from the carrier in the PN plot ?

 

5. Is there a practical way to plot phase noise for pulsed signals ?

 

That's all for now.

If anyone has clues or can point me into good articles related this would be
kind.

 

Thanks

Stephane



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Re: [time-nuts] newcomer

[Stéphane Rey]

Thanks for the details. 

This miniaturized device is nice. 

 

There is no information regarding stability. Anything there ? What's the
technology inside ? crystal, TCXO ?

What is the approx price for a such device ? 

 

The VCXO I was targetting is this one :
http://www.abracon.com/Precisiontiming/ABLNO.pdf

This should bring more or less the same level of PN once multiplied than
your ULN_1G.

However the frequency accuracy is poor and it needs to be disciplined in
most applications.

 

Cheers

Stephane

 

 

De : saidj...@aol.com [mailto:saidj...@aol.com] 
Envoyé : lundi 15 septembre 2014 18:51
À : steph@wanadoo.fr; time-nuts@febo.com
Objet : Re: [time-nuts] newcomer

 

Hi Stephanie,

 

I have a similar issue, I can never tell if my messages post or not, some I
get back instantly others never show up in my inbox. I think the mail server
was just updated.. 

 

To answer your questions:

 

1) attached is the PN plot of the 1.0GHz version.

 

2) Here is a datasheet for the part:

 

   http://www.jackson-labs.com/index.php/products/uln_1g

 

The tricky part in your proposed setup will be getting a 100MHz crystal with
low enough phase noise so that the 20log(N/M) added phase noise won't be a
problem - +20dB added after all.

 

On our part some of the tricky design issues were size and power as well as
the high output power of +22dBm, and a requirement to maintain the output
power to within 0.5dB over the entire -40C to +85C temperature range.

 

bye,

Said

 

In a message dated 9/15/2014 09:40:37 Pacific Daylight Time,
mailto:steph@wanadoo.fr steph@wanadoo.fr writes:

Hi,

It sounds like all my messages need moderator approbation. Is it the 
rule on the list or a technical problem at my side ?
Cheers
Stephane



On Mon, 15 Sep 2014 09:17:01 -0700, Said Jackson via time-nuts 
 mailto:time-nuts@febo.com time-nuts@febo.com wrote:
 Hi Stephanie,

 Welcome to the list!

 We designed a 1GHz crystal LO for PLLs (the ULN-1G) using an off the
 shelf miniature 500MHz crystal oscillator which is run at 3 rd
 overtone internally then using a diode doubler and a steep bandpass
 filter using several Mini Circuits ceramic filters and a 20dBm amp.

 Works like a charm and has phase noise very close to theoretical..

 Bye,
 Said

 Sent From iPhone

 On Sep 15, 2014, at 5:50, steph.rey  mailto:steph@wanadoo.fr
steph@wanadoo.fr wrote:

 Hi the list,

 Just wanted to introduce myself for my 1st message.
 I'm Stephane, 40, living in France, at the moment working in RF  
 electronics for a particles accelerator lab. I'm hamradio as well, and 
 I do enjoy especially weak and accurate signals.
 I'm desiging various RF circuits. Current design is a universal PLL 
 able to operate from 0.5 to 6 GHz depending on the VCO and supposed to 
 be low-jitter (1ps) regarding the application.
 I'm also starting a new design of low noise PLL and there will be 
 probably a lot of question arising... I'm starting with the 1 GHz LO 
 made upon a 100 MHz VCXO + multipliers/filters/MMICs.
 I want to focus deeper on low phase noise/jitter, synchronization 
 and low-noise PLL techniques.
 I believe this is a good place for most of these topics.


 Cheers
 Stephane


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Re: [time-nuts] newcomer

[Stéphane Rey]

Thanks for your feedback. This is indeed a bit expensive for that application.
The x5 multiplier is indeed just the harmonic 5 capture with the helical 
filter. I'll let you know the outcome. This probably won't beat any expensive 
ULN source but might be a good starting point for low cost. Worth to try

Stephane


-Message d'origine-
De : time-nuts [mailto:time-nuts-boun...@febo.com] De la part de S. Jackson via 
time-nuts
Envoyé : mardi 16 septembre 2014 02:11
À : time-nuts@febo.com
Objet : Re: [time-nuts] newcomer

Hi Stephane,
 
our customer just needed +/-50KHz free-running over all conditions including 
aging, so stability was not of major concern, and the unit easily performs 
significantly better than that. We did make a VCO version for PLL disciplining 
so you can lock it to a GPSDO or in a correlated phase noise test system etc. 
The stability is thus not really good, but sufficient for Radar applications.
 
The technology is a Crystal oscillator multiplied by 5x internally I think 
(maybe it was 3x, can't remember), then by 2x externally. Since it is a MilSpec 
 compliant part it is not that low-cost, but it is lower-cost and much 
higher-performance than the legacy part it replaces. More than $1K for sure  
though. It also has some additional tricks up its sleeve such as a built-in  
DC-DC switcher and power supply filter allowing operation from +6V to 
+15V  without affecting output power, and allowing noisy external power
supplies to be  used, and harmonics lower than -32dBc typically by using the 
steep ceramic  low-pass filters.
 
That Abracom part looks pretty nice too, and your approach should work well  
too if you can get the 5x multiplier working well. Get a good 10MHz OCXO and 
use  an AD PLL chip such as ADF4002 etc to lock that Abracom part with a pretty 
small  loop BW (100Hz), and you will have the best of both worlds.
 
Bye,
Said
 
 
In a message dated 9/15/2014 16:52:18 Pacific Daylight Time, 
steph@wanadoo.fr writes:

Thanks  for the details. 

This miniaturized device is nice.  



There is no information regarding stability. Anything there ?  What's the 
technology inside ? crystal, TCXO ?

What is the approx  price for a such device ? 



The VCXO I was targetting is this  one :
http://www.abracon.com/Precisiontiming/ABLNO.pdf

This should  bring more or less the same level of PN once multiplied than your  
ULN_1G.

However the frequency accuracy is poor and it needs to be  disciplined in most  
applications.



Cheers

Stephane

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