Re: [time-nuts] T-Bolt Temperature

[Ron Ward]

Hi again:
Okay.
Thanks!
Ron

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Hal Murray
Sent: Wednesday, August 22, 2012 8:55 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] T-Bolt Temperature

> I don't know how to search the Time-Nut archive for specific information.

>From the headers that are normally not displayed by most mail systems:
  List-archive: 

Google also works nicely.



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Re: [time-nuts] T-Bolt Temperature

[Hal Murray]

> I don't know how to search the Time-Nut archive for specific information.

>From the headers that are normally not displayed by most mail systems:
  List-archive: 

Google also works nicely.



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Re: [time-nuts] WWV

[Max Robinson]

Tom Miller wrote.

I have one of the "atomic" clocks that sets itself via WWVB to keep time. 
Yesterday, Tuesday, AM it was an hour fast. Today it went back an hour to 
the correct time.


I also have one of those and it occasionally gets an hour off.  It usually 
corrects itself at midnight.


Regards.

Max.  K 4 O DS.

Email: m...@maxsmusicplace.com

Transistor site http://www.funwithtransistors.net
Vacuum tube site: http://www.funwithtubes.net
Woodworking site 
http://www.angelfire.com/electronic/funwithtubes/Woodworking/wwindex.html

Music site: http://www.maxsmusicplace.com

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- Original Message - 
From: "Tom Miller" 
To: "Discussion of precise time and frequency measurement" 


Sent: Wednesday, August 22, 2012 3:35 PM
Subject: Re: [time-nuts] WWV


I have one of the "atomic" clocks that sets itself via WWVB to keep time. 
Yesterday, Tuesday, AM it was an hour fast. Today it went back an hour to 
the correct time.


Strange.


Tom

- Original Message - 
From: "KD0GLS" 
To: "Discussion of precise time and frequency measurement" 


Sent: Wednesday, August 22, 2012 12:58 PM
Subject: Re: [time-nuts] WWV


Brad,
Could you please elaborate on what exactly you heard, and when, so we can 
keep our ears ready?


On Aug 22, 2012, at 11:30, Brad Dye  wrote:

Thought you guys might like to read this and maybe send them some more 
reports:



-Original Message-
From: Brad Dye [
mailto:b...@braddye.com
Sent: Tuesday, August 21, 2012 2:36 PM
To: inquiry
Subject: WWV Voice Time Announcements

Have you posted any official news about WWV intermittently reporting the 
wrong time? I would like to include it in my newsletter. By the way, I 
have verified this by listening myself.


Best regards,

Brad Dye
Editor, Wireless Messaging News
P.O. Box 266
Fairfield, IL  62837 USA
Telephone: 618-599-7869
Skype: braddye
http://www.braddye.com





Dear Mr. Dye,

We have not posted a report on WWV reporting the wrong time.  We have 
had only 1 outside suggestion that there was a broadcast of the wrong 
time and our investigation has not confirmed that.  We have found a low 
voltage on a power supply board feeding the voice which may have led to 
some problems, but that has now been replaced.  If you have further 
evidence or other reports concerning this matter we would appreciate 
that information.  You are only the second person to inquire about this 
issue. We take this very seriously, but normally when there are mistakes 
or problems with our broadcast we receive dozens of reports immediatly.


Please let us know and regards,

John Lowe
WWV Station Manager








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Re: [time-nuts] T-Bolt Temperature

[Ron Ward]

Hi:
Thanks for your quick response to my questions.

I read here that there was information on controlling Thunderbolt's
temperature using the thunderbolt as a PID temperature controller. Would a
constant temperature for the thunderbolt produce a significant improvement
in performance?

I don't know how to search the Time-Nut archive for specific information.

Thanks for all of the information and help!
Ron

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Azelio Boriani
Sent: Wednesday, August 22, 2012 1:21 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] T-Bolt Temperature

Yes, ambient/board temperature, not the OCXO oven temperature.

On Wed, Aug 22, 2012 at 8:12 PM, Arthur Dent
wrote:

> >Hi:
> >What is the temp chip reading? Is it reading the oven temperature or just
> >the ambient temperature?
> >Ron
> >
>
> The DS1620 thermometer chip is in the corner of the pc board next to the
> RS232 connector and diagonally opposite the OXCO so it reads ambient
> temperature.
>
> -Arthur
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Re: [time-nuts] GPSD-Rb

[Peter Bell]

On Wed, Aug 22, 2012 at 11:27 PM, Chris Albertson  wrote:

>
> It is very hard to write a divers in software.  You have to use assembly
> language and you have to mmake sure that EVERY path in every branch is has
> exactly the same number of clock cycles.   And then you have to be lucky
> that you can work out an exact integer division.
>

It depends on what sort of processor you are using - that sort of approach
used to be
necessary when the low-cost MCUs were things like PICs that don't have
especially sophisticated on-chip timers, but even cheap devices now have
onchip
timer/counters that have reload and capture registers. Many of them also
have PLLs
on the die that are intended for clock generation but can often be abused
for other
purposes :)
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Re: [time-nuts] WWV

[paul swed]

This is true and I am actually watching and trying to correct for the wwvb
phase modulation.
Though more work to be done.
Regards
Paul
WB8TSL

On Wed, Aug 22, 2012 at 10:02 PM, Joe Leikhim  wrote:

> Brad;
> I believe there are plans to eventually phase in a more reliable phase
> modulation/demodulation system.
>
> In fact testing is being performed this week which may affect more
> critical receivers (other than inexpensive "Atomic Clock" stuff).
>
> http://www.nist.gov/pml/**div688/grp40/wwvb.cfm
>
> --
> Joe Leikhim
> President
>
> Leikhim and Associates
> Oviedo Florida
>
> 407-982-0446
>
> jleik...@leikhim.com
>
> www.leikhim.com
>
>
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[time-nuts] WWV

[Joe Leikhim]

Brad;
I believe there are plans to eventually phase in a more reliable phase 
modulation/demodulation system.


In fact testing is being performed this week which may affect more 
critical receivers (other than inexpensive "Atomic Clock" stuff).


http://www.nist.gov/pml/div688/grp40/wwvb.cfm

--
Joe Leikhim
President

Leikhim and Associates
Oviedo Florida

407-982-0446

jleik...@leikhim.com

www.leikhim.com


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Re: [time-nuts] Understanding Oliver Collins Paper "Design of Low Jitter Hard Limiters"

[Hal Murray]

jmulc...@cox.net said:
> The amount of jitter verses logic family is all over the place as well. Take
> a look at an LS verses an HCT vs an S family and you will see what I mean.
> Some of them are very nasty, and are not all created equally.

Is there any collection of hard data?  How much does it depend upon 
manufacturer or test setup?  How much couples through from power supply?

Does the jitter scale with prop-time?

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[time-nuts] WWV

[Brad Dye]

There is a thread on http://tech.groups.yahoo.com/group/FMT-nuts/ with many 
observations of WWV reporting the wrong time. Here is a clip of just one of 
them:

> FYI,
> 
> I tuned into WWV this evening (August 19, 2012 UTC), and was surprised to hear
> the station making some incorrect audio time announcements.
> 
> Specifically,
> 
> 23:20 UTC was announced as 23:28 with no audio tone
> 23:23 UTC was announced as 23:29 with an audio tone
> 23:25 UTC was announced as 23:29 with an audio tone
> 23:26 UTC was announced as 23:29 with an audio tone
> 23:27 UTC was announced as 23:29 with an audio tone
> 23:28 UTC was announced as 23:28 with an audio tone
> 23:29 UTC was announced as 23:29 but was followed by station ID
> 23:30 UTC was announced as 23:30 with an audio tone (no ID)
> 23:32 UTC was announced as 23:35 with an audio tone
> 23:44 UTC was announced as 23:49 with no audio tone
> 23:57 UTC was announced as 23:59 with no audio tone
> 23:58 UTC was announced as 23:59 with no audio tone
> 
> I did not take notice as to whether the audio tones being transmitted were the
> correct ones for the particular minute, but some of the silent periods and the
> timing of the station ID appeared to be out of character.
> 
> I notified NIST of these unusual observations.
> 
> 
> 73, de John, KD2BD

I was able to verify this by listening to WWV and comparing the time 
announcements with my GPS-DO. The time was not consistently announced wrong -- 
just every few minutes (like above). I am sorry I didn't keep a better log of 
the exact time and frequency where I heard this. I just assumed that since so 
many guys were reporting the same thing that the WWV staff would know about it. 
I was surprised when they didn't.

Best regards,

Brad Dye
Editor, Wireless Messaging News
P.O. Box 266
Fairfield, IL  62837 USA
Telephone: 618-599-7869
Skype: braddye
http://www.braddye.com


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Re: [time-nuts] Interesting Loran-C antenna pictures

[paul swed]

Great pix.
Thanks. My tower isn't quite that large. Look at the cables!
Regards
Paul
WB8TSL

On Wed, Aug 22, 2012 at 8:01 PM, Michael Blazer  wrote:

> Wow, what a view.  How does the advice go, "Don't look down"?
>
>
> On 8/22/2012 9:22 AM, Poul-Henning Kamp wrote:
>
>> http://www.jan-mayen.no/
>>
>> press "news"
>>
>> Look for 21. august.
>>
>> The last picture is particularly interesting:
>>
>> http://www.jan-mayen.no/nyhet/**2012/08_august/C-%20mast/C-**
>> mast%208b.JPG
>>
>> Here you can see both the top-hat which forms the capacitance, they
>> guy-wires which hold the mast in place and the ground-grid which
>> forms the other electrode.
>>
>>
>
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Re: [time-nuts] HP-5065a bought and finally working!

[paul swed]

Edgardo congratulations. The 5065 is a really nice unit. I have one also
but earlier and luckily my manuals are on the internet.
It could be disciplined but the fact is for me at least I do not want to.
Leave a great device as is. There are lots of cheap RBs around and even
nice oscillators that can be disciplined.
Hack those and leave 5065 clean and complete it will serve you very well.
Good luck.
Regards
Paul.

On Wed, Aug 22, 2012 at 5:18 PM,  wrote:

> You can discipline a HP 5065A easily using a Shera with the  Tbolt  1 PPS
> and a LTC 1655 DAC in stead of an AD 1861.
> Bert Kehren.
>
>
> In a message dated 8/22/2012 8:23:06 A.M. Eastern Daylight Time,
> jlt...@att.net writes:
>
> Edgardo,
>
> Congrats on getting the 5065A up and  operational.  Make sure the A11 Board
> (Temperature Controller) is all  OK.  Failure there can destroy the A12
> RVFR
> Assembly.  There is a  lot of 'expertise' on the list for this unit.
>
> What is the serial number  of your unit and what is the part number of the
> manual you have?
>
> I  have a couple of manuals and I may also have the 'change sheets'  that
> updates the manual to your serial number.  It may take me a while  to chase
> that down but if I have the 'change sheets', I can scan them and  send them
> to you.
>
> I have not heard of anyone 'disciplining' the  5065A by GPS, other than by
> hand from week to week.  However, the 105B  has a built in connection on
> the
> back that is great for that purpose  (negative slope, as I recall) and I
> have
> done that using a Brooks Shera  controller board and the 1 PPS from my
> TBolt.
> It works quite  well.
>
> Joe
>
> -Original Message-
> From:  time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
> Behalf Of  Edgardo Molina
> Sent: Wednesday, August 22, 2012 12:22 AM
> To:  time-nuts@febo.com
> Subject: [time-nuts] HP-5065a bought and finally  working!
>
>
> Dear Group,
>
> I wish you well.
>
> Do you recall a  message and thread about a month ago with my concerns
> about
> buying a used /  unknown condition HP-5065a rubidium frequency standard? I
> bit the bullet  and bought it. Almost mint condition (cosmetically
> speaking)
> and with  several operational issues.
>
> Well, It took me several weeks to put it  back to work. Several capacitors
> on
> several boards along with a couple of  transistors and an IC were replaced.
> After that any being bored by the  yellow light, it finally came off to
> allow
> a beautiful green lock condition  light. I went through the necessary steps
> to tune it and calibrate it. Now,  as I have been told recently. "You have
> been bitten by the Time Nuts bug."  I am not complaining at all.
>
> Now the technical issues if you kindly  allow:
>
> a. Does anybody have an HP-5065a manual for the latest versions?  Mine
> (which
> I downloaded from the Internet) is intended for earlier  versions. It seems
> I
> have one of the last produced units. I would kindly  appreciate any help on
> this and I am willing to pay for time and expenses  to anybody who could
> help. During the repair process I found several  differences in the earlier
> versions design and had to figure out hoy mine  works.
>
> b. Is it possible to build a GPSDRb? I would like to know if it  is
> reasonable to pursue the goal to discipline the 5065a with a TB which I
> also
> got recently.
>
> c. I am waiting for the delivery of a recent  purchase. An HP-59309a
> Digital
> Clock to go with the HP 5065a. How I wish I  could find the optional LED
> integrated optional clock and 1PPS output. Is  my purchase a good match for
> the 5065a? Any other suggestions to drive a  clock?
>
> d. I am waiting also for de delivery of an HP-105b mint  condition quartz
> frequency standard. Would a second 59309a make sense to  use it with this
> quartz standard? Or just saving it for a Cesium? Anybody  willing to sell a
> spare, dust gathering, clean unit to me?
>
> e. Any  suggestions for software of lab equipment to measure my experiments
> like  AD, jitter, phase comparisons, etc?
>
>
> While I wait I am doing some  experiments with a FE Rb standard to
> discipline
> an Adret synthesiser to  output 32.768 KHz to directly drive a Nixie clock
> kit I just finished  building.
>
> Your comments are surely welcome. Thank you!
>
> Kind  regards,
>
>
> Edgardo  Molina
> XE1XUS
> Mexico
>
>
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Re: [time-nuts] Understanding Oliver Collins Paper "Design of Low Jitter Hard Limiters"

[Jerry Mulchin]

The amount of jitter verses logic family is all over the place as well.
Take a look at an LS verses an HCT vs an S family and you will see what I mean.
Some of them are very nasty, and are not all created equally.

Jerry

At 09:58 AM 8/22/2012, you wrote:
>I was not measuring cycle to cycle jitter but the input to output
>jitter of a TTL gate itself when used as part of a delay circuit.  The
>input circuit and input waveform to the gate are very similar to what
>would be expected in a sine wave zero crossing detector.
>
>Using a 7S11/7T11 in sequential sampling mode, I could see the jitter
>fine on any analog 7000 series oscilloscope but to get a nicer photo,
>I used a 7834 in variable persistence mode.  The trigger occurs about
>80ns before the displayed fast rise pulse.  Most of the jitter is a
>product of the low power supply rejection of the TTL gate and input
>circuit.
>
>http://www.banishedsouls.org/c2df3757f1/PG506/PDJ%20Test%201b%20-%201.jpg
>
>Using hard limiting before the zero crossing detector will relax the
>design of the later significantly.  Differential signal paths would
>help considerably as well.
>
> From going through the manuals and specifications, I am just not sure
>the TDS220 or TDS3012 has the time base resolution necessary to
>compare the jitter from the two different designs.  On my 2440, it was
>very difficult to see any difference between no jitter and the jitter
>in the example I linked above.
>
>On Wed, 22 Aug 2012 15:44:10 +0200, Azelio Boriani
> wrote:
>
>>According to
>>
>>http://cp.literature.agilent.com/litweb/pdf/5989-8794EN.pdf
>>
>>the real time sampling scope (like the TDS220 or TDS3012) can measure cycle
>>to cycle jitter directly, whereas the equivalent time sampling has only one
>>sample each trigger and a little delay on the sampling point for the next
>>trigger. The displayed waveform is a sort of "sum" of more than one cycle
>>and now I can't figure out what type of picture this can give. The TDS3012
>>has also the advantage of the Digital Phosphor behavior that can be useful
>>for the jitter analysis. Maybe a stable timebase and low jitter external
>>trigger input are essential. Unfortunately the TDS3012 has a 200ppm
>>timebase...
>>
>>On Wed, Aug 22, 2012 at 2:54 PM, David  wrote:
>>
>>> Do you mean with a 7404 hex inverter?  I actually did something like
>>> this recently while adding a 75ns pre-trigger pulse to an existing
>>> fast rise pulse generator.
>>>
>>> The pre-trigger pulse ended up having significant pattern dependant
>>> jitter caused by the adjacent TTL divider chain modulating the supply
>>> voltage and the poor power supply rejection of the 7404.  I was easily
>>> able to see the jitter on my 7T11 sampling oscilloscope but on my 2440
>>> (20 GS/sec equivalent time sampling), it was barely perceptible if
>>> that despite ideal conditions.  The peak to peak jitter was about
>>> 100ps.
>>>
>>> As far as I could tell from the available online documentation, the
>>> TDS220 and TDS3012 have relatively low sample rates and do not support
>>> equivalent time sampling so I would expect them to show even less than
>>> my 2440.
>>>
>>> On Wed, 22 Aug 2012 11:55:11 +0200, Azelio Boriani
>>>  wrote:
>>>
>>> >In your opinion, if I build a 7404 ZCD and a hard limiter one, can I see
>>> >the jitter difference on a simple 'scope (Tek TDS220 or TDS3012) or do I
>>> >need the Wavecrest SIA3000?
>>> >
>>> >On Wed, Aug 22, 2012 at 1:37 AM, Bob Camp  wrote:
>>> >
>>> >> Hi
>>> >>
>>> >> Since the Collins approach "tunes" the system for a single frequency
>>> input
>>> >> (more or less), the approach is probably not the best for a "many
>>> decades"
>>> >> sort of frequency range. There are a number of things that he alludes
>>> to in
>>> >> the paper, but does not directly address. The most obvious is the
>>> >> temperature dependance of the "stuff" the system is made of. Another is
>>> the
>>> >> simple fact that a non-clipping linear amplifier is likely the best
>>> choice
>>> >> for a first stage, provide the input is not already near clipping.
>>> >>
>>> >> Bob
>>> >>
>>> >> On Aug 21, 2012, at 12:50 PM, raj_so...@agilent.com wrote:
>>> >>
>>> >> > Hello everyone,
>>> >> >
>>> >> > I am new to this forum.
>>> >> > It looks like a lively discussion on various topics.
>>> >> >
>>> >> > A colleague of mine here at Agilent pointed me to this paper entitled
>>> >> "The Design of Low Jitter Hard Limiters" by Oliver Collins. In Bruce
>>> >> Griffiths' precision time in frequency webpage, this paper is described
>>> as
>>> >> "seminal."
>>> >> > (http://www.ko4bb.com/~bruce/ZeroCrossingDetectors.html)
>>> >> >
>>> >> > Since I'm trying to create a limiter that will accept frequencies
>>> >> ranging from 1 MHz to 100 MHz, I thought it would be good to understand
>>> the
>>> >> conclusions of this paper (if not the mathematics as well).  The
>>> >> mathematics turned out to be quite challenging to decode. Has someone on
>>> >> this forum unraveled the equations? It appea

Re: [time-nuts] Trak 8821B ---- was Z3815A Internal SMA 10Mhz Output

[GandalfG8]

In a message dated 22/08/2012 21:30:36 GMT Daylight Time, b...@lysator.liu.se 
 writes:

Hi  Nigel,

>
> With regards to the Oncore VP carrier phase  measurement option, I'm  not
> too sure that the 8821B does  actually make use of that.

The "Z" is a pure software option, to enable  the phase capability already
in all of the VP receivers. So you pay extra,  but get exactly the same
hardware. Since they optimised away IRIG and other  function, I find it
unlikely they would have premium Z options in the VP if  it was not used. I
should try to snoop on the communication between the VP  and the
microcontroller in the 8821.
--
 
Hi Bjorn
 

It's obviously difficult to be sure one way or the other without checking  
as you suggest, but I was also taking into consideration some Motorola 
published  data from 1996 and 1998.
 

The information provided in "Oncore Product Summary" of October 1996, and  
"Oncore Model Number and Feature Cross-Reference" of October 1998, is quite  
concise so perhaps nowhere near the whole story, but 
it does indicate that whilst four of the six VP models available in 1996,  
two with the Z option and two without, had a specified 1PPS accuracy of less 
 than 50ns, which was otherwise matched only by the UTplus, amongst the VP 
models  available at the end of 1998 it was now only the Z versions that 
offered this  degree of accuracy.
 

Not only did the 1998 Z versions match the UTplus for 1PPS accuracy, they  
also offered a Differential GPS option which the UTplus did not, although  
perhaps that wasn't over important in this instance, and they were also the 
only  Oncores to offer Raw Satellite Data, again perhaps not particularly 
relevant but  all of which to me still suggests there could have been other 
reasons for  choosing them besides the carrier phase option, which ironically 
isn't even  listed amongst the options in the 1998 "Feature Cross-Reference" 
list:-)
 

 
I'm not trying to make a case either way, just keeping an open mind and  
still as unsure as I ever was:-), but it does seem that when these 8821Bs were 
 produced the three Z versions of the VP were probably the best all round  
performers in the range at that time, and that's not even considering the  
carrier phase option, so perhaps just generally perceived as the best bet  
regardless.
 

Aside from that, I've had my unit powered up for over 90 minutes now  and 
it seems to be settling down ok.
20 minutes or so after power up the status light came on, stayed on for a  
short while, and then proceeded to flash at what seemed like one flash per  
second for another 20 minutes or so before lighting up permanently again and 
 staying on ever since.
I don't remember seeing it flashing before, and so far I've only found  
reference in the 8821A manual to it being either on or off, any ideas on  that?
 

In what way were you seeing GPS problems?
I've got some commands from the manual that produce an error message  
rather than the indicated response but I'm assuming that's a firmware  
difference, and generally all is as I would expect, with regards to satellites  
tracked, position data, etc etc.
What I can't do right now is any accurate monitoring of the output  
frequency or 1PPS, just about everything round here is powered down whilst  I 
run 
in some new cables, but I would say all is looking pretty good so  far.
 







Regards
 

Nigel
GM8PZR
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Re: [time-nuts] Interesting Loran-C antenna pictures

[Michael Blazer]

Wow, what a view.  How does the advice go, "Don't look down"?

On 8/22/2012 9:22 AM, Poul-Henning Kamp wrote:

http://www.jan-mayen.no/

press "news"

Look for 21. august.

The last picture is particularly interesting:

http://www.jan-mayen.no/nyhet/2012/08_august/C-%20mast/C-mast%208b.JPG

Here you can see both the top-hat which forms the capacitance, they
guy-wires which hold the mast in place and the ground-grid which
forms the other electrode.




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Re: [time-nuts] T-Bolt Temperature

[Michael Blazer]

The DS1620 is located just behind the RS-232 connector. This is on the 
far corner from the oscillator.


Mike

On 8/22/2012 12:59 PM, Ron Ward wrote:

Hi:
What is the temp chip reading? Is it reading the oven temperature or just
the ambient temperature?
Ron

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Azelio Boriani
Sent: Friday, August 17, 2012 7:57 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] T-Bolt Temperature

No, IIRC the problem is indeed with the chip because the new silicon
release has no higher resolution temperature reading. The old chip allows
this reading via an unofficial feature that the new chip has no longer. The
TBolt firmware exploits this unofficial (but documented and known) method
of reading.

On Fri, Aug 17, 2012 at 3:29 PM,  wrote:


It would be a worthy hack (in the classic sense) to extract the Tbolt
firmware and patch it to work with the current temperature chips.

--

  Björn


Hi

Just in case this inadvertently heads of in the wrong direction….

Lady Heather displays exactly what the TBolt firmware comes up with. The
disconnect with the new sensor chip is between the TBolt firmware and

the

chip it's self.

Bob

On Aug 16, 2012, at 10:37 PM, Arthur Dent 
wrote:


Do you know the part number of a chip to replace the DS1620?

The part number is the same, DS1620. What is important is the
revision of the DS1620. When Dallas Semiconductor/Maxim
'improved' the chip and went from REV-D (or D2) to REV-E they
made a change in the way the data was sent to the outside world.
Lady Heather displays the temperature from REV-E chips in
distinct step instead of a smooth curve.

  I have used REV-C2 chips as replacement and they work just
fine. Note the chip revision has little or nothing to do with the
Trimble REV letter on the outside of the Thunderbolt case, the
latest Thunderbolt revision from 2005 just happens to be a
REV-E.

-Arthur
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Re: [time-nuts] HP-5065a bought and finally working!

[EWKehren]

You can discipline a HP 5065A easily using a Shera with the  Tbolt  1 PPS 
and a LTC 1655 DAC in stead of an AD 1861.
Bert Kehren.
 
 
In a message dated 8/22/2012 8:23:06 A.M. Eastern Daylight Time,  
jlt...@att.net writes:

Edgardo,

Congrats on getting the 5065A up and  operational.  Make sure the A11 Board
(Temperature Controller) is all  OK.  Failure there can destroy the A12 RVFR
Assembly.  There is a  lot of 'expertise' on the list for this unit.

What is the serial number  of your unit and what is the part number of the
manual you have?

I  have a couple of manuals and I may also have the 'change sheets'  that
updates the manual to your serial number.  It may take me a while  to chase
that down but if I have the 'change sheets', I can scan them and  send them
to you.

I have not heard of anyone 'disciplining' the  5065A by GPS, other than by
hand from week to week.  However, the 105B  has a built in connection on the
back that is great for that purpose  (negative slope, as I recall) and I 
have
done that using a Brooks Shera  controller board and the 1 PPS from my 
TBolt.
It works quite  well.

Joe

-Original Message-
From:  time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of  Edgardo Molina
Sent: Wednesday, August 22, 2012 12:22 AM
To:  time-nuts@febo.com
Subject: [time-nuts] HP-5065a bought and finally  working!


Dear Group,

I wish you well.

Do you recall a  message and thread about a month ago with my concerns about
buying a used /  unknown condition HP-5065a rubidium frequency standard? I
bit the bullet  and bought it. Almost mint condition (cosmetically speaking)
and with  several operational issues. 

Well, It took me several weeks to put it  back to work. Several capacitors 
on
several boards along with a couple of  transistors and an IC were replaced.
After that any being bored by the  yellow light, it finally came off to 
allow
a beautiful green lock condition  light. I went through the necessary steps
to tune it and calibrate it. Now,  as I have been told recently. "You have
been bitten by the Time Nuts bug."  I am not complaining at all.

Now the technical issues if you kindly  allow:

a. Does anybody have an HP-5065a manual for the latest versions?  Mine 
(which
I downloaded from the Internet) is intended for earlier  versions. It seems 
I
have one of the last produced units. I would kindly  appreciate any help on
this and I am willing to pay for time and expenses  to anybody who could
help. During the repair process I found several  differences in the earlier
versions design and had to figure out hoy mine  works.

b. Is it possible to build a GPSDRb? I would like to know if it  is
reasonable to pursue the goal to discipline the 5065a with a TB which I  
also
got recently. 

c. I am waiting for the delivery of a recent  purchase. An HP-59309a Digital
Clock to go with the HP 5065a. How I wish I  could find the optional LED
integrated optional clock and 1PPS output. Is  my purchase a good match for
the 5065a? Any other suggestions to drive a  clock?

d. I am waiting also for de delivery of an HP-105b mint  condition quartz
frequency standard. Would a second 59309a make sense to  use it with this
quartz standard? Or just saving it for a Cesium? Anybody  willing to sell a
spare, dust gathering, clean unit to me?

e. Any  suggestions for software of lab equipment to measure my experiments
like  AD, jitter, phase comparisons, etc?


While I wait I am doing some  experiments with a FE Rb standard to 
discipline
an Adret synthesiser to  output 32.768 KHz to directly drive a Nixie clock
kit I just finished  building.

Your comments are surely welcome. Thank you!

Kind  regards,


Edgardo  Molina
XE1XUS
Mexico


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Re: [time-nuts] WWV

[Tom Miller]

I have one of the "atomic" clocks that sets itself via WWVB to keep time. 
Yesterday, Tuesday, AM it was an hour fast. Today it went back an hour to 
the correct time.


Strange.


Tom

- Original Message - 
From: "KD0GLS" 
To: "Discussion of precise time and frequency measurement" 


Sent: Wednesday, August 22, 2012 12:58 PM
Subject: Re: [time-nuts] WWV


Brad,
Could you please elaborate on what exactly you heard, and when, so we can 
keep our ears ready?


On Aug 22, 2012, at 11:30, Brad Dye  wrote:

Thought you guys might like to read this and maybe send them some more 
reports:



-Original Message-
From: Brad Dye [
mailto:b...@braddye.com
Sent: Tuesday, August 21, 2012 2:36 PM
To: inquiry
Subject: WWV Voice Time Announcements

Have you posted any official news about WWV intermittently reporting the 
wrong time? I would like to include it in my newsletter. By the way, I 
have verified this by listening myself.


Best regards,

Brad Dye
Editor, Wireless Messaging News
P.O. Box 266
Fairfield, IL  62837 USA
Telephone: 618-599-7869
Skype: braddye
http://www.braddye.com





Dear Mr. Dye,

We have not posted a report on WWV reporting the wrong time.  We have had 
only 1 outside suggestion that there was a broadcast of the wrong time 
and our investigation has not confirmed that.  We have found a low 
voltage on a power supply board feeding the voice which may have led to 
some problems, but that has now been replaced.  If you have further 
evidence or other reports concerning this matter we would appreciate that 
information.  You are only the second person to inquire about this issue. 
We take this very seriously, but normally when there are mistakes or 
problems with our broadcast we receive dozens of reports immediatly.


Please let us know and regards,

John Lowe
WWV Station Manager








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Re: [time-nuts] Trak 8821B ---- was Z3815A Internal SMA 10Mhz Output

[bg]

Hi Nigel,

>
> With regards to the Oncore VP carrier phase measurement option, I'm  not
> too sure that the 8821B does actually make use of that.

The "Z" is a pure software option, to enable the phase capability already
in all of the VP receivers. So you pay extra, but get exactly the same
hardware. Since they optimised away IRIG and other function, I find it
unlikely they would have premium Z options in the VP if it was not used. I
should try to snoop on the communication between the VP and the
microcontroller in the 8821.

--

   Björn


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Re: [time-nuts] T-Bolt Temperature

[Azelio Boriani]

Yes, ambient/board temperature, not the OCXO oven temperature.

On Wed, Aug 22, 2012 at 8:12 PM, Arthur Dent wrote:

> >Hi:
> >What is the temp chip reading? Is it reading the oven temperature or just
> >the ambient temperature?
> >Ron
> >
>
> The DS1620 thermometer chip is in the corner of the pc board next to the
> RS232 connector and diagonally opposite the OXCO so it reads ambient
> temperature.
>
> -Arthur
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Re: [time-nuts] Trak 8821B ---- was Z3815A Internal SMA 10Mhz Output

[GandalfG8]

In a message dated 22/08/2012 19:21:03 GMT Daylight Time, gandal...@aol.com 
 writes:

With regards to the Oncore VP carrier phase measurement option, I'm  not 
too sure that the 8821B does actually make use of that.
 
My 8821B, manufactured in 1999, does contain the 8 channel  Oncore VP 
B8121Z116 as I mentioned previously, and the 8821 data sheet  from 2004 does 
refer to all 8821 models as using an 8 channel receiver, but  the 8821A manual 
from 1997 refers to that as using a 6 channel  receiver.
Given that the only obvious difference between the 8821A and 8821B seems  
to be the oscillator module I'm assuming the change to the 8 channel  
receiver would have occured simultaneously for both versions, and am  wondering 
if 
that might not just have been based on availability rather  than to take 
advantage of any  technical enhancements.

 
-
 
Whoops, need to get better reading glasses!
 

It was a 2002 datasheet stated the 8821 used an 8 channel receiver  and in 
an October 2003 datasheet this had increased to 12 channels, I still  
suspect that these were changes inflicted by availability.
 

Regards
 

Nigel
GM8PZR
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Re: [time-nuts] Understanding Oliver Collins Paper "Design of Low Jitter Hard Limiters"

[Bruce Griffiths]

Once the gain stages enter saturation their noise contribution decreases 
significantly in a well designed limiter stage.
The noise contribution is assumed to be zero in this state by the 
Collins paper.
In practice, at least for low frequency limiters, power supply noise may 
be an issue if the limiter output isnt diode clamped.


The slope gain g isnt equal to the voltage gain G due to the effect of 
the low pass filter on the amplifier stage output slew rate.


Bruce

raj_so...@agilent.com wrote:

Hello Everyone,

Thanks to Azelio, Bob and David for their comments.  Special thanks to Magnus 
for clarifying the intent of this paper. I think I begin to understand the 'k' 
term.

When I look at jitter, I actually look at residual phase noise using the E5500 
phase noise measurement system. One could use a sampling oscilloscope with a 
clean trigger to do something similar, but for what we do here, customers want 
to know phase noise spectral density versus frequency.  I have found the region 
between 1 Hz and 100 Hz offsets to be particularly challenging. Jason 
Breitbarth, CEO of Holtzworth, wrote a nice paper for microwave Journal on 
residual phase noise.
http://www.holzworth.com/Aux_docs/PhaseNoise_Article_MWJ_Jun08.pdf

I have thought more critically about my block diagram, and fortunately, I'm not 
trying to square up sine waves from 1 MHz to 100 MHz.  These are generated 
using ECL counters and re-clocking. Just yesterday, I proved to myself that 
this was working correctly. But there is a situation where I submit a 100 MHz 
sine wave to this limiter, which then serves as the reference for a phase lock 
loop. The residual noise of the loop is much higher when the LO is a sine wave 
as compared to when driven by a square wave.  This is straightforward to 
visualize. A zero crossing detector will be much more sensitive to noise when 
the input is a shallow sloped sine wave as compared to a sharp edged square 
wave.  Perhaps I just need to tinker with the limiter, checking supply noise 
suppression, thermal noise, etc.

Magnus makes a very good point that the paper only considers a simplified model using 
white noise as the input. Perhaps once the mathematics have been understood, one could 
extend the analysis to include 1/f noise at 10 Hz and 100 Hz. But even with white noise 
input, the mathematics seem crazy hard.  I asked around a couple of folks around here, 
and the typical response was "has been too many years since I looked at this type of 
math."  So this could be a good way for me to refresh.

In figures 2 and 3, Collins presents the basic model. An input signal rises 
from 0 V to V V between times 0 and T. The input slope 'rho_in' is V/T.  Going 
through an amplifier of gain G, the output waveform is sharper, transitioning 
from 0 V to V V between times 0 and T/G.  The output slope during the 
transition period could be related as rho_out (output slope) = g (slope gain) * 
rho_in (input slope). Dividing the basic voltage gain equation Vout = G * Vin 
by time, can we reasonably say that voltage gain G is the same as slope gain g?

Assuming white noise at the input of variance No, the autocorrelation function is 
Rxx(tau) = No*delta(tau). Submitting the amplified random signal through a simple 
RC low pass filter, we obtain the result of equation 2. In the development of 
equation 3, the author states that the noise input is not applied for all time.  
Rather, it is turned on at time 0 and turned off at time T/G. So equation 3a is a 
reasonable modification of equation 2; rather than integrate from zero to 
infinity, integrate from zero to 'th', the threshold crossing time. But equation 
3b has me spinning my wheels.  For th>  T/G, noise deposited to the capacitor 
in the filter is now dissipating? But we do not consider noise added once the 
limiter has saturated, or do we?

Yours

Raj



-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf 
Of Azelio Boriani
Sent: Wednesday, August 22, 2012 6:44 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Understanding Oliver Collins Paper "Design of Low Jitter 
Hard Limiters"

According to

http://cp.literature.agilent.com/litweb/pdf/5989-8794EN.pdf

the real time sampling scope (like the TDS220 or TDS3012) can measure cycle to cycle 
jitter directly, whereas the equivalent time sampling has only one sample each trigger 
and a little delay on the sampling point for the next trigger. The displayed waveform is 
a sort of "sum" of more than one cycle and now I can't figure out what type of 
picture this can give. The TDS3012 has also the advantage of the Digital Phosphor 
behavior that can be useful for the jitter analysis. Maybe a stable timebase and low 
jitter external trigger input are essential. Unfortunately the TDS3012 has a 200ppm 
timebase...

On Wed, Aug 22, 2012 at 2:54 PM, David  wrote:

   

Do you mean with a 7404 hex inverter?  I actually did something

Re: [time-nuts] Trak 8821B ---- was Z3815A Internal SMA 10Mhz Output

[GandalfG8]

Hi Bjorn
 
Mine did come from a UK Ebay seller in Scotland, just under four years ago, 
 and he told me at that time he had two more and we'd originally discussed  
swapping those two for a radio, until the first one arrived and my  
enthusiasm tailed off a bit:-)
 
It's been a while since I've had it running but I don't recall  any GPS 
problems, I'll run it up again later and see how it behaves now.
I do remember it needs a negative 48 Volt supply and am pretty sure also  
that it feeds 12 Volts to the antenna.
 
Although the choice of oscillator shouldn't affect the IRIG B output it did 
 occur to me after posting earlier that it might have affected the 
programming  for the Low-Rate output, and if the 1MPPS had been generated from 
10MHz 
by  a simple hardware divider, for example, then switching the oscillator 
to  16.384MHz might have been less than ideal for that function:-)
 
With regards to the Oncore VP carrier phase measurement option, I'm  not 
too sure that the 8821B does actually make use of that.
 
My 8821B, manufactured in 1999, does contain the 8 channel Oncore  VP 
B8121Z116 as I mentioned previously, and the 8821 data sheet from 2004  does 
refer to all 8821 models as using an 8 channel receiver, but the 8821A  manual 
from 1997 refers to that as using a 6 channel receiver.
Given that the only obvious difference between the 8821A and 8821B seems to 
 be the oscillator module I'm assuming the change to the 8 channel receiver 
 would have occured simultaneously for both versions, and am wondering if  
that might not just have been based on availability rather than to take  
advantage of any technical enhancements.
 
Regards
 
Nigel
GM8PZR
-
 
 
 
In a message dated 22/08/2012 14:55:03 GMT Daylight Time, b...@lysator.liu.se 
 writes:

Hi  Nigel,

Yes, I have the same version. We might have got it from the same  UK epay
source. The GPS did not work reliably, and I did start testing that  module
outside the Trak unit, and also tried VP(8chan) receivers that I  had. Did
not really conclude why the GPS did not behave properly. I was,  like you,
disappointed by the lack of IRIG and other features that are in  the
standard units. I also drew the conclusion this was a "high  volume"
special model, where it was cost effective to eliminate all - for  the
specific application - unuseful outputs.

However it is a very  decent size OCXO inside.

The phase measurement Oncore model is  interesting, since I have seen very
few GPSDOs that use phase information.  It gives the possibility to reduce
the short term GPS noise to cm/s level.  However this is probably lost in
the PPS generation hardware, since the  Oncore does not lock its internal
crystal to the external  OCXO.

--

Björn

> Hi  Bjorn
>
> Is yours also the cut down 2.084MHz version, or do you  have a "proper"
> 8821B with a more useful GPSDO frequency and all the  outputs fitted?
> I think this one was originally used in a trunked  radio  system.
>
> I've just checked and the fitted VP Oncore  is  the B8121Z116, so perhaps
> the same module, but I'd forgotten  until I  looked again that the unit is
> without the IRIG-B output  as well  as the Low-Rate output that normally
> allows a
>  variety of pre-set pulse rates,  hence my "cut down"  comment.
>
> The Low-Rate ouput speciification suggests some  interesting  
possibilities
> for experiments in conditioning other  oscillators, as  amongst some very
> slow pulse rates it also  offered an option of 1  MPPS.
> Unfortunately, not only are the  connectors not fitted but quite a lot of
> presumably associated PCB  components in that area are also missing.
>
> Do you have a manual  for the 8821B?
> I've only ever found a manual for the 8821A, although I  suspect the  only
> significant difference may be the fitting of  the larger B7A OCXO  to the
> 8821B, which necessitated the height  increase to 2U, but it would be nice
> to be
> able to compare  them.
>
> regards
>
> Nigel
>  GM8PZR
>
> In a message dated 21/08/2012 21:05:02 GMT Daylight  Time,
> b...@lysator.liu.se
>  writes:
>
> Hi   Nigel,
>
> Have one of those Trak 8821B too. It is a bit  interesting since  the
> Motorola Oncore VP inside mine has the Z  option (phase  measurement).
>
> --
>
>  Björn
>
>
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[time-nuts] T-Bolt Temperature

[Arthur Dent]

>Hi:
>What is the temp chip reading? Is it reading the oven temperature or just
>the ambient temperature?
>Ron
>

The DS1620 thermometer chip is in the corner of the pc board next to the 
RS232 connector and diagonally opposite the OXCO so it reads ambient 
temperature.

-Arthur
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Re: [time-nuts] T-Bolt Temperature

[Ron Ward]

Hi:
What is the temp chip reading? Is it reading the oven temperature or just
the ambient temperature?
Ron

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Azelio Boriani
Sent: Friday, August 17, 2012 7:57 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] T-Bolt Temperature

No, IIRC the problem is indeed with the chip because the new silicon
release has no higher resolution temperature reading. The old chip allows
this reading via an unofficial feature that the new chip has no longer. The
TBolt firmware exploits this unofficial (but documented and known) method
of reading.

On Fri, Aug 17, 2012 at 3:29 PM,  wrote:

> It would be a worthy hack (in the classic sense) to extract the Tbolt
> firmware and patch it to work with the current temperature chips.
>
> --
>
>  Björn
>
> > Hi
> >
> > Just in case this inadvertently heads of in the wrong direction….
> >
> > Lady Heather displays exactly what the TBolt firmware comes up with. The
> > disconnect with the new sensor chip is between the TBolt firmware and
the
> > chip it's self.
> >
> > Bob
> >
> > On Aug 16, 2012, at 10:37 PM, Arthur Dent 
> > wrote:
> >
> >>> Do you know the part number of a chip to replace the DS1620?
> >>
> >> The part number is the same, DS1620. What is important is the
> >> revision of the DS1620. When Dallas Semiconductor/Maxim
> >> 'improved' the chip and went from REV-D (or D2) to REV-E they
> >> made a change in the way the data was sent to the outside world.
> >> Lady Heather displays the temperature from REV-E chips in
> >> distinct step instead of a smooth curve.
> >>
> >>  I have used REV-C2 chips as replacement and they work just
> >> fine. Note the chip revision has little or nothing to do with the
> >> Trimble REV letter on the outside of the Thunderbolt case, the
> >> latest Thunderbolt revision from 2005 just happens to be a
> >> REV-E.
> >>
> >> -Arthur
> >> ___
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> >> and follow the instructions there.
> >
> >
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> >
>
>
>
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Re: [time-nuts] WWV

[KD0GLS]

Brad,
Could you please elaborate on what exactly you heard, and when, so we can keep 
our ears ready?

On Aug 22, 2012, at 11:30, Brad Dye  wrote:

> Thought you guys might like to read this and maybe send them some more 
> reports:
> 
>> -Original Message-
>> From: Brad Dye [
>> mailto:b...@braddye.com
>> Sent: Tuesday, August 21, 2012 2:36 PM
>> To: inquiry
>> Subject: WWV Voice Time Announcements
>> 
>> Have you posted any official news about WWV intermittently reporting the 
>> wrong time? I would like to include it in my newsletter. By the way, I have 
>> verified this by listening myself.
>> 
>> Best regards,
>> 
>> Brad Dye
>> Editor, Wireless Messaging News
>> P.O. Box 266
>> Fairfield, IL  62837 USA
>> Telephone: 618-599-7869
>> Skype: braddye
>> http://www.braddye.com
> 
> 
> 
>> Dear Mr. Dye,
>> 
>> We have not posted a report on WWV reporting the wrong time.  We have had 
>> only 1 outside suggestion that there was a broadcast of the wrong time and 
>> our investigation has not confirmed that.  We have found a low voltage on a 
>> power supply board feeding the voice which may have led to some problems, 
>> but that has now been replaced.  If you have further evidence or other 
>> reports concerning this matter we would appreciate that information.  You 
>> are only the second person to inquire about this issue.  We take this very 
>> seriously, but normally when there are mistakes or problems with our 
>> broadcast we receive dozens of reports immediatly.
>> 
>> Please let us know and regards,
>> 
>> John Lowe
>> WWV Station Manager
>> 
> 
> 
> 
> 
> 
> 
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Re: [time-nuts] Understanding Oliver Collins Paper "Design of Low Jitter Hard Limiters"

[David]

I was not measuring cycle to cycle jitter but the input to output
jitter of a TTL gate itself when used as part of a delay circuit.  The
input circuit and input waveform to the gate are very similar to what
would be expected in a sine wave zero crossing detector.

Using a 7S11/7T11 in sequential sampling mode, I could see the jitter
fine on any analog 7000 series oscilloscope but to get a nicer photo,
I used a 7834 in variable persistence mode.  The trigger occurs about
80ns before the displayed fast rise pulse.  Most of the jitter is a
product of the low power supply rejection of the TTL gate and input
circuit.

http://www.banishedsouls.org/c2df3757f1/PG506/PDJ%20Test%201b%20-%201.jpg

Using hard limiting before the zero crossing detector will relax the
design of the later significantly.  Differential signal paths would
help considerably as well.

>From going through the manuals and specifications, I am just not sure
the TDS220 or TDS3012 has the time base resolution necessary to
compare the jitter from the two different designs.  On my 2440, it was
very difficult to see any difference between no jitter and the jitter
in the example I linked above.

On Wed, 22 Aug 2012 15:44:10 +0200, Azelio Boriani
 wrote:

>According to
>
>http://cp.literature.agilent.com/litweb/pdf/5989-8794EN.pdf
>
>the real time sampling scope (like the TDS220 or TDS3012) can measure cycle
>to cycle jitter directly, whereas the equivalent time sampling has only one
>sample each trigger and a little delay on the sampling point for the next
>trigger. The displayed waveform is a sort of "sum" of more than one cycle
>and now I can't figure out what type of picture this can give. The TDS3012
>has also the advantage of the Digital Phosphor behavior that can be useful
>for the jitter analysis. Maybe a stable timebase and low jitter external
>trigger input are essential. Unfortunately the TDS3012 has a 200ppm
>timebase...
>
>On Wed, Aug 22, 2012 at 2:54 PM, David  wrote:
>
>> Do you mean with a 7404 hex inverter?  I actually did something like
>> this recently while adding a 75ns pre-trigger pulse to an existing
>> fast rise pulse generator.
>>
>> The pre-trigger pulse ended up having significant pattern dependant
>> jitter caused by the adjacent TTL divider chain modulating the supply
>> voltage and the poor power supply rejection of the 7404.  I was easily
>> able to see the jitter on my 7T11 sampling oscilloscope but on my 2440
>> (20 GS/sec equivalent time sampling), it was barely perceptible if
>> that despite ideal conditions.  The peak to peak jitter was about
>> 100ps.
>>
>> As far as I could tell from the available online documentation, the
>> TDS220 and TDS3012 have relatively low sample rates and do not support
>> equivalent time sampling so I would expect them to show even less than
>> my 2440.
>>
>> On Wed, 22 Aug 2012 11:55:11 +0200, Azelio Boriani
>>  wrote:
>>
>> >In your opinion, if I build a 7404 ZCD and a hard limiter one, can I see
>> >the jitter difference on a simple 'scope (Tek TDS220 or TDS3012) or do I
>> >need the Wavecrest SIA3000?
>> >
>> >On Wed, Aug 22, 2012 at 1:37 AM, Bob Camp  wrote:
>> >
>> >> Hi
>> >>
>> >> Since the Collins approach "tunes" the system for a single frequency
>> input
>> >> (more or less), the approach is probably not the best for a "many
>> decades"
>> >> sort of frequency range. There are a number of things that he alludes
>> to in
>> >> the paper, but does not directly address. The most obvious is the
>> >> temperature dependance of the "stuff" the system is made of. Another is
>> the
>> >> simple fact that a non-clipping linear amplifier is likely the best
>> choice
>> >> for a first stage, provide the input is not already near clipping.
>> >>
>> >> Bob
>> >>
>> >> On Aug 21, 2012, at 12:50 PM, raj_so...@agilent.com wrote:
>> >>
>> >> > Hello everyone,
>> >> >
>> >> > I am new to this forum.
>> >> > It looks like a lively discussion on various topics.
>> >> >
>> >> > A colleague of mine here at Agilent pointed me to this paper entitled
>> >> "The Design of Low Jitter Hard Limiters" by Oliver Collins. In Bruce
>> >> Griffiths' precision time in frequency webpage, this paper is described
>> as
>> >> "seminal."
>> >> > (http://www.ko4bb.com/~bruce/ZeroCrossingDetectors.html)
>> >> >
>> >> > Since I'm trying to create a limiter that will accept frequencies
>> >> ranging from 1 MHz to 100 MHz, I thought it would be good to understand
>> the
>> >> conclusions of this paper (if not the mathematics as well).  The
>> >> mathematics turned out to be quite challenging to decode. Has someone on
>> >> this forum unraveled the equations? It appears Collins has
>> recommendations
>> >> on the bandwidth and gain of a jitter minimizing limiter, and then
>> extends
>> >> this analysis to provide the bandwidth and gain of a cascade of
>> limiters.
>> >>  But the application is still fuzzy.  In figure 5, he shows a graph
>> showing
>> >> the dependence of jitter on crossing time.  Is the crossing time
>> (i

Re: [time-nuts] GPSD-Rb

[Azelio Boriani]

Exactly. Every GPSRb works by adjusting the C-field: sort of let me (the
algorithm/GPS pair) calibrate your Rb for the long term (aging) variation
that every Rb has. The Rb is not good in the long term (10 seconds),
not as good as a working and receiving GPS receiver. The Rb (as a whole)
*is* an expensive OCXO that has good short term stability, paired with a
disciplining algorithm and a GPS it becomes like a Cs (and maybe even
better in the short term).

On Wed, Aug 22, 2012 at 6:03 PM, Bob Camp  wrote:

> Hi
>
> The problem you run into with this approach is that it is relatively high
> jitter. You output "jumps" by what ever your microcontroller step time step
> size is every so often. Since that's going to be 10's or possibly 100's of
> ns, it's a major hit.
>
> Bob
>
> -Original Message-
> From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
> Behalf Of Michael Tharp
> Sent: Wednesday, August 22, 2012 10:47 AM
> To: time-nuts@febo.com
> Subject: Re: [time-nuts] GPSD-Rb
>
> On 08/22/2012 01:22 AM, Edgardo Molina wrote:
> > b. Is it possible to build a GPSDRb? I would like to know if it is
> reasonable to pursue the goal to discipline the 5065a with a TB which I
> also
> got recently.
>
> Some Rbs have a "C-field" input that can technically be used to
> discipline it, but this is not the approach I am going to take with
> mine. A Rb oscillator is internally an OCXO that is disciplined to the
> Rb physics package, with the goal of holding a frequency over a long
> period of time with the only variance coming from deficiencies in the
> measurement circuitry. Using the C-field to discipline it is kind of
> throwing out the long-term stability characteristics of the Rb and using
> it as an expensive OCXO. It's more interesting to me as a holdover
> source for a conventional GPSDO.
>
> The design I'm thinking of is to have a separate microcontroller clocked
> by the Rb that will generate a third pulse-per-second (the first two
> being the raw one from GPS and the divided-down local oscillator). As
> long as the GPS is locked the divider will not output pulses but will
> monitor the pulses from the local oscillator and use it to count the
> frequency of the Rb. Once lock is lost or holdover is manually engaged,
> then it stops counting and starts outputting pulse-per-second based on
> the last known average frequency it counted. The GPSDO would then
> continue normal disciplining based on the Rb pulses until GPS lock
> returns. Of course while locked the measured frequency would also be
> reported so that the Rb could be calibrated in situ.
>
> -- m. tharp
>
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Re: [time-nuts] WWV

[Brad Dye]

Thought you guys might like to read this and maybe send them some more reports:

>  -Original Message-
> From: Brad Dye [
> mailto:b...@braddye.com
> Sent: Tuesday, August 21, 2012 2:36 PM
> To: inquiry
> Subject: WWV Voice Time Announcements
> 
> Have you posted any official news about WWV intermittently reporting the 
> wrong time? I would like to include it in my newsletter. By the way, I have 
> verified this by listening myself.
> 
> Best regards,
> 
> Brad Dye
> Editor, Wireless Messaging News
> P.O. Box 266
> Fairfield, IL  62837 USA
> Telephone: 618-599-7869
> Skype: braddye
> http://www.braddye.com



> Dear Mr. Dye,
>  
> We have not posted a report on WWV reporting the wrong time.  We have had 
> only 1 outside suggestion that there was a broadcast of the wrong time and 
> our investigation has not confirmed that.  We have found a low voltage on a 
> power supply board feeding the voice which may have led to some problems, but 
> that has now been replaced.  If you have further evidence or other reports 
> concerning this matter we would appreciate that information.  You are only 
> the second person to inquire about this issue.  We take this very seriously, 
> but normally when there are mistakes or problems with our broadcast we 
> receive dozens of reports immediatly.
>  
> Please let us know and regards,
>  
> John Lowe
> WWV Station Manager
> 






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Re: [time-nuts] GPSD-Rb

[Chris Albertson]

On Wed, Aug 22, 2012 at 7:47 AM, Michael Tharp wrote:

>
> The design I'm thinking of is to have a separate microcontroller clocked
> by the Rb that will generate a third pulse-per-second


It is very hard to write a divers in software.  You have to use assembly
language and you have to mmake sure that EVERY path in every branch is has
exactly the same number of clock cycles.   And then you have to be lucky
that you can work out an exact integer division.

The above has been done but always the uP can't do anything else but the
divide down loop.  If you need some other background task use a second uP
chip.

I think a better way to do holdover is to use a stable OCXO that is phas
locked to some timing source and then, in real time you might switch to the
"best" source.   If one of your source is a 10MHz Rb then why divide that
down to 1Hz?  Use the 10Mhz output to drive the OCXO.

I can't draw a diagram so I'l use even more words... The "final" OCXO has
10Mhz output and is controlled by a PLL.   The PPL has two 10Mhz inputs
(references) it can choose from (1) the Rb and (2) a 10Mhz GPSDO.  I think
you need a uP to control the switch and also likely to manage the loop
constants inside the PLL.

I've been thinging about the because I have a few GPSes and an Rb also.
 That said this is not a high priority because in all the time I've been
doing this I've not once seen a need for holdover.  GPS seems to be 100%
reliable.

What I really want is a portable standard.  So rather then the above
I'mthinking about a GPS disiplined Rb.  Then I can unplug the GPS and take
the Rb where it is needed.



Chris Albertson
Redondo Beach, California
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Re: [time-nuts] Understanding Oliver Collins Paper "Design of Low Jitter Hard Limiters"

[raj_sodhi]

Hello Everyone,

Thanks to Azelio, Bob and David for their comments.  Special thanks to Magnus 
for clarifying the intent of this paper. I think I begin to understand the 'k' 
term.

When I look at jitter, I actually look at residual phase noise using the E5500 
phase noise measurement system. One could use a sampling oscilloscope with a 
clean trigger to do something similar, but for what we do here, customers want 
to know phase noise spectral density versus frequency.  I have found the region 
between 1 Hz and 100 Hz offsets to be particularly challenging. Jason 
Breitbarth, CEO of Holtzworth, wrote a nice paper for microwave Journal on 
residual phase noise.  
http://www.holzworth.com/Aux_docs/PhaseNoise_Article_MWJ_Jun08.pdf

I have thought more critically about my block diagram, and fortunately, I'm not 
trying to square up sine waves from 1 MHz to 100 MHz.  These are generated 
using ECL counters and re-clocking. Just yesterday, I proved to myself that 
this was working correctly. But there is a situation where I submit a 100 MHz 
sine wave to this limiter, which then serves as the reference for a phase lock 
loop. The residual noise of the loop is much higher when the LO is a sine wave 
as compared to when driven by a square wave.  This is straightforward to 
visualize. A zero crossing detector will be much more sensitive to noise when 
the input is a shallow sloped sine wave as compared to a sharp edged square 
wave.  Perhaps I just need to tinker with the limiter, checking supply noise 
suppression, thermal noise, etc.

Magnus makes a very good point that the paper only considers a simplified model 
using white noise as the input. Perhaps once the mathematics have been 
understood, one could extend the analysis to include 1/f noise at 10 Hz and 100 
Hz. But even with white noise input, the mathematics seem crazy hard.  I asked 
around a couple of folks around here, and the typical response was "has been 
too many years since I looked at this type of math."  So this could be a good 
way for me to refresh.

In figures 2 and 3, Collins presents the basic model. An input signal rises 
from 0 V to V V between times 0 and T. The input slope 'rho_in' is V/T.  Going 
through an amplifier of gain G, the output waveform is sharper, transitioning 
from 0 V to V V between times 0 and T/G.  The output slope during the 
transition period could be related as rho_out (output slope) = g (slope gain) * 
rho_in (input slope). Dividing the basic voltage gain equation Vout = G * Vin 
by time, can we reasonably say that voltage gain G is the same as slope gain g?

Assuming white noise at the input of variance No, the autocorrelation function 
is Rxx(tau) = No*delta(tau). Submitting the amplified random signal through a 
simple RC low pass filter, we obtain the result of equation 2. In the 
development of equation 3, the author states that the noise input is not 
applied for all time.  Rather, it is turned on at time 0 and turned off at time 
T/G. So equation 3a is a reasonable modification of equation 2; rather than 
integrate from zero to infinity, integrate from zero to 'th', the threshold 
crossing time. But equation 3b has me spinning my wheels.  For th > T/G, noise 
deposited to the capacitor in the filter is now dissipating? But we do not 
consider noise added once the limiter has saturated, or do we?

Yours

Raj



-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf 
Of Azelio Boriani
Sent: Wednesday, August 22, 2012 6:44 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Understanding Oliver Collins Paper "Design of Low 
Jitter Hard Limiters"

According to

http://cp.literature.agilent.com/litweb/pdf/5989-8794EN.pdf

the real time sampling scope (like the TDS220 or TDS3012) can measure cycle to 
cycle jitter directly, whereas the equivalent time sampling has only one sample 
each trigger and a little delay on the sampling point for the next trigger. The 
displayed waveform is a sort of "sum" of more than one cycle and now I can't 
figure out what type of picture this can give. The TDS3012 has also the 
advantage of the Digital Phosphor behavior that can be useful for the jitter 
analysis. Maybe a stable timebase and low jitter external trigger input are 
essential. Unfortunately the TDS3012 has a 200ppm timebase...

On Wed, Aug 22, 2012 at 2:54 PM, David  wrote:

> Do you mean with a 7404 hex inverter?  I actually did something like 
> this recently while adding a 75ns pre-trigger pulse to an existing 
> fast rise pulse generator.
>
> The pre-trigger pulse ended up having significant pattern dependant 
> jitter caused by the adjacent TTL divider chain modulating the supply 
> voltage and the poor power supply rejection of the 7404.  I was easily 
> able to see the jitter on my 7T11 sampling oscilloscope but on my 2440
> (20 GS/sec equivalent time sampling), it was barely perceptible if 
> that despite ideal conditions.  The

Re: [time-nuts] GPSD-Rb

[Bob Camp]

Hi

The problem you run into with this approach is that it is relatively high
jitter. You output "jumps" by what ever your microcontroller step time step
size is every so often. Since that's going to be 10's or possibly 100's of
ns, it's a major hit.

Bob

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Michael Tharp
Sent: Wednesday, August 22, 2012 10:47 AM
To: time-nuts@febo.com
Subject: Re: [time-nuts] GPSD-Rb

On 08/22/2012 01:22 AM, Edgardo Molina wrote:
> b. Is it possible to build a GPSDRb? I would like to know if it is
reasonable to pursue the goal to discipline the 5065a with a TB which I also
got recently.

Some Rbs have a "C-field" input that can technically be used to 
discipline it, but this is not the approach I am going to take with 
mine. A Rb oscillator is internally an OCXO that is disciplined to the 
Rb physics package, with the goal of holding a frequency over a long 
period of time with the only variance coming from deficiencies in the 
measurement circuitry. Using the C-field to discipline it is kind of 
throwing out the long-term stability characteristics of the Rb and using 
it as an expensive OCXO. It's more interesting to me as a holdover 
source for a conventional GPSDO.

The design I'm thinking of is to have a separate microcontroller clocked 
by the Rb that will generate a third pulse-per-second (the first two 
being the raw one from GPS and the divided-down local oscillator). As 
long as the GPS is locked the divider will not output pulses but will 
monitor the pulses from the local oscillator and use it to count the 
frequency of the Rb. Once lock is lost or holdover is manually engaged, 
then it stops counting and starts outputting pulse-per-second based on 
the last known average frequency it counted. The GPSDO would then 
continue normal disciplining based on the Rb pulses until GPS lock 
returns. Of course while locked the measured frequency would also be 
reported so that the Rb could be calibrated in situ.

-- m. tharp

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Re: [time-nuts] Understanding Oliver Collins Paper "Design of Low Jitter Hard Limiters"

[Bob Camp]

Hi

It depends very much on just how low a frequency sine wave you put into the
limiter. If you run low enough, then indeed you will be able to see the
difference. If the scope can display 1 ns jitter, then a 1 Hz sine wave is
likely to be low enough.

Bob

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Azelio Boriani
Sent: Wednesday, August 22, 2012 5:55 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Understanding Oliver Collins Paper "Design of Low
Jitter Hard Limiters"

In your opinion, if I build a 7404 ZCD and a hard limiter one, can I see
the jitter difference on a simple 'scope (Tek TDS220 or TDS3012) or do I
need the Wavecrest SIA3000?

On Wed, Aug 22, 2012 at 1:37 AM, Bob Camp  wrote:

> Hi
>
> Since the Collins approach "tunes" the system for a single frequency input
> (more or less), the approach is probably not the best for a "many decades"
> sort of frequency range. There are a number of things that he alludes to
in
> the paper, but does not directly address. The most obvious is the
> temperature dependance of the "stuff" the system is made of. Another is
the
> simple fact that a non-clipping linear amplifier is likely the best choice
> for a first stage, provide the input is not already near clipping.
>
> Bob
>
> On Aug 21, 2012, at 12:50 PM, raj_so...@agilent.com wrote:
>
> > Hello everyone,
> >
> > I am new to this forum.
> > It looks like a lively discussion on various topics.
> >
> > A colleague of mine here at Agilent pointed me to this paper entitled
> "The Design of Low Jitter Hard Limiters" by Oliver Collins. In Bruce
> Griffiths' precision time in frequency webpage, this paper is described as
> "seminal."
> > (http://www.ko4bb.com/~bruce/ZeroCrossingDetectors.html)
> >
> > Since I'm trying to create a limiter that will accept frequencies
> ranging from 1 MHz to 100 MHz, I thought it would be good to understand
the
> conclusions of this paper (if not the mathematics as well).  The
> mathematics turned out to be quite challenging to decode. Has someone on
> this forum unraveled the equations? It appears Collins has recommendations
> on the bandwidth and gain of a jitter minimizing limiter, and then extends
> this analysis to provide the bandwidth and gain of a cascade of limiters.
>  But the application is still fuzzy.  In figure 5, he shows a graph
showing
> the dependence of jitter on crossing time.  Is the crossing time (implied
> by equations 7) considered a design parameter one can vary? Also, on
figure
> 4, the "k" parameter has been varied to show the rising waveform as a
> function of "k".  The threshold is always assumed to be 0.5.  So could "k"
> be related to "tau", the time constant of the RC filter?
> >
> > Thanks in advance for all your help.
> >
> > Yours
> >
> > Raj
> >
> >
> >
> > ___
> > 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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Re: [time-nuts] Gray T Bolt

[Bob Camp]

Hi

The "gray" case is the original design case. For what ever reason, it turned
out to be a problem for at least one intended application. The final design
case flipped the board over to take care of what ever problem the original
orientation created.

Bob

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Michael Blazer
Sent: Tuesday, August 21, 2012 8:30 PM
To: time-nuts@febo.com
Subject: [time-nuts] Gray T Bolt

Does any one know about a gray cased Thunderbolt?  This unit is 
backwards from the gold box T-Bolt.  The circuit card is mounted on the 
non-flanged case half (that has the connector cutouts).  There is no 
serial number sticker, but does have the power supply sticker next to 
the connector.  And just for fun, the power connector is backwards from 
the gold box units.  You can guess the next line...
Does anyone need a T Bolt Aroma Therapy device?  One scent (not 
pleasant), slightly used, real cheap.

I was rearranging the bench and plugged a properly keyed power supply 
into the gray box.  The power supply that I did have on this unit 
doesn't have the keying lock.  Of course, this one has (had) the good 
DS1620 (D rev) chip.

Oh well, live and learn.

Mike

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Re: [time-nuts] GPSD-Rb

[Michael Tharp]

On 08/22/2012 01:22 AM, Edgardo Molina wrote:

b. Is it possible to build a GPSDRb? I would like to know if it is reasonable 
to pursue the goal to discipline the 5065a with a TB which I also got recently.


Some Rbs have a "C-field" input that can technically be used to 
discipline it, but this is not the approach I am going to take with 
mine. A Rb oscillator is internally an OCXO that is disciplined to the 
Rb physics package, with the goal of holding a frequency over a long 
period of time with the only variance coming from deficiencies in the 
measurement circuitry. Using the C-field to discipline it is kind of 
throwing out the long-term stability characteristics of the Rb and using 
it as an expensive OCXO. It's more interesting to me as a holdover 
source for a conventional GPSDO.


The design I'm thinking of is to have a separate microcontroller clocked 
by the Rb that will generate a third pulse-per-second (the first two 
being the raw one from GPS and the divided-down local oscillator). As 
long as the GPS is locked the divider will not output pulses but will 
monitor the pulses from the local oscillator and use it to count the 
frequency of the Rb. Once lock is lost or holdover is manually engaged, 
then it stops counting and starts outputting pulse-per-second based on 
the last known average frequency it counted. The GPSDO would then 
continue normal disciplining based on the Rb pulses until GPS lock 
returns. Of course while locked the measured frequency would also be 
reported so that the Rb could be calibrated in situ.


-- m. tharp

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[time-nuts] Interesting Loran-C antenna pictures

[Poul-Henning Kamp]

http://www.jan-mayen.no/

press "news"

Look for 21. august.

The last picture is particularly interesting:

http://www.jan-mayen.no/nyhet/2012/08_august/C-%20mast/C-mast%208b.JPG

Here you can see both the top-hat which forms the capacitance, they
guy-wires which hold the mast in place and the ground-grid which
forms the other electrode.

-- 
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
p...@freebsd.org | TCP/IP since RFC 956
FreeBSD committer   | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.

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Re: [time-nuts] Trak 8821B ---- was Z3815A Internal SMA 10Mhz Output

[bg]

Hi Nigel,

Yes, I have the same version. We might have got it from the same UK epay
source. The GPS did not work reliably, and I did start testing that module
outside the Trak unit, and also tried VP(8chan) receivers that I had. Did
not really conclude why the GPS did not behave properly. I was, like you,
disappointed by the lack of IRIG and other features that are in the
standard units. I also drew the conclusion this was a "high volume"
special model, where it was cost effective to eliminate all - for the
specific application - unuseful outputs.

However it is a very decent size OCXO inside.

The phase measurement Oncore model is interesting, since I have seen very
few GPSDOs that use phase information. It gives the possibility to reduce
the short term GPS noise to cm/s level. However this is probably lost in
the PPS generation hardware, since the Oncore does not lock its internal
crystal to the external OCXO.

--

Björn

> Hi Bjorn
>
> Is yours also the cut down 2.084MHz version, or do you have a "proper"
> 8821B with a more useful GPSDO frequency and all the outputs fitted?
> I think this one was originally used in a trunked radio  system.
>
> I've just checked and the fitted VP Oncore is  the B8121Z116, so perhaps
> the same module, but I'd forgotten until I  looked again that the unit is
> without the IRIG-B output as well  as the Low-Rate output that normally
> allows a
> variety of pre-set pulse rates,  hence my "cut down" comment.
>
> The Low-Rate ouput speciification suggests some interesting  possibilities
> for experiments in conditioning other oscillators, as  amongst some very
> slow pulse rates it also offered an option of 1  MPPS.
> Unfortunately, not only are the connectors not fitted but quite a lot of
> presumably associated PCB components in that area are also missing.
>
> Do you have a manual for the 8821B?
> I've only ever found a manual for the 8821A, although I suspect the  only
> significant difference may be the fitting of the larger B7A OCXO  to the
> 8821B, which necessitated the height increase to 2U, but it would be nice
> to be
> able to compare them.
>
> regards
>
> Nigel
> GM8PZR
>
> In a message dated 21/08/2012 21:05:02 GMT Daylight Time,
> b...@lysator.liu.se
>  writes:
>
> Hi  Nigel,
>
> Have one of those Trak 8821B too. It is a bit interesting since  the
> Motorola Oncore VP inside mine has the Z option (phase  measurement).
>
> --
>
> Björn
>
>
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Re: [time-nuts] Understanding Oliver Collins Paper "Design of Low Jitter Hard Limiters"

[Azelio Boriani]

According to

http://cp.literature.agilent.com/litweb/pdf/5989-8794EN.pdf

the real time sampling scope (like the TDS220 or TDS3012) can measure cycle
to cycle jitter directly, whereas the equivalent time sampling has only one
sample each trigger and a little delay on the sampling point for the next
trigger. The displayed waveform is a sort of "sum" of more than one cycle
and now I can't figure out what type of picture this can give. The TDS3012
has also the advantage of the Digital Phosphor behavior that can be useful
for the jitter analysis. Maybe a stable timebase and low jitter external
trigger input are essential. Unfortunately the TDS3012 has a 200ppm
timebase...

On Wed, Aug 22, 2012 at 2:54 PM, David  wrote:

> Do you mean with a 7404 hex inverter?  I actually did something like
> this recently while adding a 75ns pre-trigger pulse to an existing
> fast rise pulse generator.
>
> The pre-trigger pulse ended up having significant pattern dependant
> jitter caused by the adjacent TTL divider chain modulating the supply
> voltage and the poor power supply rejection of the 7404.  I was easily
> able to see the jitter on my 7T11 sampling oscilloscope but on my 2440
> (20 GS/sec equivalent time sampling), it was barely perceptible if
> that despite ideal conditions.  The peak to peak jitter was about
> 100ps.
>
> As far as I could tell from the available online documentation, the
> TDS220 and TDS3012 have relatively low sample rates and do not support
> equivalent time sampling so I would expect them to show even less than
> my 2440.
>
> On Wed, 22 Aug 2012 11:55:11 +0200, Azelio Boriani
>  wrote:
>
> >In your opinion, if I build a 7404 ZCD and a hard limiter one, can I see
> >the jitter difference on a simple 'scope (Tek TDS220 or TDS3012) or do I
> >need the Wavecrest SIA3000?
> >
> >On Wed, Aug 22, 2012 at 1:37 AM, Bob Camp  wrote:
> >
> >> Hi
> >>
> >> Since the Collins approach "tunes" the system for a single frequency
> input
> >> (more or less), the approach is probably not the best for a "many
> decades"
> >> sort of frequency range. There are a number of things that he alludes
> to in
> >> the paper, but does not directly address. The most obvious is the
> >> temperature dependance of the "stuff" the system is made of. Another is
> the
> >> simple fact that a non-clipping linear amplifier is likely the best
> choice
> >> for a first stage, provide the input is not already near clipping.
> >>
> >> Bob
> >>
> >> On Aug 21, 2012, at 12:50 PM, raj_so...@agilent.com wrote:
> >>
> >> > Hello everyone,
> >> >
> >> > I am new to this forum.
> >> > It looks like a lively discussion on various topics.
> >> >
> >> > A colleague of mine here at Agilent pointed me to this paper entitled
> >> "The Design of Low Jitter Hard Limiters" by Oliver Collins. In Bruce
> >> Griffiths' precision time in frequency webpage, this paper is described
> as
> >> "seminal."
> >> > (http://www.ko4bb.com/~bruce/ZeroCrossingDetectors.html)
> >> >
> >> > Since I'm trying to create a limiter that will accept frequencies
> >> ranging from 1 MHz to 100 MHz, I thought it would be good to understand
> the
> >> conclusions of this paper (if not the mathematics as well).  The
> >> mathematics turned out to be quite challenging to decode. Has someone on
> >> this forum unraveled the equations? It appears Collins has
> recommendations
> >> on the bandwidth and gain of a jitter minimizing limiter, and then
> extends
> >> this analysis to provide the bandwidth and gain of a cascade of
> limiters.
> >>  But the application is still fuzzy.  In figure 5, he shows a graph
> showing
> >> the dependence of jitter on crossing time.  Is the crossing time
> (implied
> >> by equations 7) considered a design parameter one can vary? Also, on
> figure
> >> 4, the "k" parameter has been varied to show the rising waveform as a
> >> function of "k".  The threshold is always assumed to be 0.5.  So could
> "k"
> >> be related to "tau", the time constant of the RC filter?
> >> >
> >> > Thanks in advance for all your help.
> >> >
> >> > Yours
> >> >
> >> > Raj
> >> >
> >> >
> >> >
> >> > ___
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> >> > To unsubscribe, go to
> >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> >> > and follow the instructions there.
> >>
> >>
> >> ___
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> >> and follow the instructions there.
> >>
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Re: [time-nuts] Understanding Oliver Collins Paper "Design of Low Jitter Hard Limiters"

[David]

Do you mean with a 7404 hex inverter?  I actually did something like
this recently while adding a 75ns pre-trigger pulse to an existing
fast rise pulse generator.

The pre-trigger pulse ended up having significant pattern dependant
jitter caused by the adjacent TTL divider chain modulating the supply
voltage and the poor power supply rejection of the 7404.  I was easily
able to see the jitter on my 7T11 sampling oscilloscope but on my 2440
(20 GS/sec equivalent time sampling), it was barely perceptible if
that despite ideal conditions.  The peak to peak jitter was about
100ps.

As far as I could tell from the available online documentation, the
TDS220 and TDS3012 have relatively low sample rates and do not support
equivalent time sampling so I would expect them to show even less than
my 2440.

On Wed, 22 Aug 2012 11:55:11 +0200, Azelio Boriani
 wrote:

>In your opinion, if I build a 7404 ZCD and a hard limiter one, can I see
>the jitter difference on a simple 'scope (Tek TDS220 or TDS3012) or do I
>need the Wavecrest SIA3000?
>
>On Wed, Aug 22, 2012 at 1:37 AM, Bob Camp  wrote:
>
>> Hi
>>
>> Since the Collins approach "tunes" the system for a single frequency input
>> (more or less), the approach is probably not the best for a "many decades"
>> sort of frequency range. There are a number of things that he alludes to in
>> the paper, but does not directly address. The most obvious is the
>> temperature dependance of the "stuff" the system is made of. Another is the
>> simple fact that a non-clipping linear amplifier is likely the best choice
>> for a first stage, provide the input is not already near clipping.
>>
>> Bob
>>
>> On Aug 21, 2012, at 12:50 PM, raj_so...@agilent.com wrote:
>>
>> > Hello everyone,
>> >
>> > I am new to this forum.
>> > It looks like a lively discussion on various topics.
>> >
>> > A colleague of mine here at Agilent pointed me to this paper entitled
>> "The Design of Low Jitter Hard Limiters" by Oliver Collins. In Bruce
>> Griffiths' precision time in frequency webpage, this paper is described as
>> "seminal."
>> > (http://www.ko4bb.com/~bruce/ZeroCrossingDetectors.html)
>> >
>> > Since I'm trying to create a limiter that will accept frequencies
>> ranging from 1 MHz to 100 MHz, I thought it would be good to understand the
>> conclusions of this paper (if not the mathematics as well).  The
>> mathematics turned out to be quite challenging to decode. Has someone on
>> this forum unraveled the equations? It appears Collins has recommendations
>> on the bandwidth and gain of a jitter minimizing limiter, and then extends
>> this analysis to provide the bandwidth and gain of a cascade of limiters.
>>  But the application is still fuzzy.  In figure 5, he shows a graph showing
>> the dependence of jitter on crossing time.  Is the crossing time (implied
>> by equations 7) considered a design parameter one can vary? Also, on figure
>> 4, the "k" parameter has been varied to show the rising waveform as a
>> function of "k".  The threshold is always assumed to be 0.5.  So could "k"
>> be related to "tau", the time constant of the RC filter?
>> >
>> > Thanks in advance for all your help.
>> >
>> > Yours
>> >
>> > Raj
>> >
>> >
>> >
>> > ___
>> > 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] HP-5065a bought and finally working!

[J. L. Trantham]

Edgardo,

Congrats on getting the 5065A up and operational.  Make sure the A11 Board
(Temperature Controller) is all OK.  Failure there can destroy the A12 RVFR
Assembly.  There is a lot of 'expertise' on the list for this unit.

What is the serial number of your unit and what is the part number of the
manual you have?

I have a couple of manuals and I may also have the 'change sheets' that
updates the manual to your serial number.  It may take me a while to chase
that down but if I have the 'change sheets', I can scan them and send them
to you.

I have not heard of anyone 'disciplining' the 5065A by GPS, other than by
hand from week to week.  However, the 105B has a built in connection on the
back that is great for that purpose (negative slope, as I recall) and I have
done that using a Brooks Shera controller board and the 1 PPS from my TBolt.
It works quite well.

Joe

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Edgardo Molina
Sent: Wednesday, August 22, 2012 12:22 AM
To: time-nuts@febo.com
Subject: [time-nuts] HP-5065a bought and finally working!


Dear Group,

I wish you well.

Do you recall a message and thread about a month ago with my concerns about
buying a used / unknown condition HP-5065a rubidium frequency standard? I
bit the bullet and bought it. Almost mint condition (cosmetically speaking)
and with several operational issues. 

Well, It took me several weeks to put it back to work. Several capacitors on
several boards along with a couple of transistors and an IC were replaced.
After that any being bored by the yellow light, it finally came off to allow
a beautiful green lock condition light. I went through the necessary steps
to tune it and calibrate it. Now, as I have been told recently. "You have
been bitten by the Time Nuts bug." I am not complaining at all.

Now the technical issues if you kindly allow:

a. Does anybody have an HP-5065a manual for the latest versions? Mine (which
I downloaded from the Internet) is intended for earlier versions. It seems I
have one of the last produced units. I would kindly appreciate any help on
this and I am willing to pay for time and expenses to anybody who could
help. During the repair process I found several differences in the earlier
versions design and had to figure out hoy mine works.

b. Is it possible to build a GPSDRb? I would like to know if it is
reasonable to pursue the goal to discipline the 5065a with a TB which I also
got recently. 

c. I am waiting for the delivery of a recent purchase. An HP-59309a Digital
Clock to go with the HP 5065a. How I wish I could find the optional LED
integrated optional clock and 1PPS output. Is my purchase a good match for
the 5065a? Any other suggestions to drive a clock?

d. I am waiting also for de delivery of an HP-105b mint condition quartz
frequency standard. Would a second 59309a make sense to use it with this
quartz standard? Or just saving it for a Cesium? Anybody willing to sell a
spare, dust gathering, clean unit to me?

e. Any suggestions for software of lab equipment to measure my experiments
like AD, jitter, phase comparisons, etc?


While I wait I am doing some experiments with a FE Rb standard to discipline
an Adret synthesiser to output 32.768 KHz to directly drive a Nixie clock
kit I just finished building.

Your comments are surely welcome. Thank you!

Kind regards,


Edgardo Molina
XE1XUS
Mexico


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Re: [time-nuts] Understanding Oliver Collins Paper "Design of Low Jitter Hard Limiters"

[Azelio Boriani]

In your opinion, if I build a 7404 ZCD and a hard limiter one, can I see
the jitter difference on a simple 'scope (Tek TDS220 or TDS3012) or do I
need the Wavecrest SIA3000?

On Wed, Aug 22, 2012 at 1:37 AM, Bob Camp  wrote:

> Hi
>
> Since the Collins approach "tunes" the system for a single frequency input
> (more or less), the approach is probably not the best for a "many decades"
> sort of frequency range. There are a number of things that he alludes to in
> the paper, but does not directly address. The most obvious is the
> temperature dependance of the "stuff" the system is made of. Another is the
> simple fact that a non-clipping linear amplifier is likely the best choice
> for a first stage, provide the input is not already near clipping.
>
> Bob
>
> On Aug 21, 2012, at 12:50 PM, raj_so...@agilent.com wrote:
>
> > Hello everyone,
> >
> > I am new to this forum.
> > It looks like a lively discussion on various topics.
> >
> > A colleague of mine here at Agilent pointed me to this paper entitled
> "The Design of Low Jitter Hard Limiters" by Oliver Collins. In Bruce
> Griffiths' precision time in frequency webpage, this paper is described as
> "seminal."
> > (http://www.ko4bb.com/~bruce/ZeroCrossingDetectors.html)
> >
> > Since I'm trying to create a limiter that will accept frequencies
> ranging from 1 MHz to 100 MHz, I thought it would be good to understand the
> conclusions of this paper (if not the mathematics as well).  The
> mathematics turned out to be quite challenging to decode. Has someone on
> this forum unraveled the equations? It appears Collins has recommendations
> on the bandwidth and gain of a jitter minimizing limiter, and then extends
> this analysis to provide the bandwidth and gain of a cascade of limiters.
>  But the application is still fuzzy.  In figure 5, he shows a graph showing
> the dependence of jitter on crossing time.  Is the crossing time (implied
> by equations 7) considered a design parameter one can vary? Also, on figure
> 4, the "k" parameter has been varied to show the rising waveform as a
> function of "k".  The threshold is always assumed to be 0.5.  So could "k"
> be related to "tau", the time constant of the RC filter?
> >
> > Thanks in advance for all your help.
> >
> > Yours
> >
> > Raj
> >
> >
> >
> > ___
> > 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] HP-5065a bought and finally working!

[Azelio Boriani]

I think that it is the time for you to look at the TimePod: the TimePod can
help you with Allan Deviation and phase noise measurement, the next step
after clocks is measuring equipment and the TimePod is a sort of all-in-one
for time-nuts, its place is right after the bench yellow multimeter.

On Wed, Aug 22, 2012 at 9:03 AM, Chuck Forsberg WA7KGX N2469R
wrote:

> If it is a really good Rb standard, consider adjusting the
> standard yourself by measuring the phase over several
> days once the standard has warmed up and settled down.
> A GPIB counter with phase measurement is useful for this.
>
> --
> Chuck Forsberg WA7KGX N2469R c...@omen.com   www.omen.com
> Developer of Industrial ZMODEM(Tm) for Embedded Applications
>   Omen Technology Inc  "The High Reliability Software"
> 10255 NW Old Cornelius Pass Portland OR 97231   503-614-0430
>
>
>
> ___
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Re: [time-nuts] Trak 8821B ---- was Z3815A Internal SMA 10Mhz Output

[GandalfG8]

Hi Bjorn
 
Is yours also the cut down 2.084MHz version, or do you have a "proper"  
8821B with a more useful GPSDO frequency and all the outputs fitted?
I think this one was originally used in a trunked radio  system.
 
I've just checked and the fitted VP Oncore is  the B8121Z116, so perhaps 
the same module, but I'd forgotten until I  looked again that the unit is 
without the IRIG-B output as well  as the Low-Rate output that normally allows 
a 
variety of pre-set pulse rates,  hence my "cut down" comment.
 
The Low-Rate ouput speciification suggests some interesting  possibilities 
for experiments in conditioning other oscillators, as  amongst some very 
slow pulse rates it also offered an option of 1  MPPS.
Unfortunately, not only are the connectors not fitted but quite a lot of  
presumably associated PCB components in that area are also missing.
 
Do you have a manual for the 8821B?
I've only ever found a manual for the 8821A, although I suspect the  only 
significant difference may be the fitting of the larger B7A OCXO  to the 
8821B, which necessitated the height increase to 2U, but it would be nice  to 
be 
able to compare them.
 
regards
 
Nigel
GM8PZR
 
In a message dated 21/08/2012 21:05:02 GMT Daylight Time, b...@lysator.liu.se 
 writes:
 
Hi  Nigel,

Have one of those Trak 8821B too. It is a bit interesting since  the
Motorola Oncore VP inside mine has the Z option (phase  measurement).

--

Björn


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Re: [time-nuts] HP-5065a bought and finally working!

[Chuck Forsberg WA7KGX N2469R]

If it is a really good Rb standard, consider adjusting the
standard yourself by measuring the phase over several
days once the standard has warmed up and settled down.
A GPIB counter with phase measurement is useful for this.

--
Chuck Forsberg WA7KGX N2469R c...@omen.com   www.omen.com
Developer of Industrial ZMODEM(Tm) for Embedded Applications
  Omen Technology Inc  "The High Reliability Software"
10255 NW Old Cornelius Pass Portland OR 97231   503-614-0430


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