Re: [time-nuts] PLL/GPSDO/etc learning resources for mere mortals

[John Miles]

> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@lists.febo.com] On Behalf Of
> Richard (Rick) Karlquist
> Sent: Sunday, September 02, 2018 6:12 PM
> To: Discussion of precise time and frequency measurement; Forrest
Christian
> (List Account)
> Subject: Re: [time-nuts] PLL/GPSDO/etc learning resources for mere mortals
> 
> You might try Phase Lock Techniques by Gardner.
> 
> Rick N6RK

Also worth checking out "Dean's book":

http://www.ti.com/tool/PLL_BOOK

This makes a great introductory text/prerequisite for the heavy hitters like
Gardner and Rohde.  Dean Banerjee spent many years providing customer
support for PLL chips sold by TI and NatSemi, so he's got a good sense of
how to explain the basics to non-specialists as well as encyclopedic
knowledge of things to watch out for.

-- john, KE5FX
Miles Design LLC



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[time-nuts] PLL/GPSDO/etc learning resources for mere mortals

[Forrest Christian (List Account)]

I'm trying to fill in some gaps in my knowledge about PLL's, GPSDO's, etc.,
with the goal to eventually implement some of these either in a
microcontroller or fpga or some combination thereof.

My problem is that the resources I've found either are very basic -
oriented toward just the high level understanding of what these are and the
basics of how they work (what I already know), OR are very math dense and
impenetrable to mere mortals - essentially oriented toward people who
already know what they're doing and who have the magic decoder ring as to
what the formulas are used for.

I'm hoping to find something which will help me bridge the gap.   Any ideas
where I should look?

-- 
*Forrest Christian* *CEO**, PacketFlux Technologies, Inc.*
Tel: 406-449-3345 | Address: 3577 Countryside Road, Helena, MT 59602
forre...@imach.com | http://www.packetflux.com
  

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Re: [time-nuts] Frequency over fiber (was WWV and legal issues)

[Peter Vince]

Hi Magnus,

 Could you please give us some idea of the magnitude of these effects?
Even if just whether we are talking about nano, pico, or femtoseconds?

 Thank you,

  Peter


On 2 September 2018 at 12:17, Magnus Danielson 
wrote:

> Hi Gerhard,
>
> I see that this became a separate thread.
> ...
> ...
>
> Acoustical sensitivity, low frequency changes.
>
> For optical clocks and frequency transfer, just the vibration from
> traffic and other activity causes disturbances which disturbes the group
> delay. What is done for these links is to actively compensate then using
> a return path and closing the loop with a controller, very much like a
> PLL. The length of the loop limits the bandwidth and hence how high up
> the compensation can be done, so for longer stretches, this needs to be
> repeated. They have now built links from PTB to SYRTE and NPL.
>
> Temperature shifts are slower, but also compensated though the active loop.
>
> Close proximity to strong power-currents have also been shown to cause
> modulations, so separate from power-cables if you can.
>
> Remember that the end nodes have very stable clocks, so their effects
> can be taken out of the equation. For other setups, such as telco
> operation, that's a completely different ballgame.
>
> Cheers,
> Magnus
>
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Re: [time-nuts] Exact Time Mobile Phone Apps

[Ryan Stoner]

I haven't seen that app in a long time! I got them to add the option to
include a custom NTP server. Great people!

On my Android phone I use ClockSync <
https://play.google.com/store/apps/details?id=ru.org.amip.ClockSync>. It
has a ton of features especially if your phone is rooted.



--
Ryan Stoner

On Sun, Sep 2, 2018, 08:08 D. Resor  wrote:

> I believe someone mentioned a cell phone "time" app.  This is an image of
> the one I use for my iPhone.  It is Emerald Sequoia.
>
> It queries correct time requests from four different NTP servers then picks
> the one with the least amount of response delay I believe.
>
> Of course when I'm out setting the clock on a Carillon system it has to be
> "just" right, doesn't it?
>
> I have uploaded a couple screen captures here:
>
> http://hammondorganservice.com/downloads/images/Emerald-Sequoia.jpg
> http://hammondorganservice.com/downloads/images/Emerald-Sequoia2.jpg
>
>
> A description of how it works is here:
>
> https://emeraldsequoia.com/et/index.html
>
>
>
>
> Don Resor
> N6KAW
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Re: [time-nuts] Frequency over fiber (was WWV and legal issues)

[Dana Whitlow]

Question:

Supposing you buy a bundle of a couple of dozen fibers inside one outer
jacket:  Can
anyone give me an idea of how well the individual fibers are likely to be
matched in
delay, and in delay tempco?

Dana


On Sun, Sep 2, 2018 at 1:46 PM Poul-Henning Kamp  wrote:

> 
>
> In message , Bob kb8tq
> writes:
>
> > That’s why they design a certain amount of “slack” into the structure.
>
> As far as I know, thermal expansion and contact losses are far
> bigger dimensioning factors, except for a few very active fault-lines.
>
> At these fault-lines and/or with very important fibers, special and
> site-specific precautions are usually taken.
>
> For terrestial faultlines, the cheapest and easiest mitigation is
> to cross the fault-line on poles with a slack messengerwire.
>
> For oceanfloor faultlines, plenty of slack and an oblique crossing
> is the best we've come up with yet.
>
> --
> 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] News

[Magnus Danielson]

Hi Didier,

Many thanks! Much appreciated!

It's indeed a process which comes with requirements. Turns out I have
done quite a bit of things in my professional career that makes me
distinguish myself sufficiently. To be honest, some of the stuff on my
CV looks very strange, but it strangely enough true and valid.
I should write more articles, they are usually easier to understand as
achievements.

For being a uni-dropout, I never finished my EE, since after one year I
started working for the university instead and then the dotcom happened
so. The first professor I worked under was also to my surprise one of
the referees, and I know he is keen to keep the bar high. He just
concluded that I have been busy and had no issues approving my
application. So, I didn't expect this to be possible, but the Swedish
section of IEEE reached out and pointed out that I should apply and
assisted me.

Anyway, there might be more people here which should apply, so be sure
to check the conditions up, and let me know if I can help.

Cheers,
Magnus

On 09/01/2018 01:23 PM, Didier Juges wrote:
> Congratulations Magnus, a well deserved reward for your contributions. My
> boss is a Senior Member and I know they do not just give those away.
> Well done!
> 
> Didier
> 
> On Thu, Aug 30, 2018, 3:40 PM Magnus Danielson 
> wrote:
> 
>> Hi Bob,
>>
>> On 08/30/2018 10:33 PM, Bob kb8tq wrote:
>>> Hi
>>>
>>> Magnus … do you have some news you might want to share with the group?
>>
>> Oh, well, sure:
>>
>> Today I received a nice email from IEEE starting with:
>> "It is a great pleasure to congratulate you on your elevation to the
>> grade of IEEE Senior member. IEEE Senior Membership is an honor bestowed
>> only to those who have made significant contributions to the profession."
>>
>> I'm humbled by these words, but proud of the achievement and happy for
>> the distinction. This has been a process that has been going on since
>> spring when IEEE approached me and pointed out that I should be able to
>> become senior member, writing up a modern CV and then being interviewed
>> by three Senior Members was interesting, sharing the room with very
>> senior engineers, PhDs and professors all seeking to reach the IEEE
>> Senior member elevation.
>>
>> Cheers,
>> Magnus
>>
>> ___
>> time-nuts mailing list -- time-nuts@lists.febo.com
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>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
>> and follow the instructions there.
>>
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Re: [time-nuts] Frequency over fiber (was WWV and legal issues)

[Poul-Henning Kamp]

In message , Bob kb8tq writes:

> That’s why they design a certain amount of “slack” into the structure.

As far as I know, thermal expansion and contact losses are far
bigger dimensioning factors, except for a few very active fault-lines.

At these fault-lines and/or with very important fibers, special and
site-specific precautions are usually taken.

For terrestial faultlines, the cheapest and easiest mitigation is
to cross the fault-line on poles with a slack messengerwire.

For oceanfloor faultlines, plenty of slack and an oblique crossing
is the best we've come up with yet.

-- 
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] Frequency over fiber (was WWV and legal issues)

[Bob kb8tq]

Hi

Motion at a fault line can be a bit chaotic. As that motion stretches (or stops 
stretching)
the cable the delay is likely to change. How much does it change? no idea. If 
vibration 
messes with it, stretch should as well. 

Hopefully the fiber “spiralt” inside the outer jacket is enough to keep things 
from snapping
very quickly. Ground shifts around for a lot of reasons even if you are not on 
a fault line. 
That’s why they design a certain amount of “slack” into the structure.

Bob

> On Sep 2, 2018, at 11:07 AM, Azelio Boriani  wrote:
> 
> Why should there be a variation in the fiber's delay across an active
> fault line? The fiber could only break at the fault line, lay down
> more fiber than needed, to compensate the movement, and the delay
> doesn't change.
> On Sun, Sep 2, 2018 at 4:51 PM Bob kb8tq  wrote:
>> 
>> Hi
>> 
>> Tidal effects can be very “non linear” as you approach a coast line. Lots of 
>> change
>> over a fairly short distance. If indeed the world decides to put in a global 
>> PTTI fiber
>> system, all of this would get into the mix on some links. It appears that 
>> the existing
>> technology would handle the issues.
>> 
>> Of course there’s still some guy named Bob running that back hoe without 
>> checking
>> for buried lines …..*That* we could test for … likely no need to run the 
>> experiment. :)
>> 
>> Bob
>> 
>>> On Sep 2, 2018, at 10:07 AM, Tom Van Baak  wrote:
>>> 
 I suspect there’s a longer list of “slow” environmental effects that are 
 also taken
 care of with the compensation setup. One would guess that crossing a active
 fault line would be “interesting”.
>>> 
>>> Yes, here's a back of the envelope calculation for you:
>>> 
>>> - the Pacific Northwest moves on the order of 10 cm per year [1]
>>> - 1 meter of time is 1/299792458 = 3.3 ns
>>> - 10 cm/year is 3.3 ns / 86400 / 365 = 1e-17 df/f
>>> - the best laboratory optical clocks are down to that level of stability [2]
>>> 
>>> On the other hand, in the real world you'd have to convince me that you've 
>>> found two national timing labs with 1) state-of-the-art optical clocks, 2) 
>>> which operate as phase (time) standards instead of as frequency standards, 
>>> 3) or run continuously for a year (instead of a few times per week), 4) are 
>>> connected by stabilized fiber, 5) that cross plate boundaries moving 
>>> anywhere near as much as 10 cm/year, and 6) the optical time nuts running 
>>> the clocks don't already factor geodetic effects like this into their clock 
>>> comparisons...
>>> 
>>> Unfortunately I won't be able to measure this. Even if John Miles (who also 
>>> lives near Seattle) and I find optical clocks on eBay some day, and we find 
>>> a way to run 30 miles of fiber between us without anyone noticing, we are 
>>> both on the same tectonic plate so the drift cancels out. Note that 
>>> lunar/solar tidal effects would be common mode to us as well.
>>> 
>>> /tvb
>>> 
>>> [1]
>>> https://pnsn.org/outreach/about-earthquakes/plate-tectonics
>>> https://www.eoas.ubc.ca/courses/eosc256/jan26_plates_rebound.pdf
>>> 
>>> [2]
>>> https://arxiv.org/ftp/arxiv/papers/1309/1309.1137.pdf
>>> https://arxiv.org/ftp/arxiv/papers/1704/1704.06323.pdf
>>> http://jilawww.colorado.edu/yelabs/sites/default/files/uploads/Sr%20best%20clock_Bloom_Nature.pdf
>>> 
>>> 
>>> ___
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>>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
>>> and follow the instructions there.
>> 
>> 
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Re: [time-nuts] News

[Magnus Danielson]

Hi Paul,

Many thanks! Much appreciated!

I'm committed to this field, and I try to share as much knowledge and
insight I managed to gather, as I have picked up a lot from this list
alone, but also in my strive to find answers to questions we all had.

Now, the Senior Membership of IEEE is not about that, but somewhat
related, and I hope and aim to contribute further to the field through
this list, articles, presentations and other work. I'm now also
contributing to the EFTF/IFCS conference by going through the
contributions and help select which is worthy of presentations.

I have several ideas for papers, and some more or less finished ones, I
should just get around to get some of them out.

There is also the Stable32 project to take care about, to help setting
up validation code, refactor the code and help contributing to a new
version.

So it's not that I have achieved my end goal, I've just started! :)

Cheers,
Magnus

On 09/02/2018 05:55 PM, paul swed wrote:
> Magnus
> Congratulations on becoming a Senior member of the IEEE.
> Thank you for your help over time.
> Regards
> Paul
> WB8TSL
> 
> On Sat, Sep 1, 2018 at 7:23 AM, Didier Juges  wrote:
> 
>> Congratulations Magnus, a well deserved reward for your contributions. My
>> boss is a Senior Member and I know they do not just give those away.
>> Well done!
>>
>> Didier
>>
>> On Thu, Aug 30, 2018, 3:40 PM Magnus Danielson >>
>> wrote:
>>
>>> Hi Bob,
>>>
>>> On 08/30/2018 10:33 PM, Bob kb8tq wrote:
 Hi

 Magnus … do you have some news you might want to share with the group?
>>>
>>> Oh, well, sure:
>>>
>>> Today I received a nice email from IEEE starting with:
>>> "It is a great pleasure to congratulate you on your elevation to the
>>> grade of IEEE Senior member. IEEE Senior Membership is an honor bestowed
>>> only to those who have made significant contributions to the profession."
>>>
>>> I'm humbled by these words, but proud of the achievement and happy for
>>> the distinction. This has been a process that has been going on since
>>> spring when IEEE approached me and pointed out that I should be able to
>>> become senior member, writing up a modern CV and then being interviewed
>>> by three Senior Members was interesting, sharing the room with very
>>> senior engineers, PhDs and professors all seeking to reach the IEEE
>>> Senior member elevation.
>>>
>>> Cheers,
>>> Magnus
>>>
>>> ___
>>> time-nuts mailing list -- time-nuts@lists.febo.com
>>> To unsubscribe, go to
>>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
>>> and follow the instructions there.
>>>
>> ___
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>> listinfo/time-nuts_lists.febo.com
>> and follow the instructions there.
>>
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Re: [time-nuts] News

[paul swed]

Magnus
Congratulations on becoming a Senior member of the IEEE.
Thank you for your help over time.
Regards
Paul
WB8TSL

On Sat, Sep 1, 2018 at 7:23 AM, Didier Juges  wrote:

> Congratulations Magnus, a well deserved reward for your contributions. My
> boss is a Senior Member and I know they do not just give those away.
> Well done!
>
> Didier
>
> On Thu, Aug 30, 2018, 3:40 PM Magnus Danielson  >
> wrote:
>
> > Hi Bob,
> >
> > On 08/30/2018 10:33 PM, Bob kb8tq wrote:
> > > Hi
> > >
> > > Magnus … do you have some news you might want to share with the group?
> >
> > Oh, well, sure:
> >
> > Today I received a nice email from IEEE starting with:
> > "It is a great pleasure to congratulate you on your elevation to the
> > grade of IEEE Senior member. IEEE Senior Membership is an honor bestowed
> > only to those who have made significant contributions to the profession."
> >
> > I'm humbled by these words, but proud of the achievement and happy for
> > the distinction. This has been a process that has been going on since
> > spring when IEEE approached me and pointed out that I should be able to
> > become senior member, writing up a modern CV and then being interviewed
> > by three Senior Members was interesting, sharing the room with very
> > senior engineers, PhDs and professors all seeking to reach the IEEE
> > Senior member elevation.
> >
> > Cheers,
> > Magnus
> >
> > ___
> > time-nuts mailing list -- time-nuts@lists.febo.com
> > To unsubscribe, go to
> > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> > and follow the instructions there.
> >
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Re: [time-nuts] Frequency over fiber (was WWV and legal issues)

[Azelio Boriani]

Why should there be a variation in the fiber's delay across an active
fault line? The fiber could only break at the fault line, lay down
more fiber than needed, to compensate the movement, and the delay
doesn't change.
On Sun, Sep 2, 2018 at 4:51 PM Bob kb8tq  wrote:
>
> Hi
>
> Tidal effects can be very “non linear” as you approach a coast line. Lots of 
> change
> over a fairly short distance. If indeed the world decides to put in a global 
> PTTI fiber
> system, all of this would get into the mix on some links. It appears that the 
> existing
> technology would handle the issues.
>
> Of course there’s still some guy named Bob running that back hoe without 
> checking
> for buried lines …..*That* we could test for … likely no need to run the 
> experiment. :)
>
> Bob
>
> > On Sep 2, 2018, at 10:07 AM, Tom Van Baak  wrote:
> >
> >> I suspect there’s a longer list of “slow” environmental effects that are 
> >> also taken
> >> care of with the compensation setup. One would guess that crossing a active
> >> fault line would be “interesting”.
> >
> > Yes, here's a back of the envelope calculation for you:
> >
> > - the Pacific Northwest moves on the order of 10 cm per year [1]
> > - 1 meter of time is 1/299792458 = 3.3 ns
> > - 10 cm/year is 3.3 ns / 86400 / 365 = 1e-17 df/f
> > - the best laboratory optical clocks are down to that level of stability [2]
> >
> > On the other hand, in the real world you'd have to convince me that you've 
> > found two national timing labs with 1) state-of-the-art optical clocks, 2) 
> > which operate as phase (time) standards instead of as frequency standards, 
> > 3) or run continuously for a year (instead of a few times per week), 4) are 
> > connected by stabilized fiber, 5) that cross plate boundaries moving 
> > anywhere near as much as 10 cm/year, and 6) the optical time nuts running 
> > the clocks don't already factor geodetic effects like this into their clock 
> > comparisons...
> >
> > Unfortunately I won't be able to measure this. Even if John Miles (who also 
> > lives near Seattle) and I find optical clocks on eBay some day, and we find 
> > a way to run 30 miles of fiber between us without anyone noticing, we are 
> > both on the same tectonic plate so the drift cancels out. Note that 
> > lunar/solar tidal effects would be common mode to us as well.
> >
> > /tvb
> >
> > [1]
> > https://pnsn.org/outreach/about-earthquakes/plate-tectonics
> > https://www.eoas.ubc.ca/courses/eosc256/jan26_plates_rebound.pdf
> >
> > [2]
> > https://arxiv.org/ftp/arxiv/papers/1309/1309.1137.pdf
> > https://arxiv.org/ftp/arxiv/papers/1704/1704.06323.pdf
> > http://jilawww.colorado.edu/yelabs/sites/default/files/uploads/Sr%20best%20clock_Bloom_Nature.pdf
> >
> >
> > ___
> > time-nuts mailing list -- time-nuts@lists.febo.com
> > To unsubscribe, go to 
> > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> > and follow the instructions there.
>
>
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Re: [time-nuts] Frequency over fiber (was WWV and legal issues)

[Bob kb8tq]

Hi

Tidal effects can be very “non linear” as you approach a coast line. Lots of 
change
over a fairly short distance. If indeed the world decides to put in a global 
PTTI fiber
system, all of this would get into the mix on some links. It appears that the 
existing
technology would handle the issues. 

Of course there’s still some guy named Bob running that back hoe without 
checking
for buried lines …..*That* we could test for … likely no need to run the 
experiment. :)

Bob

> On Sep 2, 2018, at 10:07 AM, Tom Van Baak  wrote:
> 
>> I suspect there’s a longer list of “slow” environmental effects that are 
>> also taken 
>> care of with the compensation setup. One would guess that crossing a active  
>> fault line would be “interesting”. 
> 
> Yes, here's a back of the envelope calculation for you:
> 
> - the Pacific Northwest moves on the order of 10 cm per year [1]
> - 1 meter of time is 1/299792458 = 3.3 ns
> - 10 cm/year is 3.3 ns / 86400 / 365 = 1e-17 df/f
> - the best laboratory optical clocks are down to that level of stability [2]
> 
> On the other hand, in the real world you'd have to convince me that you've 
> found two national timing labs with 1) state-of-the-art optical clocks, 2) 
> which operate as phase (time) standards instead of as frequency standards, 3) 
> or run continuously for a year (instead of a few times per week), 4) are 
> connected by stabilized fiber, 5) that cross plate boundaries moving anywhere 
> near as much as 10 cm/year, and 6) the optical time nuts running the clocks 
> don't already factor geodetic effects like this into their clock 
> comparisons...
> 
> Unfortunately I won't be able to measure this. Even if John Miles (who also 
> lives near Seattle) and I find optical clocks on eBay some day, and we find a 
> way to run 30 miles of fiber between us without anyone noticing, we are both 
> on the same tectonic plate so the drift cancels out. Note that lunar/solar 
> tidal effects would be common mode to us as well.
> 
> /tvb
> 
> [1]
> https://pnsn.org/outreach/about-earthquakes/plate-tectonics
> https://www.eoas.ubc.ca/courses/eosc256/jan26_plates_rebound.pdf
> 
> [2]
> https://arxiv.org/ftp/arxiv/papers/1309/1309.1137.pdf
> https://arxiv.org/ftp/arxiv/papers/1704/1704.06323.pdf
> http://jilawww.colorado.edu/yelabs/sites/default/files/uploads/Sr%20best%20clock_Bloom_Nature.pdf
> 
> 
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Re: [time-nuts] Lots of Off Topic discussion

[Bob kb8tq]

Hi

The referenced line item is $6.8 million a year. It is still very much unclear 
if that is just WWV(H)
(from the reference it must include them) or if it also includes WWWVB.  
Without any clarification, 
we are only guessing about WWVB. Given the way the budget process works, 
there’s never a
lot of clarity at this point. 

Bob

> On Sep 2, 2018, at 9:53 AM, Artek Manuals  wrote:
> 
> Does any one know what the line item $$$ amount is for the WWV/WWVB operating 
> budget?
> 
> -DC
> NR1DX
> manu...@artekmanuals.com
> 
> On 9/1/2018 11:59 PM, Peter Laws wrote:
>> On Sat, Sep 1, 2018 at 7:25 PM Bob kb8tq  wrote:
>> 
>>> I most certainly *have* seen an NTP server that ran off of WWVB and relayed
>>> the result to the internet. The fun part was that they had entered the 
>>> “delay”
>> I didn't say it COULD not -- W3HCF and his group didn't miss much in
>> the code -- but what I'm saying is that in 20+ years of dinking with
>> NTP as part of my job, I HAVE not seen any evidence of WWV being used
>> as a "refclock".  Certainly not in the last decade.  Maybe there were
>> many of them when Dr Mills first published the standards and reference
>> implementation back in the 1980s but not now.
>> 
>> I want to be outraged over this cut but until I have a coherent,
>> evidence-based argument in favor of keeping the stations, I'm going to
>> keep my powder dry.
>> 
> 
> -- 
> Dave
> manu...@artekmanuals.com
> www.ArtekManuals.com
> 
> 
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Re: [time-nuts] WWV/WWVB in NTP surveys

[Björn]

Hi,

There are LF receivers available commercially today. See links below for one 
vendor.
https://www.meinbergglobal.com/english/products/pci-express-dcf77-clock.htm

and even an USB version for the NIST signal.

https://www.meinbergglobal.com/english/products/usb-wwvb-clock.htm

And there seems to be options for wwvb reception also in 1u 19” format.

https://www.meinbergglobal.com/english/products/rack-mount-1u-ntp-server.htm

/Björn 

Sent from my iPhone

> On 2 Sep 2018, at 15:48, Tim Shoppa  wrote:
> 
> Some stats in historic NTP surveys show that WWV and WWVB based refclocks
> were relevant 20+ years ago:
> 
> 1997 - Mills survey - 47 GPS and GOES vs 74 WWV and WWVB.
> 
> 1999 - Minar MIT survey - 129 GPS and GOES vs 24 WWV and WWVB.
> 
> In those two years it is pretty obvious the world was swinging from LF and
> HF refclocks to satellite based refclocks (and also obvious that GOES was
> declining while GPS was on the upswing.)
> 
> As recently as 10 years ago I was running a WWV-based Stratum 1 - it's
> there in the 2005 Brazillian NTP survey data.
> 
> It would be much easier to make a case for continuing WWV service if there
> were commercial WWV based refclocks on the market and used in
> commercial/government applications. 10 years ago I could find WWV time
> clocks in industrial automation catalogs but today, nothing. I'm sure
> there's some installed base.
> 
> Tim N3QE
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Re: [time-nuts] Frequency over fiber (was WWV and legal issues)

[Tom Van Baak]

> I suspect there’s a longer list of “slow” environmental effects that are also 
> taken 
> care of with the compensation setup. One would guess that crossing a active  
> fault line would be “interesting”. 

Yes, here's a back of the envelope calculation for you:

- the Pacific Northwest moves on the order of 10 cm per year [1]
- 1 meter of time is 1/299792458 = 3.3 ns
- 10 cm/year is 3.3 ns / 86400 / 365 = 1e-17 df/f
- the best laboratory optical clocks are down to that level of stability [2]

On the other hand, in the real world you'd have to convince me that you've 
found two national timing labs with 1) state-of-the-art optical clocks, 2) 
which operate as phase (time) standards instead of as frequency standards, 3) 
or run continuously for a year (instead of a few times per week), 4) are 
connected by stabilized fiber, 5) that cross plate boundaries moving anywhere 
near as much as 10 cm/year, and 6) the optical time nuts running the clocks 
don't already factor geodetic effects like this into their clock comparisons...

Unfortunately I won't be able to measure this. Even if John Miles (who also 
lives near Seattle) and I find optical clocks on eBay some day, and we find a 
way to run 30 miles of fiber between us without anyone noticing, we are both on 
the same tectonic plate so the drift cancels out. Note that lunar/solar tidal 
effects would be common mode to us as well.

/tvb

[1]
https://pnsn.org/outreach/about-earthquakes/plate-tectonics
https://www.eoas.ubc.ca/courses/eosc256/jan26_plates_rebound.pdf

[2]
https://arxiv.org/ftp/arxiv/papers/1309/1309.1137.pdf
https://arxiv.org/ftp/arxiv/papers/1704/1704.06323.pdf
http://jilawww.colorado.edu/yelabs/sites/default/files/uploads/Sr%20best%20clock_Bloom_Nature.pdf


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Re: [time-nuts] Lots of Off Topic discussion

[Artek Manuals]

Does any one know what the line item $$$ amount is for the WWV/WWVB 
operating budget?


-DC
NR1DX
manu...@artekmanuals.com

On 9/1/2018 11:59 PM, Peter Laws wrote:

On Sat, Sep 1, 2018 at 7:25 PM Bob kb8tq  wrote:


I most certainly *have* seen an NTP server that ran off of WWVB and relayed
the result to the internet. The fun part was that they had entered the “delay”

I didn't say it COULD not -- W3HCF and his group didn't miss much in
the code -- but what I'm saying is that in 20+ years of dinking with
NTP as part of my job, I HAVE not seen any evidence of WWV being used
as a "refclock".  Certainly not in the last decade.  Maybe there were
many of them when Dr Mills first published the standards and reference
implementation back in the 1980s but not now.

I want to be outraged over this cut but until I have a coherent,
evidence-based argument in favor of keeping the stations, I'm going to
keep my powder dry.



--
Dave
manu...@artekmanuals.com
www.ArtekManuals.com


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Re: [time-nuts] Frequency over fiber (was WWV and legal issues)

[Bob kb8tq]

Hi

> On Sep 2, 2018, at 7:17 AM, Magnus Danielson  
> wrote:
> 
> Hi Gerhard,
> 
> I see that this became a separate thread.
> 
> On 09/02/2018 01:38 AM, Gerhard Hoffmann wrote:
>> 
>> 
>> Am 01.09.2018 um 20:40 schrieb Magnus Danielson:
>>> One should first know that there is a lot of papers now on frequency
>>> transfer over fiber. The stability achieved on the best ones so far
>>> greatly below that of the optical clocks that they want to compare.
>> 
>> Please, in a nutshell: what are the worst offenders:
>> 
>> - tranceivers (mechanical, temp, other misfeatures)
>> - cables ( bending, temp, mechanical stress)
>> - others?
>> 
>> In the case of transceivers: are there desirable modifications
>> that would alleviate the problems?
> 
> Acoustical sensitivity, low frequency changes.
> 
> For optical clocks and frequency transfer, just the vibration from
> traffic and other activity causes disturbances which disturbes the group
> delay. What is done for these links is to actively compensate then using
> a return path and closing the loop with a controller, very much like a
> PLL. The length of the loop limits the bandwidth and hence how high up
> the compensation can be done, so for longer stretches, this needs to be
> repeated. They have now built links from PTB to SYRTE and NPL.
> 
> Temperature shifts are slower, but also compensated though the active loop.

I suspect there’s a longer list of “slow” environmental effects that are also 
taken 
care of with the compensation setup. One would guess that crossing a active  
fault line would be “interesting”. 

Bob

> 
> Close proximity to strong power-currents have also been shown to cause
> modulations, so separate from power-cables if you can.
> 
> Remember that the end nodes have very stable clocks, so their effects
> can be taken out of the equation. For other setups, such as telco
> operation, that's a completely different ballgame.
> 
> Cheers,
> Magnus
> 
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[time-nuts] Lots of Off Topic discussion,

[Joe Hobart]

Scott McGrath

I am an amateur radio operator (62 years), and I have accurate 1 PPS and 10 MHz
available.  I also coordinate emergency communications for this very large 
county.

I use WWV:

   To judge propagation during normal and other than normal times

   To set clocks after a power outage

   To calibrate relatively new amateur radio transceivers (not Collins)

   To set my computer clock to better than 1/10 second for FT8 digital mode and
when I was recovering faint asteroids that were in danger of being lost

It is easy to set clocks within 1/10 second while watching the digital display
and listening to the WWV/WWVH tics.  I tend to get the wrong second when I use a
GPS clock.

Best,
Joe Hobart

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[time-nuts] Exact Time Mobile Phone Apps

[D. Resor]

I believe someone mentioned a cell phone "time" app.  This is an image of
the one I use for my iPhone.  It is Emerald Sequoia.
 
It queries correct time requests from four different NTP servers then picks
the one with the least amount of response delay I believe.
 
Of course when I'm out setting the clock on a Carillon system it has to be
"just" right, doesn't it?
 
I have uploaded a couple screen captures here:
 
http://hammondorganservice.com/downloads/images/Emerald-Sequoia.jpg
http://hammondorganservice.com/downloads/images/Emerald-Sequoia2.jpg
 
 
A description of how it works is here:
 
https://emeraldsequoia.com/et/index.html
 
 
 
 
Don Resor
N6KAW
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Re: [time-nuts] Frequency over fiber (was WWV and legal issues)

[Magnus Danielson]

Hi Gerhard,

I see that this became a separate thread.

On 09/02/2018 01:38 AM, Gerhard Hoffmann wrote:
> 
> 
> Am 01.09.2018 um 20:40 schrieb Magnus Danielson:
>> One should first know that there is a lot of papers now on frequency
>> transfer over fiber. The stability achieved on the best ones so far
>> greatly below that of the optical clocks that they want to compare.
> 
> Please, in a nutshell: what are the worst offenders:
> 
> - tranceivers (mechanical, temp, other misfeatures)
> - cables ( bending, temp, mechanical stress)
> - others?
> 
> In the case of transceivers: are there desirable modifications
> that would alleviate the problems?

Acoustical sensitivity, low frequency changes.

For optical clocks and frequency transfer, just the vibration from
traffic and other activity causes disturbances which disturbes the group
delay. What is done for these links is to actively compensate then using
a return path and closing the loop with a controller, very much like a
PLL. The length of the loop limits the bandwidth and hence how high up
the compensation can be done, so for longer stretches, this needs to be
repeated. They have now built links from PTB to SYRTE and NPL.

Temperature shifts are slower, but also compensated though the active loop.

Close proximity to strong power-currents have also been shown to cause
modulations, so separate from power-cables if you can.

Remember that the end nodes have very stable clocks, so their effects
can be taken out of the equation. For other setups, such as telco
operation, that's a completely different ballgame.

Cheers,
Magnus

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