Discussion:
WWV and legal issues
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Perry Sandeen via time-nuts
2018-08-29 23:33:45 UTC
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Yo Dudes! 
WWV and all its variations distribute what in the USA is the legal standard of time (from USNO) and frequency (NIST).
 If one is running a freq cal service IIRC it is a legal requirement to be able to have traceability to WWV.

If one was to rely on other sources, one has no guarantee that it 1. It is as accurate as claimed and 2. It can't be *diddled* with accidentally or deliberately.
Although GPSDO's are very good and popular, they come from satellites that are vulnerable to damage from earth based resources.
When your time and frequency standard(s) is under control on your own physical territory then they stand or fail on their own. 
After the atom bombing of Hiroshima and Nagasaki, one of the major inventors of the bomb (I don't remember who) went to see US president Harry Truman and essentially told him that the scientists who developed the bomb should have a say of how or when it should be used.
Truman is reported to have said for him to leave his office and told an aid that was responsible for his schedule to "never in hell let that (or any other) scientist  come to his office to influence American defense policy."
Considering its status from both a scientific and political perspective, IMNSHO it will go on as before.
To explain the political. No government official wants to see China or the Russian federation tell the world quote: See, the USA can't be trusted for something as important and simple as frequency and time.  However we are your friends who you can trust. Unquote.
Regards,





This is a case of practical use of WWV albeit over 50 years a go the fundamentals are still valid today.
At Karamursel Air station TUSLOG 234 I was assigned to the base receiver site.  Our base had to purposes.  to   




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Bob kb8tq
2018-08-29 23:38:56 UTC
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Hi

…. ummm ….. errr … not so much

GPS time is directly traceable to USNO. Given the accuracy of the various systems, you will get
much better confidence bars on GPS than on an HF or VLF system.

Bob

> On Aug 29, 2018, at 7:33 PM, Perry Sandeen via time-nuts <time-***@lists.febo.com> wrote:
>
> Yo Dudes!
> WWV and all its variations distribute what in the USA is the legal standard of time (from USNO) and frequency (NIST).
> If one is running a freq cal service IIRC it is a legal requirement to be able to have traceability to WWV.
>
> If one was to rely on other sources, one has no guarantee that it 1. It is as accurate as claimed and 2. It can't be *diddled* with accidentally or deliberately.
> Although GPSDO's are very good and popular, they come from satellites that are vulnerable to damage from earth based resources.
> When your time and frequency standard(s) is under control on your own physical territory then they stand or fail on their own.
> After the atom bombing of Hiroshima and Nagasaki, one of the major inventors of the bomb (I don't remember who) went to see US president Harry Truman and essentially told him that the scientists who developed the bomb should have a say of how or when it should be used.
> Truman is reported to have said for him to leave his office and told an aid that was responsible for his schedule to "never in hell let that (or any other) scientist come to his office to influence American defense policy."
> Considering its status from both a scientific and political perspective, IMNSHO it will go on as before.
> To explain the political. No government official wants to see China or the Russian federation tell the world quote: See, the USA can't be trusted for something as important and simple as frequency and time. However we are your friends who you can trust. Unquote.
> Regards,
>
>
>
>
>
> This is a case of practical use of WWV albeit over 50 years a go the fundamentals are still valid today.
> At Karamursel Air station TUSLOG 234 I was assigned to the base receiver site. Our base had to purposes. to
>
>
>
>
> _______________________________________________
> time-nuts mailing list -- time-***@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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Scott McGrath
2018-08-29 23:52:29 UTC
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Excellent point on LEGAL time, The problem is as always is GPS is the new shiny object.

You mentioned earth based hostile actors. But a really large solar flare or CME has the potential to take out or severely degrade ALL the GNSS systems.

Something on the order of the ‘Carrington Event’ or the flare in 1989 which took out power to much of Canada.

Things like this are why we need terrestrial time distribution systems like eLORAN which by its nature is resistant to both man made and natural interference.

On Aug 29, 2018, at 7:33 PM, Perry Sandeen via time-nuts <time-***@lists.febo.com> wrote:

Yo Dudes!
WWV and all its variations distribute what in the USA is the legal standard of time (from USNO) and frequency (NIST).
If one is running a freq cal service IIRC it is a legal requirement to be able to have traceability to WWV.

If one was to rely on other sources, one has no guarantee that it 1. It is as accurate as claimed and 2. It can't be *diddled* with accidentally or deliberately.
Although GPSDO's are very good and popular, they come from satellites that are vulnerable to damage from earth based resources.
When your time and frequency standard(s) is under control on your own physical territory then they stand or fail on their own.
After the atom bombing of Hiroshima and Nagasaki, one of the major inventors of the bomb (I don't remember who) went to see US president Harry Truman and essentially told him that the scientists who developed the bomb should have a say of how or when it should be used.
Truman is reported to have said for him to leave his office and told an aid that was responsible for his schedule to "never in hell let that (or any other) scientist come to his office to influence American defense policy."
Considering its status from both a scientific and political perspective, IMNSHO it will go on as before.
To explain the political. No government official wants to see China or the Russian federation tell the world quote: See, the USA can't be trusted for something as important and simple as frequency and time. However we are your friends who you can trust. Unquote.
Regards,





This is a case of practical use of WWV albeit over 50 years a go the fundamentals are still valid today.
At Karamursel Air station TUSLOG 234 I was assigned to the base receiver site. Our base had to purposes. to




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Scott McGrath
2018-08-29 23:54:47 UTC
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A DIY radio distribution system is not secure and traceable to NIST/USNO even if the source is GPS.



On Aug 29, 2018, at 7:52 PM, Scott McGrath <***@gmail.com> wrote:

Excellent point on LEGAL time, The problem is as always is GPS is the new shiny object.

You mentioned earth based hostile actors. But a really large solar flare or CME has the potential to take out or severely degrade ALL the GNSS systems.

Something on the order of the ‘Carrington Event’ or the flare in 1989 which took out power to much of Canada.

Things like this are why we need terrestrial time distribution systems like eLORAN which by its nature is resistant to both man made and natural interference.

On Aug 29, 2018, at 7:33 PM, Perry Sandeen via time-nuts <time-***@lists.febo.com> wrote:

Yo Dudes!
WWV and all its variations distribute what in the USA is the legal standard of time (from USNO) and frequency (NIST).
If one is running a freq cal service IIRC it is a legal requirement to be able to have traceability to WWV.

If one was to rely on other sources, one has no guarantee that it 1. It is as accurate as claimed and 2. It can't be *diddled* with accidentally or deliberately.
Although GPSDO's are very good and popular, they come from satellites that are vulnerable to damage from earth based resources.
When your time and frequency standard(s) is under control on your own physical territory then they stand or fail on their own.
After the atom bombing of Hiroshima and Nagasaki, one of the major inventors of the bomb (I don't remember who) went to see US president Harry Truman and essentially told him that the scientists who developed the bomb should have a say of how or when it should be used.
Truman is reported to have said for him to leave his office and told an aid that was responsible for his schedule to "never in hell let that (or any other) scientist come to his office to influence American defense policy."
Considering its status from both a scientific and political perspective, IMNSHO it will go on as before.
To explain the political. No government official wants to see China or the Russian federation tell the world quote: See, the USA can't be trusted for something as important and simple as frequency and time. However we are your friends who you can trust. Unquote.
Regards,





This is a case of practical use of WWV albeit over 50 years a go the fundamentals are still valid today.
At Karamursel Air station TUSLOG 234 I was assigned to the base receiver site. Our base had to purposes. to




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Bob kb8tq
2018-08-30 00:30:58 UTC
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Hi

One of the basic disconnects here seems to be the idea that radio was the “best thing” before
GPS came along. In fact that’s not really how it worked. Time was traced / coordinated by hauling
atomic clocks on airplanes as the “best thing” before satellite systems came along….That was true
for decades...

Bob

> On Aug 29, 2018, at 7:54 PM, Scott McGrath <***@gmail.com> wrote:
>
> A DIY radio distribution system is not secure and traceable to NIST/USNO even if the source is GPS.
>
>
>
> On Aug 29, 2018, at 7:52 PM, Scott McGrath <***@gmail.com> wrote:
>
> Excellent point on LEGAL time, The problem is as always is GPS is the new shiny object.
>
> You mentioned earth based hostile actors. But a really large solar flare or CME has the potential to take out or severely degrade ALL the GNSS systems.
>
> Something on the order of the ‘Carrington Event’ or the flare in 1989 which took out power to much of Canada.
>
> Things like this are why we need terrestrial time distribution systems like eLORAN which by its nature is resistant to both man made and natural interference.
>
> On Aug 29, 2018, at 7:33 PM, Perry Sandeen via time-nuts <time-***@lists.febo.com> wrote:
>
> Yo Dudes!
> WWV and all its variations distribute what in the USA is the legal standard of time (from USNO) and frequency (NIST).
> If one is running a freq cal service IIRC it is a legal requirement to be able to have traceability to WWV.
>
> If one was to rely on other sources, one has no guarantee that it 1. It is as accurate as claimed and 2. It can't be *diddled* with accidentally or deliberately.
> Although GPSDO's are very good and popular, they come from satellites that are vulnerable to damage from earth based resources.
> When your time and frequency standard(s) is under control on your own physical territory then they stand or fail on their own.
> After the atom bombing of Hiroshima and Nagasaki, one of the major inventors of the bomb (I don't remember who) went to see US president Harry Truman and essentially told him that the scientists who developed the bomb should have a say of how or when it should be used.
> Truman is reported to have said for him to leave his office and told an aid that was responsible for his schedule to "never in hell let that (or any other) scientist come to his office to influence American defense policy."
> Considering its status from both a scientific and political perspective, IMNSHO it will go on as before.
> To explain the political. No government official wants to see China or the Russian federation tell the world quote: See, the USA can't be trusted for something as important and simple as frequency and time. However we are your friends who you can trust. Unquote.
> Regards,
>
>
>
>
>
> This is a case of practical use of WWV albeit over 50 years a go the fundamentals are still valid today.
> At Karamursel Air station TUSLOG 234 I was assigned to the base receiver site. Our base had to purposes. to
>
>
>
>
> _______________________________________________
> time-nuts mailing list -- time-***@lists.febo.com
> To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.
>
> _______________________________________________
> time-nuts mailing list -- time-***@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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Scott McGrath
2018-08-30 12:01:23 UTC
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The ‘Flying Clocks’ served admirably to synchronize national standards laboratories.

But for a long time precision timing did not exist outside of national laboratories

In the modern world availability of reliable precision timing is essential to operation of modern technologies all those Thunderbolt GPSDO’s we love here they all came from cell sites or telcom CO’s

Without precision timing there is no telephone network, cell phones or internet. And that only became true in the last 20 years or so as long haul networks went from FDM on coaxial cable to TDM on fibre.

As to the effects on VLF and HF time distribution during a solar storm. Yes they will be hosed for the duration while we see interesting atmospheric effects like the northern lights in Mexico.

But any damage can be repaired easily because the systems are ground based. And once again time will be distributed after a short disruption in service which will likely be within oscillator holdover time.

Our space based systems once were fixable till a certain shrub decided to retire the repair truck which admittedly had its issues but was the ONLY vehicle which could capture a satellite and perform repairs.

Now the only fix is to launch new ones yet after a storm the old ones are a hazard because they are probably not responding to the ground control segment.



On Aug 29, 2018, at 8:30 PM, Bob kb8tq <***@n1k.org> wrote:

Hi

One of the basic disconnects here seems to be the idea that radio was the “best thing” before
GPS came along. In fact that’s not really how it worked. Time was traced / coordinated by hauling
atomic clocks on airplanes as the “best thing” before satellite systems came along….That was true
for decades...

Bob

> On Aug 29, 2018, at 7:54 PM, Scott McGrath <***@gmail.com> wrote:
>
> A DIY radio distribution system is not secure and traceable to NIST/USNO even if the source is GPS.
>
>
>
> On Aug 29, 2018, at 7:52 PM, Scott McGrath <***@gmail.com> wrote:
>
> Excellent point on LEGAL time, The problem is as always is GPS is the new shiny object.
>
> You mentioned earth based hostile actors. But a really large solar flare or CME has the potential to take out or severely degrade ALL the GNSS systems.
>
> Something on the order of the ‘Carrington Event’ or the flare in 1989 which took out power to much of Canada.
>
> Things like this are why we need terrestrial time distribution systems like eLORAN which by its nature is resistant to both man made and natural interference.
>
> On Aug 29, 2018, at 7:33 PM, Perry Sandeen via time-nuts <time-***@lists.febo.com> wrote:
>
> Yo Dudes!
> WWV and all its variations distribute what in the USA is the legal standard of time (from USNO) and frequency (NIST).
> If one is running a freq cal service IIRC it is a legal requirement to be able to have traceability to WWV.
>
> If one was to rely on other sources, one has no guarantee that it 1. It is as accurate as claimed and 2. It can't be *diddled* with accidentally or deliberately.
> Although GPSDO's are very good and popular, they come from satellites that are vulnerable to damage from earth based resources.
> When your time and frequency standard(s) is under control on your own physical territory then they stand or fail on their own.
> After the atom bombing of Hiroshima and Nagasaki, one of the major inventors of the bomb (I don't remember who) went to see US president Harry Truman and essentially told him that the scientists who developed the bomb should have a say of how or when it should be used.
> Truman is reported to have said for him to leave his office and told an aid that was responsible for his schedule to "never in hell let that (or any other) scientist come to his office to influence American defense policy."
> Considering its status from both a scientific and political perspective, IMNSHO it will go on as before.
> To explain the political. No government official wants to see China or the Russian federation tell the world quote: See, the USA can't be trusted for something as important and simple as frequency and time. However we are your friends who you can trust. Unquote.
> Regards,
>
>
>
>
>
> This is a case of practical use of WWV albeit over 50 years a go the fundamentals are still valid today.
> At Karamursel Air station TUSLOG 234 I was assigned to the base receiver site. Our base had to purposes. to
>
>
>
>
> _______________________________________________
> time-nuts mailing list -- time-***@lists.febo.com
> To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.
>
> _______________________________________________
> time-nuts mailing list -- time-***@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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Brian Lloyd
2018-08-30 12:45:15 UTC
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On Thu, Aug 30, 2018 at 7:01 AM, Scott McGrath <***@gmail.com> wrote:

>
>
>
> Without precision timing there is no telephone network, cell phones or
> internet. And that only became true in the last 20 years or so as long
> haul networks went from FDM on coaxial cable to TDM on fibre.
>

The Internet is largely asynchronous due to the store-and-forward nature of
the routers. Fiber capacity is increased through the use of wavelength
division multiplexing (WDM) which is itself a form of FDM. The Internet
functions without any sort of central synchronization.

Yes, there are portions that run over the synchronized telco services but
that is by convenience, not necessity.

--



Brian Lloyd
706 Flightline
Spring Branch, TX 78070
***@lloyd.aero
+1.210.802-8FLY (1.210.802-8359)
_______________________________________________
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Scott McGrath
2018-08-30 14:42:45 UTC
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Um no

Will the internet continue to route packets without precision timing yes it will, Yes the lambdas will stay lit on fiber but the ATM transport that runs on the lambdas will fail (note DSL is simply an ATM VC over copper). and other timing dependent services will fail

Will many services like authentication continue especially those based on multimaster replication continue to function?

No they will not, they are totally dependent on precision timing to ensure proper replication sourcing. (Microsoft Active Directory)

Banking transactions in the same boat.

Unless you’ve actually run a large network you dont realize just how dependent on precision timing the services running over the network have become especially authentication And one reason for this is increased security for the overall network.

On Aug 30, 2018, at 8:45 AM, Brian Lloyd <***@lloyd.aero> wrote:

On Thu, Aug 30, 2018 at 7:01 AM, Scott McGrath <***@gmail.com> wrote:

>
>
>
> Without precision timing there is no telephone network, cell phones or
> internet. And that only became true in the last 20 years or so as long
> haul networks went from FDM on coaxial cable to TDM on fibre.
>

The Internet is largely asynchronous due to the store-and-forward nature of
the routers. Fiber capacity is increased through the use of wavelength
division multiplexing (WDM) which is itself a form of FDM. The Internet
functions without any sort of central synchronization.

Yes, there are portions that run over the synchronized telco services but
that is by convenience, not necessity.

--



Brian Lloyd
706 Flightline
Spring Branch, TX 78070
***@lloyd.aero
+1.210.802-8FLY (1.210.802-8359)
_______________________________________________
time-nuts mailing list -- time-***@lists.febo.com
To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
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Brian Lloyd
2018-08-30 14:51:13 UTC
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On Thu, Aug 30, 2018 at 9:42 AM, Scott McGrath <***@gmail.com> wrote:

> Um no
>
> Will the internet continue to route packets without precision timing yes
> it will, Yes the lambdas will stay lit on fiber but the ATM transport that
> runs on the lambdas will fail (note DSL is simply an ATM VC over copper).
> and other timing dependent services will fail
>

You may find less ATM on the fast links than you think.


>
> Will many services like authentication continue especially those based on
> multimaster replication continue to function?
>
> No they will not, they are totally dependent on precision timing to
> ensure proper replication sourcing. (Microsoft Active Directory)


Precision timing better than NTP? Are you sure?

I guess there are some using Microsoft stuff but the fabric of the Internet
sure doesn't depend on it.



>
> Banking transactions in the same boat.
>

Same question.


>
> Unless you’ve actually run a large network you dont realize just how
> dependent on precision timing the services running over the network have
> become especially authentication And one reason for this is increased
> security for the overall network.
>

Yeah, I have some experience with running a large net. I have a little
experience with how the Internet runs. ;-)

--



Brian Lloyd
706 Flightline
Spring Branch, TX 78070
***@lloyd.aero
+1.210.802-8FLY (1.210.802-8359)
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James C Cotton
2018-08-30 15:04:43 UTC
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Time is the public key for a lot of the crypto that runs on networks.


Any large university or corporation has multiple GPS based time sources and compares them to others...


Back in the mid-1980's a fire in a CO in East Lansing, MI and a backhoe in Jackson, MI took out the Internet connections

at the university I work at. A couple of routers using time as the public key and exchanging encrypted routing packets were

isolated.


Jim Cotton

________________________________
From: time-nuts <time-nuts-***@lists.febo.com> on behalf of Scott McGrath <***@gmail.com>
Sent: Thursday, August 30, 2018 10:42:45 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] WWV and legal issues

Um no

Will the internet continue to route packets without precision timing yes it will, Yes the lambdas will stay lit on fiber but the ATM transport that runs on the lambdas will fail (note DSL is simply an ATM VC over copper). and other timing dependent services will fail

Will many services like authentication continue especially those based on multimaster replication continue to function?

No they will not, they are totally dependent on precision timing to ensure proper replication sourcing. (Microsoft Active Directory)

Banking transactions in the same boat.

Unless you’ve actually run a large network you dont realize just how dependent on precision timing the services running over the network have become especially authentication And one reason for this is increased security for the overall network.

On Aug 30, 2018, at 8:45 AM, Brian Lloyd <***@lloyd.aero> wrote:

On Thu, Aug 30, 2018 at 7:01 AM, Scott McGrath <***@gmail.com> wrote:

>
>
>
> Without precision timing there is no telephone network, cell phones or
> internet. And that only became true in the last 20 years or so as long
> haul networks went from FDM on coaxial cable to TDM on fibre.
>

The Internet is largely asynchronous due to the store-and-forward nature of
the routers. Fiber capacity is increased through the use of wavelength
division multiplexing (WDM) which is itself a form of FDM. The Internet
functions without any sort of central synchronization.

Yes, there are portions that run over the synchronized telco services but
that is by convenience, not necessity.

--



Brian Lloyd
706 Flightline
Spring Branch, TX 78070
***@lloyd.aero
+1.210.802-8FLY (1.210.802-8359)
_______________________________________________
time-nuts mailing list -- time-***@lists.febo.com
To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
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Scott McGrath
2018-08-30 15:24:03 UTC
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Bingo - we have a a Winner!!!

In a prior life as an architect at a northeastern we had Cs clocks, multiple GPS based NTP servers and CDMA NTP servers as TIME was the public key for all the crypto systems the Cs clocks were there in case GPS ‘went away’ for any reason and with service reliability as the primary goal instead of ‘maximizing shareholder value’ we made sure that precision timing could survive anything short of total destruction of the campus and our backup sites.



On Aug 30, 2018, at 11:04 AM, James C Cotton <***@wmich.edu> wrote:


Time is the public key for a lot of the crypto that runs on networks.


Any large university or corporation has multiple GPS based time sources and compares them to others...


Back in the mid-1980's a fire in a CO in East Lansing, MI and a backhoe in Jackson, MI took out the Internet connections

at the university I work at. A couple of routers using time as the public key and exchanging encrypted routing packets were

isolated.


Jim Cotton

________________________________
From: time-nuts <time-nuts-***@lists.febo.com> on behalf of Scott McGrath <***@gmail.com>
Sent: Thursday, August 30, 2018 10:42:45 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] WWV and legal issues

Um no

Will the internet continue to route packets without precision timing yes it will, Yes the lambdas will stay lit on fiber but the ATM transport that runs on the lambdas will fail (note DSL is simply an ATM VC over copper). and other timing dependent services will fail

Will many services like authentication continue especially those based on multimaster replication continue to function?

No they will not, they are totally dependent on precision timing to ensure proper replication sourcing. (Microsoft Active Directory)

Banking transactions in the same boat.

Unless you’ve actually run a large network you dont realize just how dependent on precision timing the services running over the network have become especially authentication And one reason for this is increased security for the overall network.

On Aug 30, 2018, at 8:45 AM, Brian Lloyd <***@lloyd.aero> wrote:

On Thu, Aug 30, 2018 at 7:01 AM, Scott McGrath <***@gmail.com> wrote:

>
>
>
> Without precision timing there is no telephone network, cell phones or
> internet. And that only became true in the last 20 years or so as long
> haul networks went from FDM on coaxial cable to TDM on fibre.
>

The Internet is largely asynchronous due to the store-and-forward nature of
the routers. Fiber capacity is increased through the use of wavelength
division multiplexing (WDM) which is itself a form of FDM. The Internet
functions without any sort of central synchronization.

Yes, there are portions that run over the synchronized telco services but
that is by convenience, not necessity.

--



Brian Lloyd
706 Flightline
Spring Branch, TX 78070
***@lloyd.aero
+1.210.802-8FLY (1.210.802-8359)
_______________________________________________
time-nuts mailing list -- time-***@lists.febo.com
To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
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James C Cotton
2018-08-30 15:44:24 UTC
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Management signed a PO for the previously "unneeded" Symmetricom units that had been requested a year earlier the next day...


Jim


________________________________
From: time-nuts <time-nuts-***@lists.febo.com> on behalf of Scott McGrath <***@gmail.com>
Sent: Thursday, August 30, 2018 11:24:03 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] WWV and legal issues

Bingo - we have a a Winner!!!

In a prior life as an architect at a northeastern we had Cs clocks, multiple GPS based NTP servers and CDMA NTP servers as TIME was the public key for all the crypto systems the Cs clocks were there in case GPS ‘went away’ for any reason and with service reliability as the primary goal instead of ‘maximizing shareholder value’ we made sure that precision timing could survive anything short of total destruction of the campus and our backup sites.



On Aug 30, 2018, at 11:04 AM, James C Cotton <***@wmich.edu> wrote:


Time is the public key for a lot of the crypto that runs on networks.


Any large university or corporation has multiple GPS based time sources and compares them to others...


Back in the mid-1980's a fire in a CO in East Lansing, MI and a backhoe in Jackson, MI took out the Internet connections

at the university I work at. A couple of routers using time as the public key and exchanging encrypted routing packets were

isolated.


Jim Cotton

________________________________
From: time-nuts <time-nuts-***@lists.febo.com> on behalf of Scott McGrath <***@gmail.com>
Sent: Thursday, August 30, 2018 10:42:45 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] WWV and legal issues

Um no

Will the internet continue to route packets without precision timing yes it will, Yes the lambdas will stay lit on fiber but the ATM transport that runs on the lambdas will fail (note DSL is simply an ATM VC over copper). and other timing dependent services will fail

Will many services like authentication continue especially those based on multimaster replication continue to function?

No they will not, they are totally dependent on precision timing to ensure proper replication sourcing. (Microsoft Active Directory)

Banking transactions in the same boat.

Unless you’ve actually run a large network you dont realize just how dependent on precision timing the services running over the network have become especially authentication And one reason for this is increased security for the overall network.

On Aug 30, 2018, at 8:45 AM, Brian Lloyd <***@lloyd.aero> wrote:

On Thu, Aug 30, 2018 at 7:01 AM, Scott McGrath <***@gmail.com> wrote:

>
>
>
> Without precision timing there is no telephone network, cell phones or
> internet. And that only became true in the last 20 years or so as long
> haul networks went from FDM on coaxial cable to TDM on fibre.
>

The Internet is largely asynchronous due to the store-and-forward nature of
the routers. Fiber capacity is increased through the use of wavelength
division multiplexing (WDM) which is itself a form of FDM. The Internet
functions without any sort of central synchronization.

Yes, there are portions that run over the synchronized telco services but
that is by convenience, not necessity.

--



Brian Lloyd
706 Flightline
Spring Branch, TX 78070
***@lloyd.aero
+1.210.802-8FLY (1.210.802-8359)
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Bob kb8tq
2018-08-30 15:14:26 UTC
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Hi

This is not so much a GPS issue as a system design issue. GPSDO’s are used to “smooth over” bumps in a lot
of systems out there. At the timing levels required by ATM or authentication setups, you can go a *long* time
running on a GPSDO. It’s not a matter of GPS, it’s a matter of doing things on the cheap ….

Bob

> On Aug 30, 2018, at 10:42 AM, Scott McGrath <***@gmail.com> wrote:
>
> Um no
>
> Will the internet continue to route packets without precision timing yes it will, Yes the lambdas will stay lit on fiber but the ATM transport that runs on the lambdas will fail (note DSL is simply an ATM VC over copper). and other timing dependent services will fail
>
> Will many services like authentication continue especially those based on multimaster replication continue to function?
>
> No they will not, they are totally dependent on precision timing to ensure proper replication sourcing. (Microsoft Active Directory)
>
> Banking transactions in the same boat.
>
> Unless you’ve actually run a large network you dont realize just how dependent on precision timing the services running over the network have become especially authentication And one reason for this is increased security for the overall network.
>
> On Aug 30, 2018, at 8:45 AM, Brian Lloyd <***@lloyd.aero> wrote:
>
> On Thu, Aug 30, 2018 at 7:01 AM, Scott McGrath <***@gmail.com> wrote:
>
>>
>>
>>
>> Without precision timing there is no telephone network, cell phones or
>> internet. And that only became true in the last 20 years or so as long
>> haul networks went from FDM on coaxial cable to TDM on fibre.
>>
>
> The Internet is largely asynchronous due to the store-and-forward nature of
> the routers. Fiber capacity is increased through the use of wavelength
> division multiplexing (WDM) which is itself a form of FDM. The Internet
> functions without any sort of central synchronization.
>
> Yes, there are portions that run over the synchronized telco services but
> that is by convenience, not necessity.
>
> --
>
>
>
> Brian Lloyd
> 706 Flightline
> Spring Branch, TX 78070
> ***@lloyd.aero
> +1.210.802-8FLY (1.210.802-8359)
> _______________________________________________
> time-nuts mailing list -- time-***@lists.febo.com
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> and follow the instructions there.
>
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Bob kb8tq
2018-08-29 23:57:05 UTC
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Hi

The same sort of massive solar flare that fiddles with sat systems also makes a mess of HF and VLF
systems. You have a high level of correlation in the impact. That makes them a poor “backup” in this case.

Bob

> On Aug 29, 2018, at 7:52 PM, Scott McGrath <***@gmail.com> wrote:
>
> Excellent point on LEGAL time, The problem is as always is GPS is the new shiny object.
>
> You mentioned earth based hostile actors. But a really large solar flare or CME has the potential to take out or severely degrade ALL the GNSS systems.
>
> Something on the order of the ‘Carrington Event’ or the flare in 1989 which took out power to much of Canada.
>
> Things like this are why we need terrestrial time distribution systems like eLORAN which by its nature is resistant to both man made and natural interference.
>
> On Aug 29, 2018, at 7:33 PM, Perry Sandeen via time-nuts <time-***@lists.febo.com> wrote:
>
> Yo Dudes!
> WWV and all its variations distribute what in the USA is the legal standard of time (from USNO) and frequency (NIST).
> If one is running a freq cal service IIRC it is a legal requirement to be able to have traceability to WWV.
>
> If one was to rely on other sources, one has no guarantee that it 1. It is as accurate as claimed and 2. It can't be *diddled* with accidentally or deliberately.
> Although GPSDO's are very good and popular, they come from satellites that are vulnerable to damage from earth based resources.
> When your time and frequency standard(s) is under control on your own physical territory then they stand or fail on their own.
> After the atom bombing of Hiroshima and Nagasaki, one of the major inventors of the bomb (I don't remember who) went to see US president Harry Truman and essentially told him that the scientists who developed the bomb should have a say of how or when it should be used.
> Truman is reported to have said for him to leave his office and told an aid that was responsible for his schedule to "never in hell let that (or any other) scientist come to his office to influence American defense policy."
> Considering its status from both a scientific and political perspective, IMNSHO it will go on as before.
> To explain the political. No government official wants to see China or the Russian federation tell the world quote: See, the USA can't be trusted for something as important and simple as frequency and time. However we are your friends who you can trust. Unquote.
> Regards,
>
>
>
>
>
> This is a case of practical use of WWV albeit over 50 years a go the fundamentals are still valid today.
> At Karamursel Air station TUSLOG 234 I was assigned to the base receiver site. Our base had to purposes. to
>
>
>
>
> _______________________________________________
> time-nuts mailing list -- time-***@lists.febo.com
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Mike Bafaro
2018-08-30 15:15:41 UTC
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According to what I have heard the 60KHz WWVB carrier is guaranteed accurate to the atomic standard and is considered traceable. I remember when I was in the Navy years ago I remember taking our unit's HP5245L for calibration and they used a VLF tracking receiver at 60KHz to do the calibration. If WWVB goes off the air what is the replacement for the 60KHz standard?

Mike

-----Original Message-----
From: time-nuts [mailto:time-nuts-***@lists.febo.com] On Behalf Of Perry Sandeen via time-nuts
Sent: Wednesday, August 29, 2018 6:34 PM
To: time-***@lists.febo.com
Cc: Perry Sandeen
Subject: [time-nuts] WWV and legal issues

Yo Dudes!�
WWV and all its variations distribute what in the USA is the legal standard of time (from USNO) and frequency (NIST).
�If one is running a freq cal service IIRC it is a legal requirement to be able to have traceability to WWV.

If one was to rely on other sources, one has no guarantee that it 1. It is as accurate as claimed and 2. It can't be *diddled* with accidentally or deliberately.
Although GPSDO's are very good and popular, they come from satellites that are vulnerable to damage from earth based resources.
When your time and frequency standard(s) is under control on your own physical territory then they stand or fail on their own.�
After the atom bombing of Hiroshima and Nagasaki, one of the major inventors of the bomb (I don't remember who) went to see US president Harry Truman and essentially told him that the scientists who developed the bomb should have a say of how or when it should be used.
Truman is reported to have said for him to leave his office and told an aid that was responsible for his schedule to "never in hell let that (or any other) scientist� come to his office to influence American defense policy."
Considering its status from both a scientific and political perspective, IMNSHO it will go on as before.
To explain the political. No government official wants to see China or the Russian federation tell the world quote: See, the USA can't be trusted for something as important and simple as frequency and time.� However we are your friends who you can trust. Unquote.
Regards,





This is a case of practical use of WWV albeit over 50 years a go the fundamentals are still valid today.
At Karamursel Air station TUSLOG 234 I was assigned to the base receiver site.� Our base had to purposes.� to� �




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jimlux
2018-08-30 17:23:20 UTC
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On 8/30/18 8:15 AM, Mike Bafaro wrote:
> According to what I have heard the 60KHz WWVB carrier is guaranteed accurate to the atomic standard and is considered traceable. I remember when I was in the Navy years ago I remember taking our unit's HP5245L for calibration and they used a VLF tracking receiver at 60KHz to do the calibration. If WWVB goes off the air what is the replacement for the 60KHz standard?
>
> Mike
>

The 5245L is a 1960,70s vintage thing so I assume you were doing those
cals 40 years ago when inexpensive atomic standards like the SRS FS725
didn't exist.

These days, I suspect that a $3000 Rb box or a GPSDO would have
sufficient accuracy for this sort of thing as a transfer standard, and
would be traceable. I can't imagine that a "over the air" signal
recovered from WWVB would be better than either of those two.

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David G. McGaw
2018-08-30 18:19:46 UTC
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Unfortunately, when they changed the format of WWVB recently to include
phase-modulated data it broke all the receivers that had used it as a
frequency standard, so we cannot use that argument.  A receiver to lock
to the new format has been documented here, but there may be only a
handful actually in existence.  For those looking for that type of
standard, it may be better to rely on the Navy VLF transmitters such as
NAA on 24kHz.  Who knows, but I expect they are not up to be defunded.

David N1HAC


On 8/30/18 1:23 PM, jimlux wrote:
> On 8/30/18 8:15 AM, Mike Bafaro wrote:
>> According to what I have heard the 60KHz WWVB carrier is guaranteed
>> accurate to the atomic standard and is considered traceable.  I
>> remember when I was in the Navy years ago I remember taking our
>> unit's HP5245L for calibration and they used a VLF tracking receiver
>> at 60KHz to do the calibration.  If WWVB goes off the air what is the
>> replacement for the 60KHz standard?
>>
>> Mike
>>
>
> The 5245L is a 1960,70s vintage thing so I assume you were doing those
> cals 40 years ago when inexpensive atomic standards like the SRS FS725
> didn't exist.
>
> These days, I suspect that a $3000 Rb box or a GPSDO would have
> sufficient accuracy for this sort of thing as a transfer standard, and
> would be traceable.  I can't imagine that a "over the air" signal
> recovered from WWVB would be better than either of those two.
>
> _______________________________________________
> time-nuts mailing list -- time-***@lists.febo.com
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Bob kb8tq
2018-08-30 16:27:12 UTC
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Hi

WWVB as transmitted ( = right at the input to the antenna) is a wonderfully stable signal. As soon as
that signal hits the real world things start to degrade. Propagation between transmit and receive sites
is a big deal, even at 60 KHz. On top of that, there is a *lot* of manmade noise at 60 KHz. The receive
signal to noise will never be as good as you might like it to be ….

60 KHz has a period of 16.667 us. GPS gives you ~10 ns sort of time quite quickly. Resolving the WWVB
carrier to that level is a major challenge. Identifying a single “cycle edge” as the magic timing ID with either
the old or new modulation formats …. yet another significant challenge. Net result is that you just can’t
get the same sort of timing out of WWVB.

Bob

> On Aug 30, 2018, at 11:15 AM, Mike Bafaro <***@comcast.net> wrote:
>
> According to what I have heard the 60KHz WWVB carrier is guaranteed accurate to the atomic standard and is considered traceable. I remember when I was in the Navy years ago I remember taking our unit's HP5245L for calibration and they used a VLF tracking receiver at 60KHz to do the calibration. If WWVB goes off the air what is the replacement for the 60KHz standard?
>
> Mike
>
> -----Original Message-----
> From: time-nuts [mailto:time-nuts-***@lists.febo.com] On Behalf Of Perry Sandeen via time-nuts
> Sent: Wednesday, August 29, 2018 6:34 PM
> To: time-***@lists.febo.com
> Cc: Perry Sandeen
> Subject: [time-nuts] WWV and legal issues
>
> Yo Dudes!�
> WWV and all its variations distribute what in the USA is the legal standard of time (from USNO) and frequency (NIST).
> �If one is running a freq cal service IIRC it is a legal requirement to be able to have traceability to WWV.
>
> If one was to rely on other sources, one has no guarantee that it 1. It is as accurate as claimed and 2. It can't be *diddled* with accidentally or deliberately.
> Although GPSDO's are very good and popular, they come from satellites that are vulnerable to damage from earth based resources.
> When your time and frequency standard(s) is under control on your own physical territory then they stand or fail on their own.�
> After the atom bombing of Hiroshima and Nagasaki, one of the major inventors of the bomb (I don't remember who) went to see US president Harry Truman and essentially told him that the scientists who developed the bomb should have a say of how or when it should be used.
> Truman is reported to have said for him to leave his office and told an aid that was responsible for his schedule to "never in hell let that (or any other) scientist� come to his office to influence American defense policy."
> Considering its status from both a scientific and political perspective, IMNSHO it will go on as before.
> To explain the political. No government official wants to see China or the Russian federation tell the world quote: See, the USA can't be trusted for something as important and simple as frequency and time.� However we are your friends who you can trust. Unquote.
> Regards,
>
>
>
>
>
> This is a case of practical use of WWV albeit over 50 years a go the fundamentals are still valid today.
> At Karamursel Air station TUSLOG 234 I was assigned to the base receiver site.� Our base had to purposes.� to� �
>
>
>
>
> _______________________________________________
> time-nuts mailing list -- time-***@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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Scott McGrath
2018-08-30 16:46:27 UTC
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One does not get the same instantaneous accuracy that one gets from GPS but with a long baseline the offsets to your site can be determined. With eLoran you can get similar levels of accuracy as the old Austron monitors used to prove

Content by Scott
Typos by Siri

On Aug 30, 2018, at 12:27 PM, Bob kb8tq <***@n1k.org> wrote:

Hi

WWVB as transmitted ( = right at the input to the antenna) is a wonderfully stable signal. As soon as
that signal hits the real world things start to degrade. Propagation between transmit and receive sites
is a big deal, even at 60 KHz. On top of that, there is a *lot* of manmade noise at 60 KHz. The receive
signal to noise will never be as good as you might like it to be ….

60 KHz has a period of 16.667 us. GPS gives you ~10 ns sort of time quite quickly. Resolving the WWVB
carrier to that level is a major challenge. Identifying a single “cycle edge” as the magic timing ID with either
the old or new modulation formats …. yet another significant challenge. Net result is that you just can’t
get the same sort of timing out of WWVB.

Bob

> On Aug 30, 2018, at 11:15 AM, Mike Bafaro <***@comcast.net> wrote:
>
> According to what I have heard the 60KHz WWVB carrier is guaranteed accurate to the atomic standard and is considered traceable. I remember when I was in the Navy years ago I remember taking our unit's HP5245L for calibration and they used a VLF tracking receiver at 60KHz to do the calibration. If WWVB goes off the air what is the replacement for the 60KHz standard?
>
> Mike
>
> -----Original Message-----
> From: time-nuts [mailto:time-nuts-***@lists.febo.com] On Behalf Of Perry Sandeen via time-nuts
> Sent: Wednesday, August 29, 2018 6:34 PM
> To: time-***@lists.febo.com
> Cc: Perry Sandeen
> Subject: [time-nuts] WWV and legal issues
>
> Yo Dudes!�
> WWV and all its variations distribute what in the USA is the legal standard of time (from USNO) and frequency (NIST).
> �If one is running a freq cal service IIRC it is a legal requirement to be able to have traceability to WWV.
>
> If one was to rely on other sources, one has no guarantee that it 1. It is as accurate as claimed and 2. It can't be *diddled* with accidentally or deliberately.
> Although GPSDO's are very good and popular, they come from satellites that are vulnerable to damage from earth based resources.
> When your time and frequency standard(s) is under control on your own physical territory then they stand or fail on their own.�
> After the atom bombing of Hiroshima and Nagasaki, one of the major inventors of the bomb (I don't remember who) went to see US president Harry Truman and essentially told him that the scientists who developed the bomb should have a say of how or when it should be used.
> Truman is reported to have said for him to leave his office and told an aid that was responsible for his schedule to "never in hell let that (or any other) scientist� come to his office to influence American defense policy."
> Considering its status from both a scientific and political perspective, IMNSHO it will go on as before.
> To explain the political. No government official wants to see China or the Russian federation tell the world quote: See, the USA can't be trusted for something as important and simple as frequency and time.� However we are your friends who you can trust. Unquote.
> Regards,
>
>
>
>
>
> This is a case of practical use of WWV albeit over 50 years a go the fundamentals are still valid today.
> At Karamursel Air station TUSLOG 234 I was assigned to the base receiver site.� Our base had to purposes.� to� �
>
>
>
>
> _______________________________________________
> time-nuts mailing list -- time-***@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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Bob kb8tq
2018-08-30 17:54:46 UTC
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Hi

With the Loran boxes, you were doing well to get down to the 100 ns level. When you did, it always was a
questionable sort of reading. More or less - is this real??? I spent a *lot* of time watching that data ….

Estimating what WWVB is doing over long baselines as the weather changes is not at all easy. To keep things
in sync you need solid data all the time. Guessing at your time source and then trying to discipline against it
does not make for a rational disciplining system. Again … I spent a lot of years looking at those phase plots.

Could you do pretty well for a few days with either one? Sure you could. For a system time source you are looking
at 24 hours a day / 365 days a year sort of performance. We are going round and round talking about the sort of solar flares that
haven’t happened in many decades (if ever …). The sort of stuff that disrupts WWVB or Loran (at the 10’s or 100’s of
nanoseconds level) happens many times a year, even in a good year. Ramp up the sun spots and it can get really interesting.

Is it better if I can toss rocks and hit the transmit antenna? Sure it is. Not everybody was / is within a hundred miles of a master
for Loran-C or of Ft. Colins for WWVB. If you are going to use WWVB, it’s got to work in Miami, Florida and in Bangor, Maine.
Working out carrier phase on WWVB as MSF comes in at equal strength in New England … yikes ….

There are good sound reasons why the WWVB disciplined systems gear got dumped a long time ago and replaced with GPS.
The GPS based gear performs better and is more reliable.

Bob

> On Aug 30, 2018, at 12:46 PM, Scott McGrath <***@gmail.com> wrote:
>
> One does not get the same instantaneous accuracy that one gets from GPS but with a long baseline the offsets to your site can be determined. With eLoran you can get similar levels of accuracy as the old Austron monitors used to prove
>
> Content by Scott
> Typos by Siri
>
> On Aug 30, 2018, at 12:27 PM, Bob kb8tq <***@n1k.org> wrote:
>
> Hi
>
> WWVB as transmitted ( = right at the input to the antenna) is a wonderfully stable signal. As soon as
> that signal hits the real world things start to degrade. Propagation between transmit and receive sites
> is a big deal, even at 60 KHz. On top of that, there is a *lot* of manmade noise at 60 KHz. The receive
> signal to noise will never be as good as you might like it to be ….
>
> 60 KHz has a period of 16.667 us. GPS gives you ~10 ns sort of time quite quickly. Resolving the WWVB
> carrier to that level is a major challenge. Identifying a single “cycle edge” as the magic timing ID with either
> the old or new modulation formats …. yet another significant challenge. Net result is that you just can’t
> get the same sort of timing out of WWVB.
>
> Bob
>
>> On Aug 30, 2018, at 11:15 AM, Mike Bafaro <***@comcast.net> wrote:
>>
>> According to what I have heard the 60KHz WWVB carrier is guaranteed accurate to the atomic standard and is considered traceable. I remember when I was in the Navy years ago I remember taking our unit's HP5245L for calibration and they used a VLF tracking receiver at 60KHz to do the calibration. If WWVB goes off the air what is the replacement for the 60KHz standard?
>>
>> Mike
>>
>> -----Original Message-----
>> From: time-nuts [mailto:time-nuts-***@lists.febo.com] On Behalf Of Perry Sandeen via time-nuts
>> Sent: Wednesday, August 29, 2018 6:34 PM
>> To: time-***@lists.febo.com
>> Cc: Perry Sandeen
>> Subject: [time-nuts] WWV and legal issues
>>
>> Yo Dudes!�
>> WWV and all its variations distribute what in the USA is the legal standard of time (from USNO) and frequency (NIST).
>> �If one is running a freq cal service IIRC it is a legal requirement to be able to have traceability to WWV.
>>
>> If one was to rely on other sources, one has no guarantee that it 1. It is as accurate as claimed and 2. It can't be *diddled* with accidentally or deliberately.
>> Although GPSDO's are very good and popular, they come from satellites that are vulnerable to damage from earth based resources.
>> When your time and frequency standard(s) is under control on your own physical territory then they stand or fail on their own.�
>> After the atom bombing of Hiroshima and Nagasaki, one of the major inventors of the bomb (I don't remember who) went to see US president Harry Truman and essentially told him that the scientists who developed the bomb should have a say of how or when it should be used.
>> Truman is reported to have said for him to leave his office and told an aid that was responsible for his schedule to "never in hell let that (or any other) scientist� come to his office to influence American defense policy."
>> Considering its status from both a scientific and political perspective, IMNSHO it will go on as before.
>> To explain the political. No government official wants to see China or the Russian federation tell the world quote: See, the USA can't be trusted for something as important and simple as frequency and time.� However we are your friends who you can trust. Unquote.
>> Regards,
>>
>>
>>
>>
>>
>> This is a case of practical use of WWV albeit over 50 years a go the fundamentals are still valid today.
>> At Karamursel Air station TUSLOG 234 I was assigned to the base receiver site.� Our base had to purposes.� to� �
>>
>>
>>
>>
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Attila Kinali
2018-08-30 17:54:30 UTC
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On Thu, 30 Aug 2018 12:27:12 -0400
Bob kb8tq <***@n1k.org> wrote:

> WWVB as transmitted ( = right at the input to the antenna) is a wonderfully stable signal. As soon as
> that signal hits the real world things start to degrade. Propagation between transmit and receive sites
> is a big deal, even at 60 KHz. On top of that, there is a *lot* of manmade noise at 60 KHz. The receive
> signal to noise will never be as good as you might like it to be ….

I don't know about WWVB, but for DCF77 it's known that sunrise/sunset
causes a phase shift of several 100µs at even moderate distances
(like ~500km). Unfortunately I don't have any measurements at hand.


Attila Kinali

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

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Bob kb8tq
2018-08-30 18:02:32 UTC
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Hi

Same basic problem with WWVB. If you were using it as a reference, you timed your
data collection to avoid the transition periods. You got both phase shifting and the
amplitude took a dive. Neither one was going to help you make a precision measurement.

In addition there are various weather events (terrestrial and solar) that can get into
the mix. You can see blips here and there that do not correlate with the sunrise / sunset
stuff. Again, not a big deal if you are manual evaluating the data to check your local
Rb standard or super duper OCXO. Not a good thing for disciplining a system 24 hours
a day 365 days a year.

Bob

> On Aug 30, 2018, at 1:54 PM, Attila Kinali <***@kinali.ch> wrote:
>
> On Thu, 30 Aug 2018 12:27:12 -0400
> Bob kb8tq <***@n1k.org> wrote:
>
>> WWVB as transmitted ( = right at the input to the antenna) is a wonderfully stable signal. As soon as
>> that signal hits the real world things start to degrade. Propagation between transmit and receive sites
>> is a big deal, even at 60 KHz. On top of that, there is a *lot* of manmade noise at 60 KHz. The receive
>> signal to noise will never be as good as you might like it to be ….
>
> I don't know about WWVB, but for DCF77 it's known that sunrise/sunset
> causes a phase shift of several 100µs at even moderate distances
> (like ~500km). Unfortunately I don't have any measurements at hand.
>
>
> Attila Kinali
>
> --
> It is upon moral qualities that a society is ultimately founded. All
> the prosperity and technological sophistication in the world is of no
> use without that foundation.
> -- Miss Matheson, The Diamond Age, Neal Stephenson
>
> _______________________________________________
> time-nuts mailing list -- time-***@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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ew via time-nuts
2018-08-30 19:14:29 UTC
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I started using WWVB in 1970 in Houston working for TI using a Tracor Omega receiver. Modified it for 60 KHz and used it for 40 years.  TI liked what I did and I modified quite a few for their Cal Labs in the US and Europe. Got a award and could keep all the extras. In those days TI was still in Oil exploration.
Houston OCXO, on moving to Dallas buried an OCXO 20 feet in the ground, later purchased a FRK (over 3K).  Two years later added temperature control and a year later a 12 bit blue Philrik DAC that I ran with a 3 MHZ Collins TCXO. Adjusted it once a year and only once did major change because I moved in 93 to Miami.

When I got my first Austron Loran C it was in parts E-13. Continued using it till the FRK died in 2010. The only bad thing was that you could hear the mechanical counter throughout the 2 story house day and night. Visitors did not appreciate it.
Bert Kehren
 
In a message dated 8/30/2018 2:03:49 PM Eastern Standard Time, ***@n1k.org writes:

 
Hi Same basic problem with WWVB. If you were using it as a reference, you timed your data collection to avoid the transition periods. You got both phase shifting and the amplitude took a dive. Neither one was going to help you make a precision measurement. In addition there are various weather events (terrestrial and solar) that can get into the mix. You can see blips here and there that do not correlate with the sunrise / sunset stuff. Again, not a big deal if you are manual evaluating the data to check your local Rb standard or super duper OCXO. Not a good thing for disciplining a system 24 hours a day 365 days a year. Bob > On Aug 30, 2018, at 1:54 PM, Attila Kinali <***@kinali.ch> wrote: > > On Thu, 30 Aug 2018 12:27:12 -0400 > Bob kb8tq <***@n1k.org> wrote: > >> WWVB as transmitted ( = right at the input to the antenna) is a wonderfully stable signal. As soon as >> that signal hits the real world things start to degrade. Propagation between transmit and receive sites >> is a big deal, even at 60 KHz. On top of that, there is a *lot* of manmade noise at 60 KHz. The receive >> signal to noise will never be as good as you might like it to be …. > > I don't know about WWVB, but for DCF77 it's known that sunrise/sunset > causes a phase shift of several 100µs at even moderate distances > (like ~500km). Unfortunately I don't have any measurements at hand. > > > Attila Kinali > > -- > It is upon moral qualities that a society is ultimately founded. All > the prosperity and technological sophistication in the world is of no > use without that foundation. > -- Miss Matheson, The Diamond Age, Neal Stephenson > > _______________________________________________ > time-nuts mailing list -- time-***@lists.febo.com > To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-***@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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Martin VE3OAT
2018-08-31 14:30:57 UTC
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But the diurnal phase shifts at VLF are predictable and largely
repeatable.  Ignore the phase at night and use only the phase records
during the day when an all-daylight propagation path exists.  You
might have to "correct" the absolute phase reading by some multiple of
the RF period, but with a low rate of local standard oscillator drift,
this is a simple matter of arithmetic. Back in the day, I managed
Sulzer crystal oscillators at 5 field sites from my office and could
maintain phase continuity for weeks at a time, until we had to diddle
the dial on one or several of them to correct for crystal aging.  Then
it was just more arithmetic again.  Several of the oscillators had
such low drift rates that all I needed was one daily phase reading
from the VLF phase tracking receiver (Tracor 599Js) at those sites to
know the frequency of the Sulzers there.

... Martin     VE3OAT

On Thu, 30 Aug 2018 12:27:12 -0400
Bob kb8tq<***@n1k.org> wrote:

> WWVB as transmitted ( = right at the input to the antenna) is a wonderfully stable signal. As soon as
> that signal hits the real world things start to degrade. Propagation between transmit and receive sites
> is a big deal, even at 60 KHz. On top of that, there is a*lot* of manmade noise at 60 KHz. The receive
> signal to noise will never be as good as you might like it to be ?.

> I don't know about WWVB, but for DCF77 it's known that sunrise/sunset
> causes a phase shift of several 100?s at even moderate distances
> (like ~500km). Unfortunately I don't have any measurements at hand.
>
>
> Attila Kinali
>



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Bob kb8tq
2018-08-31 15:15:46 UTC
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Hi

That works fine if you are doing things manual to check a local standard. If you are trying to
disipline a few thousand cell towers 24 hours a day … not so much. It also works for
checking frequency. What modern systems need is time. That gets you into a whole
world of resolving and identifying individual edges. The WWVB signal really was never
set up for this. Loran-C is an example of a signal that was designed to identify a specific
edge.

Bob

> On Aug 31, 2018, at 10:30 AM, Martin VE3OAT <***@storm.ca> wrote:
>
> But the diurnal phase shifts at VLF are predictable and largely repeatable. Ignore the phase at night and use only the phase records during the day when an all-daylight propagation path exists. You might have to "correct" the absolute phase reading by some multiple of the RF period, but with a low rate of local standard oscillator drift, this is a simple matter of arithmetic. Back in the day, I managed Sulzer crystal oscillators at 5 field sites from my office and could maintain phase continuity for weeks at a time, until we had to diddle the dial on one or several of them to correct for crystal aging. Then it was just more arithmetic again. Several of the oscillators had such low drift rates that all I needed was one daily phase reading from the VLF phase tracking receiver (Tracor 599Js) at those sites to know the frequency of the Sulzers there.
>
> ... Martin VE3OAT
>
> On Thu, 30 Aug 2018 12:27:12 -0400
> Bob kb8tq<***@n1k.org> wrote:
>
>> WWVB as transmitted ( = right at the input to the antenna) is a wonderfully stable signal. As soon as
>> that signal hits the real world things start to degrade. Propagation between transmit and receive sites
>> is a big deal, even at 60 KHz. On top of that, there is a*lot* of manmade noise at 60 KHz. The receive
>> signal to noise will never be as good as you might like it to be ?.
>
> > I don't know about WWVB, but for DCF77 it's known that sunrise/sunset
>> causes a phase shift of several 100?s at even moderate distances
>> (like ~500km). Unfortunately I don't have any measurements at hand.
>> Attila Kinali
>
>
> _______________________________________________
> time-nuts mailing list -- time-***@lists.febo.com
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Tom Holmes
2018-08-31 15:37:30 UTC
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Uh, folks...Would the apparently still on hiatus TVB approve of this on-going Urinary Olympiad? Just asking. And hoping post this won’t start another one.

Tom Holmes, N8ZM

-----Original Message-----
From: time-nuts <time-nuts-***@lists.febo.com> On Behalf Of Bob kb8tq
Sent: Friday, August 31, 2018 11:16 AM
To: Martin VE3OAT <***@storm.ca>; Discussion of precise time and frequency measurement <time-***@lists.febo.com>
Subject: Re: [time-nuts] WWV and legal issues

Hi

That works fine if you are doing things manual to check a local standard. If you are trying to
disipline a few thousand cell towers 24 hours a day … not so much. It also works for
checking frequency. What modern systems need is time. That gets you into a whole
world of resolving and identifying individual edges. The WWVB signal really was never
set up for this. Loran-C is an example of a signal that was designed to identify a specific
edge.

Bob

> On Aug 31, 2018, at 10:30 AM, Martin VE3OAT <***@storm.ca> wrote:
>
> But the diurnal phase shifts at VLF are predictable and largely repeatable. Ignore the phase at night and use only the phase records during the day when an all-daylight propagation path exists. You might have to "correct" the absolute phase reading by some multiple of the RF period, but with a low rate of local standard oscillator drift, this is a simple matter of arithmetic. Back in the day, I managed Sulzer crystal oscillators at 5 field sites from my office and could maintain phase continuity for weeks at a time, until we had to diddle the dial on one or several of them to correct for crystal aging. Then it was just more arithmetic again. Several of the oscillators had such low drift rates that all I needed was one daily phase reading from the VLF phase tracking receiver (Tracor 599Js) at those sites to know the frequency of the Sulzers there.
>
> ... Martin VE3OAT
>
> On Thu, 30 Aug 2018 12:27:12 -0400
> Bob kb8tq<***@n1k.org> wrote:
>
>> WWVB as transmitted ( = right at the input to the antenna) is a wonderfully stable signal. As soon as
>> that signal hits the real world things start to degrade. Propagation between transmit and receive sites
>> is a big deal, even at 60 KHz. On top of that, there is a*lot* of manmade noise at 60 KHz. The receive
>> signal to noise will never be as good as you might like it to be ?.
>
> > I don't know about WWVB, but for DCF77 it's known that sunrise/sunset
>> causes a phase shift of several 100?s at even moderate distances
>> (like ~500km). Unfortunately I don't have any measurements at hand.
>> Attila Kinali
>
>
> _______________________________________________
> time-nuts mailing list -- time-***@lists.febo.com
> To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
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Scott McGrath
2018-08-31 16:30:55 UTC
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Strangely enough there are these devices called ‘computers’ which are rumored to be able to perform measurements and mathematical calculations.

One of these ‘computers’ might be profitably employed to perform the necessary measurements calculations and deliver a useful output,

Employing a Mentat would be expensive for this task...


On Aug 31, 2018, at 11:37 AM, Tom Holmes <***@woh.rr.com> wrote:

Uh, folks...Would the apparently still on hiatus TVB approve of this on-going Urinary Olympiad? Just asking. And hoping post this won’t start another one.

Tom Holmes, N8ZM

-----Original Message-----
From: time-nuts <time-nuts-***@lists.febo.com> On Behalf Of Bob kb8tq
Sent: Friday, August 31, 2018 11:16 AM
To: Martin VE3OAT <***@storm.ca>; Discussion of precise time and frequency measurement <time-***@lists.febo.com>
Subject: Re: [time-nuts] WWV and legal issues

Hi

That works fine if you are doing things manual to check a local standard. If you are trying to
disipline a few thousand cell towers 24 hours a day … not so much. It also works for
checking frequency. What modern systems need is time. That gets you into a whole
world of resolving and identifying individual edges. The WWVB signal really was never
set up for this. Loran-C is an example of a signal that was designed to identify a specific
edge.

Bob

> On Aug 31, 2018, at 10:30 AM, Martin VE3OAT <***@storm.ca> wrote:
>
> But the diurnal phase shifts at VLF are predictable and largely repeatable. Ignore the phase at night and use only the phase records during the day when an all-daylight propagation path exists. You might have to "correct" the absolute phase reading by some multiple of the RF period, but with a low rate of local standard oscillator drift, this is a simple matter of arithmetic. Back in the day, I managed Sulzer crystal oscillators at 5 field sites from my office and could maintain phase continuity for weeks at a time, until we had to diddle the dial on one or several of them to correct for crystal aging. Then it was just more arithmetic again. Several of the oscillators had such low drift rates that all I needed was one daily phase reading from the VLF phase tracking receiver (Tracor 599Js) at those sites to know the frequency of the Sulzers there.
>
> ... Martin VE3OAT
>
> On Thu, 30 Aug 2018 12:27:12 -0400
> Bob kb8tq<***@n1k.org> wrote:
>
>> WWVB as transmitted ( = right at the input to the antenna) is a wonderfully stable signal. As soon as
>> that signal hits the real world things start to degrade. Propagation between transmit and receive sites
>> is a big deal, even at 60 KHz. On top of that, there is a*lot* of manmade noise at 60 KHz. The receive
>> signal to noise will never be as good as you might like it to be ?.
>
>> I don't know about WWVB, but for DCF77 it's known that sunrise/sunset
>> causes a phase shift of several 100?s at even moderate distances
>> (like ~500km). Unfortunately I don't have any measurements at hand.
>> Attila Kinali
>
>
> _______________________________________________
> time-nuts mailing list -- time-***@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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Bob kb8tq
2018-08-31 17:21:54 UTC
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Hi

Well if you have a magic piece of code that will do the trick, why don’t you share it with the
rest of us? In …. errr …. 50+ years of looking at the problem, nobody else seems to have
come up with an answer. It’s not because people have not tried. They’ve been working on
this sort of thing since at least the 60’s. It was at the heart of some really big problems the
DOD had with HF and VLF links. They poured some massive chunks of money into it.

Bob

> On Aug 31, 2018, at 12:30 PM, Scott McGrath <***@gmail.com> wrote:
>
> Strangely enough there are these devices called ‘computers’ which are rumored to be able to perform measurements and mathematical calculations.
>
> One of these ‘computers’ might be profitably employed to perform the necessary measurements calculations and deliver a useful output,
>
> Employing a Mentat would be expensive for this task...
>
>
> On Aug 31, 2018, at 11:37 AM, Tom Holmes <***@woh.rr.com> wrote:
>
> Uh, folks...Would the apparently still on hiatus TVB approve of this on-going Urinary Olympiad? Just asking. And hoping post this won’t start another one.
>
> Tom Holmes, N8ZM
>
> -----Original Message-----
> From: time-nuts <time-nuts-***@lists.febo.com> On Behalf Of Bob kb8tq
> Sent: Friday, August 31, 2018 11:16 AM
> To: Martin VE3OAT <***@storm.ca>; Discussion of precise time and frequency measurement <time-***@lists.febo.com>
> Subject: Re: [time-nuts] WWV and legal issues
>
> Hi
>
> That works fine if you are doing things manual to check a local standard. If you are trying to
> disipline a few thousand cell towers 24 hours a day … not so much. It also works for
> checking frequency. What modern systems need is time. That gets you into a whole
> world of resolving and identifying individual edges. The WWVB signal really was never
> set up for this. Loran-C is an example of a signal that was designed to identify a specific
> edge.
>
> Bob
>
>> On Aug 31, 2018, at 10:30 AM, Martin VE3OAT <***@storm.ca> wrote:
>>
>> But the diurnal phase shifts at VLF are predictable and largely repeatable. Ignore the phase at night and use only the phase records during the day when an all-daylight propagation path exists. You might have to "correct" the absolute phase reading by some multiple of the RF period, but with a low rate of local standard oscillator drift, this is a simple matter of arithmetic. Back in the day, I managed Sulzer crystal oscillators at 5 field sites from my office and could maintain phase continuity for weeks at a time, until we had to diddle the dial on one or several of them to correct for crystal aging. Then it was just more arithmetic again. Several of the oscillators had such low drift rates that all I needed was one daily phase reading from the VLF phase tracking receiver (Tracor 599Js) at those sites to know the frequency of the Sulzers there.
>>
>> ... Martin VE3OAT
>>
>> On Thu, 30 Aug 2018 12:27:12 -0400
>> Bob kb8tq<***@n1k.org> wrote:
>>
>>> WWVB as transmitted ( = right at the input to the antenna) is a wonderfully stable signal. As soon as
>>> that signal hits the real world things start to degrade. Propagation between transmit and receive sites
>>> is a big deal, even at 60 KHz. On top of that, there is a*lot* of manmade noise at 60 KHz. The receive
>>> signal to noise will never be as good as you might like it to be ?.
>>
>>> I don't know about WWVB, but for DCF77 it's known that sunrise/sunset
>>> causes a phase shift of several 100?s at even moderate distances
>>> (like ~500km). Unfortunately I don't have any measurements at hand.
>>> Attila Kinali
>>
>>
>> _______________________________________________
>> time-nuts mailing list -- time-***@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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Magnus Danielson
2018-09-01 09:29:25 UTC
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Hi,

It was very telling when I crashed a research group into the reality of
phase/time transfer over fiber compared to frequency transfer. Armed
with a whiteboard and pens, I derived the forumulas and showed how they
worked and not worked. It's a completely different ball-game and their
"known tricks" ain't doing nothing good as it comes to time.

I had to figure much of this out myself as I did nation-wide system
design to achieve the goal. It's a combination of many skills that goes
into designing the full system from scratch and make it fit together.
It's not hard stuff, it's just many details one needs to get right.

Oh the fun.

Cheers,
Magnus

On 08/31/2018 05:15 PM, Bob kb8tq wrote:
> Hi
>
> That works fine if you are doing things manual to check a local standard. If you are trying to
> disipline a few thousand cell towers 24 hours a day … not so much. It also works for
> checking frequency. What modern systems need is time. That gets you into a whole
> world of resolving and identifying individual edges. The WWVB signal really was never
> set up for this. Loran-C is an example of a signal that was designed to identify a specific
> edge.
>
> Bob
>
>> On Aug 31, 2018, at 10:30 AM, Martin VE3OAT <***@storm.ca> wrote:
>>
>> But the diurnal phase shifts at VLF are predictable and largely repeatable. Ignore the phase at night and use only the phase records during the day when an all-daylight propagation path exists. You might have to "correct" the absolute phase reading by some multiple of the RF period, but with a low rate of local standard oscillator drift, this is a simple matter of arithmetic. Back in the day, I managed Sulzer crystal oscillators at 5 field sites from my office and could maintain phase continuity for weeks at a time, until we had to diddle the dial on one or several of them to correct for crystal aging. Then it was just more arithmetic again. Several of the oscillators had such low drift rates that all I needed was one daily phase reading from the VLF phase tracking receiver (Tracor 599Js) at those sites to know the frequency of the Sulzers there.
>>
>> ... Martin VE3OAT
>>
>> On Thu, 30 Aug 2018 12:27:12 -0400
>> Bob kb8tq<***@n1k.org> wrote:
>>
>>> WWVB as transmitted ( = right at the input to the antenna) is a wonderfully stable signal. As soon as
>>> that signal hits the real world things start to degrade. Propagation between transmit and receive sites
>>> is a big deal, even at 60 KHz. On top of that, there is a*lot* of manmade noise at 60 KHz. The receive
>>> signal to noise will never be as good as you might like it to be ?.
>>
>>> I don't know about WWVB, but for DCF77 it's known that sunrise/sunset
>>> causes a phase shift of several 100?s at even moderate distances
>>> (like ~500km). Unfortunately I don't have any measurements at hand.
>>> Attila Kinali
>>
>>
>> _______________________________________________
>> time-nuts mailing list -- time-***@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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and foll
Scott McGrath
2018-09-01 14:00:39 UTC
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There was a paper published when NASA did something similar for LC39 and the VAB. Anyone have a copy because the link i have is dead.

As I recall it was some trick and compensating for thermal effects on the fiber itself was a large part of the effort.



On Sep 1, 2018, at 5:29 AM, Magnus Danielson <***@rubidium.dyndns.org> wrote:

Hi,

It was very telling when I crashed a research group into the reality of
phase/time transfer over fiber compared to frequency transfer. Armed
with a whiteboard and pens, I derived the forumulas and showed how they
worked and not worked. It's a completely different ball-game and their
"known tricks" ain't doing nothing good as it comes to time.

I had to figure much of this out myself as I did nation-wide system
design to achieve the goal. It's a combination of many skills that goes
into designing the full system from scratch and make it fit together.
It's not hard stuff, it's just many details one needs to get right.

Oh the fun.

Cheers,
Magnus

> On 08/31/2018 05:15 PM, Bob kb8tq wrote:
> Hi
>
> That works fine if you are doing things manual to check a local standard. If you are trying to
> disipline a few thousand cell towers 24 hours a day … not so much. It also works for
> checking frequency. What modern systems need is time. That gets you into a whole
> world of resolving and identifying individual edges. The WWVB signal really was never
> set up for this. Loran-C is an example of a signal that was designed to identify a specific
> edge.
>
> Bob
>
>> On Aug 31, 2018, at 10:30 AM, Martin VE3OAT <***@storm.ca> wrote:
>>
>> But the diurnal phase shifts at VLF are predictable and largely repeatable. Ignore the phase at night and use only the phase records during the day when an all-daylight propagation path exists. You might have to "correct" the absolute phase reading by some multiple of the RF period, but with a low rate of local standard oscillator drift, this is a simple matter of arithmetic. Back in the day, I managed Sulzer crystal oscillators at 5 field sites from my office and could maintain phase continuity for weeks at a time, until we had to diddle the dial on one or several of them to correct for crystal aging. Then it was just more arithmetic again. Several of the oscillators had such low drift rates that all I needed was one daily phase reading from the VLF phase tracking receiver (Tracor 599Js) at those sites to know the frequency of the Sulzers there.
>>
>> ... Martin VE3OAT
>>
>> On Thu, 30 Aug 2018 12:27:12 -0400
>> Bob kb8tq<***@n1k.org> wrote:
>>
>>> WWVB as transmitted ( = right at the input to the antenna) is a wonderfully stable signal. As soon as
>>> that signal hits the real world things start to degrade. Propagation between transmit and receive sites
>>> is a big deal, even at 60 KHz. On top of that, there is a*lot* of manmade noise at 60 KHz. The receive
>>> signal to noise will never be as good as you might like it to be ?.
>>
>>> I don't know about WWVB, but for DCF77 it's known that sunrise/sunset
>>> causes a phase shift of several 100?s at even moderate distances
>>> (like ~500km). Unfortunately I don't have any measurements at hand.
>>> Attila Kinali
>>
>>
>> _______________________________________________
>> time-nuts mailing list -- time-***@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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jimlux
2018-09-01 14:25:16 UTC
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On 9/1/18 7:00 AM, Scott McGrath wrote:
> There was a paper published when NASA did something similar for LC39 and the VAB. Anyone have a copy because the link i have is dead.
>
> As I recall it was some trick and compensating for thermal effects on the fiber itself was a large part of the effort.
>
>

I don't know about at the Cape (I'm not sure what the *need* for
precision timing at that level might be, but it could be there).

There's a whole lot of stuff that's been published about distributing
frequency references and holding tight phase tolerances at the Deep
Space Network stations, since they do arraying using multiple apertures,
as well as run of the mill VLBI stuff.

https://deepspace.jpl.nasa.gov/dsndocs/810-005/304/304B.pdf is the
"production" system for DSN, but as mentioned therein, there are various
improved schemes in development.

You might search for publications by Bob Tjoelker.


While there are JPL papers in IEEE sources behind paywalls, almost
always, they're also available in NTRS (https://ntrs.nasa.gov/) or JPL's
piece (https://trs.jpl.nasa.gov/). If the paper isn't online for free in
that location, you can send an email to NASA (there's a form at
ntrs.nasa.gov) or the JPL librarian (link at the trs site) and they'll
send it to you. Another good place to look for DSN related stuff is here:

https://ipnpr.jpl.nasa.gov/

The Chinese seem to have been publishing lots of papers on Arxiv
recently about "joint time and frequency distribution"

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Bob Martin
2018-09-01 17:06:04 UTC
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Jim,

You can still find the Deep Space Network fiber-optic
distribution equipment for sale on the Microsemi website:

https://www.microsemi.com/product-directory/modular-synchronization-systems/4168-time-code-translator

I designed the hardware for NASA's DSN upgrade while at Timing
Solutions Corp. I remember having to design and lay out 23 circuit
boards within about 5 months when we got that contract. The Time
Code Translator was the hardest to get right because it did so much.

I never paid much attention to where it went because it was "on to
the next project" as soon as it was completed. Still it's nice to
see that it got deployed and (hopefully) worked.

Bob Martin


On 9/1/2018 8:25 AM, jimlux wrote:
> On 9/1/18 7:00 AM, Scott McGrath wrote:
>> There was a paper published when NASA did something similar for
>> LC39 and the VAB.    Anyone have a copy because the link i have is
>> dead.
>>
>> As I recall it was some trick and compensating for thermal effects
>> on the fiber itself was a large part of the effort.
>>
>>
>
> I don't know about at the Cape (I'm not sure what the *need* for
> precision timing at that level might be, but it could be there).
>
> There's a whole lot of stuff that's been published about
> distributing frequency references and holding tight phase tolerances
> at the Deep Space Network stations, since they do arraying using
> multiple apertures, as well as run of the mill VLBI stuff.
>
> https://deepspace.jpl.nasa.gov/dsndocs/810-005/304/304B.pdf is the
> "production" system for DSN, but as mentioned therein, there are
> various improved schemes in development.
>
> You might search for publications by Bob Tjoelker.
>
>
>  While there are JPL papers in IEEE sources behind paywalls, almost
> always, they're also available in NTRS (https://ntrs.nasa.gov/) or
> JPL's piece (https://trs.jpl.nasa.gov/). If the paper isn't online
> for free in that location, you can send an email to NASA (there's a
> form at ntrs.nasa.gov) or the JPL librarian (link at the trs site)
> and they'll send it to you.  Another good place to look for DSN
> related stuff is here:
>
> https://ipnpr.jpl.nasa.gov/
>
> The Chinese seem to have been publishing lots of papers on Arxiv
> recently about "joint time and frequency distribution"
>
> _______________________________________________
> time-nuts mailing list -- time-***@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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Magnus Danielson
2018-09-01 18:40:33 UTC
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Hi Bob,

Thanks for the paper.

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.

Then, for those links able to transfer phase/time, most of them is for
point-to-point systems, many relating to relatively short distances.

Only a few relates to larger distances and some form of network style, mesh.

They fill different purposes, and should not be compared between the
groups, as it changes widely what is meaningful.

I did a presentation some EFTFs ago on some experiences of time-transfer
systems. We had some "interesting" failures where the delay jumped 1 ms.
That is what happens when underlying system re-route one side of a
two-way transfer under the feet of you. These are challenges others
don't see, but that comes with commercial telco setups. For some reason
I know far more about behavior and delays in radio links now than I
thought I would need to, again for reasons that would never show up in
dedicated systems. So, the challenges shifts with the field.

Cheers,
Magnus

On 09/01/2018 08:18 PM, Bob Martin wrote:
>
> Here is an interesting paper on using fiber:
>
> https://pdfs.semanticscholar.org/a37e/04164c01a6bfea2154c8f0dd97f49d1673b0.pdf
>
>
> I believe it used some of the gear that is(was) used in the GPS ground
> stations around the world.
>
> Bob Martin
>
> On 9/1/2018 3:29 AM, Magnus Danielson wrote:
>> Hi,
>>
>> It was very telling when I crashed a research group into the reality of
>> phase/time transfer over fiber compared to frequency transfer. Armed
>> with a whiteboard and pens, I derived the forumulas and showed how they
>> worked and not worked. It's a completely different ball-game and their
>> "known tricks" ain't doing nothing good as it comes to time.
>>
>> I had to figure much of this out myself as I did nation-wide system
>> design to achieve the goal. It's a combination of many skills that goes
>> into designing the full system from scratch and make it fit together.
>> It's not hard stuff, it's just many details one needs to get right.
>>
>> Oh the fun.
>>
>> Cheers,
>> Magnus
>>
>> On 08/31/2018 05:15 PM, Bob kb8tq wrote:
>>> Hi
>>>
>>> That works fine if you are doing things manual to check a local
>>> standard. If you are trying to
>>> disipline a few thousand cell towers 24 hours a day … not so much. It
>>> also works for
>>> checking frequency. What modern systems need is time. That gets you
>>> into a whole
>>> world of resolving and identifying individual edges. The WWVB signal
>>> really was never
>>> set up for this. Loran-C is an example of a signal that was designed
>>> to identify a specific
>>> edge.
>>>
>>> Bob
>>>
>>>> On Aug 31, 2018, at 10:30 AM, Martin VE3OAT <***@storm.ca> wrote:
>>>>
>>>> But the diurnal phase shifts at VLF are predictable and largely
>>>> repeatable.  Ignore the phase at night and use only the phase
>>>> records during the day when an all-daylight propagation path
>>>> exists.  You might have to "correct" the absolute phase reading by
>>>> some multiple of the RF period, but with a low rate of local
>>>> standard oscillator drift, this is a simple matter of arithmetic.
>>>> Back in the day, I managed Sulzer crystal oscillators at 5 field
>>>> sites from my office and could maintain phase continuity for weeks
>>>> at a time, until we had to diddle the dial on one or several of them
>>>> to correct for crystal aging.  Then it was just more arithmetic
>>>> again.  Several of the oscillators had such low drift rates that all
>>>> I needed was one daily phase reading from the VLF phase tracking
>>>> receiver (Tracor 599Js) at those sites to know the frequency of the
>>>> Sulzers there.
>>>>
>>>> ... Martin     VE3OAT
>>>>
>>>> On Thu, 30 Aug 2018 12:27:12 -0400
>>>> Bob kb8tq<***@n1k.org>  wrote:
>>>>
>>>>> WWVB as transmitted ( = right at the input to the antenna) is a
>>>>> wonderfully stable signal. As soon as
>>>>> that signal hits the real world things start to degrade.
>>>>> Propagation between transmit and receive sites
>>>>> is a big deal, even at 60 KHz. On top of that, there is a*lot*  of
>>>>> manmade noise at 60 KHz. The receive
>>>>> signal to noise will never be as good as you might like it to be ?.
>>>>
>>>>> I don't know about WWVB, but for DCF77 it's known that sunrise/sunset
>>>>> causes a phase shift of several 100?s at even moderate distances
>>>>> (like ~500km). Unfortunately I don't have any measurements at hand.
>>>>>                 Attila Kinali
>>>>
>>>>
>>>> _______________________________________________
>>>> time-nuts mailing list -- time-***@lists.febo.com
>>>> To unsubscribe, go to
>>>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
>>>> and follow the instructions there.
>>>
>>>
>>> _______________________________________________
>>> time-nuts mailing list -- time-***@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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Gerhard Hoffmann
2018-09-01 23:38:05 UTC
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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?

best regards, Gerhard



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Magnus Danielson
2018-09-02 11:17:20 UTC
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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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Bob kb8tq
2018-09-02 13:08:12 UTC
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Hi

> On Sep 2, 2018, at 7:17 AM, Magnus Danielson <***@rubidium.dyndns.org> 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
>
> _______________________________________________
> time-nuts mailing list -- time-***@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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Tom Van Baak
2018-09-02 14:07:48 UTC
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> 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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Bob kb8tq
2018-09-02 14:49:47 UTC
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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 <***@leapsecond.com> 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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> and follow the instructions there.


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Azelio Boriani
2018-09-02 15:07:03 UTC
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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 <***@n1k.org> 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 <***@leapsecond.com> 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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> > and follow the instructions there.
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Bob kb8tq
2018-09-02 18:13:42 UTC
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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 <***@gmail.com> 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 <***@n1k.org> 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 <***@leapsecond.com> 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-***@lists.febo.com
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>>> and follow the instructions there.
>>
>>
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Poul-Henning Kamp
2018-09-02 18:45:23 UTC
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--------

In message <C3C70D17-3E2D-44C6-924C-***@n1k.org>, 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
***@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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Dana Whitlow
2018-09-02 20:09:07 UTC
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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 <***@phk.freebsd.dk> wrote:

> --------
>
> In message <C3C70D17-3E2D-44C6-924C-***@n1k.org>, 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
> ***@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.
>
> _______________________________________________
> time-nuts mailing list -- time-***@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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Peter Vince
2018-09-02 20:13:05 UTC
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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 <***@rubidium.dyndns.org>
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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Anders Wallin
2018-09-03 07:38:13 UTC
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FWIW the round-trip delay on our 900km White Rabbit link looks like so
(lower graphs. upper are a local Cs-clock vs. the fiber-time):
http://monitor.mikes.fi/mikes_kaja/
No fault-lines, earthquakes, or volcanoes in Finland I'm afraid. That's a
standard 2-fiber (separate TX and RX fibers) DWDM system with amplifiers,
multiplexers, and dispersion-compensation fibers - in addition to the
actual fiber-spans.
diurnals on the 10.5 ms RTT seem to be around 80ns this time of the year.
Larger jumps are fiber/equipment repairs.

The recent earthquake paper on the London-Paris link is this one I think:
https://arxiv.org/ftp/arxiv/papers/1801/1801.02698.pdf


Anders


On Sun, Sep 2, 2018 at 11:14 PM Peter Vince <***@gmail.com>
wrote:

> 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 <***@rubidium.dyndns.org
> >
> 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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Daniel Schultz
2018-09-01 22:47:17 UTC
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Make sure that your fiber optic connectors are properly mated, or else this
could happen to you:
----------------------------------------------------------
Loose Cable May Unravel Faster-Than-Light Result
Science 02 Mar 2012:
Vol. 335, Issue 6072, pp. 1027
DOI: 10.1126/science.335.6072.1027
http://science.sciencemag.org/content/335/6072/1027

Anomalous data suggesting that neutrinos can travel faster than light probably
resulted from a faulty connection in a GPS timing system, physicists from the
OPERA collaboration revealed last week. Scientists who wish not to be
identified say a few persistent OPERA researchers spotted the problem during
tests the collaboration's leaders at first opposed.

OPERA, or Oscillation Project with Emulsion tRacking Apparatus, is a particle
detector housed under the Gran Sasso mountain in central Italy. In September
2011, 171 scientists from the international collaboration announced that
thousands of measurements made between 2009 and 2011 seemed to show that
neutrinos from the CERN laboratory near Geneva, Switzerland, were reaching
Gran Sasso some 60 billionths of a second (60 nanoseconds) earlier than light
would—a finding at odds with Einstein's special theory of relativity
(Science, 30 September 2011, p. 1809). In November, measurements with shorter,
easier-to-time pulses confirmed the anomaly, but many physicists remained
skeptical (Science, 2 December 2011, p. 1200).

That skepticism has grown with the latest announcement. From December 2011
until a couple of weeks ago, a small group of OPERA researchers carefully
measured how much time it takes light pulses to travel along an 8-kilometer
optical fiber that connects an external GPS receiver to the Gran Sasso
laboratory. The “time stamps” encoded by these pulses are also sent to
CERN to synchronize timing at the two labs, but the time that the pulses take
to travel along the fiber must be added to the time stamp to ensure that the
neutrinos' arrival times are recorded accurately.

The investigators discovered that the pulses' transit time varied by several
tens of nanoseconds depending on how tightly the coaxial fiber cable was
plugged into a socket attached to a card inside the experiment's master-clock
computer. The card converts the light pulses into electronic signals. Any
loose connection was supposed to stop the pulses from being registered, but
instead it appears that the card allowed the delayed pulses to get through. So
a loose connection during the experiment would have stamped neutrino pulses
with arrival times suggesting faster-than-light travel. Although researchers
can't be sure the cable was loose during the experiment, the size of the
delays involved is highly suggestive.

The travel times of pulses along the fiber had been measured in 2008 by
collaboration member Dario Autiero of the University of Lyon in France. A
source familiar with the experiment says some researchers thought the
measurement should have been rechecked before the neutrino velocity results
were submitted to a journal in November, but OPERA's scientific management
resisted carrying out such a check.

https://en.wikipedia.org/wiki/Faster-than-light_neutrino_anomaly#CITEREFCartlidge2012c


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