Re: [time-nuts] The future of UTC
Le 23/07/2011 01:39, Horst Schmidt a écrit : Ha, you may well ask. The reason to hate DST is given to us in the southern parts of Australia, by our Queensland cousins: The problems with DST is : 1. The Cows get very confused and the farmers have problems milking them. 2. The chickens don't know anymore when to lay the eggs. it is rumoured, that the shape of the eggs may suffer. However, this has not been proven, since Queensland never had DST. and 3. most importantly, The extra daylight fades the curtains more, and as every housewife will tell you: That will never do Not having DST looks dangerous to mental health. Luckily, my brother, who lives on the west coast has regular doses of DST and should not be affected. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Discipline an oscillator with NTP?
Yes, it can be done. Meinberg have a box which accepts a number of sync sources including NTP. http://www.meinberg.de/english/products/lantime-m300-mrs.htm Rob K -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Jason Rabel Sent: 22 July 2011 7:28 PM To: time-nuts@febo.com Subject: [time-nuts] Discipline an oscillator with NTP? I was just thinking (dangerous I know)... Has anyone attempted to build a stand-alone oscillator that is disciplined via NTP? i.e. NTP keeps it on-frequency... And I'm not talking about NTP that is locked to a local GPS, I'm curious about purely syncing to other NTP servers over a network. (The presumption is that you have no access to GPS, WWVB, Cellular, or similar.) Is it even possible or am I just day dreaming? ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The future of UTC
The problem is: multiple users in a wide area application, where manual reset of the new time is required - and some don't bother.. I have to process CCTV images from a wide range of separate, individual organisations, over whom I have no control. Some of them do a reset, others do not. Twice per year a lot of my time is wasted sorting out who has gone to DST (or vice versa) and who hasn't. Just as some users realise their system time is out by one hour, it's the time of year to change again! Automatic resets are the answer, but the smaller cheap-skate organisations will not spend the money. As soon as this illogical twice-yearly fiasco is ended, the better. Daylight Saving Time is a misnomer anyway - it's really Daylight Shifting Time. If you want more daylight, get out of bed earlier. Hate DST, keep UTC Universal. Ron The One - Original Message - From: Jim Palfreyman jim77...@gmail.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Friday, July 22, 2011 8:19 AM Subject: Re: [time-nuts] The future of UTC Mr HeathKid, What is your reason for hating dst. The changeover is a pain - but after that, what is the problem? Jim On 22 July 2011 14:23, Heathkid heath...@heathkid.com wrote: I live at 39° 57' 46 N and I absolutely HATE DST! Yes, Indiana... we haven't had DST for too long. It's bad and I hope some day we go back to not having it. - Original Message - From: Rob Kimberley r...@timing-consultants.com To: 'Discussion of precise time and frequency measurement' time-nuts@febo.com Sent: Tuesday, July 19, 2011 1:57 PM Subject: Re: [time-nuts] The future of UTC My earlier reply about flexible working practices still holds. Why not just move with the seasons. Before clocks, I'm sure that's what we did - we got up when it was light, and went to bed when it was dark. The bit in between just happens to be elastic... I live at 53 degrees North in the UK by the way. Rob K -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-bounces@**febo.comtime-nuts-boun...@febo.com] On Behalf Of Jim Palfreyman Sent: 19 July 2011 1:58 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] The future of UTC Far out. I've just read so many logical fallacies and government conspiracies I'm embarrassed for this high quality list. Let's inject some facts here. I live at 43 degrees south. At the winter solstice (June 21) the sun rises at 7:41 and sets at 16:43. At the summer solstice (December 21) the sun rises (no DST) at 04:28 and sets at 19:49. Sunrise at 04:28 is ridiculous. Including twilight it starts getting light at 3:30. Switch to DST and sunrise moves to 05:28 and sets at 20:49. Much more reasonable. Nice summer evenings too. We have DST for 6 months of the year and wouldn't swap it for anything. I understand it's different the closer to the equator you are, but for mid latitudes it really works. Jim On Tuesday, 19 July 2011, Thomas A Frank ka2...@cox.net wrote: BLOCK: This may be kind of an urban legend, but I thought I had heard that one of the backers behind extending Daylight Saving Time into the beginning of November was the candy industry, and it all had to do with Halloween. Mr. DOWNING: This is no kind of legend. This is the truth. For 25 years, candy-makers have wanted to get trick-or-treat covered by Daylight Saving, figuring that if children have an extra hour of daylight, they'll collect more candy. In fact, they went so far during the 1985 hearings on Daylight Saving as to put candy pumpkins on the seat of every senator, hoping to win a little favor. I would say it backfired. At least here in Rhode Island, the extra daylight resulted in the compression of the trick or treating schedule, since all the little goblins and ghouls wanted to go out after dark (to better scare the homeowners and enjoy their glow in the dark costumes), but they also were expected home by 8pm (local). Net result is less candy given out. At least that has been my experience. Proving you shouldn't tamper with time. Measure yes, tamper, no. :-) Tom Frank, KA2CDK __**_ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/**mailman/listinfo/time-nutshttps://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. __**_ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/**mailman/listinfo/time-nutshttps://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. __**_ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/** mailman/listinfo/time-nutshttps://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions
Re: [time-nuts] Discipline an oscillator with NTP?
I may be reading way to much into the question.
But the goal discipline the local oscillator as an alternate to GPS or WWVB
etc
Further assumption get the same types of services out of the oscillator
Frequency and time plus pulses.
That said if its one ntp source you look at, potentially far down stream
with many network hops, doesn't that make your reference only as good as
that ntp server as it jitters around?
Would it be better to track say 3 servers hopefully up toward the top of the
ntp service. Analyze their behavior to each other to attempt to account for
network behaviors and the server behaviors.
Essentially compare all three and derive a number to adjust the local
oscillator.
I might add that by adding any 1 pps source from radio or GPS while
available would really let you understand what jitter and path delays you
are getting and then establish the adjustment. (Fully understand that the
path is variable in IP.
Love simple but I suspect, its much tougher then that otherwise why mess
with GPS at all.
;-) Its that darn radio stuff.
Regards
Paul
WB8TSL
On Fri, Jul 22, 2011 at 10:25 PM, Chris Albertson albertson.ch...@gmail.com
wrote:
Yes but in this case it really is easy; Below is an outline (don't
try to compile it.). It has a slight problem because just using
sleep is kind of simplistic. One should wait on the new second and
add some error chacking Point here is just to show that this is not
weeks and weeks worth of work. The below pulse a bit every second
and if the system is running NTP then the length of a second is
controlled by NTP.
Main()
{
int status;
int fd;
int pw = 1000 /* pulse width in uS */
fd=open(dev/tty,O_RDWR);
while(1) {
status = 1;
ioctl(fd, TIOCMSET, status);
ussleep(pw);
status = 0;
ioctl(fd, TIOCMSET, status);
ussleep(100-pw);
}
}
On Fri, Jul 22, 2011 at 6:08 PM, Jim Lux jim...@earthlink.net wrote:
On 7/22/11 3:46 PM, brent evers wrote:
After that all you need to do is write some code to...
Oh - if I had a nickel for every time I've heard that!
Brent
When I worked in the physical effects business, we'd get a set of
storyboards from a director, and we'd have to figure out how we were
going
to build a rig or arrange the effect as required. The catch phrase was
always then, all you gotta do is...
representing some sort of incredibly difficult, tedious, or impractical
activity. Sure, install 10,000 lightbulb sockets into a frame and wire
them
up before tomorrow morning's call time at 6AM.. *all you gotta do* is get
50
people to each wire 200 sockets, screw in the bulbs and test them.
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
--
Chris Albertson
Redondo Beach, California
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Re: [time-nuts] Rubidium stability
On 07/22/11 11:48 PM, Perry Sandeen wrote: List, Someone asked about surplus rubidium stability. It was me. Here are my results. I had five Lucent Rubidium’s. Three were from RDR in centennial, CO and two were from the Huntsville hamfest. Before measuring stability, I ran them for a week on the bench. Using A Lucent GPS and a HP 5370B counter I found all of mine between 200 to 800 pico-seconds above or below 10 Mhz. Like someone else, I'm not sure what you mean by ps in this context. Dave ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Discipline an oscillator with NTP?
Yes but zero beat by ear is terrible. Are you talking a scope and I think
thats only 1 X 10-7 as I recall.
Regards
Paul.
On Sat, Jul 23, 2011 at 12:42 PM, Bob Camp li...@rtty.us wrote:
Hi
The simple answer is that normal NTP via the net will give you accuracy
similar to the zero beat to WWV approach. It will take a few days to get
to that level. Much faster to fire up the radio and use WWV.
Bob
On Jul 23, 2011, at 12:29 PM, paul swed wrote:
I may be reading way to much into the question.
But the goal discipline the local oscillator as an alternate to GPS or
WWVB
etc
Further assumption get the same types of services out of the oscillator
Frequency and time plus pulses.
That said if its one ntp source you look at, potentially far down stream
with many network hops, doesn't that make your reference only as good as
that ntp server as it jitters around?
Would it be better to track say 3 servers hopefully up toward the top of
the
ntp service. Analyze their behavior to each other to attempt to account
for
network behaviors and the server behaviors.
Essentially compare all three and derive a number to adjust the local
oscillator.
I might add that by adding any 1 pps source from radio or GPS while
available would really let you understand what jitter and path delays you
are getting and then establish the adjustment. (Fully understand that the
path is variable in IP.
Love simple but I suspect, its much tougher then that otherwise why mess
with GPS at all.
;-) Its that darn radio stuff.
Regards
Paul
WB8TSL
On Fri, Jul 22, 2011 at 10:25 PM, Chris Albertson
albertson.ch...@gmail.com
wrote:
Yes but in this case it really is easy; Below is an outline (don't
try to compile it.). It has a slight problem because just using
sleep is kind of simplistic. One should wait on the new second and
add some error chacking Point here is just to show that this is not
weeks and weeks worth of work. The below pulse a bit every second
and if the system is running NTP then the length of a second is
controlled by NTP.
Main()
{
int status;
int fd;
int pw = 1000 /* pulse width in uS */
fd=open(dev/tty,O_RDWR);
while(1) {
status = 1;
ioctl(fd, TIOCMSET, status);
ussleep(pw);
status = 0;
ioctl(fd, TIOCMSET, status);
ussleep(100-pw);
}
}
On Fri, Jul 22, 2011 at 6:08 PM, Jim Lux jim...@earthlink.net wrote:
On 7/22/11 3:46 PM, brent evers wrote:
After that all you need to do is write some code to...
Oh - if I had a nickel for every time I've heard that!
Brent
When I worked in the physical effects business, we'd get a set of
storyboards from a director, and we'd have to figure out how we were
going
to build a rig or arrange the effect as required. The catch phrase
was
always then, all you gotta do is...
representing some sort of incredibly difficult, tedious, or impractical
activity. Sure, install 10,000 lightbulb sockets into a frame and wire
them
up before tomorrow morning's call time at 6AM.. *all you gotta do* is
get
50
people to each wire 200 sockets, screw in the bulbs and test them.
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
--
Chris Albertson
Redondo Beach, California
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Re: [time-nuts] Discipline an oscillator with NTP?
Hi
There is a range in what NTP will do, just as there is a range in what you can
do via zero beat to WWV. You can get to a ppm or so via zero beat most of the
time. Under good conditions you can get to 0.1 ppm. A practial NTP system
running to servers over the net has roughly the same accuracy. Time constant of
10,000 seconds, time accuracy / stability of 1 to 10 ms.
Bob
On Jul 23, 2011, at 12:49 PM, paul swed wrote:
Yes but zero beat by ear is terrible. Are you talking a scope and I think
thats only 1 X 10-7 as I recall.
Regards
Paul.
On Sat, Jul 23, 2011 at 12:42 PM, Bob Camp li...@rtty.us wrote:
Hi
The simple answer is that normal NTP via the net will give you accuracy
similar to the zero beat to WWV approach. It will take a few days to get
to that level. Much faster to fire up the radio and use WWV.
Bob
On Jul 23, 2011, at 12:29 PM, paul swed wrote:
I may be reading way to much into the question.
But the goal discipline the local oscillator as an alternate to GPS or
WWVB
etc
Further assumption get the same types of services out of the oscillator
Frequency and time plus pulses.
That said if its one ntp source you look at, potentially far down stream
with many network hops, doesn't that make your reference only as good as
that ntp server as it jitters around?
Would it be better to track say 3 servers hopefully up toward the top of
the
ntp service. Analyze their behavior to each other to attempt to account
for
network behaviors and the server behaviors.
Essentially compare all three and derive a number to adjust the local
oscillator.
I might add that by adding any 1 pps source from radio or GPS while
available would really let you understand what jitter and path delays you
are getting and then establish the adjustment. (Fully understand that the
path is variable in IP.
Love simple but I suspect, its much tougher then that otherwise why mess
with GPS at all.
;-) Its that darn radio stuff.
Regards
Paul
WB8TSL
On Fri, Jul 22, 2011 at 10:25 PM, Chris Albertson
albertson.ch...@gmail.com
wrote:
Yes but in this case it really is easy; Below is an outline (don't
try to compile it.). It has a slight problem because just using
sleep is kind of simplistic. One should wait on the new second and
add some error chacking Point here is just to show that this is not
weeks and weeks worth of work. The below pulse a bit every second
and if the system is running NTP then the length of a second is
controlled by NTP.
Main()
{
int status;
int fd;
int pw = 1000 /* pulse width in uS */
fd=open(dev/tty,O_RDWR);
while(1) {
status = 1;
ioctl(fd, TIOCMSET, status);
ussleep(pw);
status = 0;
ioctl(fd, TIOCMSET, status);
ussleep(100-pw);
}
}
On Fri, Jul 22, 2011 at 6:08 PM, Jim Lux jim...@earthlink.net wrote:
On 7/22/11 3:46 PM, brent evers wrote:
After that all you need to do is write some code to...
Oh - if I had a nickel for every time I've heard that!
Brent
When I worked in the physical effects business, we'd get a set of
storyboards from a director, and we'd have to figure out how we were
going
to build a rig or arrange the effect as required. The catch phrase
was
always then, all you gotta do is...
representing some sort of incredibly difficult, tedious, or impractical
activity. Sure, install 10,000 lightbulb sockets into a frame and wire
them
up before tomorrow morning's call time at 6AM.. *all you gotta do* is
get
50
people to each wire 200 sockets, screw in the bulbs and test them.
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
--
Chris Albertson
Redondo Beach, California
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Re: [time-nuts] Discipline an oscillator with NTP?
On 7/23/11 9:42 AM, Bob Camp wrote: Hi The simple answer is that normal NTP via the net will give you accuracy similar to the zero beat to WWV approach. It will take a few days to get to that level. Much faster to fire up the radio and use WWV. Bob If you aren't somewhere that has no radio (e.g. underground, in a electrically noisy EMI environment, underwater, etc.) ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Discipline an oscillator with NTP?
Hi Same issue with NTP. As long as you aren't on a link with nasty asymmetry problems or highly variable delays. There's also the basic do I trust the server issue. You can indeed trust WWV as transmitted. Bob On Jul 23, 2011, at 1:24 PM, Jim Lux wrote: On 7/23/11 9:42 AM, Bob Camp wrote: Hi The simple answer is that normal NTP via the net will give you accuracy similar to the zero beat to WWV approach. It will take a few days to get to that level. Much faster to fire up the radio and use WWV. Bob If you aren't somewhere that has no radio (e.g. underground, in a electrically noisy EMI environment, underwater, etc.) ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Discipline an oscillator with NTP?
Hi WWV as transmitted is massively more accurate than it is as received. There are a lot of NTP servers out there with offsets in the ms to fraction of a ms range. Even if your path was perfect, those issues would keep you from getting to the us level. You could indeed build up some custom servers and take care of the issue. At least as I understood the original question, random servers on the net were the time source. I assume you would pick them for short path to your location, and then reject any that did really stupid stuff. Bob On Jul 23, 2011, at 2:02 PM, Chris Albertson wrote: On Sat, Jul 23, 2011 at 10:40 AM, Bob Camp li...@rtty.us wrote: There's also the basic do I trust the server issue. You can indeed trust WWV as transmitted. NTP's clock selection algorithm is pretty good. If you choose a diverse set of servers then NTP will only use the subset of them that are self consistent. Pool servers are assigned randomly so even if there were many bad servers in the world the chance of randomly picking five that were are bad in the exact same way is about zero. Typically when a server has a problem it does not match another randomly selected ntp server. So I think you can trust the consensus time from a set of five randomly selected pool servers. It would be far easier to spoof WWV, just set up a transmitter. -- Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Discipline an oscillator with NTP?
Indeed thats why I was saying choose 3 servers. Now I see in the thread that you can pick pools of servers so thats good. Then average what they say the time is and drive oscillator. Wonder if you could look towards the stratum 1 servers. But that said I could easily believe that it might ot be any better then wwv. Good thread. Things to learn as we all seek a backup to GPS I assume. Regards Paul WB8TSL On Sat, Jul 23, 2011 at 2:17 PM, Bob Camp li...@rtty.us wrote: Hi WWV as transmitted is massively more accurate than it is as received. There are a lot of NTP servers out there with offsets in the ms to fraction of a ms range. Even if your path was perfect, those issues would keep you from getting to the us level. You could indeed build up some custom servers and take care of the issue. At least as I understood the original question, random servers on the net were the time source. I assume you would pick them for short path to your location, and then reject any that did really stupid stuff. Bob On Jul 23, 2011, at 2:02 PM, Chris Albertson wrote: On Sat, Jul 23, 2011 at 10:40 AM, Bob Camp li...@rtty.us wrote: There's also the basic do I trust the server issue. You can indeed trust WWV as transmitted. NTP's clock selection algorithm is pretty good. If you choose a diverse set of servers then NTP will only use the subset of them that are self consistent. Pool servers are assigned randomly so even if there were many bad servers in the world the chance of randomly picking five that were are bad in the exact same way is about zero. Typically when a server has a problem it does not match another randomly selected ntp server. So I think you can trust the consensus time from a set of five randomly selected pool servers. It would be far easier to spoof WWV, just set up a transmitter. -- Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Discipline an oscillator with NTP?
I think the original question - is it possible has been answered - yes, it can be (and has been) done. The real question becomes what specs can one achieve using a specific feedback loop (and what is the best method to discipline). After one year of NTP queries, assume you have a 100ms jitter on the network time, you could at most tweak your oscillator, based on past performance, to 6E-9. This would be simple for a perfectly stable oscillator just in need of frequency adjustment. It gets more complicated if it is actually a mere mortal, aging, drifty oscillator (like most of us). You'd have to start modeling the drift, drift of the drift, temperature, etc. - similar to what HP calls 'Smart Clock' to use the NTP only as long interval calibrator and oscillator drift estimator. I don't see much use in this exercise, jitter is too high (even after massaging, averaging, voting, etc.) to get to time-nuts worthiness in less than weeks or months' time. It is the same as instead of 1 pulse per second, GPS gave us one pulse per month (but with 10ms uncertainty). The generic question becomes: given one reference of such Allan Variance, how can it be combined with another one (of different Allan Variance spectrum) to generate a device that is better than both (typically we want the short term stability of one, disciplined by the better long term of another). The mathematicians on duty could estimate the best achievable plot for a sample HP oven osc trained by NTP (with some periodic query, filtering, etc.) Same problem as Can I set my watch by the Rooster's call every morning? (no DST needed here!) -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob Camp Sent: Saturday, July 23, 2011 11:18 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Discipline an oscillator with NTP? Hi WWV as transmitted is massively more accurate than it is as received. There are a lot of NTP servers out there with offsets in the ms to fraction of a ms range. Even if your path was perfect, those issues would keep you from getting to the us level. You could indeed build up some custom servers and take care of the issue. At least as I understood the original question, random servers on the net were the time source. I assume you would pick them for short path to your location, and then reject any that did really stupid stuff. Bob On Jul 23, 2011, at 2:02 PM, Chris Albertson wrote: On Sat, Jul 23, 2011 at 10:40 AM, Bob Camp li...@rtty.us wrote: There's also the basic do I trust the server issue. You can indeed trust WWV as transmitted. NTP's clock selection algorithm is pretty good. If you choose a diverse set of servers then NTP will only use the subset of them that are self consistent. Pool servers are assigned randomly so even if there were many bad servers in the world the chance of randomly picking five that were are bad in the exact same way is about zero. Typically when a server has a problem it does not match another randomly selected ntp server. So I think you can trust the consensus time from a set of five randomly selected pool servers. It would be far easier to spoof WWV, just set up a transmitter. -- Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Discipline an oscillator with NTP?
In message cabbxvhuz+yo+fch1qb3xsuppfpcnpbghoe1jbqsrdgql_c+...@mail.gmail.com , Chris Albertson writes: On Sat, Jul 23, 2011 at 10:40 AM, Bob Camp li...@rtty.us wrote: NTP's clock selection algorithm is pretty good. If you choose a diverse set of servers then NTP will only use the subset of them that are self consistent. That depends a lot on your definition of good. If you give the clock selection algoritm more than 5 choices, it tends to be fickle and change reference server far too often. The same will happen with fewer really good (=close) servers. So I think you can trust the consensus time from a set of five randomly selected pool servers. It would be far easier to spoof WWV, just set up a transmitter. NTPd does build a consensus, it picks a winner. If you want to do something like this, the one thing you want to do is hand-pick the NTP server you use, and clamp its minpoll/maxpoll to the same value. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Discipline an oscillator with NTP?
In message 022101cc4970$b24a4b80$16dee280$@com, Jose Camara writes: After one year of NTP queries, assume you have a 100ms jitter on the network time, you could at most tweak your oscillator, based on past performance, to 6E-9. It is a lot more complicated than that, we need to talk allan-deviation here, not scalar numbers. The main problem here is that the 'default' NTPd software is not really written for something like this, and has attributes which makes it truly sucky for the task. If you want to do this, you want to write your own software and you want to give it an entirely different modus operandi. As with all oscillator discplining, what you are looking for is the so called allan intercept where the two sources allan deviation cross. With a NTP reference, its location varies depending on stochastic network properties, which depends what's between the server and you. If you control the network topology (as in: Can make sure there is no other traffic), you're fine, normal PLL style stuff works. If you don't control the network topology, the RTT between you and the server becomes a BIG problem, because the fundamental NTP assumption that it is symmetric is almost always wrong. You can average over long tau's, but then your ISP upgrades their routed and a systematic change in RTT screws your integrator over for several weeks. Alternatively, if your LO is stable enough (=Rb/Cs), you can operate on first derivative of the RTT, which turns the routed upgrade into a single spiky sample, but the cost is an overall higher noise in your error signal. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] 5370 firmware hacking status report
Some progress since February's discussion: My m6800 emulator running the 5370 firmware has been moved from the Linux box to a little 32-bit microcontroller on it's own small evaluation-kit board. Pictures here: http://jks.com (click on images for larger versions) You talk to it over an Ethernet connection. The 5370 device bus connects to the general-purpose I/O pins of the micro. Since the micro has 256KB Flash 128KB SRAM no off-chip memory is required. Everything just fits: emulator, firmware, lightweight TCP/IP stack, minimal C runtime, device drivers, performance hacks, ... All the front panel controls seem to work as expected. The operator verification section of the manual checks out. The HPIB hardware remote programming work, but I have a limited ability to test it currently. I have no computer-based GPIB card yet, just a 4396A with HPIB + Instrument Basic (yuk). But I also have a mode that fools the firmware into thinking the 5370 has the HPIB card installed (when it doesn't) and instead sends the transactions over Ethernet (USB also possible). More about this in a bit. Measurement performance is improved 40% on average and as much as 70% for some functions (see the spreadsheet and charts). The ultimate goal is to produce a drop-in replacement for the CPU card which would also allow you to toss the ROM card (older 5370s) and HPIB card. You'd get serial, Ethernet and USB connectivity to replace the HPIB. Now all this is fine, and somewhat amusing, but it's not clear there is any particular advantage. It's not as though there are piles of 5370s lying around with dead or missing CPU cards. Or that it's impossible to deal with HPIB anymore. One interesting possibility is adding new front-panel accessible measurement functions. Since the emulator has complete bus access it can detect new key press combinations before the firmware does and go into a mode where it gathers raw TI samples, processes them, and puts the results in the display. When an existing key sequence occurs the firmware is resumed and it doesn't even know it was paused while the new function was running. But I discovered something else that's even more interesting (note that I am relatively new to this time-nut stuff, so please correct my nutty mistakes). There was a discussion about how the 5372 is nice because of the high-speed readout option and the lack of dead-time, but how it doesn't match the 5370 one-shot resolution. The 5370 of course has this binary HPIB mode to get raw TI samples sent as fast as possible (roughly 6000/sec). I decided to try the same thing but from C code running on the (much faster) micro. I disassembled the firmware loop that reads samples from the TI count chain registers into the HPIB data-out register. I found that I could move 100K samples/sec out of the TI regs into a memory buffer (not a typo, one hundred K). Adding code to stream 512 samples per Ethernet packet back to a host computer dropped the rate to 80K/sec. The screen shot of the logic analyzer shows this process. This trace has little jitter so as long as the host on the other end is reasonably fast, and the network isn't loaded, this streaming rate should be sustainable. Obviously there is huge dead-time while the network code runs, but there might be ways around this. I should mention that because I have more processing power now on the instrument side I can do some pre-computation and only send 2-bytes per sample as opposed to the 5370 which sends 5. So 512 * 2 bytes = 1024 bytes/packet. The last screen shot is of the host side. So far all the TI values seem to be reasonable. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 5370 firmware hacking status report
John Seamons wrote: Some progress since February's discussion: My m6800 emulator running the 5370 firmware has been moved from the Linux box to a little 32-bit microcontroller on it's own small evaluation-kit board. Pictures here: http://jks.com (click on images for larger versions) You talk to it over an Ethernet connection. The 5370 device bus connects to the general-purpose I/O pins of the micro. Since the micro has 256KB Flash 128KB SRAM no off-chip memory is required. Everything just fits: emulator, firmware, lightweight TCP/IP stack, minimal C runtime, device drivers, performance hacks, ... All the front panel controls seem to work as expected. The operator verification section of the manual checks out. The HPIB hardware remote programming work, but I have a limited ability to test it currently. I have no computer-based GPIB card yet, just a 4396A with HPIB + Instrument Basic (yuk). But I also have a mode that fools the firmware into thinking the 5370 has the HPIB card installed (when it doesn't) and instead sends the transactions over Ethernet (USB also possible). More about this in a bit. Measurement performance is improved 40% on average and as much as 70% for some functions (see the spreadsheet and charts). The ultimate goal is to produce a drop-in replacement for the CPU card which would also allow you to toss the ROM card (older 5370s) and HPIB card. You'd get serial, Ethernet and USB connectivity to replace the HPIB. Now all this is fine, and somewhat amusing, but it's not clear there is any particular advantage. It's not as though there are piles of 5370s lying around with dead or missing CPU cards. Or that it's impossible to deal with HPIB anymore. One interesting possibility is adding new front-panel accessible measurement functions. Since the emulator has complete bus access it can detect new key press combinations before the firmware does and go into a mode where it gathers raw TI samples, processes them, and puts the results in the display. When an existing key sequence occurs the firmware is resumed and it doesn't even know it was paused while the new function was running. But I discovered something else that's even more interesting (note that I am relatively new to this time-nut stuff, so please correct my nutty mistakes). There was a discussion about how the 5372 is nice because of the high-speed readout option and the lack of dead-time, but how it doesn't match the 5370 one-shot resolution. The 5370 of course has this binary HPIB mode to get raw TI samples sent as fast as possible (roughly 6000/sec). I decided to try the same thing but from C code running on the (much faster) micro. I disassembled the firmware loop that reads samples from the TI count chain registers into the HPIB data-out register. I found that I could move 100K samples/sec out of the TI regs into a memory buffer (not a typo, one hundred K). Adding code to stream 512 samples per Ethernet packet back to a host computer dropped the rate to 80K/sec. The screen shot of the logic analyzer shows this process. This trace has little jitter so as long as the host on the other end is reasonably fast, and the network isn't loaded, this streaming rate should be sustainable. Obviously there is huge dead-time while the network code runs, but there might be ways around this. I should mention that because I have more processing power now on the instrument side I can do some pre-computation and only send 2-bytes per sample as opposed to the 5370 which sends 5. So 512 * 2 bytes = 1024 bytes/packet. The last screen shot is of the host side. So far all the TI values seem to be reasonable. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. One potential problem with very high sample rates is that the PLL associated with the 5370's 200MHz vernier oscillators fail to lock if the sample rate is too high. Bruce ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Discipline an oscillator with NTP?
Poul and others? As usual, I suddenly had a thought ripple across my otherwise placid cortex, and have forgotten if there was a previous answer on this thread. What does a NTP server look like on the network? There are now several small net appliances/eval boards available. I run a program called NMEAtime on my Windoze computers that currently get info from a net NTP server. I also have some simple net appliances. So, using my GPS 10 MHZ or 1 sec signals, or Rb 10 MHZ, how might I generate a local NTP server? I hope I don't put this awkwardly; what is the protocol? What does the supplicant client see and how does it ask for service? Best to all of you, Don Poul-Henning Kamp In message 022101cc4970$b24a4b80$16dee280$@com, Jose Camara writes: After one year of NTP queries, assume you have a 100ms jitter on the network time, you could at most tweak your oscillator, based on past performance, to 6E-9. It is a lot more complicated than that, we need to talk allan-deviation here, not scalar numbers. The main problem here is that the 'default' NTPd software is not really written for something like this, and has attributes which makes it truly sucky for the task. If you want to do this, you want to write your own software and you want to give it an entirely different modus operandi. As with all oscillator discplining, what you are looking for is the so called allan intercept where the two sources allan deviation cross. With a NTP reference, its location varies depending on stochastic network properties, which depends what's between the server and you. If you control the network topology (as in: Can make sure there is no other traffic), you're fine, normal PLL style stuff works. If you don't control the network topology, the RTT between you and the server becomes a BIG problem, because the fundamental NTP assumption that it is symmetric is almost always wrong. You can average over long tau's, but then your ISP upgrades their routed and a systematic change in RTT screws your integrator over for several weeks. Alternatively, if your LO is stable enough (=Rb/Cs), you can operate on first derivative of the RTT, which turns the routed upgrade into a single spiky sample, but the cost is an overall higher noise in your error signal. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Neither the voice of authority nor the weight of reason and argument are as significant as experiment, for thence comes quiet to the mind. R. Bacon If you don't know what it is, don't poke it. Ghost in the Shell Dr. Don Latham AJ7LL Six Mile Systems LLP 17850 Six Mile Road POB 134 Huson, MT, 59846 VOX 406-626-4304 www.lightningforensics.com www.sixmilesystems.com ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] Change of Email Address
Hi All, My email address has changed to: j...@quikus.com (The change is adding the letters us to the ISP name.) Please change your address book settings appropriately. If you have sent me anythying personally since about noon, Thursday, it is liklely lost and gone forever, so please resend it if possible. Needless to say, I am not entirely thrilled with this, but it's beyond my control. Thanks, -John = Forgot to delete the old address. -Original Message- From: schw214...@aol.com To: j...@quik.com Sent: Sat, Jul 23, 2011 4:20 pm Subject: Re: CHANGE OF EMAIL ADDRESS John - glad to hear that the two recent undeliverable e-mails have such a benign problem. Given some of your medical issues, I was afraid that something had happened to you and that your bill had gone unpaid. I forgot that I had saved your phone message from about 7 years ago and had your phone number. But also, things have been hectic around here both at home and at 'work'. This is the big birthday week / month in our family with birthdays on July 10, 21, 24, 25, 26 and 27 in the immediate family as well as several other birthdays of cousins and friends. At work, we are scrambling hard to raise $1.6 MM to match $1.0 MM from the state so we can build a prototype processor to convert 2.5 ton/hr of mixed waste polymers into 1.75 ton/hr of petroleum (essentially 'topped' crude oil, i.e., a distilled crude oil without the heavy asphalt high boiling tail found in most crude oils), and enough 'non-condensable' gas to run the entire process. The balance is mainly the fillers found in most modern plastics (clays, talcs, fiberglass, etc.) and wire and some carbon black found in tires. The beauty of the process is that it can take a wide range of polymer waste without the need to sort or rigorously clean it. We tend to avoid PVC (commonly found in Construction and Demolition debris - siding, plumbing pipe, waste piping, etc.) since! it decomposes by giving off HCl which is hard on the metals of construction for a plant. The small amount found in the typical municipal solid waste stream is not too much of a problem, but when you realize that PVC is 56.77% chlorine, it doesn't take too much to generate a lot of acid. Anyway, glad to hear that your problem with e-mail falls in the category of severe annoyance rather than major problem. Stay cool. Dick -Original Message- From: J. Forster [1]j...@quik.com To: [2]j...@quikus.com Sent: Sat, Jul 23, 2011 2:17 pm Subject: CHANGE OF EMAIL ADDRESS Hi, My email address has changed to: [3]j...@quikus.com (The change is adding the letters us to the end.) Please change your address book settings appropriately. If you have sent me ANYTHING since about noon, Thursday, it is liklely lost and gone forever, so please resend it if possible. I would appreciate you confirming the change. Needless to say, I am not entirely thrilled with this, but it's beyond my control. Thanks, -J == References 1. mailto:j...@quik.com 2. mailto:j...@quikus.com 3. mailto:j...@quikus.com ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Discipline an oscillator with NTP?
Hi Don, 1PPS is useful. 10MHz is not direcly useful. You also need some kind of timecode, telling ntpd which second the 1pps indicated. The software side is normally ntpd configured with one of its drivers (called refclock) for the GPS protocol your receiver has. Again the most used is probably refclock_NMEA. (http://www.eecis.udel.edu/~mills/ntp/html/drivers/driver20.html) look if there is anything else fitting your receivers. http://www.eecis.udel.edu/~mills/ntp/html/refclock.html Then wire a (preferably) serial cable with rx, tx and gnd in the usual places, add your 1PPS on DCD (pin 1). Depending on your serial port you could get away without levelshifting the 1pps to rs232-levels. Last but not least, for OS select your favorite unix derivative. -- Björn Poul and others? As usual, I suddenly had a thought ripple across my otherwise placid cortex, and have forgotten if there was a previous answer on this thread. What does a NTP server look like on the network? There are now several small net appliances/eval boards available. I run a program called NMEAtime on my Windoze computers that currently get info from a net NTP server. I also have some simple net appliances. So, using my GPS 10 MHZ or 1 sec signals, or Rb 10 MHZ, how might I generate a local NTP server? I hope I don't put this awkwardly; what is the protocol? What does the supplicant client see and how does it ask for service? Best to all of you, Don Poul-Henning Kamp In message 022101cc4970$b24a4b80$16dee280$@com, Jose Camara writes: After one year of NTP queries, assume you have a 100ms jitter on the network time, you could at most tweak your oscillator, based on past performance, to 6E-9. It is a lot more complicated than that, we need to talk allan-deviation here, not scalar numbers. The main problem here is that the 'default' NTPd software is not really written for something like this, and has attributes which makes it truly sucky for the task. If you want to do this, you want to write your own software and you want to give it an entirely different modus operandi. As with all oscillator discplining, what you are looking for is the so called allan intercept where the two sources allan deviation cross. With a NTP reference, its location varies depending on stochastic network properties, which depends what's between the server and you. If you control the network topology (as in: Can make sure there is no other traffic), you're fine, normal PLL style stuff works. If you don't control the network topology, the RTT between you and the server becomes a BIG problem, because the fundamental NTP assumption that it is symmetric is almost always wrong. You can average over long tau's, but then your ISP upgrades their routed and a systematic change in RTT screws your integrator over for several weeks. Alternatively, if your LO is stable enough (=Rb/Cs), you can operate on first derivative of the RTT, which turns the routed upgrade into a single spiky sample, but the cost is an overall higher noise in your error signal. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Neither the voice of authority nor the weight of reason and argument are as significant as experiment, for thence comes quiet to the mind. R. Bacon If you don't know what it is, don't poke it. Ghost in the Shell Dr. Don Latham AJ7LL Six Mile Systems LLP 17850 Six Mile Road POB 134 Huson, MT, 59846 VOX 406-626-4304 www.lightningforensics.com www.sixmilesystems.com ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Discipline an oscillator with NTP?
Hi Bjorn: Thanks very much for the sources! I was afraid I was not clear when I sent my question(s). I want to generate a network server rather than a client. I looked up man ntpd, and it seems at first glance to be a Linux/Unix client that will sync up a local computer. I want to generate a network server that ntpd or other clients can access. Perhaps I did not read closely enough, and if not, I apologize. Don b...@lysator.liu.se Hi Don, 1PPS is useful. 10MHz is not direcly useful. You also need some kind of timecode, telling ntpd which second the 1pps indicated. The software side is normally ntpd configured with one of its drivers (called refclock) for the GPS protocol your receiver has. Again the most used is probably refclock_NMEA. (http://www.eecis.udel.edu/~mills/ntp/html/drivers/driver20.html) look if there is anything else fitting your receivers. http://www.eecis.udel.edu/~mills/ntp/html/refclock.html Then wire a (preferably) serial cable with rx, tx and gnd in the usual places, add your 1PPS on DCD (pin 1). Depending on your serial port you could get away without levelshifting the 1pps to rs232-levels. Last but not least, for OS select your favorite unix derivative. -- Björn Poul and others? As usual, I suddenly had a thought ripple across my otherwise placid cortex, and have forgotten if there was a previous answer on this thread. What does a NTP server look like on the network? There are now several small net appliances/eval boards available. I run a program called NMEAtime on my Windoze computers that currently get info from a net NTP server. I also have some simple net appliances. So, using my GPS 10 MHZ or 1 sec signals, or Rb 10 MHZ, how might I generate a local NTP server? I hope I don't put this awkwardly; what is the protocol? What does the supplicant client see and how does it ask for service? Best to all of you, Don Poul-Henning Kamp In message 022101cc4970$b24a4b80$16dee280$@com, Jose Camara writes: After one year of NTP queries, assume you have a 100ms jitter on the network time, you could at most tweak your oscillator, based on past performance, to 6E-9. It is a lot more complicated than that, we need to talk allan-deviation here, not scalar numbers. The main problem here is that the 'default' NTPd software is not really written for something like this, and has attributes which makes it truly sucky for the task. If you want to do this, you want to write your own software and you want to give it an entirely different modus operandi. As with all oscillator discplining, what you are looking for is the so called allan intercept where the two sources allan deviation cross. With a NTP reference, its location varies depending on stochastic network properties, which depends what's between the server and you. If you control the network topology (as in: Can make sure there is no other traffic), you're fine, normal PLL style stuff works. If you don't control the network topology, the RTT between you and the server becomes a BIG problem, because the fundamental NTP assumption that it is symmetric is almost always wrong. You can average over long tau's, but then your ISP upgrades their routed and a systematic change in RTT screws your integrator over for several weeks. Alternatively, if your LO is stable enough (=Rb/Cs), you can operate on first derivative of the RTT, which turns the routed upgrade into a single spiky sample, but the cost is an overall higher noise in your error signal. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Neither the voice of authority nor the weight of reason and argument are as significant as experiment, for thence comes quiet to the mind. R. Bacon If you don't know what it is, don't poke it. Ghost in the Shell Dr. Don Latham AJ7LL Six Mile Systems LLP 17850 Six Mile Road POB 134 Huson, MT, 59846 VOX 406-626-4304 www.lightningforensics.com www.sixmilesystems.com ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Neither the voice of authority nor the weight of reason and argument are as significant as experiment, for thence comes quiet to the mind. R. Bacon If you don't know what it is,
Re: [time-nuts] Discipline an oscillator with NTP?
At 06:45 PM 7/23/2011, Don Latham wrote: than a client. I looked up man ntpd, and it seems at first glance to be a Linux/Unix client that will sync up a local computer. I want to generate a network server that ntpd or other clients can access. Perhaps ntpd is the server. -- newell N5TNL ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Discipline an oscillator with NTP?
ntpd is the server. Scott: OK. Here's what I get from man ntpd: The ntpd program is an operating system daemon which sets and maintains the system time of day in synchronism with Internet standard time servers. What I want to do is build a little local net only standard time server The man goes on to say: The ntpd program operates by exchanging messages with one or more configured servers at designated poll intervals. When started, whether for the first or subsequent times, the program requires several exchanges from the majority of these servers so the signal processing and mitigation algorithms can accumulate and groom the data and set the clock So, I essentially want to feed ntpd and its MSoft equivalents. I found the www.ntp.net site, that apparently has open software to do this. As I looked further, there seem to be a LOT of so-called primary NTP servers out there that are quite simply malware sites using NTP to infiltrate. Yikes. as usual, I go looking for some simple thing, and find I've whacked the tarbaby another lick... (see Uncle Remus Stories). Thanks for the input!!! Don ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Neither the voice of authority nor the weight of reason and argument are as significant as experiment, for thence comes quiet to the mind. R. Bacon If you don't know what it is, don't poke it. Ghost in the Shell Dr. Don Latham AJ7LL Six Mile Systems LLP 17850 Six Mile Road POB 134 Huson, MT, 59846 VOX 406-626-4304 www.lightningforensics.com www.sixmilesystems.com ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Discipline an oscillator with NTP?
Hi Don, ntpd is both server and client. For a ublox with usb i did the following a few days ago. sudo ln -s /dev/ttyACM0 /dev/gps0 add this to the /etc/ntp.conf server 127.127.20.0 mode 81 and then /etc/init.d/ntp restart This particular setup without 1pps gives a lousy time (some 150ms late with 50ms jitter). I apologize if I was not clear enough in my previous answer. -- Björn Hi Bjorn: Thanks very much for the sources! I was afraid I was not clear when I sent my question(s). I want to generate a network server rather than a client. I looked up man ntpd, and it seems at first glance to be a Linux/Unix client that will sync up a local computer. I want to generate a network server that ntpd or other clients can access. Perhaps I did not read closely enough, and if not, I apologize. Don b...@lysator.liu.se Hi Don, 1PPS is useful. 10MHz is not direcly useful. You also need some kind of timecode, telling ntpd which second the 1pps indicated. The software side is normally ntpd configured with one of its drivers (called refclock) for the GPS protocol your receiver has. Again the most used is probably refclock_NMEA. (http://www.eecis.udel.edu/~mills/ntp/html/drivers/driver20.html) look if there is anything else fitting your receivers. http://www.eecis.udel.edu/~mills/ntp/html/refclock.html Then wire a (preferably) serial cable with rx, tx and gnd in the usual places, add your 1PPS on DCD (pin 1). Depending on your serial port you could get away without levelshifting the 1pps to rs232-levels. Last but not least, for OS select your favorite unix derivative. -- Björn Poul and others? As usual, I suddenly had a thought ripple across my otherwise placid cortex, and have forgotten if there was a previous answer on this thread. What does a NTP server look like on the network? There are now several small net appliances/eval boards available. I run a program called NMEAtime on my Windoze computers that currently get info from a net NTP server. I also have some simple net appliances. So, using my GPS 10 MHZ or 1 sec signals, or Rb 10 MHZ, how might I generate a local NTP server? I hope I don't put this awkwardly; what is the protocol? What does the supplicant client see and how does it ask for service? Best to all of you, Don Poul-Henning Kamp In message 022101cc4970$b24a4b80$16dee280$@com, Jose Camara writes: After one year of NTP queries, assume you have a 100ms jitter on the network time, you could at most tweak your oscillator, based on past performance, to 6E-9. It is a lot more complicated than that, we need to talk allan-deviation here, not scalar numbers. The main problem here is that the 'default' NTPd software is not really written for something like this, and has attributes which makes it truly sucky for the task. If you want to do this, you want to write your own software and you want to give it an entirely different modus operandi. As with all oscillator discplining, what you are looking for is the so called allan intercept where the two sources allan deviation cross. With a NTP reference, its location varies depending on stochastic network properties, which depends what's between the server and you. If you control the network topology (as in: Can make sure there is no other traffic), you're fine, normal PLL style stuff works. If you don't control the network topology, the RTT between you and the server becomes a BIG problem, because the fundamental NTP assumption that it is symmetric is almost always wrong. You can average over long tau's, but then your ISP upgrades their routed and a systematic change in RTT screws your integrator over for several weeks. Alternatively, if your LO is stable enough (=Rb/Cs), you can operate on first derivative of the RTT, which turns the routed upgrade into a single spiky sample, but the cost is an overall higher noise in your error signal. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Neither the voice of authority nor the weight of reason and argument are as significant as experiment, for thence comes quiet to the mind. R. Bacon If you don't know what it is, don't poke it. Ghost in the Shell Dr. Don Latham AJ7LL Six Mile Systems LLP 17850 Six Mile Road POB 134 Huson, MT, 59846 VOX 406-626-4304 www.lightningforensics.com www.sixmilesystems.com ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the
Re: [time-nuts] Discipline an oscillator with NTP?
ntpd is both a client (getting time info from other ntp servers) and a server (responding to requests from other clients on the network.) Access to the server part is controlled by firewall rules and restrict lines in the ntp.conf file (see example below). An explanation of these can be found at http://support.ntp.org/bin/view/Support/AccessRestrictions Steve -- # /etc/ntp.conf, configuration for ntpd; see ntp.conf(5) for help driftfile /var/lib/ntp/ntp.drift # Garmin 18xLVS GPS + PPS # mode 1use $GPRMC sentence server 127.127.20.1 mode 1 minpoll 4 prefer # flag1 1enable PPS signal processing # flag3 1kernel discipline fudge 127.127.20.1 flag1 1 flag3 1 # North-American Pool servers for backup/sanity check server 0.north-america.pool.ntp.org server 1.north-america.pool.ntp.org server 2.north-america.pool.ntp.org # Access control configuration; see /usr/share/doc/ntp-doc/html/accopt.html for # details. The web page http://support.ntp.org/bin/view/Support/AccessRestrictions # might also be helpful. # # Note that restrict applies to both servers and clients, so a configuration # that might be intended to block requests from certain clients could also end # up blocking replies from your own upstream servers. # By default, exchange time with everybody, but don't allow configuration. restrict -4 default kod notrap nomodify nopeer noquery restrict -6 default kod notrap nomodify nopeer noquery # Local users may interrogate the ntp server more closely. restrict 127.0.0.1 restrict ::1 -- On 7/23/2011 4:53 PM, Scott Newell wrote: At 06:45 PM 7/23/2011, Don Latham wrote: than a client. I looked up man ntpd, and it seems at first glance to be a Linux/Unix client that will sync up a local computer. I want to generate a network server that ntpd or other clients can access. Perhaps ntpd is the server. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Discipline an oscillator with NTP?
ntpd acts at the same time as a server and as a client, it is included with all linux distiributions and also FreeBSD and other BSDs. Meinberg has a pre-compiled ntp for Windows. The Windows Time Service included in windows xp and 7 is a particular interpretation of microsoft of any standard (not the first one standard that suffers from outrangeous microsoft interpretations to pervert it). It can get time from ntp servers, but does not provide clock disciplining, and it can server time to other clients, but with lots of un-compliances to the ntp protocol. Regards, Javier El 24/07/2011 02:17, Don Latham escribió: ntpd is the server. Scott: OK. Here's what I get from man ntpd: The ntpd program is an operating system daemon which sets and maintains the system time of day in synchronism with Internet standard time servers. What I want to do is build a little local net only standard time server The man goes on to say: The ntpd program operates by exchanging messages with one or more configured servers at designated poll intervals. When started, whether for the first or subsequent times, the program requires several exchanges from the majority of these servers so the signal processing and mitigation algorithms can accumulate and groom the data and set the clock So, I essentially want to feed ntpd and its MSoft equivalents. I found the www.ntp.net site, that apparently has open software to do this. As I looked further, there seem to be a LOT of so-called primary NTP servers out there that are quite simply malware sites using NTP to infiltrate. Yikes. as usual, I go looking for some simple thing, and find I've whacked the tarbaby another lick... (see Uncle Remus Stories). Thanks for the input!!! Don ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Discipline an oscillator with NTP?
OK, Steve and Bjorn. I will have to get busy and see what I can do. Thanks very much for your input. Don Steve Longcor ntpd is both a client (getting time info from other ntp servers) and a server (responding to requests from other clients on the network.) Access to the server part is controlled by firewall rules and restrict lines in the ntp.conf file (see example below). An explanation of these can be found at http://support.ntp.org/bin/view/Support/AccessRestrictions Steve -- # /etc/ntp.conf, configuration for ntpd; see ntp.conf(5) for help driftfile /var/lib/ntp/ntp.drift # Garmin 18xLVS GPS + PPS # mode 1use $GPRMC sentence server 127.127.20.1 mode 1 minpoll 4 prefer # flag1 1enable PPS signal processing # flag3 1kernel discipline fudge 127.127.20.1 flag1 1 flag3 1 # North-American Pool servers for backup/sanity check server 0.north-america.pool.ntp.org server 1.north-america.pool.ntp.org server 2.north-america.pool.ntp.org # Access control configuration; see /usr/share/doc/ntp-doc/html/accopt.html for # details. The web page http://support.ntp.org/bin/view/Support/AccessRestrictions # might also be helpful. # # Note that restrict applies to both servers and clients, so a configuration # that might be intended to block requests from certain clients could also end # up blocking replies from your own upstream servers. # By default, exchange time with everybody, but don't allow configuration. restrict -4 default kod notrap nomodify nopeer noquery restrict -6 default kod notrap nomodify nopeer noquery # Local users may interrogate the ntp server more closely. restrict 127.0.0.1 restrict ::1 -- On 7/23/2011 4:53 PM, Scott Newell wrote: At 06:45 PM 7/23/2011, Don Latham wrote: than a client. I looked up man ntpd, and it seems at first glance to be a Linux/Unix client that will sync up a local computer. I want to generate a network server that ntpd or other clients can access. Perhaps ntpd is the server. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Neither the voice of authority nor the weight of reason and argument are as significant as experiment, for thence comes quiet to the mind. R. Bacon If you don't know what it is, don't poke it. Ghost in the Shell Dr. Don Latham AJ7LL Six Mile Systems LLP 17850 Six Mile Road POB 134 Huson, MT, 59846 VOX 406-626-4304 www.lightningforensics.com www.sixmilesystems.com ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 5370 firmware hacking status report
Now all this is fine, and somewhat amusing, but it's not clear there is any particular advantage. It's not as though there are piles of 5370s lying around with dead or missing CPU cards. Or that it's impossible to deal with HPIB anymore. One interesting possibility is adding new front-panel accessible measurement functions. Since the emulator has complete bus access it can detect new key press combinations before the firmware does and go into a mode where it gathers raw TI samples, processes them, and puts the results in the display. When an existing key sequence occurs the firmware is resumed and it doesn't even know it was paused while the new function was running. One thing that would be really nice is if you could do frequency readings with a 10-second gate time, as opposed to the current maximum of 1 second. That would make the LSD meaningful instead of completely random, as it is now. -- john, KE5FX ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Discipline an oscillator with NTP?
Indeed thats why I was saying choose 3 servers. Now I see in the thread that you can pick pools of servers so thats good. Then average what they say the time is and drive oscillator. Wonder if you could look towards the stratum 1 servers. But that said I could easily believe that it might ot be any better then wwv. Good thread. Things to learn as we all seek a backup to GPS I assume. Regards Paul WB8TSL Paul, be aware that three servers is not the best choice, as if one fails you are left with two servers, and you don't know which is correct. IIRC four, five and seven servers allow for the failure of 1, 2 or 3 of them, but do choose more than three. 73, David GM8ARV ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] My Custom GPS clock
Hello, Bert - Not having that much experience, I am wondering whether I could retrofit their DE-DP22811 http://www.sureelectronics.net/goods.php?id=1164 to make an 8 digits clock having 1/100s: 23 59 59 99 Based in NYC and ideally I would feed it UTC reference, either by GPS minus 15 seconds (as leap seconds are likely to be dropped) or any other source. I only need 1/100 s accuracy, might even drive from power line. I'd be glad to pay someone to implement. I have Paypal. The closest thing I found was a director's clock, yet frames from 0 to 24 instead of hundreds of seconds from 0 to 99. Thanks, Christopher On Fri, Jul 22, 2011 at 16:53, Bert, VE2ZAZ ve2...@yahoo.ca wrote: Hi Brooke, I go by memory here, but I believe it is a pair of DE-DP13112 (P4 32X8 3208 Red LED Dot Matrix Unit Board SPI Like), which are currently on sale for $11 ea. I bought mine on eBay. Cheers, Bert, VE2ZAZ From: Brooke Clarke bro...@pacific.net To: Bert, VE2ZAZ ve2...@yahoo.ca; Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Friday, July 22, 2011 4:36:33 PM Subject: Re: [time-nuts] My Custom GPS clock Hi Bert: Which Sure Electronics display board did you use (they make a bunch of different ones)? http://www.sureelectronics.net/category.php?id=60 Have Fun, Brooke Clarke http://www.PRC68.com http://www.prc68.com/ http://www.End2PartyGovernment.com/ http://www.end2partygovernment.com/ Bert, VE2ZAZ wrote: Hello Everyone, I thought some of you might be interested in the following. A few months ago, a few time-nuts discussed what they had done to convert existing equipment to a large GPS clock. I elected to design my own clock display instead. Mine is fed by a Garmin GPS-35 GPS and it uses a 64 x 8 LED array for the display. It is driven by a PIC18F1220 with custom firmware. I have posted a Youtube video that shows the unit in action: http://www.youtube.com/watch?v=RJE-PeUtxfU The unit is described in more detail on my website at: http://ve2zaz.net/GPS_Clock/GPS_Clock.htm Cheers, Bert, VE2ZAZ ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
