Re: [time-nuts] Discipline an oscillator with NTP?
On Sat, Jul 23, 2011 at 8:17 PM, Don Latham d...@montana.com wrote: 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 Use http://www.ntp.org/ instead. You can also look at the Public NTP pool project, http://www.pool.ntp.org/. Additional NTP links: http://support.ntp.org/bin/view/Main/ExternalTimeRelatedLinks US NIST Primary NTP servers http://tf.nist.gov/tf-cgi/servers.cgi Canadian government NTP servers http://www.nrc-cnrc.gc.ca/eng/services/inms/time-services/network-time.html UK National Physics Lab NTP servers http://www.npl.co.uk/science-technology/time-frequency/time/products-and-services/time-synchronisation-of-computers-to-utc%28npl%29 ___ 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 The standard NTP software does a best of the bunch selection when given a large number of servers. What it considers best and what you would pick likely are not the same thing. You stick at a few ms of error rather than getting say a 10X improvement with 100 servers. Custom code, custom hardware, stable routing - you can do *much* better. Of the three, routing is normally the biggest source of error. If it's not you have a very unusual ISP / connection / server. Bob On Jul 24, 2011, at 12:50 AM, David J Taylor david-tay...@blueyonder.co.uk wrote: 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. ___ 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] 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] 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.
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.
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] 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.
[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.
Re: [time-nuts] Discipline an oscillator with NTP?
On Fri, Jul 22, 2011 at 2:27 PM, Jason Rabel ja...@extremeoverclocking.com wrote: I was just thinking (dangerous I know)... Has anyone attempted to build a stand-alone oscillator that is disciplined via NTP? I believe the Symmetricom NTP servers do this, whether or not they have external access to the oscillator or not I'm not sure. I know that even their most basic model has OCXO and/or Rubidium upgrade options. [1] The SyncServer S100 can be disciplined by either NTP via networking or GPS. I think all NTP server appliances have this functionality by their nature, whether or not the oscillator is of particular high quality (low noise) or not. Many of the low-end ones likely just use a standard oscillator in a can [2] that the embedded processor uses. [1] http://www.symmetricom.com/products/ntp-servers/ntp-network-appliances/SyncServer-S100/ [2] such as http://www.foxonline.com/thru_hole_oscillators.htm ___ 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 must say Jason, Yes, you are day dreaming, but hey, that is where ideas come from. I do not play with NTP, but isn't that the same thing ( or similar) as disciplining my local clock when I have it update against a reference like NIST over the Internet ? In other words, NTP is used to keep the local computer clock in sync and thus is basically keeping an oscillator disciplined so to speak. As to how you would directly make the hardware deal with the oscillator instead of just updating a register dealing with the time, I do not know. I am sure it can probably be done. BillWB6BNQ Jason Rabel wrote: 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] Discipline an oscillator with NTP?
No exactly. A PPS generator syncrhonized with UTC time, using a GPS ntp server in the same LAN. Not too bad... but several microseconds jittery :) enough for my application then. Probably with long time constants it is doable, but if the ntp server is in the internet, and not in a LAN, I suspect that to get good results can be a bit difficult :) Regards, Javier El 22/07/2011 20:27, Jason Rabel escribió: 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] Discipline an oscillator with NTP?
El 22/07/2011 20:39, michael taylor escribió: I think all NTP server appliances have this functionality by their nature, whether or not the oscillator is of particular high quality (low noise) or not. Many of the low-end ones likely just use a standard oscillator in a can [2] that the embedded processor uses. No, ntp algorithm does not adjust the oscillator itself. Regards, Javier ___ 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 07/22/2011 11:48 AM, Javier Herrero wrote: El 22/07/2011 20:39, michael taylor escribió: I think all NTP server appliances have this functionality by their nature, whether or not the oscillator is of particular high quality (low noise) or not. Many of the low-end ones likely just use a standard oscillator in a can [2] that the embedded processor uses. No, ntp algorithm does not adjust the oscillator itself. Regards, Javier ___ 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. Until LightSquared goes online we will have GPS available almost everywhere high speed internet is available. NTP disicipline is possible but the necessary time constants might approach the MTFB of associated systems. -- Chuck Forsberg WA7KGX N2469R c...@omen.com www.omen.com Developer of Industrial ZMODEM(Tm) for Embedded Applications Omen Technology Inc The High Reliability Software 10255 NW Old Cornelius Pass Portland OR 97231 503-614-0430 ___ 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 7/22/11 11:59 AM, Chuck Forsberg WA7KGX N2469R wrote: On 07/22/2011 11:48 AM, Javier Herrero wrote: El 22/07/2011 20:39, michael taylor escribió: I think all NTP server appliances have this functionality by their nature, whether or not the oscillator is of particular high quality (low noise) or not. Many of the low-end ones likely just use a standard oscillator in a can [2] that the embedded processor uses. No, ntp algorithm does not adjust the oscillator itself. Until LightSquared goes online we will have GPS available almost everywhere high speed internet is available. Except that GPS requires a view of the sky (or cabling to a place with a view of the sky).. There are a quite a lot of applications where you might have a network connection, but not view of the sky. The question is whether NTP is decent for disciplining. (PTP would almost certainly work) NTP disicipline is possible but the necessary time constants might approach the MTFB of associated systems. ___ 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?
This is exactly what an NTP server does. It adjusts the rate of a local clock so that the local clock advances at the same rate is the set of Internet servers that have passed a clock selection test. NTP does this very well considering the uncertainly of the lag over the internet. There is a good argument the NTP is optimal but the best you can get using Internet time servers is about a milli second or 0.001 second. It would be nearly trivial to write software to produce a PPS output on one of the control line of a serial port. SO you NTP disciplined computer can produce PPS with about .001 second error Send this PPS to the normal GPSDXO in place of the GPS' PPS. The computer is only about 1000 times worse than a GPS and might work OK if you drastically increase the time constant on the GPSDXO's control loop. I think your NTPDXO might be as good as GPSDXO is measured over a long enough period, like months. Short term it might be about as good as the TTL can oscillator inside the PC. On Fri, Jul 22, 2011 at 11:27 AM, Jason Rabel ja...@extremeoverclocking.com wrote: 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. -- 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.
Re: [time-nuts] Discipline an oscillator with NTP?
On Fri, Jul 22, 2011 at 2:48 PM, Javier Herrero jherr...@hvsistemas.es wrote: El 22/07/2011 20:39, michael taylor escribió: I think all NTP server appliances have this functionality by their nature, whether or not the oscillator is of particular high quality (low noise) or not. Many of the low-end ones likely just use a standard oscillator in a can [2] that the embedded processor uses. No, ntp algorithm does not adjust the oscillator itself. Yes, while the NTP algorithm or protocol does not adjust the oscillator (or RTC) hardware directly, it does pass trimming or de-skewing recommendations via software (ntp_adjtime, adjustime, or hardpps) to OS, allowing the OS to adjust its system's clock. But in the case of a NTP appliance (or embedded device), having intimate knowledge of a single design means that the appliance's Operating System could implement ntp_adjustime or hardpps to a VCO (voltage controlled oscillator) via a DAC, a DDS or similar, to actually fine time the device's master oscillator. Which becomes worthwhile if there is an high quality oscillator driving (or steering) the computer hardware's system clock, such as an OCXO or Rubidium oscillator. ___ 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 The easy way is to take a pps off of your external oscillator and feed that into a port on your NTP server. Let NTP tell you where that pps is. Don't let NTP lock to the pps, just let it report it's position. After that all you need to do is write some code to read the location of the pulse and implement a *long* time constant loop. Taking the 1 ms number and a 1x10^-10 goal, the time constant would need to be around 4 months. There are a few minor details about drift of the local reference and how valid 1 ms is over long time periods. A reasonable GPSDO will likely be much more stable and much more accurate. To get it into the range of being practical, you have to get the NTP setup into single digit microseconds. In the us range you still would not beat the GPSDO, but at least you would have a useful device. 1 us can be done on a LAN with NTP. It's tough to do better than 1 ms over the net. Since PTP suffers the same issues over the net that NTP does, it's not a lot of help in this situation. Bob On Jul 22, 2011, at 5:30 PM, Javier Herrero wrote: I've found a plot of the ntp-synthesized GPS output compared with the UTC-aligned GPS from a Thunderbolt. The generated PPS output was 1us wide, and it is represented in infinite persistence to get an idea of the jitter. The offset was around 50us, and the jitter around 8us, so not very bad (it was at least one order of magnitude better than my requirements, so I did not bother to optimize it further). The ntp source was a M12-based ntp server (a blackfin running uClinux, not a Soekris :) ). Driving the PPS output to a serial port from the ntp is not as trivial as you think. This PPS output is from an oscillator disciplined to the system clock - really a stearable divider from the system clock (it is an embedded system using uClinux). If you try to drive a digital output directly from the timer interrupt to get the PPS, you would get far more jitter and error. Best regards, Javier P.S. not sure if the attachment will show up... El 22/07/2011 22:19, Chris Albertson escribió: This is exactly what an NTP server does. It adjusts the rate of a local clock so that the local clock advances at the same rate is the set of Internet servers that have passed a clock selection test. NTP does this very well considering the uncertainly of the lag over the internet. There is a good argument the NTP is optimal but the best you can get using Internet time servers is about a milli second or 0.001 second. It would be nearly trivial to write software to produce a PPS output on one of the control line of a serial port. SO you NTP disciplined computer can produce PPS with about .001 second error Send this PPS to the normal GPSDXO in place of the GPS' PPS. The computer is only about 1000 times worse than a GPS and might work OK if you drastically increase the time constant on the GPSDXO's control loop. I think your NTPDXO might be as good as GPSDXO is measured over a long enough period, like months. Short term it might be about as good as the TTL can oscillator inside the PC. On Fri, Jul 22, 2011 at 11:27 AM, Jason Rabel ja...@extremeoverclocking.com wrote: 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. PPSAGPS.pdf___ 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?
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 On Fri, Jul 22, 2011 at 6:07 PM, Bob Camp li...@rtty.us wrote: Hi The easy way is to take a pps off of your external oscillator and feed that into a port on your NTP server. Let NTP tell you where that pps is. Don't let NTP lock to the pps, just let it report it's position. After that all you need to do is write some code to read the location of the pulse and implement a *long* time constant loop. Taking the 1 ms number and a 1x10^-10 goal, the time constant would need to be around 4 months. There are a few minor details about drift of the local reference and how valid 1 ms is over long time periods. A reasonable GPSDO will likely be much more stable and much more accurate. To get it into the range of being practical, you have to get the NTP setup into single digit microseconds. In the us range you still would not beat the GPSDO, but at least you would have a useful device. 1 us can be done on a LAN with NTP. It's tough to do better than 1 ms over the net. Since PTP suffers the same issues over the net that NTP does, it's not a lot of help in this situation. Bob On Jul 22, 2011, at 5:30 PM, Javier Herrero wrote: I've found a plot of the ntp-synthesized GPS output compared with the UTC-aligned GPS from a Thunderbolt. The generated PPS output was 1us wide, and it is represented in infinite persistence to get an idea of the jitter. The offset was around 50us, and the jitter around 8us, so not very bad (it was at least one order of magnitude better than my requirements, so I did not bother to optimize it further). The ntp source was a M12-based ntp server (a blackfin running uClinux, not a Soekris :) ). Driving the PPS output to a serial port from the ntp is not as trivial as you think. This PPS output is from an oscillator disciplined to the system clock - really a stearable divider from the system clock (it is an embedded system using uClinux). If you try to drive a digital output directly from the timer interrupt to get the PPS, you would get far more jitter and error. Best regards, Javier P.S. not sure if the attachment will show up... El 22/07/2011 22:19, Chris Albertson escribió: This is exactly what an NTP server does. It adjusts the rate of a local clock so that the local clock advances at the same rate is the set of Internet servers that have passed a clock selection test. NTP does this very well considering the uncertainly of the lag over the internet. There is a good argument the NTP is optimal but the best you can get using Internet time servers is about a milli second or 0.001 second. It would be nearly trivial to write software to produce a PPS output on one of the control line of a serial port. SO you NTP disciplined computer can produce PPS with about .001 second error Send this PPS to the normal GPSDXO in place of the GPS' PPS. The computer is only about 1000 times worse than a GPS and might work OK if you drastically increase the time constant on the GPSDXO's control loop. I think your NTPDXO might be as good as GPSDXO is measured over a long enough period, like months. Short term it might be about as good as the TTL can oscillator inside the PC. On Fri, Jul 22, 2011 at 11:27 AM, Jason Rabel ja...@extremeoverclocking.com wrote: 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. PPSAGPS.pdf___ 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 Fri, 22 Jul 2011 13:27:34 -0500 Jason Rabel ja...@extremeoverclocking.com wrote: 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? There is something similar. Somewhere on the net, a guy described how he build a frequency counter using ntp. Unfortunately i'm unable to find it. AFAIK it worked pretty well with decent results, if the integration time was in the hours (iirc less than a day). Attila Kinali -- Why does it take years to find the answers to the questions one should have asked long ago? ___ 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 07/23/2011 12:07 AM, Bob Camp wrote: Hi The easy way is to take a pps off of your external oscillator and feed that into a port on your NTP server. Let NTP tell you where that pps is. Don't let NTP lock to the pps, just let it report it's position. After that all you need to do is write some code to read the location of the pulse and implement a *long* time constant loop. Taking the 1 ms number and a 1x10^-10 goal, the time constant would need to be around 4 months. There are a few minor details about drift of the local reference and how valid 1 ms is over long time periods. A reasonable GPSDO will likely be much more stable and much more accurate. To get it into the range of being practical, you have to get the NTP setup into single digit microseconds. In the us range you still would not beat the GPSDO, but at least you would have a useful device. 1 us can be done on a LAN with NTP. It's tough to do better than 1 ms over the net. Since PTP suffers the same issues over the net that NTP does, it's not a lot of help in this situation. There are people already hacking an OCXO into the system clock of their NTP server. Now, look at the correction log (frequency and phase) of the system, low-pass filter that and use it to steer a secondary loop steering the oscillator. It should be fairly easy and not require much of hacking to achieve. Cheers, Magnus ___ 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 Fri, Jul 22, 2011 at 2:30 PM, Javier Herrero jherr...@hvsistemas.es wrote: I've found a plot of the ntp-synthesized GPS output compared with the UTC-aligned GPS from a Thunderbolt. The generated PPS output was 1us wide, and it is represented in infinite persistence to get an idea of the jitter. The offset was around 50us, and the jitter around 8us, so not very bad (it was at least one order of magnitude better than my requirements, so I did not bother to optimize it further). The ntp source was a M12-based ntp server (a blackfin running uClinux, not a Soekris :) ). Driving the PPS output to a serial port from the ntp is not as trivial as you think. This PPS output is from an oscillator disciplined to the system clock - really a stearable divider from the system clock (it is an embedded The software PPS on the serial port that i suggested would be an intermediate step. What you measured was the output of what I called a NTPDXO decided down. I think we are talking about the same kind of design. I guessed that the jitter on the final PPS would be 1000x worse than from a GPS and your 8uS measurement is spot on that. The M12 has a handful of nS error 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.
Re: [time-nuts] Discipline an oscillator with NTP?
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.
Re: [time-nuts] Discipline an oscillator with NTP?
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.
Re: [time-nuts] Discipline an oscillator with NTP?
First, catch your rabbit... Jim Lux 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. -- 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.
