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 <[email protected]> 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 < >> [email protected] >>>> 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(1000000-pw); >>>> } >>>> } >>>> >>>> On Fri, Jul 22, 2011 at 6:08 PM, Jim Lux <[email protected]> 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 -- [email protected] >>>>> 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 -- [email protected] >>>> To unsubscribe, go to >>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>> and follow the instructions there. >>>> >>> _______________________________________________ >>> time-nuts mailing list -- [email protected] >>> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> and follow the instructions there. >> >> >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
