[time-nuts] Discipline an oscillator with NTP?

paul swed paulswedb at gmail.com
Sat Jul 23 16:29:12 UTC 2011


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


More information about the time-nuts mailing list