[time-nuts] Discipline an oscillator with NTP?

[Bob Camp]

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.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.
>>> 
>>> _______________________________________________
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>> 
>> 
>> 
>> --
>> 
>> Chris Albertson
>> Redondo Beach, California
>> 
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