[time-nuts] WWVB PM Time Questions

[paul swed]

What may be helpful to the wwvb projects is what is always fixed. This
comes out of the NIST document. Assume you have a fairly good oscillator.
If it can hold within 1/2 cycle of 60 KHz (10 us) for 47 seconds you can
simply sample the top minute sync word. Thats from 59-11 seconds. Always
fixed. But thats a bit too easy. NIST gave us a bit more of a challenge. At
10 and 40 past the hour the slow code runs and its format is different. But
has a 106 second sync word thats always fixed and always at the same
location.
If you have a locked oscillator then the timecode recovery is reasonable.
Decoding the actual timecode is a serious pain.
Good luck
Paul
WB8TSL


On Fri, Jul 31, 2020 at 6:07 PM Poul-Henning Kamp <phk at phk.freebsd.dk>
wrote:

> --------
> Bob kb8tq writes:
>
> > It also *very* much depends on the stability of your local reference and
> the
> > stability of the ionosphere. Unless both are 'pretty darn good' a
> hundred second
> > integration is utter nonsense
>
> This is why Loran-C was so superior to any and all CW based modulations.
>
> --
> Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
> phk at 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.
>
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