[time-nuts] WWVB phase plots

[Hal Murray]

> It is also the case the DCF77's phase modulation probably isn't as good as
> it could be if the goal is to find it in the noise since it only swings +/-
> 15 degrees rather than +/- 90.  Its big advantage might be that it is high
> speed, with lots of transitions, so you can probably measure phase alignment
> pretty accurately with that.  As a national time service, however, it only
> needs to serve a fairly compact country relative to WWVB's intended coverage
> area, so that plus WWVB's crappy AM format probably pushed them to forget
> about trying to match DCF77 and to just concentration on doing the best they
> could to improve coverage. 

Could somebody please say a bit more about that area.  My Shannon level 
theory is weak.

Why does more transitions help anything?  Or what does it help?

I can see how it might make it easier/faster to get synced up, but if the 
goal is to accurately measure frequency or phase, I'd expect that you are 
already locked and looking for the next layer of detail.  In that case, I'd 
expect better results with fewer transitions.  Fewer transitions means lower 
bandwidth so you can use a narrower bandwidth filter and get rid of more 
noise.


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