[time-nuts] WWVB BPSK Receiver Project?

[David I. Emery]

On Wed, Mar 14, 2012 at 05:13:47PM -0700, J. Forster wrote:
> Now it looks like they are going to kill WWVB, which is a bit more
> involved, but works.
> 
> GPS is not an option without a tall tower.

	Everything you say up to this makes perfect sense, but what makes
you think GPS timing fails to work with less than a tall tower ?

	I believe it is readily possible to get to the 10-30 ns of
UTC/TAI TOD area with just reasonable sky view, not 100% as implied by a
tower. And certainly 1E-11 or 1E-12 frequency accuracy is also readily
available with less than perfect sky view depending on your taus...

	Perhaps ultimate performance requires really unobstructed sky view
in order to absolutely minimize multipath but then you are probably 
talking 1E-13 or better... 


> This is NOT progress, IMO.

	Virtually ANY GPS timing solution ought to easily get you inside of
a couple of microseconds of UTC/TAI, I am pretty sure it is quite difficult
to get within 10-100 us with the current AM modulation of WWVB, possibly
even 1-10  ms is difficult.   And anything close to this requires accurate
knowledge of geographic position and 60 KHz propagation corrections.

	I'm not clear how accurately one can resolve the phase transition
in the new scheme, but I suspect probably unambiguously to 1 cycle of
the 60 KHz... and from there is merely a function of how accurately one
can resolve the phase of the 60 KHz.    This potentially can supply a
much higher resolution time hack than the AM envelope.

	The real question being how important is preserving backward
compatibility with antique equipment versus better performance...

	I agree that ALWAYS is a trade off...


> 
> -John
> 
> ==============
> 
> 
> > Hi John:
> >
> > They are going to maintain the existing AM modulation format so all the
> > WWVB "Atomic Clocks" will still work.  The phase
> > modulation is added on top of that.
> >
> > Yes, I expect my HP 117 may no longer work, but I'd much rather have the
> > improved s/n and timing accuracy.
> >
> > Have Fun,
> >
> > Brooke Clarke
> > http://www.PRC68.com
> > http://www.end2partygovernment.com/Brooke4Congress.html
> >
> >
> > J. Forster wrote:
> >> All very nice, but if this change renders all existing receivers
> >> useless.
> >> How does that improve things?
> >>
> >> All it does is wipe out all the existing phase tracking infrastructure.
> >>
> >> The only benefit is to the government who can reuse the WWVB transmitter
> >> and frequency allocation. Everybody else will have to buy new stuff.
> >>
> >> Sounds a lot like HDTV fiasco. Making jobs (in China or Korea) by making
> >> scrap.
> >>
> >> YMMV,
> >>
> >> -John
> >>
> >> ==============
> >>
> >>
> >>> Dear Time-Nuts,
> >>>
> >>>
> >>>> I sure would like a WWVB BPSK receiver for the new modulation. (..)
> >>>>
> >>>> I'm sure in time there will be plenty of low cost ICs designed to
> >>>> receive the
> >> [SNIP}
> >>
> >>
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> >>
> >
> >
> 
> 
> 
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-- 
  Dave Emery N1PRE/AE, die at dieconsulting.com  DIE Consulting, Weston, Mass 02493
"An empty zombie mind with a forlorn barely readable weatherbeaten
'For Rent' sign still vainly flapping outside on the weed encrusted pole - in 
celebration of what could have been, but wasn't and is not to be now either."