[time-nuts] WWVB a different approach to d-bpsk-r (cheating)

Bob Camp lists at rtty.us
Sat Jul 14 20:32:31 UTC 2012


Hi

The "zero crossing" is very arbitrary. If it's correct at the transmit site, it will then be off everywhere else by the speed of light / distance. You will appear to be correct  once every wavelength away from Colorado (roughly every 3 miles). You won't really be correct because you are looking at a different zero crossing.

As long as you don't have sunset or sunrise between you and the transmitter,  WWVB is reasonably stable. At night you will get more signal, but also can have some skywave "stuff" in the mix. 

Bob
   
On Jul 14, 2012, at 3:50 PM, paul swed wrote:

> OK have been doing a lot of experimenting.
> I was curious what is the GPS tick in relationship to wwvb. Especially
> since it is a reliable 1 sec marker.
> Using a Tbolt since everyone has one on the list. ;-) And monitoring the 10
> us tick to the wwvb 60 Khz carrier on a scope. Amazingly and over at least
> 2 hours now, the rising cycle of 60 Khz aligns to the 10 us Tbolt tick
> rising edge. Expected some form of drift.
> 
> Would not have actually thought there should be such a relationship or its
> truly pot luck today.
> WWVB today is also not running bpsk.
> 
> Should such a relationship actually exist?
> There is a clue in a 1985 article in ham radio magazine.
> It went something like this. At any given instant the 60 Khz may jitter.
> But for every 1 sec period there will be exactly 60,000 cycles.
> 
> If it does stay aligned, then the cheating d-bpsk-r gets to be interesting
> and very implementable.
> 
> The approach using a micro to sample a squared up 60 Khz after the Tbolt
> tic.
> Perform 2-3 1 usec samples in the leading 90 degree signal.
> Decide is it a 0 or 1 phase.
> Select a inverted or non inverted 60 Khz into the output path to maintain a
> constant phase 60 Khz for the old recvrs.
> 
> Sure its cheating. But if this relationship is real I should be able to
> implement the answer very quickly as a proof point.
> 
> Have not heard if the NIST testing is completed or when the next one is.
> But for today all of the rcvrs are working just fine.
> Regards
> Paul
> WB8TSL
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