> The transitions (where the phase change!) are what you correlate,
> the more, the better S/N you get.

Yes---it's too bad that the proposed WWVB changes don't increase the
number of transitions at all.  Could they not do the
low-modulation-index DCF77-like signal on top of the BPSK?  That is,
put some small, fast phase wiggles on top of the slow 180-degree
transitions (or 120-degree transitions if NIST can be convinced to
change to that)?

But maybe some Loran-like tricks could be tried with an ordinary WWVB
signal and a receiver with a few kHz bandwidth.  The first part of the
exponential decay of the carrier amplitude (at the on-second marks)
might be relatively uncorrupted by sky wave, just as with Loran.
Considerable averaging would be needed I guess.  If the
characteristics of the transmitting antenna are known, a model of the
pulse decay could be used to estimate the transmit time.

The phase transitions happen during the low-power intervals (-17 dB),
so they would seem to be less useful than the amplitude transitions:
an 11 dB penalty, counting the gain from the antipodal signaling.

What is the inherent bandwidth of the DCF77 system, by the way?

John, if you're reading this, would your receiver be capable of
recording with wider RF bandwidth?  Your recordings made during the
test period have a bandwidth of about 30 Hz; can it go any wider?  I
think your web page says you're using an active whip antenna, which is
good because the resonant loops would impose their own bandwidth
limit.  If you could eliminate the narrowband receiver and record the
antenna signal directly with the 192 ksa/s ADC, that would be ideal.
(I should really cobble up a system of my own, but I'm a fair distance
from Colorado.)


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