[time-nuts] WWVB BPSK Receiver Project?
pmonta at gmail.com
Thu Mar 15 08:03:56 UTC 2012
> In thinking about it a bit further, one might be able to take the 60 kHz
> received sine at some point in the receiver, full wave rectify and HP
> filter it (which doubles the frequency) then divide by two in a Flip-Flop
> and heavily filter the resultant. This is a hybrid solution... analog and
> digital... with not a uP in sight!!
> That would preserve the frequency, but ditch the phase reversals of the
> BPSK. Depending on the guts of the particular receiver, it might be
> possible to simply retrofit a PCB.
There would be an SNR penalty for this, though, called "squaring
loss". A PIC that knew when the transitions would happen and inverted
the original signal would be free of squaring loss, since its
reversing-signal would be noiseless.
My worry, though, is that even this preprocessing doesn't look like it
would give as good a signal as the original WWVB. Eyeballing the
phase data derived from John Seamons' capture seems to show some phase
variation from bit to bit, even those bits with the same nominal
carrier phase. Some nonlinearity in the transmitter when hit with
these phase transients perhaps. How quickly does it average out in a
carrier-phase receiver? Unknown.
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