John Hasler wrote: > Bill Unruh writes: >> The bandwidth of whatever marks it has to be pretty narrow, or the >> transmitter would interfer with everything around it. Ie, that means a >> large time uncertainty. > > The 60KHz WWVB signal is synchronously amplitude-modulated at a 1Hz > rate. The exact cycle on which the amplitude changes can be locked in > by a digital phase-locked loop. A VCXO can be phase-locked to the > carrier to within a small fraction of a cycle. Thus with a strong > signal the PPS error should be dominated by variations in propagation > delay. In practice accuracies of +-100usec are reportedly achievable, > but my very casual research indicate that even the fancy receivers don't > bother to include the hardware necessary to do so. > > Too bad NIST can't find the money for the PRNG phase modulation DCF77 > has.
Perhaps the "NAVSTAR" satellites and GPS provide more/better results than a VLF broadcast. _______________________________________________ questions mailing list questions@lists.ntp.org https://lists.ntp.org/mailman/listinfo/questions
