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. -- John Hasler jhas...@newsguy.com Dancing Horse Hill Elmwood, WI USA _______________________________________________ questions mailing list questions@lists.ntp.org https://lists.ntp.org/mailman/listinfo/questions
