Guys, I've just gone through a round of audio driver upgrades for the WWV and CHU radio services and the IRIG signal. The documentation has been rewritten as well. I'm hoping that the CHU upgrade might find users in Canada to support the continued operation of CHU with three frequencies, even if the 7335 kHz frequency is moved. As it is, that frequency is clobbered from sundown to sunup by broadcasters that should be using the Internet.
All three drivers have much better accuracy and lower jitter to the point the radio drivers can track movements of the ionosphere. Expected accuracy without prior calibration, but with accurate propagation delay configuration, within 0.5 ms with IRIG, 1 ms with WWV and 2 ms with CHU. When calibrated relative to a PPS signal from a GPS receiver, the accuracy is .02 ms for IRIG, 0.5 ms for WWV and 1 ms for CHU. With WWV the residual errors are dominated by ionospheric movements. These figures are for FreeBSD 6.1 running on a Pentium 4. Forget Solaris; it is a terrible platform for squeaky clean time. In addition to the accuracy improvements, the radio drivers have better behavior under marginal signal conditions, especially the maximum-likelihood UART and majority decoder used in the CHU driver. As we are at the nadir of sunspot cycle, propagation conditions have been truely awful, but does present the opportunity to improve the algorithms to separate weak signals from real trash. To Canada (my father was born there): get the CHU thing running and make sure the NRC knows it. Dave _______________________________________________ questions mailing list [email protected] https://lists.ntp.isc.org/mailman/listinfo/questions
