The WWV signal is still accurate within a few milliseconds. Light is fast. Really fast.
-mel > On May 12, 2016, at 10:19 AM, Jean-Francois Mezei > <jfmezei_na...@vaxination.ca> wrote: > > On 2016-05-11 10:30, Mel Beckman wrote: > >> Read deeper into the thread and you'll find where I sourced inexpensive >> RF-based NTP servers using CDMA, GSM, and even WWV. > > For shortwave, you would need to calculate propagation delay between > transmitter and receiver. (does signal reach via line of sight, bounce > against ionosphere ?). > > Since CDMA is dead outside the USA and drying in USA, I wouldn't rely on > that. If GSM towers rely on a GPS receiver on the tower and those > towers are near enough to your location (< 30km), then chances are that > blocked GPS signals at your location would also jam the signals at the > GSM antenna. > > And if you are setup to be totally autonomous in case of power failures, > you need to know whether the GSM antenna you are relying on is also on > permanent power backup or only has autonomy of a few hours.
