I have several clocks in my house (and a watch) that all set their time using the 60 kHz radio broadcast time signal originating from Fort Collins, Colorado (callsign WWVB).
http://en.wikipedia.org/wiki/WWVB One clock reliably gets the signal, but the others don't, and it seems like over the last decade, the signal has diminished, as they used to. Jon 'maddog' Hall assured me via Twitter that he receives the signal just fine in NH, so it may be local signal interference, or changes in buildings or trees that have diminished the signal in the Boston area. Oddly enough, according to Wikipedia, the transmitter power was actually increased in 2005. Sure seems like it worked better before then. The page notes that they recently introduced phase-shift keying modulation, which "allows a more sophisticated receiver to distinguish 0 and 1 bits far more clearly, allowing improved reception on the East Coast of the United States where the WWVB signal level is weak, radio frequency noise is high, and the MSF time signal from the U.K. also interferes sometimes." Maybe I'm getting interference from the UK? And: "WWVB's Colorado location makes the signal weakest on the U.S. east coast, where urban density also produces considerable interference. In 2009, NIST raised the possibility of adding a second time code transmitter, on the east coast, to improve signal reception there and provide a certain amount of robustness to the overall system should weather or other causes render one transmitter site inoperative. Such a transmitter would use the same time code, but a different frequency." This hasn't happened, but when/if it does, using a different frequency means my existing devices won't receive it anyway. In any case, I've periodically searched online to see if anyone has built a circuit that either acts as a repeater for the WWVB signal, or emulates it, using a GPS receiver or Internet NTP server as a time source. I haven't searched in a year or more, but last time I did I ran across a description of a graduate student project to build a repeater. Anyone seen a circuit or product that does this? With small, hacker friendly Linux devices becoming increasingly cheap, it should be quite possible to hit a sub-$50 price point for such a device, providing the AM transmitter doesn't require much. For something like this I'd rather buy a finished product, or at least a kit with the radio supplied as a built module, as I don't have the equipment to debug an RF transmitter. -Tom _______________________________________________ Hardwarehacking mailing list [email protected] http://lists.blu.org/mailman/listinfo/hardwarehacking
