In message: <[EMAIL PROTECTED]> Ashley Yakeley <[EMAIL PROTECTED]> writes: : On Jan 2, 2007, at 11:40, Warner Losh wrote: : : > The second technical problem is that the length of a second is : > implicitly encoded in the carrier for many of the longwave time : > distribution stations. 10MHz is at SI seconds. For rubber seconds, : > the broadcast would drift into adjacent bands reserved for other : > things. : : At 1000ns, the carrier would drift by 10Hz. Surely the bandwidth is : big enough for that?
Likely. I hasn't done the math. I didn't know if the rubber seconds idea was only on leapday, or for the whole year. : > Also, GPS would have to remain in SI seconds. The error in GPS time : > translates directly to an error in position. Approximately 1m/ns of : > error (give of take a factor of 3). Rubber seconds would require that : > the rubber timescale be off by as much as .5s. So GPS has to remain : > in GPS time (UTC w/o leap seconds, basically). That means that the : > rubberness of the seconds would need to be broadcast in the : > datastream. : : GPS is TAI. I'm not proposing abandoning TAI for those applications : that need it. GPS is also used for UTC today. Many ntpd's are stratum 1 tied to a GPS receiver. ntpd is UTC, by definition. The gymnastic necessary to produce UTC timing signals from GPS (non-rubber) timing signals with rubber UTC secods would be, ummm, very interesting. Warner