[email protected] said: > Your ears are correct; the 100 Hz code began in 1960. See: > http://tf.boulder.nist.gov/general/pdf/1670.pdf > http://tf.boulder.nist.gov/general/pdf/1681.pdf > http://tf.nist.gov/stations/wwvhistory.htm > http://tf.boulder.nist.gov/general/pdf/1731.pdf
Fun reading. Thanks. I think I found a better one: http://tf.nist.gov/general/pdf/1969.pdf NIST Special Publication 250-67 NIST Time and Frequency Radio Stations: WWV, WWVH, and WWVB January 2005 Here is a chunk from page 14: (postscript page 14, document page 5) An experimental time code containing year, month, day, and precise time-of-day began in April 1960 [14] and was made part of the regular broadcast in January 1961 [15]. This time code, known as the NASA 36-bit code, was produced at a 100 Hz rate using 1000 Hz modulation. Believed to be the first digital time code broadcast in the United States, it made it possible for the first time for self-setting, radio controlled clocks to appear. Earlier radio controlled clocks required human interaction to initially synchronize. The current time code format (modified slightly over the years) was a modified version of the IRIG-H code format. It was initiated on July 1, 1971 using a 1 Hz rate and 100 Hz modulation. The new code included a daylight saving time (DST) indicator [16]. The telegraphic time code was also permanently removed on this date. So the 100 Hz subcarrier (that I didn't remember) didn't start until 1971. That was long after I was listening to WWV as a kid. -- These are my opinions, not necessarily my employer's. I hate spam. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
