A Step in Time: Changes in Standard-frequency and Time-signal Broadcasts -- January 1, 1972An improved coordinated universal time (UTC) system has been adopted by the International Radio Consultative Committee. It was implemented internationally by the standard-frequency and time-broadcast stations on 1 Jan. 1972. The new UTC system eliminates the frequency offset of 300 parts in 10 to the 10th power between the old UTC and atomic time, thus making the broadcast time interval (the UTC second) constant and defined by the resonant frequency of cesium atoms. The new time scale is kept in synchronism with the rotation of the Earth within plus or minus 0.7 s by step-time adjustments of exactly 1 s, when needed. A time code has been added to the disseminated time signals to permit universal time to be obtained from the broadcasts to the nearest 0.1 s for users requiring such precision. The texts of the International Radio Consultative Committee recommendation and report to implement the new UTC system are given. The coding formats used by various standard time broadcast services to transmit the difference between the universal time (UT1) and the UTC are also given. For users' convenience, worldwide primary VLF and HF transmissions stations, frequencies, and schedules of time emissions are also included. Actual time-step adjustments made by various stations on 1 Jan. 1972, are provided for future reference. |
Common terms and phrases
1-kHz modulation 24h in summerg 59 is omitted Al-type second pulsesd atomic clock atomic standards BIH announced BIH Circular Bureau of Standards CCIR code is given coordinated universal cycles D3-Foreign radio station emphasized seconds markers Frequency kHz FSK-cw given by lengthening given in Appendix improved UTC system International de l'Heure International Telecommunication Union January laboratories Location Radiated Power minute marker minute pulses minutes 15 Morse code National Bureau negative leap second Neuchâtel Observatoire de Paris Physikalisch-Technische Bundesanstalt positive leap second preceding the indicated pulses are prolonged pulsesd are emitted Radiated Power kW Radio Consultative Committee Recommendation 460 rhythmic signals rotation second marker 59 Second pulses occur Service Announcements standard-frequency and time-signal Station Location Radiated step step-time adjustments Study Group summerg Between minutes Table D3-Foreign radio time-signal emissions timekeeping U.S. Naval Observatory users USNO UTC(i value of DUT1 voice announces WWVB WWVH