Information provided by Richard B. Langley, University of New Brunswick
Station: TDF, Allouis, France Address: Centre National d'Etudes des Telecommunications PAB - STC - Etalons de frequence et de temps 196 avenue Henri Ravera F - 92220 Bagneux France Coordinates: 47d 10' N, 2d 12' E Frequency: 162 kHz Power: 2,000 kW Schedule: continuous except every Tuesday from 01:00 to 05:00 UTC Form of Time Signals: TDF is an amplitude modulated longwave broadcasting station, transmitting the programs of the France-Inter Network of Telediffusion de France (TDF). Time signals are transmitted by phase modulation of the carrier by + and -1 radian in 0.1 s every second except the 59th second of each minute. This modulation is doubled to indicate binary 1. The numbers of the minute, hour, day of the month, day of the week, month and year are transmitted each minute from the 21st to the 58th second, in accordance with the French legal time scale. In addition, a binary 1 at the 17th second indicates that the local time is 2 hours ahead of UTC (i.e., summer time), a binary 1 at the 18th second indicates when the local time is 1 hour ahead of UTC (i.e., winter time). A binary 1 at the 14th second indicates that the current day is a public holiday (14 July, Christmas, etc.) and a binary 1 at the 13th second indicates that the current day is the day before a public holiday. Relative Uncertainty of the Carrier Frequency: 2 parts in 10^12. Radio Clocks Available: Horloge 59 HF BHL Electronique Zone Industrielle B.P. 8 F - 14540 Bourguebus France Recepteur horaire sur France-Inter G-O Dyna Electronique 36 avenue Gambetta F - 75980 Paris Cedex 20 France RTD 101 telematique SA Zirst-chemin des pres F - 38240 Meylan France Information Sources: Annual Report of the BIPM Time Section for 1989, Bureau International des Poids et Mesures, Pavillon de Breteuil, F - 92312 Sevres Cedex, France. Zeitzeichensender / Time Signal Stations (bilingual: German and English) by Gerd Klawitter, Siebel Verlag, Bonhoeffer Weg 16, D-5309 Meckenheim, Germany. The phase modulation pattern. ----------------------------- One signal element consists of the following : the phase of the carrier is advanced linearly up to +1 radian in 0.025 second, then retarded linearly up to -1 rad in 0.050 second, then advanced again to reach zero after another 0.025 second. One signal element is always sent at each second between 0 and 58. The epoch is when the down ramp crosses zero. If a '1' bit is to be stransmitted, two signal elements are sent in sequence. Since the phase is the integral of the frequency, to this triangular phase modulation corresponds a square frequency modulation with an amplitude of about + and - 6Hz. binary '0' binary '1' / \ / \ / \ phase ___ / \ ___ ___ / \ / \ ___ \ / \ / \ / \ / \ / \ / (0.025 s | | | | | | | | | | | | | | ticks) | | epoch epoch __ __ __ _____ __ | | | | | | | | | | frequency ___| | | |___ ___| | | | | |___ | | | | | | |_____| |_____| |_____| Both the average phase and the average frequency deviation are thus zero. More data is sent by phase modulation during the rest of each second. But the second marker (and data bit) is always preceded by 0.1 second without modulation. There is no marker at the beginning of the 59th second, nor any data sent during the entire duration of that second. The binary encoding of date and time data. ------------------------------------------ Seconds 20 to 58 carry exactly the same information as the signal of the German transmitter DCF77.