Time and Standard Frequency Station TDF (France)
Last update: June 24, 2022 21:25 UTC (3a8d52d62)
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.