Францияның 162 кГц уақыт сигналы радиостансасы

French longwave time signal radio station

ALS162 is a French longwave time signal and standard frequency radio station and is used for the dissemination of the Metropolitan French national legal time to the public. TéléDiffusion de France broadcast the ALS162 time signal, provided by LNE SYRTE and LNE LTFB time laboratories under ANFR (state body for radio frequencies) responsibility, from the Allouis longwave transmitter at 162 kHz, with a power of 800 kW. The current time signal is generated by extremely accurate caesium atomic clocks and phase modulated on the 162 kHz ( wavelength) carrier signal in a way that is inaudible when listening to the signal using normal Longwave receivers. The ALS162 phase modulated time signal service requires a more complex receiver than the popular German DCF77 amplitude modulated time signal service, but the much more powerful transmitter (16 times DCF77's 50 kW) gives it a much greater range of 3,500 km. The signal transmission is almost continuous, but there is a regularly scheduled interruption for maintenance and tests every Tuesday from 08:00 to 12:00. The transmitter building contains two caesium atomic clocks which are used to generate the time signal and which are monitored through the SYREF system and GPS common view measurements, to align with the official French UTC(OP) time scale. The ALS162 time signal exactitude should be in excess of 1 millisecond uncertainty. The monitoring of the ALS162 signal is jointly conducted by LNE SYRTE, LNE LTFB and the trade body France Horlogerie and measurement results are published in real time. The time signal is critical for over 300,000 devices (clocks in public places, information panels, traffic lights, public lighting, parking meters, etc.) deployed within French enterprises and state entities, such as French Railways (SNCF), electricity distributor Enedis, airports, hospitals, municipalities, etc. which depend on the signal in France and abroad.

The transmitter was previously known as TDF, FI or France Inter because the signal was formerly best known for radio broadcasting the France Inter AM signal. The transmission of audio (sound) signal ceased at the end of 2016, but the Allouis transmitter remains in use for the dissemination of the time signal and other digital signals. As of 2017 the transmitter has been renamed to ALS162. The call sign ALS162 stands for ALS = Allouis transmitter, 162 = frequency: 162 kHz. On 1 February 1986, the frequency was changed to its current value of 162 kHz (still an accurately controlled frequency standard) to bring it to a multiple of 9 kHz in accordance with the Geneva Frequency Plan of 1975. Before 2017 the period used for scheduled signal interruptions for maintenance and tests was on Tuesday from 01:03 to 05:00.

One signal element consists of the phase of the carrier shifted linearly by +1 rad in 25 ms (known as "ramp A"), then shifted linearly by −2 rad over 50 ms ("ramp B"), then shifted linearly again by +1 rad for another 25 ms ("ramp C"), returning the phase to zero. One signal element is always sent at each second between 0 and 58. Two signal elements are sent in sequence to represent a binary one; otherwise it is interpreted as binary zero. During ramp B of the initial signal element, the exact point the signal phase is at zero represents the top of the UTC second. Since the phase is the integral of the frequency, this triangular phase modulation at 40 rad/s corresponds to a square frequency modulation with a deviation of 20/π ≈ 6.37 Hz. Both the average phase and the average frequency deviation are thus zero. Additional non timing data is sent by phase modulation during the rest of each second. But the second marker (and data bit) is always preceded by 100 ms without any phase modulation. The signal is not phase modulated at all during the 59th second past the minute.