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PTB time service prolonged

In the future radio alarm and station clocks as well as many other time services will continue to receive legal time from PTB via the DCF77 transmitter located near Frankfurt. The contract with Telekom affiliate T-Systems MediaBroadcast has been renewed and extended until the end of 2013.

PTB time signals – emitted by the DCF77 long-wave transmitter – can be received by normal radio clocks within a radius of approx. 2000 km.

Long waves are practically not hindered by obstacles. They can be received inside buildings by means of small antennae and relatively simple circuits. Therefore, even in the age of GPS, long-wave emission of time signals is still very attractive. In addition, the PTB time service excels by virtue of its reliability and availability. In the contract now renewed, T-Systems guarantees PTB, as under the previous contract, unrestricted use of the long-wave transmitter DCF77 in Mainflingen near Frankfurt for 99,7 percent of the year. In 2002, nearly 99,95 percent usage was achieved. At the transmitter the time information is coded as a data stream and transmitted with a power of approx. 30 kW by means of three atomic clocks and a complex electronic control and monitoring system. Thus PTB supplies legal time for the whole of Germany as an infrastructural service of the State. The signal provides station clocks, traffic light systems, switch clocks in power distribution systems, private radio clocks, broadcasting and television companies and many other users with the exact time.

The other possibilities of using the DCF77 transmitter also remain unaltered by the new contract. Apart from the transmission of the time information, the additional modulation of the carrier phase of the DCF77 transmitter is used for high precision applications. Furthermore, the carrier frequency, 77,5 kHz, is derived from the atomic clocks in Mainflingen so that the relative deviation of the carrier frequency from the nominal value averaged over one day is below 1 · 10-12. Permanent comparisons with the primary atomic clocks in Braunschweig, which are among the most precise clocks in the world, ensure the correctness of the signals emitted.


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