DCF77 is a long wave time signal and standard-frequency radio station. Its primary
and backup transmitter are located in Mainflingen, about 25 km south-east of Frankfurt
am Main, Germany. It is operated by Media Broadcast GmbH (previously a subsidiary
of Deutsche Telekom AG), on behalf of the Physikalisch-Technische Bundesanstalt,
Germany's national physics laboratory. DCF77 has been in service as a standard-frequency
station since 1959; date and time information was added in 1973. The timestamp sent
is either in UTC+1 or UTC+2 depending on daylight saving time.[1]
The 77.5 kHz carrier signal is generated from local atomic clocks that are linked
with the German master clocks in Braunschweig. With a relatively-high power of 50
kW, the station can be received in large parts of Europe, as far as 2000 km from
Frankfurt (and further away depending on signal propagation and local interference.
As an example, reception with high-grade consumer clocks is possible in Portugal
and Gibraltar (during night hours). Its signal carries an amplitude-modulated, pulse-width
coded 1 bit/s data signal. The same data signal is also phase modulated onto the
carrier using a 512-bit long pseudo random sequence (direct-sequence spread spectrum
modulation).
The transmitted data repeats each minute.
- Current date and time;
- Leap second warning bit;
- Summer time bit;
- Primary/backup transmitter identification bit;
- Several parity bits.
-
The call sign DCF77 stands for D=Deutschland (Germany), C=long wave signal, F=Frankfurt,
77=frequency: 77.5 kHz.
