General information about DCF77
The radio clocks made by Meinberg receive the signal from the long wave transmitter
DCF77. This long wave transmitter installed in Mainflingen near Frankfurt/Germany
transmits the reference time of the Federal Republic of Germany. This time reference is
either the Central European Time (Mitteleuropäische Zeit, MEZ) or the Central Euro-
pean Summer Time (Mitteleuropäische Sommerzeit, MESZ). The transmitter is control-
led by the atomic clock plant at the Federal Physical Technical Institute (PTB) in
Braunschweig/Germany and transmits the current time of day, date of month and day of
week in coded second pulses. Once every minute the complete time information is
available.
At the beginning of every second the amplitude of the high precision 77.5 kHz carrier
frequency is lowered by 75% for a period of 0.1 or 0.2 sec. The length of these time
marks represent a binary coding scheme using the short time mark for logical zeroes and
the long time mark for logical ones. The information on the current date and time as well
as some parity and status bits can be decoded from the time marks of the 15th up to the
58th second every minute. The absence of any time mark at the 59th second of a minute
signals that a new minute will begin with the next time mark.
Our radio clocks decode the highly accurate information on date and time within a
wide range around Germany. So some of our clocks are installed in Bilbao/Spain as well
as in the city of Umeå in northern Sweden - fully satisfying the requirements of the users.
The radio clocks automatically switch to summertime and back. The reception of the
time information is free of charge and does not need to be registered.
Generally it is important to position the antenna in an optimal way. It should be
mounted at least 30 centimeters away from the clock unit and from solid steel. The
antenna should be aligned at a right angle to the direction of the transmitter (Frankfurt).
Figure: decoding scheme
