Meinberg UA32S - Manual (Page 5)

5
General Information about DCF77
The radio remote 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 European Summer Time (Mitteleuropäische Sommerzeit, MESZ). The transmit-
ter is controlled 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 remote 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 require-
ments of the users. The radio remote 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
M Start of Minute (0.1 sec)
R RF Transmission via secondary antenna
A1 Announcement of a change in daylight sa-
ving
Z1, Z2 Time zone identification
A2 Announcement of a leap second
S Start of time code information
P1, P2, P3 Parity bits