Meinberg DCF77 UA509 - Manual (Page 9)

9
Installation
Power Supply
The System requires a single supply voltage of 5V/250mA. The power supply should
be longitudinal regulated. If a switched mode power supply is used the negative pole is
to ground directly or via a capacitor >0,1F. The voltage feed should be applied low
impedance and via the pins a1 and c1.
Mounting the Antenna
Generally it is important to position the antenna in an optimal way. The antenna
should be aligned at a right angle to the direction of the transmitter (Frankfurt). It
should be mounted at least 30 centimeters away from the clock unit and from solid
steel. A distance of several meters is recommended to all TVs or computer monitors.
The scope of supply includes an active ferrite antenna for indoor mounting (AI01)
and 5m of RG175 coaxial cable. When mounting the antenna outdoor the weather
proof Antenna AW02 is to use.
Powering Up the System
After connecting the power supply and the antenna the system is ready to operate.
Time or date is displayed on the 8 digit LED display (the timebase choosen for COM0
is displayed).
The brighness of the “Feld” LED in the front panel depends on the signal strength of
the DCF77 carrier. In order to get the maximum signal, the antenna should be aligned
in two steps. First it should be turned slowly until the “Feld” LED is mostly dimmed.
Finally the antenna must be turned by 90° from this position to obtain maximum
signal. If the antenna is installed properly and the signal from DCF77 can be received
without strong distortions, the "Mod." LED starts blinking exactly once per second,
corresponding to the time marks from DCF77. If this LED flashes intermediately,
there is some electrical noise around which prevents the microprocessor from deco-
ding the time message. So a better location for the antenna must be found. In case of
correct reception it takes up to three minutes after power-up until the clock is
synchronized and the "Freil." LED is turned off. It is turned on again to indicate the
loss of or an error in reception. Without RF signal the clock runs on XTAL with an
accuracy of 10
-6 (after 24 hours of synchronous operation, otherwise: 10 -5 ). If the
clock have lost reception for more than 12 hours the "Freil." LED starts blinking.
The serial outputs are enabled immediately after power up. Baudrate, framing,
output mode and time zone can be configured separately by two DIL switches.