Receiving "Real-Time" Via Dcf77 Or Gps - Alpermann+Velte AV-MTD G 30 TTT Operating Manual

Operating Manual AV-MTD G 30 TTT
Page 12

Receiving "Real-Time" via DCF77 or GPS

There are two standard configurations:
• G 30 TTT with built-in DCF77 receiver. The antenna has to be connected at the insulated
BNC socket at the rear panel. Three LED's at the front of G 30 TTT indicate the status of
the built-in receiver:
LED free (red) = free-run mode. The receiver outputs the time in free-run mode as long
as this LED lights up.
LED mod. (green) = modulation. Flashes every second to indicate the decoding of the
time telegram.
LED field (green)
Connection of an external DCF77 or GPS receiver. Using a serial (RS232) interface
•
(connected at a 9-pin D-Sub) G30TTT receives every second time, date and status data.
Two LED's at the front of G 30 TTT indicate the status of the serial data:
LED free (red)
LED mod. (green)
Positioning the DCF77 antenna:
The status LED's mod. and field serve to find out the optimum antenna position. With the
DCF77 receiver built-in in G 30 TTT, these LED's are located at the front panel of G 30 TTT;
with an external DCF77 receiver, these LED's are located at the housing of this receiver. In the
latter case the mod. LED at G 30 TTT indicates the reception only of serial data, not of the
radio telegram.
Put the antenna upright and turn slowly until a minimum luminosity of the field LED
appears. Then turn the antenna for 90° in order to achieve the best position. If now the field
LED fully lights up and the mod. LED blinks regularly - without any flickering! - the free LED
should go out after a few minutes. Otherwise the antenna should be installed at another
position.
Please note: the 60th second in the radio telegram is characterised by omitting the seconds
pulse, i.e. in this case the mod. LED of the receiver does not flash.
The DCF77 receiver has an independent clock which runs freely without receiving any signals.
In case of a power failure an accumulator will keep the clock running with a precision of 10
If a synchronisation has once been achieved, the clock is adjusted and a new synchronisation
once or twice a day will be sufficient.
The LTC time information as "real-time":
Pressing the real-time button selects this generator operating mode. Every time the real-time
button is pressed the actual time of the receiver will be transferred to the generator; otherwise
the generator continues to count on the time locked to the video or free running thus avoiding
the generation of frame jumps. At a pre-selected hour another transfer of the receiver time is
made automatically (i.e. in this case a frame jump of the generator can be expected, for
example at 3:00 at night). This hour can be set using the menu (see chapter "Description of
the menu lines"). G 30 TTT looks for a match of this selected hour with the reference time
input from the GPS or DCF77 receiver.
If this operating mode is used without having a receiver built-in or connected, any MTD user
console may be used to set "real-time" and date. Please notice REAL on/off at chapter
"Description of the menu lines".
= field strength of the antenna signal.
= free-run mode, the receiver has not been synchronised until
this LED is extinguished.
= modulation, flashes every second to indicate reception of
serial data.
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