DCF77 - No Signal detected
The data sheet says: -


Earth
Operating voltage 1.2 … 1.5 V- (although the German DS appears to say 15 V)
DCF output
DCF output inverted


Outputs 3 and 4 of open collectors npn max. 30 V 1 mA

So it looks like you have powered it with too much voltage (unless you read the German DS) and you don't understand what an open collector is - it requires a pull-up resistor.