Hi thank you for your comment. What do you think about the following thought: I take two old radioscanners each has 12.5 kHz channel pattern ("Kanalraster") , Tetra uses 25 kHz. Then I make for each scanner a FM modulation in Software or on FPGA and after a signal addition. Now i should have the modulated Pi/4-DQPSK signal back. Or haven’t I?