I need a person that understands RF and signals to explain to me like i'm a retard. I want to know how a receiver knows what amplitudes are available in QAM modulated signal for example. Does a transmitter needs to transmit some sort of a preambla for a receiver to catch and try and sync onto and detect the distinct voltage levels for different levels... (Because if one transmitter is closer and using the samo output power he will have higher Voltage amplituDes then the transmitter which is far further away...) Pic unrelated misc RF magic pcb shot.