Welcome to our site! EDAboard.com is an international Electronic Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.
The modulation is 16 or 64 QAM. It is claimed that this can be done on existing short wave transmitters. I suspect that the carrier phase is set at the oscillator and the amplitude is set by the usual AM modulation. This way a vector is made to the constalation point. I ffurther suspect that the output signal is sampled and demodulated as part of a feedback loop to compensate for any nonlinearity in the AM modulation process.