Most professional DRM exciters, like AM stereo, produce a phase modulated carrier signal and a envelope signal to feed the transmitter. To produce a compliant signal of sufficient quality to decode, a lot of alignment has to be done in the exciter to compensate for the response and group delay in the transmitter. I did one trial about 8 years ago. The signal output by dream can be either I/Q or just the composite waveform. In my case, the IF input on my upconverter was used to modulate the DRM signal as double sideband. By the time it fought its way through the amplifier chain I had about 50-75W of DRM power and it was heard by one guy. It does work, I'm just not convinced of the utility of it with the power levels that most of us play with.
+-RH