Dario Alberto might correct me here, but it seems to me that if the phase shifted audio is within the TX audio channel +/- 5 kHz. Then low pass bandpass audio filters in the I/Q outputs to the transmitter might work?
I'd like to think that this is the answer to the problem. Cutting off images above and below the channel. However, since we don't know where the images is in your comment here, it's frequency; I am then only guessing. We'll get some input here as this thread goes on. The filters I suspect have to be closely identical and not phase shift your signal and not skew it in any way. Capacitors parallel to your outputs, and hence parallel to the TX input might reduce the audio bandwidth without phase shifting or skewing. Caps like this reduce the bandwidth -3 dB per octave. If you calculate them right. Dan
