This patent describes a method which allows multiple DAB transmission signals to be modulated, up-converted, filtered and combined prior to a High Power Amplifier (HPA), thus reducing the multiple up-conversion and HPA to a single unit and eliminating the need for a high power combiner. This significantly reduces the equipment needed for multi-channel transmissions and the consequent cost. In addition the techniques described provide signal timing alignment as required in Single Frequency Networks (SFN).