Development of a fully solid state wideband (3 to 26 MHz) short-wave transmitter using PSM

We developed an evolutional wideband (3M~26MHz) short-wave transmitter with an output of 1kW using PSM (pulse step modulation) that digital (DRM: Digital Radio Mondiale) and analog AM modulation are possible. This equipment employs digital processed PSM method that high sound quality can be easily achieved in the modulation section and class E amplification for obtaining higher efficiency in the PA section composed of eight 125W PA. In addition, new output circuit for phase compensation of the load impedance. As a result, in the 125W PA, a drain efficiency of 95% at 3.925MHz and 86% at 25.885MHz was obtained. As analog AM characteristics, S/N of 54dB and above, distortion factor of 4% and under were obtained ranging from 3M to 26MHz. In digital modulation (DRM), S/N of about 24.5dB (at 25.885MHz at 16QAM) that satisfies target performance sufficiently was obtained.