“…However, relatively recently, there have been efforts dedicated to developing PCL techniques and systems in the HF regime [see, e.g., Ringer and Frazer , ; Thomas et al , ; Fabrizio et al , ; Xianrong et al , ]. The new long wavelength (> 10 m) radio broadcasting format, Digital Radio Mondiale, which is recently being adopted by radio stations in many countries, has been the focus of much of this effort [see, e.g., Thomas et al , ; Xianrong et al , ].…”