Shortwave is good for broadcasting very long distances. The shortwave signals bounce off the ionosphere that surrounds the Earth, back to the ground and then back to the ionosphere.
短波有利于长距离传输广播节目，短波信号被围绕地球的电离层反射，能在大地和电离层间来回反射。
2
732 medium- and short-wavebroadcasting transmitting and relay stations, covering 92.1 percent of the population;