广播电视在我国出现已经近半个世纪了,它的传输形式经历了从无线到有线——电视信号从电视台无线发射,老百姓家中的电视机用电视天线接收。这种早期的电视信号传输方式,信号单一,一个城市也就几个台,而且信号接收质量较差。 Radio and television have been in our country for nearly half a century, and its transmission has gone through from wireless to cable television signals transmitted wirelessly from television stations. The television sets of ordinary people are received by television antennas. This early television signal transmission, a single signal, a few cities in a few, but the signal reception quality is poor.