调频同步广播可以使在地下街道中的听众很清楚地收听到调频广播。而在没有同步广播以前,用袖珍收音机从地面上一边收听调频广播,一边沿台阶往地下街道走下去时,当走到某一深度时,就会听不到广播了。 FM synchronous broadcasts make it easy for listeners in underground streets to listen to FM radio. In the absence of simultaneous broadcasts, the FM radio was used to listen to FM radio from the ground while walking down the steps to the underground streets, and when it reached a certain depth, no radio was heard.