不少人有这样的经验:在火车车厢中,如果不是靠近窗口,收音机的收听效果会大打折扣。这是为什么?原来火车车厢相当于一个大金属容器,它能阻止车厢外部的电磁波进入车厢,这就是我们通常所说的屏蔽现象。在钢筋水泥建筑物里收看无线电视节目一般要加室外天线,否则钢筋网格的屏蔽作 Many people have such experience: in the train car, if not close to the window, the radio listening effect will be greatly reduced. This is why? The original train car is equivalent to a large metal container, which can prevent the electromagnetic waves outside the compartment into the car, which is what we usually call the shielding phenomenon. In reinforced concrete buildings to watch TV programs generally increase the outdoor antenna, or reinforced grid shielding