[电] effective length of receiving an-tenna

jiē shōu tiān xiàn yǒu xiào cháng dù ㄐㄧㄝ ㄕㄡ ㄊㄧㄢ ㄒㄧㄢˋ ㄧㄡˇ ㄒㄧㄠˋ ㄔㄤˊ ㄉㄨˋ