What is the best antenna length for FM radio?

There are many kinds of radio antennas: FM AM Antenna, FM AM Radio Antenna, FM AM Antenna for CAR, Fm AM Antenna Marine, FM AM Antenna for home Stereo rod antenna, long line antenna, loop antenna, magnetic rod antenna, Yagi antenna , shark fin antenna and other types, their functions are basically the same, in order to adapt to the model, the shape of the antenna is constantly improved. Their function is to receive the radio magnetic field signal, and then send the radio electromagnetic wave to the detection, filtering, and amplifying circuits. Sound signal, the function of the radio antenna is to better receive the radio signal, so that the unreceived signal can be received, and the sound quality can be smoother and clearer, and the material of FM AM Antenna is waterproof, sunscreen, anti- Ray's, can be used outdoors. Better for outdoor reception!