The alternating current in a piece of metal wire can emit alternating induced electric fields and induced magnetic fields into space, which is the emission of radio signals. On the contrary, the alternating electromagnetic field in space can induce an alternating current when it encounters a metal wire, which corresponds to the reception of wireless signals.
When the radio station is transmitting and receiving, it is hoped that the alternating current in the wire can be effectively converted into an electromagnetic wave in the space, or the electromagnetic wave in the space can be most effectively converted into an alternating current in the wire. This requires the wire used for transmitting and receiving to obtain the best conversion efficiency. The wire used for transmitting and receiving wireless electromagnetic wave signals that meets such requirements is called an antenna.
Theory and practice have proved that when the length of the antenna is 1/4 of the wavelength of the radio signal, the transmission and reception conversion efficiency of the antenna is the highest. Therefore, the length of the antenna will be determined according to the frequency or wavelength of the transmitted and received signals. As long as you know the center frequency of the corresponding transmission and reception, you can use the following formula to calculate the wavelength of the corresponding radio signal, and then divide the calculated wavelength by 4 to get the corresponding optimal antenna length.