The antenna ensures a transformation between two forms of energy. In transmission, it converts an electrical energy supplied by the transceiver into radiating electromagnetic energy, and reciprocally into reception. The ideal antenna for 27MHz should have a theoretical wavelength of 11 meters. Under these conditions, an elementary 1/4 wave dipole should measure 2.75 meters. To improve performance, the antenna is extended: 1/2, 5/8, or 7/8 wave. The use of a self (copper wire at the base) allows to produce models of different sizes, which are even more efficient.