Small Antennas for High Frequencies

 When an alternating electric current flows through a conductor (wire), Electric-E and Magnetic-H fields are created around the conductor.  If the length of the conductor is very short compared to a wavelength (<< λ/4), the electric and magnetic fields will decrease dramatically within a distance of one or two wavelengths.  However, as the conductor is lengthened, the intensity of the fields enlarges and part of the energy escapes into the space. When the length of the conductor approaches a quarter of a wavelength (λ/4) at the frequency of the applied alternating current, most of the energy will escape in the form of electromagnetic radiation.