Quarter-wave antenna#Quarter-wave monopole

A quarter-wave radiator, also Marconi antenna after the Italian physicist and electrical engineer Guglielmo Marconi, is a transmitting antenna ( rod, pole, wire ), whose length corresponds to a quarter of the radiated wavelength λ. A quarter-wave radiator is half a half -wave dipole; the other pole is to be formed by a " counterweight ", which can accommodate the same current as of the quarter-wave radiator. For large wavelengths, this is a ground network to the transmission tower around, with smaller wavelengths used star-shaped rods ( see ground plane antenna) or, for example, the vehicle body, the board or the housing of the device: used hand tools to even the human body. Roughly in this order also the electrical quality of the " counterweight " and thus the efficiency deteriorates.

36 Ω, the impedance of a quarter-wave radiator is approximately half as large as that of a balanced open λ/2-Dipoles ( about 73 Ω ) and one eighth of a Faltdipoles (240 Ω ).

Quarter-wave radiator are ( partially electrically shortened rod, mobile antennas, CB radio ) for FM ( radio services, vehicles) and partly also for KW, MW and LW performed on a self- radiating transmission tower.

A vertical quarter-wave radiator radiates along the surface of the earth in all directions equally, while there is a minimum of radiation directly above him. A quarter-wave radiator to a conductive surface of a vertical half-wave dipole radiates towards enhanced in the angle range of 50 to 70 degrees upwardly.

λ/4-Strahler can as well as other dipole antennas are mechanically shortened by close to the foot to insert an inductor. Thus, the radiation deteriorates, the impedance is guaranteed with proper size of the inductor. If the entire antenna from a filament ( eg in the so-called rubber sausages of many handheld radios ), they are often referred to as a helical antenna not quite correct, although the direction of radiation continue those (transverse to the extension ) corresponds to a dipole.