MF AM grounded dipole for stereo and digital transmissions

Modern MF AM transmitter output impedance has been chosen to be 50 ohms unbalanced. For this reason high power 50 ohms coaxial lines have been designed and manufactured, rigid or almost flexible in order to connect the transmitter in the station building and the far away radiating system at one or more wavelengths. At MF frequencies the radiating system is generally a standard classical monopole where a matching system close to the monopole is needed to obtain maximum radiation efficiency. The proposal here is to use a radiating system made up of a grounded tower close to half a wavelength tall with a cylindrical skirt around the tower's lower part. The skirt is fed directly from the 50 ohm coaxial line at a point whose impedance is very close to 50 ohms, avoiding the matching system and improving the radiation efficiency within a good bandwidth suitable for stereo or digital transmissions. Design permits a low standing wave ratio within the information passband necessary to obtain the lowest information distortion. Scale models have been designed, constructed and measured obtaining similar results as predicted by calculations in the MF frequencies. The advantages of a grounded tower are discussed.