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The folded unipole antenna is a type of monopole mast radiator antenna used as a transmitting antenna mainly in the medium wave band for AM radio broadcasting stations. It consists of a vertical metal rod or mast mounted over and connected at its base to a grounding system consisting of buried wires.
This is the type of antenna used in most portable AM broadcast receivers (other than car radios): The standard AM antenna is a loop of wire wound around a ferrite rod (a "loopstick antenna"). The loop is resonated by a coupled tuning capacitor, which is configured to match the receiver's tuning, in order to keep the antenna resonant at the ...
AM broadcasting is radio broadcasting using amplitude modulation (AM) transmissions. It was the first method developed for making audio radio transmissions, and is still used worldwide, primarily for medium wave (also known as "AM band") transmissions, but also on the longwave and shortwave radio bands.
The rise of FM radio and television broadcasting in the 1940s–1950s created a need for even taller masts. The earlier AM broadcasting used LF and MF bands, where radio waves propagate as ground waves which follow the contour of the Earth. The ground-hugging waves allowed the signals to travel beyond the horizon, out to hundreds of kilometers.
Mast radiators make good ground wave antennas, and are the main type of transmitting antennas used by AM radio stations, as well as other radio services in the MF and LF bands. They also can radiate enough power at higher elevation angles for skywave (skip) radio transmission. Most radio stations use single masts.
This design is used for AM radio broadcasting antennas in the MF and LF bands. [11] Another variant is the folded unipole antenna. [12] At lower frequencies in the LF and VLF band, the tallest antenna masts that can be practically constructed are electrically short, significantly shorter than one-quarter
A typical AM broadcast radio loop antenna wound on ferrite may have a cross sectional area of only 1 cm 2 (0.16 sq in) at a frequency at which an ideal (lossless) antenna would have an effective area some hundred million times larger. Even accounting for the resistive losses in a ferrite rod antenna, its effective receiving area may exceed the ...
A radio transmitter or just transmitter is an electronic device which produces radio waves with an antenna. Radio waves are electromagnetic waves with frequencies between about 30 Hz and 300 GHz. The transmitter itself generates a radio frequency alternating current, which is applied to the antenna. When excited by this alternating current, the ...