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The current distribution on the mast determines the radiation pattern. The radio frequency current flows up the mast and reflects from the top, and the direct and reflected current interfere, creating an approximately sinusoidal standing wave on the mast with a node (point of zero current) at the top and a maxima one quarter wavelength down [6] [8]
A radio mast base showing how virtually all lateral support is provided by the guy-wires. The terms "mast" and "tower" are often used interchangeably. However, in structural engineering terms, a tower is a self-supporting or cantilevered structure, while a mast is held up by stays or guy-wires. [1] A mast
A tower array is an arrangement of multiple radio towers which are mast radiators in a phased array. [1] They were originally developed as ground-based tracking radars. [2] Tower arrays can consist of free-standing or guyed towers or a mix of them. Tower arrays are used to constitute a directional antenna of a mediumwave or longwave radio station.
The diamond-shaped tower was patented by Nicholas Gerten and Ralph Jenner for Blaw-Knox July 29, 1930. [5] and was one of the first mast radiators.[1] [6] Previous antennas for medium and longwave broadcasting usually consisted of wires strung between masts, but in the Blaw-Knox antenna, as in modern AM broadcasting mast radiators, the metal mast structure functioned as the antenna. [1]
Guyed radio masts are typically tall enough that they require several sets of guy lines, 2 to 4, attached at different heights on the mast, to prevent them from buckling. An exception to multiple guys was the Blaw-Knox tower , widely used during the 1930s, whose distinctive wide diamond ( rhomboidal ) shape gave it the shear strength that it ...
So at low frequencies, even a 'T'-antenna can have very low radiation resistance, often less than 1 ohm, [5] [11] so the efficiency is limited by other resistances in the antenna and the ground system. The input power is divided between the radiation resistance and the 'ohmic' resistances of the antenna+ground circuit, chiefly the coil and the ...
The folded unipole antenna was first devised for broadcast use by John H. Mullaney, an American radio broadcast pioneer, and consulting engineer. [2] It was designed to solve some difficult problems with existing medium wave (MW), frequency modulation (FM), and amplitude modulation (AM) broadcast antenna installations.
Beam tilt is used in radio to aim the main lobe of the vertical plane radiation pattern of an antenna below (or above) the horizontal plane.. The simplest way is mechanical beam tilt, where the antenna is physically mounted in such a manner as to lower the angle of the signal on one side.