Dipole antennas
are key elements of radio transmission, and have been used throughout Europe and the United States since the early days of radio. These simple antennae are electrical conductors that receive and send high-frequency radio signals across relatively long distances.
History
In 1886, German physicist Heinrich Rudolph Hertz created the dipole antenna to transmit ultra high frequency (UHF) radio waves. These simple and effective antennae have been used in Western countries since the dawn of radio, and are still in widespread use today.
Identification Function
The dipole antenna is a radio apparatus that is united at the center by a frequency feed point. Named because it has two halves, this antenna is balanced and has two perfectly symmetrical poles. Basic dipoles are made with simple wires of the same length that open out in two opposite directions from the central feed point.
Signifiance
Dipole antennas are considered to be the simplest type of antenna used to transmit or receive radio signals. This electrical medium acts as a radio frequency conductor, either on its own or within larger, more complicated types of antennae. Measuring one half of a wavelength from one end to the other, the antenna is linked in the center to receive and emit radio frequencies.
There are several different types of dipole antennae, but each have the same function of transmitting and receiving radio signals.
Types
Ideal half-wavelength dipoles are a unique type, with each wire measuring exactly one fourth of the electromagnetic wavelength, making it a total of one half of a wavelength.
Folded dipole antennae have an additional wire that connects the two ends of the half-wave dipole. The folded dipole has a much higher radiation resistance than the normal model.
Short, or Hertzian dipole antennas, are theoretical models that are not yet produced, with an antenna much smaller than the wavelength it would transmit or receive.
Applications
Dipole antennas are used in a variety of everyday electronics. For example, a dipole antenna is used on television sets to receive broadcasts (the iconic "bunny ears"). However, as of February 17, 2009, these will be obsolete.
A folded dipole is a highly effective method for receiving FM signals for radios as well.
Radio towers--such as the Warsaw radio mast--are also considered dipole antennas. These are effective in broadcasting radio signals for many miles.
Dipole antennas are also widely used in the military, where they are built into equipment such as navigation devices and radios.
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