Tradução e análise de palavras por inteligência artificial ChatGPT
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half wave antenna - tradução para grego
![Feedpoint impedance of (near-) half-wave dipoles versus electrical length in wavelengths. Black: [[radiation resistance]]; blue: reactance for 4 different values of conductor diameter.](https://commons.wikimedia.org/wiki/Special:FilePath/DipoleImpedance.png?width=200 "Feedpoint impedance of (near-) half-wave dipoles versus electrical length in wavelengths. Black: [[radiation resistance]]; blue: reactance for 4 different values of conductor diameter.")
![induced EMF method]], an approximation that breaks down at larger conductor diameters (dashed portion of graph).](https://commons.wikimedia.org/wiki/Special:FilePath/DipoleReductionFactor.jpg?width=200 "induced EMF method]], an approximation that breaks down at larger conductor diameters (dashed portion of graph).")
![Q factor]] that the feed voltage is much smaller in relation to the standing wave. Since the antenna is fed at its resonant frequency, the input voltage is in phase with the current (blue bar), so the antenna presents a pure resistance to the feedline. The energy from the driving current provides the energy radiated as radio waves. In a receiving antenna the phase of the voltage at the transmission line would be reversed, since the receiver absorbs energy from the antenna.](https://commons.wikimedia.org/wiki/Special:FilePath/Dipole antenna standing waves animation 6 - 5fps.gif?width=200 "Q factor]] that the feed voltage is much smaller in relation to the standing wave. Since the antenna is fed at its resonant frequency, the input voltage is in phase with the current (blue bar), so the antenna presents a pure resistance to the feedline. The energy from the driving current provides the energy radiated as radio waves. In a receiving antenna the phase of the voltage at the transmission line would be reversed, since the receiver absorbs energy from the antenna.")
![Dipole antenna used by the [[radar altimeter]] in an airplane](https://commons.wikimedia.org/wiki/Special:FilePath/Dipole radar altimeter antenna.jpg?width=200 "Dipole antenna used by the [[radar altimeter]] in an airplane")
![Animated diagram of a [[half-wave dipole]] antenna receiving a radio wave. The antenna consists of two metal rods connected to a receiver ''R''. The [[electric field]] ''(<span style="color:green;">E, green arrows</span>)'' of the incoming wave pushes the [[electron]]s in the rods back and forth, charging the ends alternately positive ''<span style="color:red;">(+)</span>'' and negative ''<span style="color:blue;">(−)</span>''. Since the length of the antenna is one half the [[wavelength]] of the wave, the oscillating field induces [[standing wave]]s of voltage ''(<span style="color:red;">V, represented by red band</span>)'' and current in the rods. The oscillating currents ''(black arrows)'' flow down the transmission line and through the receiver (represented by the resistance ''R'').](https://commons.wikimedia.org/wiki/Special:FilePath/Dipole receiving antenna animation 6 800x394x150ms.gif?width=200 "Animated diagram of a [[half-wave dipole]] antenna receiving a radio wave. The antenna consists of two metal rods connected to a receiver ''R''. The [[electric field]] ''(<span style=\"color:green;\">E, green arrows</span>)'' of the incoming wave pushes the [[electron]]s in the rods back and forth, charging the ends alternately positive ''<span style=\"color:red;\">(+)</span>'' and negative ''<span style=\"color:blue;\">(−)</span>''. Since the length of the antenna is one half the [[wavelength]] of the wave, the oscillating field induces [[standing wave]]s of voltage ''(<span style=\"color:red;\">V, represented by red band</span>)'' and current in the rods. The oscillating currents ''(black arrows)'' flow down the transmission line and through the receiver (represented by the resistance ''R'').")
!["Rabbit-ears" VHF [[television antenna]] (the small loop is a separate UHF antenna).](https://commons.wikimedia.org/wiki/Special:FilePath/Rabbit-ears dipole antenna with UHF loop 20090204.jpg?width=200 "\"Rabbit-ears\" VHF [[television antenna]] (the small loop is a separate UHF antenna).")
![A [[reflective array antenna]] for radar consisting of numerous dipoles fed in-phase (thus realizing a ''broadside array'') in front of a large reflector (horizontal wires) to make it uni-directional.](https://commons.wikimedia.org/wiki/Special:FilePath/SCR-270 Radar Antenna2.jpg?width=200 "A [[reflective array antenna]] for radar consisting of numerous dipoles fed in-phase (thus realizing a ''broadside array'') in front of a large reflector (horizontal wires) to make it uni-directional.")
![UTR-2]] radio telescope. The 8 m by 1.8 m diameter galvanized steel wire dipoles have a bandwidth of 8–33 MHz.](https://commons.wikimedia.org/wiki/Special:FilePath/UTR-2 - P3094042 (wiki).jpg?width=200 "UTR-2]] radio telescope. The 8 m by 1.8 m diameter galvanized steel wire dipoles have a bandwidth of 8–33 MHz.")
Definição
Wikipédia
In radio and telecommunications a dipole antenna or doublet is the simplest and most widely used class of antenna. The dipole is any one of a class of antennas producing a radiation pattern approximating that of an elementary electric dipole with a radiating structure supporting a line current so energized that the current has only one node at each end. A dipole antenna commonly consists of two identical conductive elements such as metal wires or rods. The driving current from the transmitter is applied, or for receiving antennas the output signal to the receiver is taken, between the two halves of the antenna. Each side of the feedline to the transmitter or receiver is connected to one of the conductors. This contrasts with a monopole antenna, which consists of a single rod or conductor with one side of the feedline connected to it, and the other side connected to some type of ground. A common example of a dipole is the "rabbit ears" television antenna found on broadcast television sets.
The dipole is the simplest type of antenna from a theoretical point of view. Most commonly it consists of two conductors of equal length oriented end-to-end with the feedline connected between them. Dipoles are frequently used as resonant antennas. If the feedpoint of such an antenna is shorted, then it will be able to resonate at a particular frequency, just like a guitar string that is plucked. Using the antenna at around that frequency is advantageous in terms of feedpoint impedance (and thus standing wave ratio), so its length is determined by the intended wavelength (or frequency) of operation. The most commonly used is the center-fed half-wave dipole which is just under a half-wavelength long. The radiation pattern of the half-wave dipole is maximum perpendicular to the conductor, falling to zero in the axial direction, thus implementing an omnidirectional antenna if installed vertically, or (more commonly) a weakly directional antenna if horizontal.
Although they may be used as standalone low-gain antennas, dipoles are also employed as driven elements in more complex antenna designs such as the Yagi antenna and driven arrays. Dipole antennas (or such designs derived from them, including the monopole) are used to feed more elaborate directional antennas such as a horn antenna, parabolic reflector, or corner reflector. Engineers analyze vertical (or other monopole) antennas on the basis of dipole antennas of which they are one half.
