sentence-transformers/squad huggingface dataset:
Passage: An antenna (plural antennae or antennas), or aerial, is an electrical device which converts electric power into radio waves, and vice versa. It is usually used with a radio transmitter or radio receiver. In transmission, a radio transmitter supplies an electric current oscillating at radio frequency (i.e. a high frequency alternating current (AC)) to the antenna's terminals, and the antenna radiates the energy from the current as electromagnetic waves (radio waves). In reception, an antenna intercepts some of the power of an electromagnetic wave in order to produce a tiny voltage at its terminals, that is applied to a receiver to be amplified.

Question: What device is able to change electric powerinto radio waves and also do the reverse?

Question: What device is often used in conjuntion with the antenna?

Question: What process associated with antennas produces a high frequency alternating current?

Question: What else can radio waves be called?

Question: When does an antenna catch electromagnetic waves?
Passage: Typically an antenna consists of an arrangement of metallic conductors (elements), electrically connected (often through a transmission line) to the receiver or transmitter. An oscillating current of electrons forced through the antenna by a transmitter will create an oscillating magnetic field around the antenna elements, while the charge of the electrons also creates an oscillating electric field along the elements. These time-varying fields radiate away from the antenna into space as a moving transverse electromagnetic field wave. Conversely, during reception, the oscillating electric and magnetic fields of an incoming radio wave exert force on the electrons in the antenna elements, causing them to move back and forth, creating oscillating currents in the antenna.

Question: What is frequently used to connect elements to the receiver?

Question: During transmission does the electric field wave move closer to the antenna?

Question: What particles are pushed through the antenna by a transmitter?

Question: During what process would electrons be vacillating in the antenna?
Passage: The words antenna (plural: antennas in US English, although both "antennas" and "antennae" are used in International English) and aerial are used interchangeably. Occasionally the term "aerial" is used to mean a wire antenna. However, note the important international technical journal, the IEEE Transactions on Antennas and Propagation. In the United Kingdom and other areas where British English is used, the term aerial is sometimes used although 'antenna' has been universal in professional use for many years.

Question: What is an acceptable synonym for antenna?

Question: What can sometimes be meant by the term aerial specifically?

Question: What is one way of referring to more than one antenna?

Question: What is the most widely accepted term for an electrical device that converts electric power into radio waves?
Passage: The origin of the word antenna relative to wireless apparatus is attributed to Italian radio pioneer Guglielmo Marconi. In the summer of 1895, Marconi began testing his wireless system outdoors on his father's estate near Bologna and soon began to experiment with long wire "aerials". Marconi discovered that by raising the "aerial" wire above the ground and connecting the other side of his transmitter to ground, the transmission range was increased. Soon he was able to transmit signals over a hill, a distance of approximately 2.4 kilometres (1.5 mi). In Italian a tent pole is known as l'antenna centrale, and the pole with the wire was simply called l'antenna. Until then wireless radiating transmitting and receiving elements were known simply as aerials or terminals.

Question: Who is most associated with the emergence of the word antenna?

Question: When did experimentation with electromagnetic waves begin?

Question: What is a way to increase the strength of a radio transmission?

Question: How far was Marconi able to get his signal to go using this technique?
Passage: Antennas are required by any radio receiver or transmitter to couple its electrical connection to the electromagnetic field. Radio waves are electromagnetic waves which carry signals through the air (or through space) at the speed of light with almost no transmission loss. Radio transmitters and receivers are used to convey signals (information) in systems including broadcast (audio) radio, television, mobile telephones, Wi-Fi (WLAN) data networks, trunk lines and point-to-point communications links (telephone, data networks), satellite links, many remote controlled devices such as garage door openers, and wireless remote sensors, among many others. Radio waves are also used directly for measurements in technologies including radar, GPS, and radio astronomy. In each and every case, the transmitters and receivers involved require antennas, although these are sometimes hidden (such as the antenna inside an AM radio or inside a laptop computer equipped with Wi-Fi).

Question: What is essential for the mating of the elements that create radio waves?

Question: How fast are signals produced by antenna transmitted?

Question: What is one system that uses electromagnetic waves?

Question: What mobile locator and direction finder technology takes advantage of radio waves?

Question: What often inconspicuous part of a laptop computer allows for internet usage?
Passage: One example of omnidirectional antennas is the very common vertical antenna or whip antenna consisting of a metal rod (often, but not always, a quarter of a wavelength long). A dipole antenna is similar but consists of two such conductors extending in opposite directions, with a total length that is often, but not always, a half of a wavelength long. Dipoles are typically oriented horizontally in which case they are weakly directional: signals are reasonably well radiated toward or received from all directions with the exception of the direction along the conductor itself; this region is called the antenna blind cone or null.

Question: What is the main element of an omnidirectional antenna?

Question: What type of antenna would most likely be a half a wavelength long?

Question: In which direction would you expect to find a dipole?

Question: What is meant by the area where signals cannot be accepted well along the conductor?
Passage: Both the vertical and dipole antennas are simple in construction and relatively inexpensive. The dipole antenna, which is the basis for most antenna designs, is a balanced component, with equal but opposite voltages and currents applied at its two terminals through a balanced transmission line (or to a coaxial transmission line through a so-called balun). The vertical antenna, on the other hand, is a monopole antenna. It is typically connected to the inner conductor of a coaxial transmission line (or a matching network); the shield of the transmission line is connected to ground. In this way, the ground (or any large conductive surface) plays the role of the second conductor of a dipole, thereby forming a complete circuit. Since monopole antennas rely on a conductive ground, a so-called grounding structure may be employed to provide a better ground contact to the earth or which itself acts as a ground plane to perform that function regardless of (or in absence of) an actual contact with the earth.

Question: Are basic antennas expensive?

Question: What is the foundation most often used when creating new antenna models?

Question: What category do vertical antennas fall under?

Question: What is used to close the circuit of a dipole antenna?
Passage: Antennas more complex than the dipole or vertical designs are usually intended to increase the directivity and consequently the gain of the antenna. This can be accomplished in many different ways leading to a plethora of antenna designs. The vast majority of designs are fed with a balanced line (unlike a monopole antenna) and are based on the dipole antenna with additional components (or elements) which increase its directionality. Antenna "gain" in this instance describes the concentration of radiated power into a particular solid angle of space, as opposed to the spherically uniform radiation of the ideal radiator. The increased power in the desired direction is at the expense of that in the undesired directions. Power is conserved, and there is no net power increase over that delivered from the power source (the transmitter.)

Question: What are different designs aimed at increasing?

Question: What is different from a monopole antenna with most other antenna types?

Question: Gain when referring to an antenna refers to what about radiated power?

Question: Where is the power that is distributed originating from?
Passage: For instance, a phased array consists of two or more simple antennas which are connected together through an electrical network. This often involves a number of parallel dipole antennas with a certain spacing. Depending on the relative phase introduced by the network, the same combination of dipole antennas can operate as a "broadside array" (directional normal to a line connecting the elements) or as an "end-fire array" (directional along the line connecting the elements). Antenna arrays may employ any basic (omnidirectional or weakly directional) antenna type, such as dipole, loop or slot antennas. These elements are often identical.

Question: How many antenna would make up a phased array?

Question: What determines if the antenna creates a broadside array or an end fire array?

Question: What are the two standard antenna types?

Question: How are antennas oriented when arranged with specific spacing?
Passage: However a log-periodic dipole array consists of a number of dipole elements of different lengths in order to obtain a somewhat directional antenna having an extremely wide bandwidth: these are frequently used for television reception in fringe areas. The dipole antennas composing it are all considered "active elements" since they are all electrically connected together (and to the transmission line). On the other hand, a superficially similar dipole array, the Yagi-Uda Antenna (or simply "Yagi"), has only one dipole element with an electrical connection; the other so-called parasitic elements interact with the electromagnetic field in order to realize a fairly directional antenna but one which is limited to a rather narrow bandwidth. The Yagi antenna has similar looking parasitic dipole elements but which act differently due to their somewhat different lengths. There may be a number of so-called "directors" in front of the active element in the direction of propagation, and usually a single (but possibly more) "reflector" on the opposite side of the active element.

Question: What type of antenna formation is made up of multiple dipole elements of varying lengths?

Question: What is the benefit of this formation type?

Question: What is a variation of this antenna type?

Question: What is the main application of these set ups?
Passage: At low frequencies (such as AM broadcast), arrays of vertical towers are used to achieve directionality and they will occupy large areas of land. For reception, a long Beverage antenna can have significant directivity. For non directional portable use, a short vertical antenna or small loop antenna works well, with the main design challenge being that of impedance matching. With a vertical antenna a loading coil at the base of the antenna may be employed to cancel the reactive component of impedance; small loop antennas are tuned with parallel capacitors for this purpose.

Question: For radio broadcast that one would hear in their car what type of towers are used?

Question: If one wished to take an antenna to different locations, which type would be best?

Question: Why is this specific antenna type used?

Question: What is a problem one might encounter when using a portable antenna?
Passage: An antenna lead-in is the transmission line (or feed line) which connects the antenna to a transmitter or receiver. The antenna feed may refer to all components connecting the antenna to the transmitter or receiver, such as an impedance matching network in addition to the transmission line. In a so-called aperture antenna, such as a horn or parabolic dish, the "feed" may also refer to a basic antenna inside the entire system (normally at the focus of the parabolic dish or at the throat of a horn) which could be considered the one active element in that antenna system. A microwave antenna may also be fed directly from a waveguide in place of a (conductive) transmission line.

Question: What is mainly responsible for the connection of the antenna to its end destinations?

Question: What is the group of elements used to join the elements of an antenna?

Question: What are the type of antennas used with satellite television called?

Question: What can be used in place of a standard transmission line?
Passage: Monopole antennas consist of a single radiating element such as a metal rod, often mounted over a conducting surface, a ground plane. One side of the feedline from the receiver or transmitter is connected to the rod, and the other side to the ground plane, which may be the Earth. The most common form is the quarter-wave monopole which is one-quarter of a wavelength long and has a gain of 5.12 dBi when mounted over a ground plane. Monopoles have an omnidirectional radiation pattern, so they are used for broad coverage of an area, and have vertical polarization. The ground waves used for broadcasting at low frequencies must be vertically polarized, so large vertical monopole antennas are used for broadcasting in the MF, LF, and VLF bands. Small monopoles are used as nondirectional antennas on portable radios in the HF, VHF, and UHF bands.

Question: Monopole antennas consist of what element?

Question: What are small monopoles used as?

Question: What the most common form?

Question: What has vertical polarization?
Passage: The most widely used class of antenna, a dipole antenna consists of two symmetrical radiators such as metal rods or wires, with one side of the balanced feedline from the transmitter or receiver attached to each. A horizontal dipole radiates in two lobes perpendicular to the antenna's axis. A half-wave dipole the most common type, has two collinear elements each a quarter wavelength long and a gain of 2.15 dBi. Used individually as low gain antennas, dipoles are also used as driven elements in many more complicated higher gain types of antennas.

Question: What is the most widley used antenna class?

Question: What radiates two lobes perpendicular to the antennas axis?

Question: Besides low gain antennas, what is also used as driven elements in complicated higher gain types of antennas?

Question: How much gain does a half-wave dipole have?
Passage: A necessary condition for the aforementioned reciprocity property is that the materials in the antenna and transmission medium are linear and reciprocal. Reciprocal (or bilateral) means that the material has the same response to an electric current or magnetic field in one direction, as it has to the field or current in the opposite direction. Most materials used in antennas meet these conditions, but some microwave antennas use high-tech components such as isolators and circulators, made of nonreciprocal materials such as ferrite. These can be used to give the antenna a different behavior on receiving than it has on transmitting, which can be useful in applications like radar.

Question: What must be true of the antenna and transmission medium for the repiprocity rule to apply ?

Question: What is one material that does not have this quality?

Question: How can the lack of this quality be used in an everyday way?

Question: What is called when the direction of the elctrical current does not make a difference to the current?
Passage: Antennas are characterized by a number of performance measures which a user would be concerned with in selecting or designing an antenna for a particular application. Chief among these relate to the directional characteristics (as depicted in the antenna's radiation pattern) and the resulting gain. Even in omnidirectional (or weakly directional) antennas, the gain can often be increased by concentrating more of its power in the horizontal directions, sacrificing power radiated toward the sky and ground. The antenna's power gain (or simply "gain") also takes into account the antenna's efficiency, and is often the primary figure of merit.

Question: How could one deide what type of antenna is nedded for a project?

Question: What would most likely be the main concern in making this decision?

Question: How would you distribute power to allow for a greater gain?

Question: What is often the most imprtant crediting factor of antennas?
Passage: Resonant antennas are expected to be used around a particular resonant frequency; an antenna must therefore be built or ordered to match the frequency range of the intended application. A particular antenna design will present a particular feedpoint impedance. While this may affect the choice of an antenna, an antenna's impedance can also be adapted to the desired impedance level of a system using a matching network while maintaining the other characteristics (except for a possible loss of efficiency).

Question: Which antenna type would be best for a project requiring a specific frequency?

Question: How could an antenna be made to coordinate with the needed frequency?

Question: What factor would result in a desired feedback independence?

Question: If you were unable to choose the antenna you wanted how could you still achieve this result?
Passage: An antenna transmits and receives radio waves with a particular polarization which can be reoriented by tilting the axis of the antenna in many (but not all) cases. The physical size of an antenna is often a practical issue, particularly at lower frequencies (longer wavelengths). Highly directional antennas need to be significantly larger than the wavelength. Resonant antennas usually use a linear conductor (or element), or pair of such elements, each of which is about a quarter of the wavelength in length (an odd multiple of quarter wavelengths will also be resonant). Antennas that are required to be small compared to the wavelength sacrifice efficiency and cannot be very directional. Fortunately at higher frequencies (UHF, microwaves) trading off performance to obtain a smaller physical size is usually not required.

Question: What is the essential difference in radio waves transmitted by an antenna?

Question: How can this be adjusted more easily than changing antenna types?

Question: When might the size of an antenna cause an issue?

Question: What size antenna would not be good when the antenna needs to be directional?

Question: There is a relationship between the size of the antenna and the size of the wavelength with what antenna type?
Passage: The majority of antenna designs are based on the resonance principle. This relies on the behaviour of moving electrons, which reflect off surfaces where the dielectric constant changes, in a fashion similar to the way light reflects when optical properties change. In these designs, the reflective surface is created by the end of a conductor, normally a thin metal wire or rod, which in the simplest case has a feed point at one end where it is connected to a transmission line. The conductor, or element, is aligned with the electrical field of the desired signal, normally meaning it is perpendicular to the line from the antenna to the source (or receiver in the case of a broadcast antenna).

Question: What particle's migration does the resonance principle rely on?

Question: What is the basis for the way most antennas are developed?

Question: What type of surface is formed by the tip of a conductor?

Question: How would you place the conductor in relation to the signal you wished to obtain?
Passage: The radio signal's electrical component induces a voltage in the conductor. This causes an electrical current to begin flowing in the direction of the signal's instantaneous field. When the resulting current reaches the end of the conductor, it reflects, which is equivalent to a 180 degree change in phase. If the conductor is 1⁄4 of a wavelength long, current from the feed point will undergo 90 degree phase change by the time it reaches the end of the conductor, reflect through 180 degrees, and then another 90 degrees as it travels back. That means it has undergone a total 360 degree phase change, returning it to the original signal. The current in the element thus adds to the current being created from the source at that instant. This process creates a standing wave in the conductor, with the maximum current at the feed.

Question: What part of the radio signal creates voltage?

Question: What would the electric current always gravitate to?

Question: What is the outcome when a curren is reflected>

Question: What amount of phase change would return a signal to its originial state?
Passage: The ordinary half-wave dipole is probably the most widely used antenna design. This consists of two 1⁄4-wavelength elements arranged end-to-end, and lying along essentially the same axis (or collinear), each feeding one side of a two-conductor transmission wire. The physical arrangement of the two elements places them 180 degrees out of phase, which means that at any given instant one of the elements is driving current into the transmission line while the other is pulling it out. The monopole antenna is essentially one half of the half-wave dipole, a single 1⁄4-wavelength element with the other side connected to ground or an equivalent ground plane (or counterpoise). Monopoles, which are one-half the size of a dipole, are common for long-wavelength radio signals where a dipole would be impractically large. Another common design is the folded dipole, which is essentially two dipoles placed side-by-side and connected at their ends to make a single one-wavelength antenna.

Question: What is the most popular antenna type?

Question: What is the current usually beng put into it or pulled out of?

Question: Elements in a half wave dipole and on an identical axis are said to be what?

Question: What antenna type is a portion of the half wave dipole?

Question: What popular type combines more that one antenna?
Passage: The standing wave forms with this desired pattern at the design frequency, f0, and antennas are normally designed to be this size. However, feeding that element with 3f0 (whose wavelength is 1⁄3 that of f0) will also lead to a standing wave pattern. Thus, an antenna element is also resonant when its length is 3⁄4 of a wavelength. This is true for all odd multiples of 1⁄4 wavelength. This allows some flexibility of design in terms of antenna lengths and feed points. Antennas used in such a fashion are known to be harmonically operated.

Question: What frequency are antennas normally designed to be?

Question: What can be added to f0 to create a standing wave pattern?

Question: What multiple is essential for wavelengths?

Question: How are waves which are used in the ways discussed controlled?
Passage: The quarter-wave elements imitate a series-resonant electrical element due to the standing wave present along the conductor. At the resonant frequency, the standing wave has a current peak and voltage node (minimum) at the feed. In electrical terms, this means the element has minimum reactance, generating the maximum current for minimum voltage. This is the ideal situation, because it produces the maximum output for the minimum input, producing the highest possible efficiency. Contrary to an ideal (lossless) series-resonant circuit, a finite resistance remains (corresponding to the relatively small voltage at the feed-point) due to the antenna's radiation resistance as well as any actual electrical losses.

Question: How do quarter wave elements act in relation to a series relevant electrical element?

Question: What frequency develops a current peak?

Question: How would you describe a current that has maximum efficiency?

Question: What could be the best possible output versus input ratio?