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An antenna (or aerial) is an electrical device which converts electric currents into radio waves, and vice versa. It is usually used with a radio transmitter or radio receiver. In transmission, a radio transmitter applies an oscillating radio frequency electric current 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. An antenna can be used for both transmitting and receiving.
Antennas are essential components of all equipment that uses radio. They are used in systems such as radio broadcasting, Broadcast Television, two-way radio, communications receivers, radar, cell phones, and satellite communications, as well as other devices such as garage door openers, wireless microphones, bluetooth enabled devices, wireless computer networks, baby monitors, and RFID tags on merchandise.
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 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.
Antennas may also contain reflective or directive elements or surfaces not connected to the transmitter or receiver, such as parasitic elements, parabolic reflectors or horns, which serve to direct the radio waves into a beam or other desired radiation pattern. Antennas can be designed to transmit or receive radio waves in all directions equally (omnidirectional antennas), or transmit them in a beam in a particular direction, and receive from that one direction only (directional or high gain antennas).
The first antennas were built in 1888 by German physicist Heinrich Hertz in his pioneering experiments to prove the existence of electromagnetic waves predicted by the theory of James Clerk Maxwell. Hertz placed dipole antennas at the focal point of parabolic reflectors for both transmitting and receiving.
What else can I help you with?
What are the disadvantage of yagi-uda antenna?
bandwidth is less..
Which antenna is not wideband?
Electrically small antennas are always narrow-band. The bandwidth of a small antenna has a theoretical maximum defined by the Chu Limit.
What is relation between antenna gain and beamwidth?
bandwidth refers to the amount of the frequency spectrum that a signal resides in.example, the spacing between channels on radio are determined by their bandwidth. beamwidth is a physical characteristic of an antenna. they generally mark the point bore sight of a directional antenna that are at -3dB or half power
What feature in a radio prevents overlapping stations?
All stations are fed into the radio by the antenna. The IF filters narrow the bandwidth down to the size of just one channel
What is effect of change in the length of a dipole antenna?
The length of a dipole antenna directly affects its resonant frequency; a longer antenna typically resonates at a lower frequency, while a shorter antenna resonates at a higher frequency. This is because the length of the antenna is generally optimized to be around half the wavelength of the frequency it is intended to transmit or receive. Additionally, changes in length can impact the antenna's impedance, bandwidth, and radiation pattern. Therefore, adjusting the length alters its efficiency and performance for specific frequency ranges.
What is the difference between yagi antenna and dipole antenna?
I don't think it has. Bandwidth depends on the diameter to length ratio of the antenna. The greater the diameter of the elements the wider the bandwidth. The inductance goes down and the capacitance goes up, giving the antenna a lower Q. the folded dipole has a greater effective diameter (at least double for the same materials). You can increase a normal dipole's bandwidth by increasing the diameter, hence the old time birdcage aerials.
What is ringing effect of antenna?
The ringing effect of an antenna refers to the oscillatory response that occurs when an antenna is excited by a pulse or transient signal. This phenomenon results from the antenna's resonant properties and can lead to unwanted distortion in the received signal. The ringing can introduce additional frequencies and affect the overall bandwidth and performance of the antenna, making it crucial to design antennas that minimize this effect for clearer signal transmission and reception. Proper filtering and damping techniques can help mitigate the ringing effect in practical applications.
What is the bandwidth of a frequency independent antenna?
OK, so if it's *really* frequency independent, then the bandwidth must be infinite. i.e., from the 10 kHz used by the Omega submarine comms system to at least the current top end of 95 GHz used by point-to-point communications. Maybe you need to get a better handle on the range over which your "frequency independent" antenna is used. For starters, do a web search. There are plenty of good references on line.
Why modulation is necessary in wired network?
Reasons for modulation in wired media........... 1. If we use square wave directly it will require high bandwidth so we convert it to sine wave which requires low bandwidth. 2. If the wire length is smaller than wavelength it will radiate the signal and act as an antenna.
Why normally you consider length of an antenna greater than lamda by 4?
The length of an antenna is often considered to be greater than one wavelength (λ) by about 4λ for certain designs, like those used in specific types of resonant or broadband antennas. This extended length helps to enhance the antenna's bandwidth and improve its radiation efficiency. Additionally, longer antennas can support multiple resonant frequencies, allowing for better performance across a range of frequencies. Ultimately, this design choice aims to optimize the antenna's operational characteristics.
Difference between hertz antenna and marconi antenna?
Hertz Antenna is lambda by 2 antenna & marconi antenna is lambda by 4 antenna...
How do you build a Robinson Barnes hf broadband antenna?
To build a Robinson Barnes HF broadband antenna, start by constructing a dipole antenna with a center feed point, typically using a lightweight, durable wire for the elements. The length of each element should be approximately a half-wavelength for your target frequency, but adjust the lengths to optimize for a wider bandwidth. Use a good quality balun at the feed point to ensure proper impedance matching and reduce feedline radiation. Finally, ensure the antenna is installed high and clear of obstructions to maximize its performance.
