Ad
related to: does a dipole need balun
Search results
Results From The WOW.Com Content Network
A balun is required to use coaxial cable with a dipole antenna. The balun transfers power between the single-ended coax and the balanced antenna, sometimes with an additional change in impedance. A balun can be implemented as a transformer which also allows for an impedance transformation.
G5RV Antenna without balun. The G5RV antenna is a dipole with a symmetric resonant [ 1 ] feeder line , which serves as impedance matcher for a 50 Ω coax cable to the transceiver . [ 2 ] [ 3 ]
A balun can take many forms and may include devices that also transform impedances but need not do so. Sometimes, in the case of transformer baluns, they use magnetic coupling but need not do so. Common-mode chokes are also used as baluns and work by eliminating, rather than rejecting, common mode signals.
The balun is a 16:1 ratio, thereby transforming the 50 Ω (ohm) coax to an 800 Ω feed at the antenna. The resistor load is also 800 Ω, non-inductive. This allows the antenna impedance to swing from 400–1,600 Ω over the frequency range intended and thus keep the SWR at the transmitter 2:1 or lower.
To connect balanced and unbalanced components, a two port device called a balun is used. A balun is a transformer that couples between balanced and unbalanced transmission line components. For example, to feed a dipole antenna from an unbalanced feedline like coaxial cable, the feedline is connected to the antenna through a balun. Without the ...
Twin-lead also can serve as a convenient material with which to build a simple folded dipole antenna. Such antennas may be fed either by using a 300 Ω twin-lead feeder or by using a 300-to-75 Ω balun and using coaxial feedline and will usually handle moderate power loads without overheating.
Often random wire antennas are also (inaccurately) referred to as long-wire antennas.There is no accepted minimum size, but actual long-wire antennas must be greater than at least a quarter-wavelength ( 1 / 4 λ) or perhaps greater than a half ( 1 / 2 λ) at the frequency the long wire antenna is used for, and even a half-wave may only be considered "long-ish" rather than "truly ...
Consider a Yagi–Uda consisting of a reflector, driven element, and a single director as shown here. The driven element is typically a 1 ⁄ 2 λ dipole or folded dipole and is the only member of the structure that is directly excited (electrically connected to the feedline). All the other elements are considered parasitic. That is, they ...