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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 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.
A balun / ˈ b æ l ʌ n / (from "balanced to unbalanced", originally, but now derived from "balancing unit") [1] is an electrical device that allows balanced and unbalanced lines to be interfaced without disturbing the impedance arrangement of either line. [2] A balun can take many forms and may include devices that also transform impedances ...
In order for the signals to add together, they need to arrive in-phase.Consider two dipole antennas placed in a line end-to-end, or collinear.If the resulting array is pointed directly at the source signal, both dipoles will see the same instantaneous signal, and thus their reception will be in-phase.
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.
For a monopole antenna (a), the Earth acts as a ground plane to reflect radio waves directed downwards, making them seem to come from a virtual "image antenna" (b).In Telecommunications, a ground plane is a flat or nearly flat horizontal conducting surface that serves as part of an antenna, to reflect the radio waves from the other antenna elements.
A halo antenna, or halo, is a center-fed 1 / 2 wavelength dipole antenna, which has been bent into a circle, with a break directly opposite the feed point. The dipole's ends are close, but do not touch, and the ends on either side of the gap may be flared out to form a larger air gap capacitor , whose spacing is used to fine-adjust the ...
The size of the induced dipole moment is equal to the product of the strength of the external field and the dipole polarizability of ρ. Dipole moment values can be obtained from measurement of the dielectric constant. Some typical gas phase values given with the unit debye are: [7] carbon dioxide: 0; carbon monoxide: 0.112 D; ozone: 0.53 D