File:Antenne gp vhf 4.jpg
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Captions
Captions
A ground plane antenna
Summary[edit]
| Description |
Français : L'antenne ground plane ou GPA (Ground Plane Antenna) est un dipôle dans lequel on a remplacé la moitié par un « plan de sol », la moitié conservée étant normale à cette surface. Si le plan de sol est suffisamment grand, le demi-dipôle se comporte exactement comme un dipôle entier (type: dipôle demi-onde λ/2) car sa réflexion dans le plan de sol forme la partie manquante. Dans ce cas, son gain théorique est de 2,14 dBi (où les dBi sont des décibels avec un « i » ajouté pour rappeler qu'il s'agit d'un gain par rapport à une antenne isotrope), la longueur physique est environ égale au quart de la longueur d'onde de la fréquence sur laquelle l'antenne est accordée. Ces brins, disposés en cercle en nombre de 4, ils constituent une surface conductrice de l'électricité, même si cette surface n'est pas parfaite pour être alimenté par un câble coaxial de 50 ohms
English: VHF ground plane antenna. This is a folded quarter-wave whip antenna with four grounded quarter-wave conductors projecting horizontally from the base of the whip to form a "ground plane". Ground plane antennas have an omnidirectional radiation pattern, radiating equal signal strength in all azimuthal directions, with the radiated power maximum in a horizontal direction and decreasing with elevation angle to zero on the antenna axis. The ground conductors serve to lower the radiation pattern so more power is radiated in horizontal directions. The folded vertical element increases the radiation resistance so it is a closer match to standard coaxial cable feedline. |
| Date | |
| Source | Own work |
| Author | F1jmm |
| Camera location |   | View this and other nearby images on: OpenStreetMap |  |
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This is a retouched picture, which means that it has been digitally altered from its original version. Modifications: Gestionnaire d'images lumineuses.
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| current | 21:39, 26 March 2017 | | 2,269 × 1,708 (561 KB) | F1jmm (talk | contribs) | User created page with UploadWizard |
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