Saturday, August 31, 2013

antenna in the form of a long wire and a matching device for her

It is commonly assumed that the length of the antenna to be resonant at the connection to the antenna feed line should be only reactive component of the resistance. This condition can soften or simply ignored if used simple wire antenna (in the form of a long wire ) . A simple wire antenna can be seen as a modernized antenna "L -type " , but there are differences - the length of a wire antenna can be chosen arbitrary , as well as the need for a grounding system . Wire antenna with an arbitrary length can handle the entire range of the HF bands, some bands antenna will have repercussions in the other will have to reckon with the reactive component of the input impedance . If a wire antenna to connect a coaxial cable , you must use a transformer resistance , to take measures to compensate for the reactance . Diagram of a complex shape and is close to the antenna radiation pattern of harmonic in some areas will have an asymmetrical shape. To work in a multi-band wire antenna should have a matching device . And to improve the characteristics of the antenna wire requires the use of special earthing system (Figure) . The length of wire grounding wire antenna must comply with the wavelength at which the antenna is working , it is advisable to use two wires. One wire should pass under the antenna and the other at the other end . The wires may be arranged on the surface or buried to a depth of 20 centimeters. To match the wire antenna with a coaxial cable can be used for matching devices shown in the figures below. If the input impedance of the antenna wire is less than or equal to the resistance of the cable you need to use the first pattern matching device if more then a second picture of the matching device. In the second picture below 4:1 transformer used .

as a long antenna wire

antenna in the form of a long wire and a matching device for her

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