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Design of a Horizontal Half-wave-dipole Antenna System

Author: Edmund A. Laport

Any antenna must be designed to fit the propagation conditions and the geometry of the particular path required for communication. The radiation pattern for a half-wave dipole is therefore chosen for the best frequency, orientation, and vertical angles of radiation. These factors determine the height, length, and orientation of the antenna. Weather conditions encountered in the locality determine the structural specifications for the antenna.

The required vertical angles of fire as functions of layer height and hop length are shown in Fig. 3.14.

When the radiation pattern has been selected, there follow the steps involved in the circuital design of the system - the potentials and currents to be expected for the power to be transmitted, the insulation and conductor sizes, the configuration of the feeders and the method of coupling antenna to feeder, the bandwidth requirements for the kind of transmission to be used, and all matters of impedances at certain points in the antenna and feeder system.

Finally, with these all predetermined, there follows the mechanical design of the antenna, feeder, and supports, together with their layout on the available land. The methods of bringing the feeder to the transmitter, of making bends and angles in the line without introducing impedance changes or unbalances, and of switching feeders must be studied in detail. Then there are the problems of stresses, temperature changes, and ice loadings and the other structural details which suit the system to its climatic environment.

When all this is done, the mechanical simplicity of the system completely belies the amount of expert study that preceded its construction.

Last Update: 2011-03-19