September 1966 | Technical Report IER 8 ITSA 8

Linear High Frequency Antennas over a Finitely Conducting Spherical Earth

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Leslie A. Berry

Abstract: Vertical radiation patterns of vertical quarter-wave monopoles, and of vertical and horizontal half-wave dipoles located at various heights up to twenty wavelengths over several typical types of ground are shown. Vertical antennas have the best low-angle patterns at low heights and at medium heights over land. For low and medium antenna heights, only vertically polarized antennas over water radiate appreciable energy at zero or negative elevation angles. The propagation factor used to calculate the antenna patterns can be accurately evaluated with the simple two-ray theory for elevation angles greater than one or two degrees. For smaller, and negative, elevation angles the full wave theory for diffraction by a sphere must be used.

Keywords: propagation; antenna patterns; low angle radiation; HF antenna

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