Distortion of Polar Diagram Due to Interposition of Wooden Screen in the Vicinity of a VHF Radiator

Abstract

A teak wood structure in the proximity of a VHF radiator distorts the polar diagram. Experiments showed that the distortion in the polar diagram is due to the “reflection” and “transmission” properties of teak wood and “absorption” is only of a second order of magnitude. The relationship between the reflection coefficient, frequency, dielectric constant and thickness of wood is determined. The agreement between the theoretically calculated and experimentally observed values of distortion is close. The distortion due to deal wood, perspex, wetting and painting of teak wood was also measured. Laboratory measurement of dielectric constants substantiated the field measurements. The optimum dimensions of a shelter enclosing the radiator for minimum distortion are indicated.