Date of Award:

1971

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Electrical and Computer Engineering

Advisor/Chair:

Glen L. Smerage

Abstract

The purpose of this thesis is to determine feasibility and to investigate some of the problems encountered in making soil moisture measurements using radio wave propagation. The procedure consists of propagating a vertically polarized wave over the earth and measuring the field strength attenuation. A brief summary of present methods of measuring soil moisture is given.

Certain aspects of radio wave propagation theory are discussed, covering such topics as the surface wave, the space wave, the skin depth, and the effect of the dielectric constant on radio wave propagation. Based on this theory, measurement parameters such as frequency, antenna separation, and antenna height were chosen for optimum performance. Using these parameters and information gained from preliminary measurements, the instrumentation was designed and is given in detail.

Measurement variables such as antenna height, reflections, temperature, and vegetation were investigated with the use of experimental data. The width of the area affecting the propagating wave was also looked at experimentally. A relationship between soil moisture and signal strength is presented from measurements taken for various values of soil moisture content.

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