ANTENNA AND RADIO WAVE PROPAGATION CHARACTERISTICS AT VHF NEAR AND IN THE GROUND
Abstract
The radiation pattern and radiation impedance of a half wavelength dipole at VHF, in and near the ground, have been measured and are reported here. The variation of the field strength of VHF sig nals, in and near the ground, have been measured and are reported. Good correlation was found between the measured and theoretical radiation patterns and field strength variation for above ground conditions. Theoretically, for the same incident field strength, a larger signal is found for a few feet below the surface of the ground at VHF than at 1.0 mc/s. The difference in the attenuation and transmission characteristics at these frequencies account for this. Large vari ations in the field strength occur for various soil conditions at any given depth. The half wavelength dipole appears to be acceptable as an antenna for underground reception, although it does suffer a large loss in capture area when cut to the proper length for local ground condi tions. It appears that a better antenna system than the unshielded dipole used in this study is desirable if one is to take advantage of the available field strength, at VHF, below the earth's surface. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 01, 1963
- Accession Number
- AD0416468
Entities
People
- Douglas M. Schwartz
Organizations
- University of Texas at Austin