NCJ Number
118002
Date Published
1989
Length
52 pages
Annotation
Research using monopole standard antennae and monopole test antennae was conducted to determine the feasibility of making acceptably accurate measurements of impedance and gain on a ground plane of reduced size rather than under the ideal conditions involving an infinite, perfectly conducting ground plane.
Abstract
Theoretical calculations show that the radius of a highly conducting ground plane should be at least twice the wave length. At 25 megahertz, the lowest frequency considered, such a ground plane would require a space at least 48 meters in diameter. Model impedance measurements and calculations presented in this study imply that a space of about 10 meters by 11 meters may be sufficient if the researcher uses 16 resistively-loaded wire radials to extend a solid metal ground plane measuring 3.66 meters by 4.88 meters. Measured insertion loss data gathered using a scale model ground plane with resistively-loaded radials indicate that this area is large enough for gain measurements as well. Further measurements on a full-scale ground plane verified the results of the model measurements. Figures, appended computer programs, and 11 references. (Author summary modified)