Modeling antennas on automobiles in the VHF and UHF frequency bands, comparisons of predictions and measurements

This paper describes comparisons of analysis and measurements of antenna patterns on automobiles in the VHF and UHF frequency bands. The actual measurements and analysis were performed at six different frequencies ranging from 41 MHz to 918 MHz. An antenna on a vehicle in a roadway environment in the presence of Earth does not have antenna patterns or input impedances as if it were located in free space or over a perfectly conducting ground plane. Antenna patterns of a whip antenna on a vehicle were measured on an outdoor antenna range with the vehicle on a 10 meter diameter turntable. Patterns were also measured with the vehicle over real ground away from the turntable to determine the effects of the steel turntable on antenna patterns. The three-antenna gain measurement technique was used to measure antenna gain. The measured patterns and gains were compared to predictions using the numerical electromagnetics code (NEC-4) [G.J. Burke, Jan 1992].