Investigation of antennas for two-way mobile communications in the VHF and UHF regions

Due to the nature of two-way mobile communications the normal requirement is for base station antennas, as well as the vehicular antennas, to have radiation characteristics which are omnidirectional in azimuth. It is therefore necessary first to investigate the spatial distribution of energy and then to investigate means for confining the radiation in the elevation plane so far as possible to that region of space which represents the path for communication. Scale model techniques have been employed using 1/20 scale automobile mounted on a turntable ground plane to yield useful radiation pattern information for the mobile unit. Data are given for the quarter-wave roof mounted whip antenna and a bumper mounted coaxial antenna, plus a colinear array. For the base station, as well as the mobile unit, it is pointed out that the majority of communication takes place within one degree of the horizon. Pattern shaping techniques and tower and pole mounting effects are shown for various situations of side tower mounted arrays, both to allow for the tower consideration in those systems where side of tower mounting is a necessity and to enable the designer to take advantage of tower shaping situations where they can be used to increase gain in the desired directions. A newly developed three wavelength aperture colinear array for the vehicular unit for the 450 mc range is described. This unit is approximately 6 feet long over-all and tests indicate a great improvement in systems performance over standard quarter-wave whip or dipole type antennas.