Abstract: An antenna has an odd number of upwardly diverging monopoles equiangularly spaced about a vertical axis.

Abstract: A module for forming the side walls of a cavity resonance device comprises a metal extrusion shaped in cross-section to be of a rectangular U-shape. The walls forming the free ends of the U are provided adjacent each of their free edges with first shaped portions forming part of the extrusion and extending longitudinally therealong. At least one of the walls forming the U-shape module is provided adjacent each edge of the outer surface of said wall with second shaped portions forming part of said extrusion and extending longitudinally therealong. The first shaped portions and the second shaped portions are respectively designed so that the two first shaped portions of one module may respectively be slid longitudinally into to interfit with, the two second shaped portions of another module to connect such modules mechanically and electrically at each interfitting of a first and a second shaped portion.