Abstract:
A television broadcast antenna includes a high-gain pylon consisting of a vertical array of slots in a conductive cylinder for radiating with high gain towards distant locations. An auxiliary low-gain vertically-polarized portion of the antenna has its phase center coincident with or near the phase center of the pylon for radiating a vertically polarized signal component. This position of the auxiliary portion reduces wind load and feed-line length by comparison with a location above the pylon. In a particularly advantageous embodiment of the invention, the horizontally-polarized radiation pattern of the pylon in the region within a few degrees below the main beam, which is the region directed towards local television viewers, has a low but relatively constant amplitude and phase. The auxiliary portion of the antenna produces a vertically-polarized radiation component in this region which has about the same amplitude as the horizontal component and which is approximately in phase quadrature with the horizontally-polarized component, and which therefore provides local (often urban) viewers with circular polarization for reducing ghosting. Distant viewers receive the benefits of high gain and high radiated power in the horizontally-polarized component.