Anti-skywave AM broadcast antenna design

Abstract

This thesis investigates the design of an anti-skywave (ASW) AM broadcast antenna. The parameters of a typical AM broadcast antenna are presented first. Then the design proposed by Richard L. Biby is studied by numerical modeling with the Numerical Electromagnetic Code (NEC). Biby's proposed design involves a ring of short radiators with a conventional monopole operating over finite ground. To analyze the behaviour of Biby's proposed ASW antenna, a generic radiator study is conducted to test the ability of different sized radiators to launch the sky wave and the ground wave first as isolated elements and then as closely coupled radiators with cancelling phasing. Finally, some potential candidate structures are proposed for AM broadcast transmission which might achieve the desired characteristics of ground wave enhancement and sky wave suppression.