Vertical radiation and tropical broadcasting

National stations in the Tropics should use short-wave vertical incidence aerials consisting of 16-element binomial arrays; with 5-kW transmitters these would be capable of serving 90,000 square miles of territory. Co-channel stations should be separated by 1,500 miles. The stations require 2 or 3 frequencies in the 2·5, 3·5, 5 and 9 Mc/s bands depending on location; so far as possible the 3·5 and 5 Mc/s bands only should be used. Use of the minimum number of frequencies and frequency changes assists listeners. Stations intended to serve small, densely populated areas can operate in the medium-wave band.