On the Determination of the Optimum Radiation Angle for Horizontal Antennas

A standard of (directional) radiation at 15 meters was constructed consisting of a vertical half-wave antenna placed one-half wave above the earth, suitably excited, placed in front of a reflector consisting of five reflector wires slightly more than one-half wave long on a parabolic surface of opening of one wavelength. This was found to give directional characteristics showing a broad maximum of field strength twice that of the simple antenna without reflector. A parabolic reflector and radiating system rotatable about a horizontal axis perpendicular to the line to the distant station were then constructed near Berlin. The antenna at the focal axis of the paraboloid was one wave long, one-quarter wavelength from the parabola apex; and the parabolic reflector was of one wavelength opening and consisted of 9 wires along the paraboloid each approximately a half-wave long. The entire system was rotated while reception audibility measurements were made at Buenos Aires, a 2-kw transmitter being employed. The horizontally aimed system was found most effective. This held for both 15 and 20 meters. Similar results were obtained for reception on directional antennas. The conclusion is drawn that horizontal short-wave radiation is most desirable.