Horizontal-Polar-Pattern Tracer for Directional Broadcast Antennas

Making space-pattern calculations for the 3-element array is very much more difficult than for the more common 2-element array. Many problems of broadcast coverage or interference have their solution only in the nonsymmetrical patterns of 3-element directional antennas. This paper includes the derivation of the equations for the relative field strength in a horizontal plane of such an array. A mechanical tracer is described which automatically plots the horizontal pattern for 2- or 3-element arrays once the adjustments of tower configuration and current magnitudes and phasings are made. Patterns traced by this machine are shown to have an accuracy usually within the width of the line of the recording pen. Its simplicity and rapidity of operation adapt it particularly to preliminary exploration to find a pattern which meets certain coverage or interference problems.