Moxon Rectangle Calculator

How the compact beam gets directionality

The Moxon rectangle is a compact two-element directional antenna formed by a driven element and a reflector whose ends fold toward each other. The image on this page is a construction-oriented layout rather than a generic antenna symbol, so the relationship between the feedpoint, driven element, reflector and gap is visible. Those dimensions are what make the Moxon useful when a Yagi-style directional pattern is wanted without the full boom length of a conventional multi-element array.

The calculator provides approximate dimensions derived from the design frequency. The values are intended as starting dimensions because the final performance depends on wire or tubing diameter, element spacing, support structure and the mechanical accuracy of the corners. The small gap between the driven element and reflector is especially important. Changing it can alter both feedpoint impedance and front-to-back ratio. Nearby metal can detune the antenna, so the final adjustment should be made with the antenna installed at a realistic height.

Build the rectangle accurately and make the two sides symmetrical. If the design uses wire supported by spreaders, keep the corners secure and the reflector-to-driven spacing consistent. Do not assume that the calculated gain or front-to-back ratio will appear exactly in a real garden or portable setup; the surrounding environment and height above ground matter. After assembly, measure the feedpoint impedance and SWR at the intended operating frequency, then make small dimensional changes if necessary. A Moxon is particularly sensitive to geometry, so trimming by large amounts can destroy the intended relationship between the two elements. The image provides the builder with the exact geometry that the calculator numbers describe.