Moxon Antenna Calculator

Overview

The Moxon Antenna Calculator helps amateur radio operators, RF engineers, antenna designers, researchers, and students calculate the approximate dimensions of a Moxon Rectangle antenna from its operating frequency. A Moxon antenna is a compact two-element directional antenna derived from the Yagi-Uda design. It offers moderate forward gain, excellent front-to-back ratio, low feed-point impedance variation, and a significantly smaller physical footprint than a conventional two-element Yagi. By entering the operating frequency in MHz, the calculator determines the free-space wavelength, driven element length, reflector length, overall antenna width, overall antenna height, and estimated feed-point impedance. It is widely used for HF, VHF, UHF, amateur radio, portable field operations, contest stations, emergency communication, and directional wireless communication systems.

Input Guide

Enter Frequency exactly as shown on the calculator. Confirm every unit, selected option, and decimal position before calculating so the moxon antenna result matches the intended specific antenna types design case.

Output Guide

The output section reports Wavelength, Driven Element Length, Reflector Length, Overall Width, Overall Height, Estimated Feed Impedance for the values you entered. Use these values as design targets, then compare them with available space, component limits, feed system behavior, installation environment, and measured performance before finalizing the design.

How This Calculator Works

The Moxon Antenna applies lambda = 300 / f Driven Element ≈ lambda × 0.48 Reflector ≈ lambda × 0.50 Width ≈ lambda × 0.33 Height ≈ lambda × 0.17 Feed Impedance ≈ 50 ohms to the entered values. Calculate approximate Moxon Rectangle antenna dimensions from operating frequency. Use the result as a first-pass specific antenna types target, then validate it against losses, tolerances, mounting, nearby conductors, feed-line effects, and measurement conditions.

Design Notes

This calculator is based on well-established proportional relationships between wavelength and the geometry of a Moxon Rectangle antenna. The first step calculates the free-space wavelength using lambda = 300 / f, where lambda is the wavelength in metres and f is the operating frequency in megahertz. Since radio wavelength becomes shorter as frequency increases, every physical dimension of the antenna decreases proportionally with increasing frequency. After calculating the wavelength, the driven element is estimated as approximately 0.48 lambda. This value is intentionally slightly shorter than a half-wave element because the folded element ends, conductor diameter, and coupling between the two elements electrically lengthen the antenna. The reflector is calculated as approximately 0.50 lambda, making it slightly longer than the driven element so it reflects RF energy toward the forward direction and improves antenna directivity. The overall width is estimated as approximately 0.33 lambda, while the overall height is approximately 0.17 lambda. These dimensions create the compact rectangular geometry that gives the Moxon antenna its excellent front-to-back ratio while occupying much less space than a traditional Yagi antenna. The calculator also assumes a typical feed-point impedance of around 50 ohms, allowing direct connection to standard 50-ohm coaxial feed lines in many practical installations. These equations provide reliable starting dimensions for antenna construction, although final optimisation should always be performed using practical measurements or electromagnetic simulation.

Build and Tuning Notes

Use the calculated dimensions as the initial design before constructing the antenna. Build the driven element and reflector accurately, maintaining consistent spacing and element alignment because even small dimensional changes can noticeably affect resonance, impedance, and radiation pattern. Leave the driven element slightly longer than calculated and trim it gradually while monitoring resonant frequency and VSWR with a vector network analyser (VNA) or antenna analyser. Install the antenna well above surrounding conductive objects to minimise pattern distortion and unwanted coupling. If possible, verify front-to-back ratio, gain, feed-point impedance, bandwidth, and radiation pattern inside an antenna test range or by field measurements. Electromagnetic simulation using NEC, EZNEC, 4NEC2, CST Studio Suite, Ansys HFSS, or FEKO is recommended for optimising element spacing, wire diameter, folded-end geometry, and overall antenna performance before final construction.