Small Loop Antenna Calculator

The Small Loop Antenna Calculator helps RF engineers, amateur radio operators, antenna designers, EMC specialists, researchers, and students calculate the electrical characteristics of electrically small loop antennas. By entering the operating frequency and loop diameter, the calculator determines wavelength, loop circumference, loop area, circumference-to-wavelength ratio, radiation resistance, electrical size, and estimated antenna gain. It is widely used for HF communication, magnetic loop antennas, receiving antennas, direction-finding systems, EMI measurements, amateur radio, and compact wireless communication applications.

Enter Frequency, Loop Diameter exactly in the units shown by this small loop antenna. Check the operating band, unit prefix, and decimal position before calculating; these are the inputs used by the formula.

• Frequency — use MHz.
• Loop Diameter — use cm.

The results describe the calculated small loop antenna values for the inputs you entered. Check each value against the available space, selected components, feed system, and operating conditions before making a final design decision.

The Small Loop Antenna uses Rr = 31,200 × (A/λ²)². Supply Frequency (MHz), Loop Diameter (cm) in the displayed units, then use the calculated values as the first engineering target for this resonant antennas design or analysis.

A small loop antenna is an electrically small antenna whose circumference is typically less than one-tenth of the operating wavelength. Unlike resonant full-wave or half-wave loop antennas, a small loop primarily behaves as a magnetic field radiator and exhibits very low radiation resistance. Because radiation resistance is extremely small, conductor losses, tuning capacitor quality, and feed system losses have a significant impact on antenna efficiency. Increasing loop diameter or operating frequency generally increases radiation resistance and improves efficiency. Practical antenna performance also depends on conductor diameter, number of turns, Q factor, capacitor losses, nearby conductive objects, mounting environment, and tuning accuracy. Small loop antennas are valued for their compact size, low noise reception, and directional characteristics, making them particularly useful where installation space is limited.

Use the calculated loop dimensions as the starting point for antenna construction. Build the loop using low-loss conductive tubing or heavy-gauge wire and minimise connection resistance throughout the antenna. Use a high-voltage, low-loss variable capacitor to tune the loop accurately to the desired operating frequency. After installation, adjust the tuning capacitor for minimum VSWR and maximum received or transmitted signal strength while monitoring the antenna with a vector network analyser (VNA) or antenna analyser. Verify resonant frequency, impedance, return loss (S11), and bandwidth before operation. Electromagnetic simulation using CST Studio Suite, Ansys HFSS, FEKO, or NEC is recommended to evaluate efficiency, current distribution, radiation pattern, and matching network performance before final construction.