Discone Antenna Calculator

The Discone Antenna Calculator helps RF engineers, amateur radio operators, scanner enthusiasts, public safety communication professionals, researchers, and students calculate the primary dimensions of a discone antenna from its lowest operating frequency. By entering the desired minimum frequency, the calculator estimates the wavelength, cone length, disc diameter, disc radius, cone diameter, feed gap distance, recommended cone angle, estimated upper operating frequency, and approximate bandwidth ratio. Discone antennas are renowned for their extremely wide bandwidth, omnidirectional radiation pattern, and low VSWR across multiple frequency bands. They are commonly used for VHF, UHF, airband, marine radio, amateur radio, public safety monitoring, emergency communication, military monitoring, SDR receivers, spectrum monitoring, and broadband RF measurement systems.

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

• Lowest Operating Frequency — use MHz.

The results describe the calculated discone 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 Discone Antenna uses Cone Length ≈ 0.25λ, Disc Diameter ≈ 0.17λ, Gap ≈ 0.008λ. Supply Lowest Operating Frequency (MHz) in the displayed units, then use the calculated values as the first engineering target for this specific antenna types design or analysis.

This calculator is based on the classical geometric design rules developed for broadband discone antennas. The first step calculates the free-space wavelength using λ = 300 ÷ f, where λ is the wavelength in metres and f is the lowest operating frequency in megahertz. Since the physical dimensions of a discone antenna scale directly with wavelength, lower operating frequencies require a larger antenna structure while higher frequencies allow a more compact design. The cone length is estimated as approximately 0.25λ because the conical radiator behaves similarly to a quarter-wave radiator, providing efficient broadband impedance characteristics. The disc diameter is approximated as 0.17λ, creating the capacitive loading necessary to achieve a stable feed impedance across a wide frequency range. The disc radius is simply one-half of the disc diameter and is useful when fabricating circular or radial disc structures. The cone diameter is estimated as approximately 0.50λ, providing sufficient aperture for stable omnidirectional radiation while maintaining broadband performance. The feed gap is calculated as approximately 0.008λ because the spacing between the disc and cone strongly influences impedance matching and VSWR. Even small variations in this gap can significantly affect return loss and operating bandwidth. A cone angle of approximately 60° is commonly recommended because it provides an effective compromise between impedance stability, radiation efficiency, and broadband operation. Unlike resonant antennas such as dipoles or Yagi antennas, the discone is a travelling-wave broadband antenna capable of operating over a frequency range approaching 10:1 under well-designed conditions. The calculator therefore estimates the upper operating frequency as roughly ten times the selected lowest operating frequency, providing an approximate operating bandwidth for initial antenna design. These equations are widely used during the preliminary design of scanner antennas, SDR antennas, broadband receiving antennas, spectrum monitoring systems, and VHF/UHF communication antennas before detailed electromagnetic optimisation.

Use the calculated dimensions as an initial engineering design rather than the final manufactured dimensions. During construction, maintain accurate symmetry between the disc and cone to preserve the omnidirectional radiation pattern and broadband impedance characteristics. The feed gap should be manufactured precisely because small dimensional changes can noticeably affect VSWR and impedance matching. Stainless steel rods, aluminium tubing, brass rods, or copper elements are commonly used depending on mechanical strength and corrosion resistance. Install the antenna well above nearby metallic structures whenever possible to minimise pattern distortion and unwanted coupling. After construction, verify resonance, return loss (S11), VSWR, feed-point impedance, radiation pattern, and operating bandwidth using a Vector Network Analyzer (VNA) or antenna analyzer. Electromagnetic simulation using CST Studio Suite, Ansys HFSS, FEKO, NEC2, NEC4, or Altair Feko is recommended for optimising cone angle, disc diameter, feed gap, support structure, and radiation performance before fabrication. Practical bandwidth may vary depending on conductor diameter, mounting hardware, feedline routing, nearby objects, and manufacturing tolerances.