What is a Discone Antenna?

A discone antenna is an omnidirectional, wideband antenna that consists of a disc-shaped element mounted above a cone-shaped structure. These antennas are usually mounted vertically, with the disc positioned on top and the cone at the bottom. The disc serves as the radiating element, while the cone acts as the ground plane. The name is a combination of the words ‘disc’ and ‘cone’. This unique and versatile design offers a powerful blend of broadband coverage, omnidirectional reception, and compact design for radio enthusiasts and professionals alike.

Structure of a Discone Antenna

There are four main elements of a Discone Antenna – Disc, Cone, Insulator and Feed.

Disc: The disc is typically located at the top of the antenna structure. Its diameter should be 0.7 times a quarter wavelength of the antenna’s lowest frequency and serve as the receiving element for the antenna. The disc is usually made high-quality conductive metals like copper for smaller antennas. For larger discone antennas, especially those designed for VHF and UHF coverage, using a solid metal sheet becomes impractical due to weight and wind resistance. In these cases, manufacturers use metal rods or wires in a spoke configuration as seen in the figure above. This approach achieves a similar electrical effect to a solid sheet while being lighter and more manageable for outdoor use.

Cone: The cone serves as a ground plane. Its length should be a quarter wavelength of the antenna’s lowest operating frequency.

Insulator: Discone antennas use an insulator element to separate the disc and cone sections while maintaining their positioning. It is made from an insulating material and holds the disc and the cone elements in place, keeping them a fixed distance apart. This distance is one of the factors which determine the overall frequency of the antenna.

Feed: The feed point of this antenna is usually at the center of the disc and is fed by a 50 ohm coaxial cable.

Features & Applications of Discone Antennas 

Discone antennas have very wide bandwidths with a frequency range ratio of 10:1 or more. This means that the antenna's maximum frequency can be 10 times higher than its minimum frequency. This wideband reception makes discone antennas ideal for applications where monitoring various frequencies is crucial such as amateur radio, scanner monitoring, military communications, and spectrum monitoring.

One of the main disadvantages of Discone antennas is their narrow radiation pattern in the vertical plane, i.e., they have lower reception for signals originating very close to the antenna or directly overhead.