Types of Omni-Directional Antennas

An omnidirectional antenna is used in radio communication to radiate or receive signals equally in a 360-degree radiation pattern. It is also called a "non-directional" antenna since it doesn't favor any particular direction like directional antennas that broadcast and receive signals in a single direction. There are four basic types of omnidirectional antennas that use the E plane (horizontal) and H plane (vertical).

  1. Horizontally Polarized Antennas

    • Horizontally polarized antennas are used for both short- and long-range applications and are known as “loop” antennas. Small loop (short-range) antennas have a smaller radiating resistance that causes a weaker signal than other omnidirectional antennas. They are usually used on applications where antenna efficiency is not as important, such as in pagers. Larger loop (long-range) antennas can help address the inefficiency problem; however, they also decrease the distribution of current. Citizen Band radios used for ground-air and ship-shore applications are common examples of long-range applications.

    Vertically Polarized Antennas

    • Vertically polarized omnidirectional antennas can be used for both short-range and long range applications, such as intelligent traffic applications that control traffic and check speed cameras. This type of antenna transmits an electromagnetic wave with the E field that is perpendicular to the Earth's surface and is useful for tracking and managing containers, enabling short-range meshed networks for cellphones and maximizing wireless repeater systems for broadband connections.

    Multimode Antennas

    • Multimode antennas are used when different services are needed for the same antenna and each needs its own frequency strength, such as cars that provide a tracking system for the vehicle and mobile phone capabilities. Its electromagnetic horn type is made up of two or more modes of antenna that create nearly identical E and H plane radiation patterns, eliminating the need for two separate antennas.

    Rotatable Antennas

    • Rotatable antennas are desirable in situations where high-power communication between a fixed station and a mobile one is needed. Possible applications for this feature include communication between shipping stations and their ships, air traffic control stations and military deployments where communication is essential between a base and a tactical unit. The distance and frequency strength needed in each of these examples varies, and a rotatable antenna creates flexibility in these situations so communication channels remain open.

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