Sometimes referred to as a nondirectional antenna, an omnidirectional antenna is a receiving device that is capable of sending and receiving signals from any direction. An antenna of this type may be used to pick up broadcast television signals or audio broadcasts from radio stations, or allow robotic devices to be operated using microwave or wireless technology. Mobile or cellular telephone services, as well as wireless Internet connections, make use of an omnidirectional antenna as part of the process of broadcasting stable signals to these devices.
In design, the omnidirectional antenna is either structured as an external or internal sending or receiving device. An internal design for the omnidirectional antenna is usually very simple, and may employ a simple design that is not unlike a dipole antenna. While compact, antennas of this type are extremely powerful, and can often pick up a stable signal for long distances. Surveillance equipment used by law enforcement may include the use of this type of antenna in handheld surveillance equipment, making it practical for monitoring the activities of a suspect. Cell phones and other small wireless devices will also have an internal antenna device that makes it possible to pick up signals that are emitted by a gateway or some other type of sending equipment.
An external omnidirectional antenna is often used for controlling electronic devices, such as robotic machinery in a manufacturing plant. The antenna will be incorporated into the design of the robotics, allowing the devices to be controlled from a remote point by means of a broadcast signal on a specific frequency. Thanks to the nature of the antenna, neither the device nor the control station must be stationary in order for the signal to remain strong and stable. This makes it much easier for the device to move about the plant floor with ease, and still be under the control of the remote operator, without any difficulties.
With all examples of the omnidirectional antenna, the signal pattern is often described as doughnut-shaped. This is true for antenna systems that are used to broadcast a signal as well as those designed to receive a signal. Many are designed with a specific range in mind. For example, an antenna that captures broadcast HDTV television signals or wifi signals may be configured to lock onto signals that are broadcast from various points around the local area. By contrast, an antenna that is used for military or law enforcement surveillance may receive signals from a much larger geographical area.