An omnidirectional antenna is an antenna that sends and receives radio signals equally in every horizontal direction, 360 degrees around it. Also written omni-directional, or shortened to omni antenna, it is the standard choice for cellular routers, vehicles and most IoT devices, because it works without being pointed at a particular mast.

An omnidirectional antenna's coverage is shaped like a doughnut: strong all round the sides and weak directly above and below. A simple dipole, the most basic omnidirectional design, has a gain of 2.14 dBi. Antenna gain in dBi measures how strongly an antenna concentrates energy compared with an isotropic antenna, a theoretical source that radiates equally in all directions.

An omnidirectional antenna gets more gain by flattening its doughnut, not by adding power. The higher the gain of an omnidirectional antenna, the narrower its vertical beamwidth. A high-gain omni reaches further towards the horizon, but it can do worse than a lower-gain model when the mast is close by, or well above or below the antenna, because the mast then sits outside the narrower beam.

An omnidirectional antenna suits urban and suburban sites, vehicles and other moving assets, and any location that can see several masts. Because an omni antenna can connect to whichever cell is available, it copes better when one cell site is congested or out of service. The trade-off is that an omni also picks up interference from every direction, which lowers SINR and with it the data speed the connection can carry.

Most omnidirectional antennas for 4G and 5G routers are MIMO antennas, with two or four elements in one housing and a cable for each of the router's antenna ports. Where the signal is weak and comes from one distant mast, a directional antenna usually does better. We supply omnidirectional and directional cellular antennas for routers and IoT devices, and we can help you choose between them for a given site.

‍