Omni Directional Antenna

An omnidirectional antenna is an antenna which radiates most of its power in one plane e.g. 360°. A omnidirectional antenna can also be made for either vertical or horizontal polarisation. All Air-Stream Wireless Access Points currently operate on the 2.4Ghz band.

Omnidirectional antenna is a type used in wireless LAN and without going into too much theoretical detail it is primarily used for Access Points in a community wireless network, but is sometimes used for surveying signal around an area either by foot or car. It is not generally recommended for client connections.

In a community wireless network the aim of a omnidirectional antenna is to provide coverage to as many users over the greatest distance and this may not be as straight forward as it may sound.

Increasing the gain of antenna does increase the effective range of an antenna but it also narrows the beam width effectively reducing the area of coverage.

But decreasing the gain increases the beam width it also decreases the range, so what is the optimum?

This is usually dependant on topography of the land and where most of the users are in relation to the height of the Access Point, but as a general rule of thumb the optimum gain for an Omnidirectional antenna is around 8dbi to get the best long-term compromise between distance and coverage where the 3dB Vertical Beamwidth is somewhere about 18° but also has some down tilt.