An omni directional antenna is designed to provide a 360-degree dispersed wave pattern. This type of antenna is used when coverage in all directions from the antenna is required. Omni directional antennas are good to use when a broad-based signal is required. Because of the dispersed nature of omni directional antennas, the signal is weaker overall and therefore accommodates shorter signal distances. Omni directional antennas are great in an environment in which there is a clear line of path between the senders and receivers. The power is evenly spread to all points, making omni directional antennas well suited for linking several home and small office users.
Directional antennas are designed to focus the signal in a particular direction. This focused signal allows for greater distances and a stronger signal between two points. The greater distances enabled by directional antennas allow a viable alternative for connecting locations, such as two offices, in a point-to-point configuration.
Directional antennas are also used when you need to tunnel or thread a signal through a series of obstacles. This concentrates the signal power in a specific direction and allows you to use less power for a greater distance than an omni directional antenna.