Antenna types

People might not give much attention to antenna selection while setting up a Wireless LAN or buying an access point. But the fact remains that antenna selection and its appropriate placement really helps in improving the range of the access point.

Antennas can be classified into two broad categories: omni-directional and directional.

Omni-directional



The default antenna that comes fitted with most of the access points is the 'Dipole' antenna. Dipole antenna covers the area around it in a circular fashion. So a Dipole ensures that signal strength is same in the area around it, but the signal strength above and below the access point will be weak. For example, if you set up an access point with a Dipole antenna on the first floor of a building, then the signal strength on that floor would be strong and equal, all around, but on the ground and second floor the strength of the signal would be comparatively weak.

Directional



Directional antennas are meant to focus the signal or output of the access point in one direction either vertical or horizontal. Uni-directional does not mean that the signal would be in a single line. The signal has a coverage area that can be measured in degrees. The purpose of a directional antenna is to help you focus your signal and have it where you want it. The security factor is also there as the signal does not go in unwanted areas and is not extended unnecessarily. Directional antennas are of the following two types: 

Yagi: These are in the form of a cylinder and contain a boom, which is used to propagate the signal. This creates a narrow beam of the signal whose width varies from 20 to 80 degrees. 

Patch: These are usually mounted on top of walls or ceilings. The width of the signal produced by a patch antenna varies from 30 to 180 degrees.

Buying or choosing the right antenna is not the only thing you need to do for getting good signal strength. Apart from the type of antennas there are many factors that need to be kept in mind for the appropriate placement of the antenna.

While setting up an access point indoors you must take into account factors like the height of the ceiling, building construction i.e. the walls or obstructions that might come in the way of the signal. While setting it up outdoors, obstructions such as buildings and trees must be taken into account. The height of the antenna has to be decided upon accordingly. 

Finally, try and keep the antennas away from metal objects such as air conditioners, power cables etc. Use professional help while installing an antenna for proper and safe installation. One way of increasing the coverage area of the antenna is to place it as high as possible.