Types of Antennas

There are several types of antenna available for home Wi-Fi networks. The type of antenna you choose will depend on how you are planning on extending the signal to increase the coverage area. Some of the available antenna types are described in the following subsections.

Omni directional Vertical Polarity Antennas:

This type of antenna is omni directional only on the horizontal plane. The signal spreads horizontally from the antenna, which narrows the vertical beam-width. This type of antenna is built into many access points and is sometimes called an omni directional vertical gain antenna.

Inside insight: Most antennas used in WLANs have linear polarization, usually vertical. When you're extending your WLAN, make sure that your antennas have matching polarity. If the polarity of two antennas, especially directional ones, is misaligned, it will cause signal degradation.

Panel or Patch Antennas:

Flat panel or patch antennas are used to direct WLAN signals both indoors and out. Generally, they have a radiation pattern of less than 90 degrees, which makes them ideal for directing a signal into a specific room or section of a home. For indoor use, you should probably use the smaller panel sizes with a gain of 8 dBi or less. Larger panel antennas are good for bridging between buildings

Cables and Connectors:

Most antennas in WLAN equipment use reverse polarity connectors. Unlike regular connectors, these reversed polarity (RP) connectors, which are also known as reversed gender, have the center pin switched so that it is in the opposite connector from the "normal" polarity connectors.

The reason for this was simple; the FCC didn't want you to start modifying your WLAN equipment with higher-gain antennas, so they required all manufacturers to use non-standard, proprietary connectors to make it harder for the average person to modify an access point.

Unfortunately for them, the FCC failed to consider the power of a free market economy. If people want to modify their equipment, someone is going to manufacture what they need and sell it to them. As a result, reverse polarity connectors are no longer an oddity; they are a standard.

When you choose to upgrade your antenna, check what type of connector is on your WLAN, and purchase (or build) an antenna with a compatible connector. In fact, make sure you can upgrade your antenna in the first place. Some access points don't have a connector for an external antenna. If this is the case, you may have to consider upgrading to a newer access point.

When you are connecting an external antenna, keep the length of the coaxial cable to a minimum. Your manufacturer's documentation should tell you what the maximum cable length is; make sure you don't exceed it. Using an excessively long cable can actually end up reducing your signal rather than increasing it.

Client Antennas:

The antennas that come with many wireless NICs, especially PCMCIA cards, are terrible. The typical laptop NIC has a tiny integrated bulge antenna, which is practically worthless. Unfortunately, most PCMCIA NICs don't allow for the connection of an external antenna.

If your desktop's NIC has an external connector, you can get an appropriate antenna to improve its signal strength and reception. A good choice would be a simple omni directional dipole antenna, which is available at most stores that sell Wi-Fi equipment. Upgrading your AP's antenna is a good centralized way to start, but, if your performance is still lacking, consider upgrading your client antennas, too.