Every element of your wireless infrastructure is critical — and the WiFi Antenna is no exception. In another post, I’ll talk about the different types of antennas. For now, let’s stick with the basics.
Here are the basics of antenna characteristics:
- Frequency. For wireless LANs, you need to use an antenna tuned for either 2.4 GHz (802.11b) or 5 GHz (802.11a). An antenna will only work efficiently if the frequency of the antenna and radio matches.
- Power. Antennas can handle a specific amount of power put out by the transmitter. In the case of 802.11, the antenna will generally be rated greater than 1 watt in order to handle the maximum peak transmit power of the radio NIC or access point. For most applications, the antenna power specification won’t be of too much concern to you because of the relatively low power that wireless LANs transmit.
- Radiation Pattern. The radiation pattern defines the radio wave propagation of the antenna. The most basic radiation pattern is isotropic, which means the antenna transmits radio waves in all directions equally. An isotropic radiation pattern resembles the shape of a beach ball, with an antenna at its center. Other radiation patterns are also possible.
- Gain. The gain of an antenna represents how well it increases effective signal power, with decibels (dB) as the unit of measure. Most antenna manufacturers specify gain as dBi, which is the gain relative to an isotropic source. In other words, dBi is how much the antenna increases the transmitter’s power compared to using a fictitious, isotropic antenna. dBi represents the true gain that the antenna provides to the transmitter output.
Keep your antenna up for future posts about the various types of RF antenna.