Wi-Fi wireless networking sends radio transmissions on specific frequencies where listening devices can receive them. The radio transmitters and receivers are built into Wi-Fi enabled equipment such as routers, laptops, and phones. Antennas are key components of these radio communication systems. Antennas pick up incoming signals or radiate outgoing Wi-Fi signals. Some Wi-Fi antennas, particularly on routers, are mounted externally, while others are embedded inside the device's hardware enclosure.
Antenna Power Gain
The connection range of a Wi-Fi device depends on the antenna power gain. A numeric quantity measured in relative decibels (dB), gain represents the maximum effectiveness of an antenna compared to a standard reference antenna. Industry manufacturers use one of two standards when quoting gain measures for radio antennas:dBi: Decibels relative to an isotropic reference antenna.dBd: Decibels relative to a dipole reference antenna.
Most Wi-Fi antennas use dBi as the standard measure rather than dBd. Dipole reference antennas work at 2.14 dBi, which corresponds to 0 dBd. Higher values of gain indicate an antenna is capable of working at higher levels of power, which usually results in greater range.
Omnidirectional Wi-Fi Antennas
Some radio antennas work with signals sent out and received from all directions. These omnidirectional antennas are commonly used on Wi-Fi routers and mobile adapters — devices that support connections from multiple directions. Factory Wi-Fi gear often uses basic dipole antennas of the rubber duck design. This design is a helix shape that is sealed in a protective jacket of rubber or plastic that protects the antenna, similar to those used on walkie-talkie radios. These have a gain between 2 and 9 dBi.
Directional Wi-Fi Antennas
Because the power of an omnidirectional antenna is spread across 360 degrees, its gain measured in any one direction is lower than directional antennas that focus more energy in one direction. Directional antennas are typically used to extend the range of a Wi-Fi network into hard-to-reach corners of buildings or in situations where 360-degree coverage isn't needed.
Cantenna is a brand name of Wi-Fi directional antennas. The Super Cantenna supports 2.4 GHz signaling with a gain of up to 12 dBi and a beamwidth of about 30 degrees, suitable for indoor or outdoor use. The term cantenna also refers to generic do-it-yourself antennas using a simple cylindrical design.
A Yagi (more properly called Yagi-Uda) antenna is another type of directional radio antenna that can be used for long-distance Wi-Fi networking. These antennas are extremely high gain, usually 12 dBi or higher, and are used to extend the range of outdoor hotspots in specific directions or to reach an outbuilding. Do-it-yourselfers can make Yagi antennas, although the process requires more effort than making cantennas.
Upgrading Wi-Fi Antennas
Wireless networking problems caused by weak signal strength can be solved by installing upgraded Wi-Fi radio antennas on the affected equipment. On business networks, professionals typically perform a comprehensive site survey to map the Wi-Fi signal strength in and around office buildings and strategically install wireless access points where needed. Antenna upgrades can be a simpler and more cost-effective option to fix Wi-Fi signal problems, particularly on home networks.
Consider the following when planning an antenna upgrade strategy for a home network:Some Wi-Fi gear does not support aftermarket antenna upgrades. Consult the manufacturer documentation.Upgrading a router's omnidirectional antennas can improve connectivity with all devices in the home and resolve basic signal issues. Upgrading client devices only benefits each one individually.Evaluate both gain and directional radius support properties of antennas when choosing one. Software packages that map Wi-Fi signal strength in a home are available to use for planning.
Wi-Fi Antennas and Signal Boosting
Installing aftermarket antennas on Wi-Fi equipment increases the effective range. However, because radio antennas only concentrate and direct signals, the range of a Wi-Fi device is limited by the power of its radio transmitter rather than only its antenna. For these reasons, signal boosting a Wi-Fi network may be necessary and is usually accomplished by adding repeater devices that amplify and relay signals at intermediate points between network connections.