What is WiFi Antennas?
Antennas are critical for wireless local area networks (WLAN). They facilitate the wireless signal we use to browse the web, stream movies, work from home, and play video games. In addition, they also play a role in signal strength and range.
If you’re looking to improve your signal, replace your WiFi antennas, or create a long-range wireless network, choosing the right antenna is a critical step.
How do WiFi Antennas Work?
Wireless devices use radio waves to wirelessly communicate with each other. These wireless signals are nothing but electromagnetic waves (EM waves) containing packets of information. WiFi antennas convert the EM waves into electrical signals, and vice versa.
Wireless networking devices, such as wireless routers, smartphones, laptops, tablets, and hotspots, have receiving and transmitting antennas. The receiving antennas pick up on the EM waves containing packets of information and convert them into electrical signals for the device to process. In contrast, the transmitting antennas convert electrical signals into EM waves to transmit the information packets.
Types of WiFi Antennas
There are two main types of WiFi antennas – omnidirectional and directional.
Omnidirectional antennas radiate a signal at a 360-degree angle to deliver the widest signal coverage. Think of an omnidirectional antenna as an un-shaped incandescent lightbulb. When the lightbulb is on, it will evenly distribute light in every direction to illuminate an entire room.
Typically, the antenna’s range is much shorter than a directional antenna, but their coverage area is much larger. In other words, the lightbulb's light won’t extend as far as it would with a directional antenna, but it can illuminate an entire room. Omni antennas are often found indoors and outdoors.
Types of omnidirectional WiFi antennas:
Outdoor Omni Antennas: Used to improve WiFi signal outdoors. To successfully improve the wireless coverage outside, they are typically connected to a router, access point, or an outdoor access point.
Ceiling Dome Antennas: Connect to a WiFi router or access point via coaxial cable and are installed on the ceiling of a home, office building, or warehouse.
Rubber Duck Antennas or Dipole Antennas: Typically found on routers, access points, and WiFi USB adapters.
Directional antennas, as their name suggests, focus all of their power in one direction. A directional antenna works similarly to a flashlight. When you turn on a flashlight, it illuminates the area that the light is being shined on. The flashlight's beamwidth (radiation pattern) is triangular shaped, anything outside of that triangle does not receive an ounce of light.
Since the antenna’s power is more focused, they are able to send and receive a wireless signal from a further distance, but with a much smaller coverage area. In other words, the light has the ability to reach beyond one room, but it won’t illuminate a whole room. Directional WiFi antennas are often used for long-range point to point WiFi networks to bridge the internet connection between two buildings, and long-range point to multipoint WiFi networks where multiple directional antennas communicate with an omnidirectional antenna.
Types of directional WiFi antennas:
Yagi Antennas: The most popular directional antenna. Most Yagi antennas are shaped like arrows. To work, they must point in the direction they are sending a signal to or receiving a signal from. A typical Yagi antenna has a radiation pattern of 45 degrees.
Mini Panel Antennas: Low-profile antennas designed to transmit radio waves to and from a specific area. These antennas are most commonly used to improve your WiFi signal indoors. They could replace a rubber duck antenna on a router, access point, or WiFi USB adapter. To eliminate connectivity issues, the antenna must point in the direction where you want to send a signal to and receive a signal from. These types of antennas have a radiation pattern of 60 degrees.
Panel Antennas: Strong antennas that can be used to transmit or receive a signal from far distances. They can either be connected to a router to transmit data further or to a USB WiFi adapter to receive data from further distances. Panel antennas are more directional than mini panel antennas; they have a radiation pattern of 35 degrees.
Parabolic Grid Antenna: These antennas have ultra-high gain and are extremely directional. They tend to have a very narrow beamwidth, usually between 3-20 degrees. Therefore, parabolic antennas are able to send and receive signals from miles away, making them perfect for point-to-point WiFi networks. Plus, due to their design, they can withstand extreme weather conditions.
WiFi Antenna Frequencies, Wavelengths, and Range
As mentioned earlier, WiFi devices communicate with each other through radio waves. Similar to all waves, radio waves are measured in frequencies – the rate, typically Hertz (Hz) per second, at which data is sent and received within a specific interval.
Depending on the WiFi technology, WiFi antennas utilize several frequencies to transmit information: 900 MHz, 2.4 GHz, 3.6 GHz, 4.9 GHz, 5 GHz, 5.9 GHz, and 60 GHz. The most common frequencies used in WiFi communication are 2.4GHz and 5 GHz, which correspond to wavelengths of 12.5cm and 6cm.
As you can see, lower frequency waves have longer wavelengths. Since the wavelength is longer, WiFi antennas that utilize lower frequencies have an easier time penetrating obstacles, such as floors and walls, allowing them to transmit information further. The only drawback is that information is transferred at a slower rate. In contrast, shorter wavelengths travel much faster, enabling high-speed data transmissions. However, shorter waves have a harder time penetrating physical obstacles, which reduces the signal’s range.
Each WiFi antenna is built differently to match the frequency and wavelength of the signal that is being transmitted. In other words, a 2.4GHz WiFi antenna cannot replace a 5GHz antenna, and vice versa. Additionally, some WiFi antennas are built to utilize both frequencies (known as dual-band antennas). Depending on the antenna, they can operate under one frequency at a time or at the same time.
WiFi Antenna Polarization
Polarization depicts the orientation in which the wireless signal is being transmitted with respect to the ground.
EM waves propagate with linear, circular, or elliptical polarization. The most common polarization method used in WiFi communication is linear. Linear polarization can take two forms: vertical and horizontal.
Horizontal Polarization- Radio waves that travel parallel to the ground.
Vertical Polarization- Radio waves that travel perpendicular to the ground. WiFi antennas are almost always vertically polarized.
For the best signal possible, the polarization between antennas must match. If the radio wave's polarization does not perfectly match that of the WiFi antenna, there will be a decrease in signal. Additionally, the signal will be eliminated if the polarization of the WiFi antenna and the radio waves are the complete opposite of each other. In other words, vertically polarized WiFi antennas cannot receive horizontally polarized waves, and vice versa. Some WiFi antennas utilize dual polarity to support more traffic. These antennas can send or receive horizontal and vertical radio waves simultaneously.
Understanding WiFi Antenna Gain
Gain is a measurement used to represent the antenna's strength and ability to direct electromagnetic waves in a specific direction. >Antenna gain is measured in decibels (dB) over an isotope (dBi), relative to an isotropic antenna. An isotropic antenna has 0 gain or 0 dBi and sends and receives an equal amount of signal in every direction.
It might sound like antennas with higher dBi measurements are better because they are stronger and can reach further, but higher dBi doesn’t always mean better. As the antenna’s dBi increases, so does their range, but their coverage area decreases.
For example, think about an isotropic antenna as a symmetrical ball of playdoh. If you press down (add gain) on the ball, the sides will expand, and the more pressure you add to the ball, the flatter the ball becomes. Adding gain to the ball alters the beamwidth from a sphere to a pancake. As a result, the electromagnetic waves can reach much further but within a smaller coverage area.
Outdoor WiFi Antenna Installation Best Practices
Radio waves are easily weakened or blocked by a variety of obstacles. To provide the best signal possible over a long distance, the antennas must be optimally installed.
WiFi Antennas Must Have a Clear Line of Sight
Outdoors antennas work best when their signal is not being blocked by trees and buildings. When installing long-range point-to-point or point-to-multipoint antennas, make sure their line of sight is not blocking by any obstacles. If it’s not possible to remove the obstacles, the antennas can always be installed higher to transmit the signal over the obstructions.
WiFi Antenna Alignment
To successfully share a long-range network, the antennas must be directly aligned with each other. For example, a point-to-point network requires there to be a directional antenna on each building. If antennas are pointing in the direction of each other, but one antenna was installed higher than the other, there won’t be a line of communication between the two buildings.
WiFi Antenna Orientation
It's important to correctly orientate or phase the antenna with respect to the base antennas (either a directional or omnidirectional antenna that is the source of the wireless signal).
As mentioned earlier, most WiFi antennas are vertically polarized, meaning that vertically polarized outdoor antennas should be vertically aligned with each other to create a successful network. The antennas won’t be able to communicate with each other if a directional antenna is horizontally orientated while the base antenna is vertically orientated.
Know how much Gain you Really Need
If your goal is to transmit a signal over long distances, you will need antennas with higher gain. On the other hand, if you are trying to improve the signal in your backyard, a high-gain antenna is not always ideal. An outdoor high gain antenna might stretch the signal out too far, causing the signal to be better further away and weaker within your backyard.
Use the Shortest Cable Possible
Wireless signals can be lost across cables, so to protect as much of the signal, use the minimum cable length needed. If you happen to use a longer cable, do not wrap or coil the cable around anything.
Indoor WiFi Antenna Installation Best Practices
Indoor antennas work best when their signal is not being blocked by walls, metal, doors, floors, and furniture. To mitigate interference, provide the best signal strength, and improve the signal’s range, the antennas must be located in the best possible location. Ideally, the antennas should be placed in a central location where they are not being confined by obstacles.
Additionally, the orientation of the router's omnidirectional antennas can affect the signal. According to a former Apple WiFi engineer, your wireless signal is not optimized if the router’s antennas are straight up. You will experience better speeds and coverage if one of the antennas is straight up and the other is horizontal. This way the router can successfully communicate with both types of linear polarities.