The frequencies, wavelengths, and range of WiFi antennas
WiFi devices talk to each other using radio waves. Radio waves are measured in frequency the same way as all other waves. The frequency rate is Hertz (Hz) per second.
900 MHz, 2.4 GHz, 3.6 GHz, 4.9 GHz, 5 GHz, 5.9 GHz, and 60 GHz are some of the frequencies that WiFi antennas use to send information. Most WiFi communication happens at 2.4GHz and 5GHz, which have wavelengths of 12.5cm and 6cm, respectively.
The wavelengths of waves are longer when the frequency is low. Since the wavelength is longer at lower frequencies, it is easier for WiFi antennas that use those frequencies to go through things like floors and walls. This lets them send information farther with wavelengths that are higher and shorter, but sent slowly. Wavelengths that are shorter move much faster, allowing for high-speed data transfer. But shorter waves have a harder time getting through real things, which makes the signal’s range smaller.
Each WiFi antenna is made in a different way so that it can match the frequency and wavelength of the signal being sent. In other words, you can’t switch a 2.4GHz WiFi antenna for a 5GHz one, and vice versa. Some WiFi antennas are made so that they can work on both frequencies (known as dual-band antennas). Depending on the antenna, they can run on one frequency at a time or both at the same time.
WiFi Antenna Polarization
Polarization is a way to show how the wireless signals are sent to the ground.
EM waves can move in a straight line, a circle, or an ellipse. Linear polarization is the most common way for WiFi to talk to each other. Linear polarization can be either straight up or straight down.
- Horizontal – Radio waves that move parallel to the ground are said to have horizontal polarization.
- Vertical – Radio waves that travel perpendicular to the ground are said to have vertical polarization. WiFi antennas are almost always polarized in the vertical direction.
The polarization of both antennas needs to be the same for the best signal possible. If the radio wave’s polarization is different from the WiFi antenna’s, the signal will be weaker.
Additionally, if the WiFi antenna’s polarization is different from that of the radio waves, the signal will be completely lost. In other words, WiFi antennas that are polarized vertically cannot detect signals that are polarized horizontally and vice versa.
So they can handle more traffic, some WiFi antennas have two polarities. These antennas can send or receive both horizontal and vertical radio waves at the same time.
Understanding WiFi Antenna Gain
Gain is a way to measure how strong an antenna is and how well it can send electromagnetic waves in a certain direction. The antenna gain is measured in decibels (dB) over an isotope (dBi), which is an antenna that has the same gain everywhere. An isotropic antenna has no gain, or 0 dBi, and sends and receives the same amount of signal in all directions.
It might seem like antennas with higher dBi measurements are better because they are stronger and can reach farther, but this isn’t always the case. As the dBi of an antenna goes up, so does its range, but the area it can cover gets smaller.
For example, think of an isotropic antenna as a ball of playdoh that is the same on both sides. If you press down on the ball (called “adding gain”), the sides will grow, and the more pressure you add, the flatter the ball gets. The beamwidth changes from a sphere to a pancake when gain is added to the ball. Because of this, the electromagnetic waves can travel much farther, but they can only cover a smaller area.