Experimental verification: Can WiFi signal amplifier is not very effective

The WiFi signal at home is not strong? Don't worry, put a WiFi signal amplifier made of cans on the wireless router, and the signal will be enhanced. Recently, a Weibo post titled "Homemade WiFi Signal Amplifier Made of Cans" went viral online. Is this homemade signal amplifier reliable? After some verification, the reporter found that in theory, cans can enhance WiFi signals, but in practice they are not very effective.

　　The popular online guide introduces the production process of a WiFi signal amplifier.

　　To make a WiFi signal amplifier, you need an aluminum can, a pair of scissors, and a wireless router. First, rinse an empty can with water, cut off the bottom of the can first, then cut the top of the can, leaving about 2 cm of the can near the can mouth. Cut the can body in half along the can body opposite the can mouth, and spread the aluminum skin into a fan shape. Then turn the aluminum can upside down, pass the antenna through the can mouth, and use tape to stick the aluminum can and the router together.

　　Since it was the first attempt, it took the reporter a full hour to complete the production of the WiFi signal amplifier. Under the guidance of professionals, the reporter conducted the experiment.

　　In the living room, I turned on my laptop computer with wireless network function and downloaded a WiFi signal test software from the Internet. Without sticking the aluminum can and the router together, I moved the laptop computer close to the wireless router in the living room. The test software showed that the WiFi signal strength was between -13dBm and -14dBm. dBm is a unit that indicates the strength of WiFi signal. The value is negative. The smaller the absolute value, the stronger the WiFi signal.

　　Then we came to the bedroom, which is 20 meters away from the wireless router and separated by two walls. At this time, the WiFi signal strength fluctuated around -50dBm. It can be seen that with the increase of distance and the obstruction of walls, the WiFi signal strength is also weakening.

　　After obtaining the data of normal status, the reporter put a WiFi signal amplifier made of a can on the antenna of the wireless router. When the laptop was close to the wireless router, the WiFi signal strength varied between -12dBm and -15dBm. When the laptop was placed in the bedroom, the WiFi signal strength varied between -49dBm. The reporter also tried to adjust the direction of the WiFi signal amplifier opening. When the opening was facing the laptop, the strongest signal strength was -47dBm, and the signal was enhanced.

　　Through experiments, it can be found that although the WiFi signal amplifier made of cans has some effect, the increased signal is almost negligible. Why is this?

　　"In remote areas, many people use cans as antennas to receive TV signals. Using cans to make WiFi signal amplifiers is based on the same principle," explained Fang Peiyu, a doctor who studied in Japan. Now, Fang Peiyu is the technical leader of a high-tech enterprise specializing in WiFi mobile phones.

　　Fang Peiyu said that the inner surface of the can reflects radio waves, which enhances the antenna's ability to transmit and receive signals. However, this enhancement is directional, not amplification, which means that the signal at the back is reflected to the front, thereby enhancing the signal at the front of the open area, but attenuating the signal at the back. This is the same as the reflector of a flashlight. "If made properly, a WiFi signal amplifier made of a can can increase the signal by 20% in a directional manner."

　　However, this is only theoretical. "To maximize the signal, it depends on the shape of the can's fan-shaped surface, the location of the antenna, the wavelength of the signal, etc. It is difficult for ordinary citizens to master these skills," said Fang Peiyu.