Let's improve the radio wave flight with the antenna of the Wi-Fi router

From the last time, when using with a smartphone, I have explained how to improve the jump of Wi-Fi radio waves even a little. This time, let's deepen our understanding of antennas, which play an important role in the transmission and reception of radio waves by Wi-Fi routers.

He seems to be saying, "Antenna is very important for Wi-Fi radio waves!" Wi-Fi routers with exposed antennas are really easy to understand, but even if they are not exposed, the antenna is built inside. This is the same for smartphones and PCs, and they always have a built-in antenna.

Antennas work much more efficiently when there are no obstacles around them. As explained in the previous article on the characteristics of radio waves, radio waves can pass through plastics and wood. However, it is decided that radio waves pass better when there are no obstacles.

It is best to choose a model whose Wi-Fi router antenna is exposed outside the main unit [*1] and use the smartphone without a case, considering the radio waves. . Occasionally, I see a smartphone case made of metal such as aluminum, but this blocks radio waves, so it is not very good from the perspective of transmitting and receiving radio waves.

[*1]……Actually, the metal part of the external antenna is not exposed but inside the plastic case, so it can be said that it is similar to the built-in model. However, the model that is exposed outside the main unit has a large antenna itself and has the advantage of being able to change its orientation.

Most of the antennas used in Wi-Fi are of a type called "single type". Basically, a whip-type rod antenna made of a single metal wire is used by standing vertically. If the antenna is exposed, this is the state in which the rod is upright, and if it is built in, the state in which the main body is upright [*2]. And when it is installed in this state, it is called "omnidirectional", and radio waves fly in both directions with respect to the horizontal direction of the antenna.

[*2]……Models with built-in antennas can be turned upright or laid down. It is often omnidirectional. Read and understand the instruction manual carefully

In the vertical direction, there is some directivity, like a figure 8 or a donut shape, where the radio waves are strongest in the direction perpendicular to the antenna rod[*3]. Somehow I want to point it in that direction, but I would like to note that there is not much radio waves in the direction the rod is pointing (upward in the vertical state).

[*3]……The antenna of a smartphone is often built in near the top of the main unit, but it is difficult to tell whether the antenna is facing vertically or horizontally because it differs depending on the product. Laptops have antennas along the perimeter of the liquid crystal

The directivity of a single-type whip antenna. There is an antenna in the center, and the left is from the top and the right is from the side

In other words, if the antenna rod is set up vertically, the radio waves will be transmitted in the horizontal direction, and if it is tilted horizontally, the radio waves will be transmitted in the vertical direction. to fly strongly. The trick is to point the antenna toward the place you use it often. For example, if you have a large room, you can use it vertically, and if you have a tall three-story house, you can use it horizontally.

Depending on the tilt of the antenna, the direction in which the radio waves are sent and received will change. In the left state, it is stronger in the vertical direction, and in the right state, it is stronger in the horizontal direction

Modern Wi-Fi routers have multiple antenna rods due to the MIMO function. These are diversity-operated, so if you don't limit the position where you use them, you can use them in a wide space without any interruptions, including the reflection of radio waves, by placing them in various orientations by mixing vertical and horizontal. .

Random orientation like this is suitable for use without determining the position

If the positional relationship between the Wi-Fi router and the location of use is fixed to some extent, for example, it is possible to use the Wi-Fi router horizontally in only one room. If you only need to move in one direction, set it at the same height as where you use your smartphone all the time, and set the antenna rods all upright to get the strongest signal. In this state, the effect of beam forming is more likely to be obtained, so it is recommended.

On the other hand, if you sit at a desk and work on your smartphone or laptop a lot, it is best to install the Wi-Fi router on a shelf of the same height so that the top is not covered with a shelf board, etc. is good [*4]. In this usage, I want to avoid tilting the antenna in a strange way, because tilting it will make it look nice and cool.

[*4]……Wi-Fi routers are often placed near the line connection device installed at the entrance, but considering the radio waves, bring it to the room where you use your smartphone etc. is best. This solution will be introduced later.

It is also a good idea to place the Wi-Fi router in a position where you can see the multiple antennas. It is recommended to place the antennas side by side if they are near the wall. The effect of MIMO is weakened if it is in a row when viewed from the user side.

If you use it at the same height as the Wi-Fi router with the antenna vertical, the signal quality will be good.

A final note. Antennas are made to tune to the wavelength of the frequencies they use. One wavelength is 6 cm for the 5 GHz band and 12.5 cm for the 2.4 GHz band. A simple one-wavelength antenna is precisely made for both lengths. It should be noted that the gain does not increase even if an uncalculated and meaninglessly long antenna is attached.

In addition, there is also a model for corporations that can replace the external antenna, which can be used when you want to use it in a specific position with higher directivity. However, it is not OK to replace the antenna with anything. Replacing without taking this into consideration would be a violation of the Radio Law[*5]. In the first place, the external antenna is not recommended because the attenuation in the connection cable is very large.

[*5]……Wi-Fi devices are basically allowed to emit radio waves without a license when they are sold as they are. Modification is therefore illegal. We will discuss this in more detail later when we discuss the output.