In the past two days, there has been a lot of controversy on the Internet around a technical science video of station B.
In the video, in order to test the signal, a certain UP master straightened the antenna.
The UP master may think that after the antenna is straightened, the antenna can produce a directional signal radiation effect.
So, is it really the right thing to do?
In addition, many people often ask: the Wi-Fi router at home has multiple antennas. How should these antennas be pointed in order to have a better propagation effect?
Today, I will briefly tell you about this knowledge.
Antennas are actually familiar to everyone. But wherever there is wireless technology, there are basically antennas. Its purpose is to send and receive radio waves.
(图片来源:veer图库)
More technically, an antenna is a "converter" – a guide wave propagating on a transmission line that is transformed into an electromagnetic wave propagating in free space, or vice versa.
The role of the antenna
How does the antenna convert between a guided wave and a space wave?
Take a look at the diagram below:
↓↓↓
After a high school physics, when two parallel wires have an alternating current, electromagnetic radiation will be formed.
When the two wires are in close proximity, the radiation is weak (the wire currents are in opposite directions, and the induced electromotive force generated is almost canceled out).
When the two wires are opened, the radiation is intensified (the wire current is in the same direction and the induced electromotive force is generated in the same direction).
When the length of the wire is increased to 1/4 of the wavelength, a more significant radiation effect can be formed!
With an electric field, there is a magnetic field, and with a magnetic field, there is an electric field, and so on, there is an electromagnetic field and electromagnetic waves......
Electricity generates magnetism, and magnetism generates electricity
Let's take another GIF, let's feel this beautiful process:
The change in the direction of the wire current creates a changing electric field
The two straight wires that generate the electric field are called oscillators.
What does an oscillator look like in the real world?
That's it—
It's such a piece of metal... Half-wave symmetrical oscillator (non-compatible)
Well, in fact, the above is just a traditional form of the oscillator, and it also has N transformations:
A strangely shaped oscillator
You may ask: The antenna we see in real life is not like this?
The reason is simple: to be exact, the oscillator is not a complete antenna. The oscillator is the core component of the antenna, and its shape changes with the shape of the antenna.
And the form of the antenna, there are too many...
All in all, hundreds and thousands ...
Sometimes, there will also be a radome on the outside of the antenna, which obscures the real oscillator inside. This can lead to misunderstandings about the actual shape of the antenna.
The appearance of the antenna is very strange, and according to the similarity, it can be roughly classified as follows:
Whip antennas
Parabolic antennas
Yagi antenna
PS: The Yagi antenna is not eight woods, although I am not good at math, but I can still count eight. The reason why it is called Yagi is because it was invented by the Japanese Yagi Shuji and Uda Tai Hao in the 20s of the twentieth century, called "Yagi Uda Antenna", referred to as "Yagi Antenna".
As mentioned at the beginning of this article, the antenna in the video is the most common vertically polarized rubber pole antenna, which is similar to the whip antenna and is also an omnidirectional antenna.
So, this antenna, how does its signal propagate outward?
Take a look at its signal pattern and you can see that:
Yes, its signal is transmitted around the vertical direction of the "stick". Professionally speaking, it is "the smallest axial direction and the largest normal direction". (Actually, the previous GIF has already spoiled it.) ）
As you can see, the signal propagation direction is perpendicular to the antenna. In other words, the direction in which the top of the antenna is pointing, the signal is weakest.
Therefore, if you want to maximize the effect of this antenna, then it should be placed like this:
In the same way, if you want to get better results from the router at home, it is also recommended that the antenna be placed vertically.
The antenna swings horizontally, and it will look like this:
Pointing to the pendulum, it is even more wrong, and the signal is the worst.
Of course, if your router is placed relatively high, or relatively short, it is also possible to adjust the antenna angle appropriately.
There are some common senses to pay attention to in the placement of antennas:
1. If uploaded on the Internet, the way of putting a can on the antenna will enhance the signal. This is wrong and does not produce a greater gain.
2. Do not get too close to each other, otherwise there will be interference between them.
3. The more router antennas the better. Different antennas serve different purposes, such as 2.4GHz or 5GHz signals. There is a limit to the MIMO (multi-antenna transceiver) supported by mobile phones, generally 2x2 or 4x4, not that your router has 100 antennas, and a mobile phone can communicate with it. Nowadays, many routers have a lot of antennas, in fact, it may just be to increase the number of belts.
Okay, about the way the antenna is placed, has everyone learned to "waste"?