WiFi signal is not good! Is the high gain antenna really so god?

In the eyes of many people, the high-gain antenna is the king of routing coverage. Just change an antenna and you can effectively enhance the wireless signal. So, how do you replace the high-gain antenna yourself with wireless routing? And how does the high gain antenna help the signal?




Why does the antenna have gain?

What is the antenna gain? That is, the ratio of the power density of the signal produced by the actual antenna to the ideal radiating element at the same point in space, under the condition of equal input power. Of course, this explanation is a bit sloppy. In layman's terms, the gain indicates how many times the antenna can amplify the signal. This problem is coming again. The antenna is a passive device. It does not need a power supply. How can it be amplified? Is this not a violation of the most basic principle of energy conservation?

Of course, there are many ways to achieve high gain in the antenna. Here, we talk about the gain principle of the commonly used rod antenna. The scientific name of this type of antenna is called a spiral inverted antenna. Structurally, it is a hybrid structure of a linear vibrator and a helical inverter. Wherein, the vibrator portion of the line is responsible for transmitting the signal, and the spiral inverter is responsible for changing the phase of the signal. Thus, the two vibrators emit signals of different phases, and after being combined, the signal forms a larger amplitude signal. In this way, the signal is enhanced.

However, after the signal is combined, the radiation angle of the beam becomes smaller. As a rod antenna, although the radial signal is still 360-degree coverage, the axial coverage angle is greatly reduced. In other words, the coverage of the rod-shaped high-gain antenna does not change. (In fact, after multiple inversions and attenuations, the attenuation of the signal on the antenna will reduce its emission function.) This is the conservation of energy. The principle is determined, but it is equivalent to thinning the entire signal, so that the signal coverage is increased, but the coverage height is reduced.









How many high-gain antennas do you need for home use?

Of course, what bothers you is that family routing requires high-gain antennas? High-gain antennas, can you immediately improve your home's WIFI signal? After the antenna of the SMA interface is replaced, the antenna replacement becomes simple. Then, the antennas with different gains are used to test the performance of their signals at home.

In the test, we chose three antennas, one is a conventional antenna with a nominal gain of 6dbi, and its length is basically the same as that of the original antenna. It is also the most frequently used antenna type when many DIY fans change antennas. The high-gain antenna with a length of 40cm and a nominal gain of 10dbi is favored by enthusiasts. It is believed to greatly improve the signal, but such a giant object is installed on the route, making the route feel top-heavy. As for the unconventional nominal gain of 17dbi antenna, the shape is more robust, of course, the price is also a lot higher, it is added, only to verify the home route, the higher the antenna gain, the better.



Point A: One meter or so in front of the route, without any obstacles, to test the transmission capability of the route. During the test, the signal strength changes are still very large, especially when changing the holding angle of the mobile phone and the tablet, the signal is often There will be more than a dozen dbw changes, mainly because of the change in the angle between the built-in antenna and the wireless signal, so that it accepts a great change in signal strength. This is also the difference between us using two routes and using the difference to determine the ability to generate.

As can be seen from the data, when using 6dbi and 9dbi gain antennas, the signal strength is enhanced by 1DB and 5DB compared to the original antenna, which is basically the theoretical difference of antenna gain. However, when testing the 17dbi gain antenna, there was an unexpected reversal. The 17dbi antenna not only did not enhance the signal, but also showed 4db and 2db attenuation. Why is this so? We believe that the biggest possibility is because the multiple spiral inverters and more radiated oscillators in the antenna create a great attenuation of the signal.

In this case, the signal strength does not rise and fall. Perhaps, in high-power routing, this situation will improve, and even the situation reverses, but at least, in the case of national regulations, the transmission power of the home router is only 100mW. The use of ultra-high-gain antennas in the home does not work, but may cause problems.

In the test process, we also found that the height of the handheld device has a great impact on the signal strength, especially when the angle between the device and the antenna is large, and when using a high-gain antenna, the signal strength will be greatly reduced, even Let the signal of the 10dbi antenna be lower than the original antenna. This is mainly because the signal emission angle is small when the antenna gain is high.

In this case, once the angle between the device and the antenna is large, the device will not receive the direct wave, but the reflected wave of the wall, and the signal will naturally attenuate greatly. This also tells us that if your HTPC, network top When using WIFI, and the placement distance is close to the route, pay attention to the height of the equipment, so as to improve the signal strength.



Point B: 4.5 meters away from the route, and separated by a load-bearing wall, this is also the use plan we often encounter. From the results, the 17dbi antenna encounters Waterloo again, which also confirms our idea that the structure of the high-gain antenna greatly attenuates the signal. The performance of the 6dbi antenna and the 10dbi antenna is basically normal, and the original antenna still maintains certain advantages.

In the test process, there is also a small discovery that once the person is standing between the route and the device, the signal will be seriously attenuated, and if the device is moved to the door direction even if it is only 50cm, the signal will increase by more than 10db. In fact, this also illustrates the problem that we often say the ability of the signal to penetrate the wall.

However, in many cases, the routing signal is not through the wall, but more by diffraction or reflection. In this case, it is not important whether the equipment or route, the linear distance has a bearing wall, Instead, it is as close as possible to the opening such as a window, which is easy to let the signal penetrate, so that it is beneficial to enhance the wifi signal.



Point C: The D power installed on the balcony is 6 meters away from the route. There are also two load-bearing walls. It is thought that the signal will decay rapidly, but the overall signal strength is limited. This should be attributed to the open-plan design of the balcony and the window near point C, which is good for signal transmission. In terms of specific performance, the 17dbi antenna will not be discussed, and the 10dbi antenna is still ahead of the original antenna, but the lead is further reduced, almost consistent with the 6dbi antenna.

In fact, this is closely related to the reflection transmission. After all, the high-gain antenna relies on reducing the radiation angle to obtain a stronger signal. However, after the reflection and refraction of these signals, the radiation angle will inevitably spread, and the signal intensity will follow. reduce. Therefore, in a complex multipath transmission environment indoors, the high gain obtained by controlling the direction and angle of the wave wave by the beam wave, with the increase of the transmission distance, the effect of the high gain when the refraction reflection becomes the main transmission mode, and Not obvious.




Summary: no need to replace the high gain antenna

From the test data, 17dbi's high-gain antenna can be completely eliminated from our catalog, and the low-power consumption of home routing and the high attenuation of ultra-high-gain antennas make it impossible to work. The 6dbi antenna, the overall signal has 1 ~ 2db improvement, it seems that there is less point, then, the key to purchase is the high-gain antenna around 10dbi, is not worth buying. Therefore, we hold the mobile phone and move it in every corner of the home, and use the signal intensity map of the WIFI analyzer to record the signals in different areas. In general, the ssid is the route of jfli when using the 10dbi antenna, the overall signal is ljf compared to the ssid. The route using the same model is slightly stronger, but the signal fluctuation is slightly larger.