The wireless signal received by the wireless terminal is transmitted through a built-in or external antenna in the wireless AP. Looking at the wireless AP in the market, you will find there is an important parameter indicator, that is, the antenna gain, looks like a very professional, very advanced word, but you know what this means? Why does a wireless AP have to use a booster antenna?

Antenna gain

    Refers to the ratio of the power density of the signal generated by the antenna and the ideal radiating element at the same point in space under the same input power conditions. The gain of the antenna can be used to describe the degree of radiation concentration of an antenna input power. In general, increasing the antenna gain mainly depends on reducing the vertical facing radiation width while maintaining the omnidirectional radiation performance on the horizontal plane, so increasing the gain can increase the network coverage in a certain direction. The antenna gain can be represented by dBi.

    In other words, under the same conditions, the higher the gain, the farther the wireless signal travels. The author personally experienced Fengrunda's in-wall AP and ceiling-mounted AP. The model does not remember, only remember that the former gain is 3dBi, the latter is 5dBi, and the latter's transmission distance is indeed farther than the former (the same distance, the latter has Signal, the former does not).

What is dBi

    dBi is the unit of antenna gain. The reference is an omnidirectional antenna. We can simply understand it as the radiation ability of the antenna in all directions. Through the following picture, we can clearly see that as the gain of the antenna increases, the lobe width becomes smaller and smaller, and the propagation distance increases.

In simple terms, when the transmit power is the same, the wireless signal transmitted by the 3dBi booster antenna is shaped like “()”, much like a semicircle. The 5dBi antenna, which emits a signal similar to "<>", is more like a flattened oval.

    The higher the gain, the smaller the vertical angle, which clearly shows the relationship between the coverage area and the shielding angle. Therefore, if used within a certain range, the gain of 3-5 dBi is beneficial to signal reception. It would be a mistake to know how to say that wireless APs will increase the number of antennas and think that it will bring better results. The antenna gain is not as great as possible.

    In normal circumstances, the antenna gain of the indoor AP does not exceed 5 dBi, while the antenna gain of the outdoor AP can exceed 5 dBi.