Let's talk about what antenna gain is and whether it's better to have a larger gain.
Actually, it all depends on where the antenna is used. Just like a flashlight, if the reflector is removed, the flashlight will definitely not be as bright. But if an omnidirectional light source is needed to uniformly illuminate the room, removing the reflector and spreading the light evenly is obviously more suitable. Similarly, if the goal is to create a laser, then concentrating all the light from the bulb through a lens into a narrow laser beam is undoubtedly an improvement. But if the purpose is to illuminate the entire room, then this concentrated light is not very suitable.
The phenomenon of concentrating light in a specific direction is called directionality, and the degree of concentration is called gain. In the field of antennas, these two concepts are very similar to the behavior of light sources. Imagine if an antenna were like a candle, radiating energy uniformly in all directions, then it would be an isotropic radiator without directionality. On a technical level, this situation is called 0 dBi, which means that the radiated energy in each direction is the same.
Now, if a mirror is placed next to the candle, it will change the distribution of light energy and give the candle directionality. Mirrors make half of the room darker and the other half brighter because light is reflected and concentrated in one direction. This approach of enhancing energy in certain directions by stealing and redirecting energy from unfavorable directions is also applicable to antennas.
Therefore, for antennas, they do not generate radio energy, they simply transfer, guide, or concentrate it in a certain direction. This directional feature is called gain. A mirror can redirect half of the energy of a candle and make it appear twice as bright in certain directions, resulting in two candles. In this case, we say that the mirror provides a gain of 3 dB because it doubles the energy.
The unit of measurement for antenna gain mentioned here is decibels (dB). But it is usually relative to the reference antenna, usually using the radiation intensity of an omnidirectional antenna or half wave dipole antenna with the same input power in a certain direction as the reference value. When using an omnidirectional antenna as a reference, it is referred to as dBi (i-isotropic), and when using a half wave symmetric dipole antenna as a reference, it is referred to as dBd (d-dipole).
From the definition of antenna gain, we can understand that antenna gain refers to the ratio of the square of the field strength generated by the actual antenna and the ideal radiating element at the same point in space under the condition of equal input power, that is, the power ratio. It quantitatively describes the degree to which an antenna concentrates the input power for radiation.
The gain performance of an antenna in different directions is represented by the antenna gain pattern (or pattern), where the narrower the main lobe and the smaller the side lobes, the higher the gain.
All antennas exhibit a certain degree of directionality, and the variation of gain in different directions reflects this directionality. Even omnidirectional antennas have "blind spots" or "zeros" in their radiation patterns.
After understanding the true meaning of gain, we can better determine whether more or less gain is better for any specific application. A high gain antenna, like a flashlight, needs to point in a specific direction. Although antennas do not create new RF energy, their directional performance effectively sends signals to the target location.
However, if you want wireless signals to evenly cover the entire room, then you may not need gain or the directionality it brings. Because gain essentially "steals" radiation energy from certain directions to enhance signals in other directions.
