What is the effect of an antenna's gain?

An antenna's gain primarily describes its ability to focus radiated energy in a particular direction, which enhances signal strength in that direction compared to an isotropic radiator—an idealized antenna that radiates energy uniformly in all directions. This focusing effect allows for more effective communication over longer distances or in specific areas, as the energy is concentrated rather than spread out.

In practical terms, a higher gain can significantly improve the performance of a communication system by allowing signals to be transmitted further away or received more clearly from a specific direction. As a result, antennas with higher gain are often used for applications that require long-distance communication or precise directional transmission and reception. This characteristic makes gain an important factor in the design and selection of antennas for various amateur radio operations and other communications technologies.

The other options do not accurately describe the function of gain. For example, reducing range or interference does not directly relate to the concept of gain, as these are influenced by other factors in the communication system.