To achieve long-range radio transmissions, which waves are utilized?

Sky waves are indeed used for long-range radio transmissions because they can reflect off the ionosphere, allowing signals to travel beyond the horizon. This ionospheric reflection is particularly effective at certain frequencies, especially those in the HF (High Frequency) range, typically between 3 MHz and 30 MHz.

When radio waves are transmitted, they can travel at various angles to the ground, and sky waves are those that are directed upward and bounce back down to the Earth after interacting with the ionosphere. This phenomenon enables communication over vast distances, making it ideal for long-range transmissions.

In contrast, ground waves primarily travel along the surface of the Earth and are limited by the curvature of the Earth, making them more suitable for shorter distances. Direct waves, on the other hand, travel in a straight line from the transmitter to the receiver, which is effective for line-of-sight communication but not for long-range applications. The term "dark waves" does not have a recognized meaning in the context of radio transmission or communication systems.