What term describes the reflection of radio waves from the ionosphere?

The term that describes the reflection of radio waves from the ionosphere is "Skywave propagation." This type of propagation occurs when radio waves are transmitted at angles that allow them to travel upward into the ionosphere, where they are reflected back down to Earth. The ionosphere acts like a mirror for certain frequencies of radio waves, particularly in the HF (High Frequency) band, which allows for long-distance communication.

Skywave propagation is particularly effective for communications over distances that exceed the horizon, making it a vital aspect of amateur radio operation and other forms of radio communication. This propagation mode can enable signals to bounce off the ionosphere, covering greater distances than what would be possible with line-of-sight or groundwave propagation alone.

Groundwave propagation, on the other hand, refers to the travel of radio waves along the surface of the Earth. Line-of-sight propagation means that the communication path is unobstructed, typically used for VHF and UHF frequencies. Direct wave propagation involves signals traveling directly from transmitter to receiver without the influence of the ionosphere or other reflecting mediums.

Understanding these different propagation methods is crucial for amateur radio operators to effectively communicate over varying distances and conditions.