What frequency range supports sky wave propagation?

Sky wave propagation, also known as high-frequency (HF) propagation, primarily occurs in the frequency range of approximately 3 to 30 MHz, where the ionosphere can effectively reflect radio waves back to Earth. Within this range, the effective frequencies for sky wave propagation tend to be found in the lower end, approximately 2 to 12 MHz, which allows for better long-range communications, especially under different atmospheric conditions.

The ionosphere reflects these frequencies, enabling signals to travel over the horizon, making them suitable for long-distance communication. Frequencies below or above this range may not effectively utilize the ionosphere's reflective properties, limiting their long-range capabilities. Thus, the choice pertaining to the frequency range of 2-12 MHz accurately identifies the optimal frequencies for sky wave propagation.