Which value is used to denote the high-frequency (HF) range in megahertz?

• A. 3 to 30
• B. 30 to 300
• C. 300 to 3000
• D. 0.3 to 3

Answer: (A)

High-frequency radio communications use ionospheric reflection to reach far beyond the transmitter’s line of sight. The HF band is defined as 3 to 30 megahertz, where signals can be refracted or reflected by the ionosphere, enabling long-distance, world-wide communication for ships at sea. Frequencies below this range don’t provide the same reliable long-range skywave propagation, while frequencies above this range tend to travel mainly by line of sight. So the 3 to 30 MHz range is the one that enables HF propagation and long-range reach.