Which statement about HF frequency is correct?

• A. HF covers 300-3000 MHz
• B. HF covers 3-30 MHz
• C. HF covers 0.3-3 MHz
• D. HF covers 30-300 MHz

Answer: (B)

High frequency refers to the portion of the radio spectrum from about 3 to 30 MHz. This band is known for ionospheric propagation, where signals are reflected by the ionosphere, allowing long-range communications beyond the horizon. That’s why HF is used for worldwide contact in maritime and military contexts, though performance depends on solar activity and time of day. The lower limit near 3 MHz marks the start of HF, while approaching 30 MHz changes the propagation characteristics and can reduce long-range reach. The other ranges listed correspond to different bands: roughly 0.3–3 GHz is UHF, 0.3–3 MHz is MF, and 30–300 MHz is VHF. So the 3–30 MHz range is the correct description of HF.