The HF radio provides long-range OTH communications and operates in which band?

• A. VHF band
• B. UHF band
• C. HF band
• D. SHF band

Answer: (C)

Long-range, beyond-the-horizon communications rely on radio waves that bounce off the ionosphere. The frequency range that makes this skip propagation practical is the HF band, about 3 to 30 MHz. At these wavelengths, signals can reflect off the ionospheric layers (especially the F layer) and return to Earth, allowing transmissions to travel thousands of kilometers depending on the time of day and ionospheric conditions.

Higher bands like VHF and UHF are generally limited to line-of-sight paths; they don’t reflect well off the ionosphere and are more easily blocked by the terrain. SHF lies even higher in frequency and is typically used for point-to-point links and satellite or radar applications, requiring direct paths rather than ionospheric reflection.

So for long-range OTH communications, the HF band is the appropriate choice.