HF radio band covers which range and characteristic?

• A. 3 MHz to 30 MHz; bounces off the ionosphere for global broadcasts
• B. 30 MHz to 300 MHz; used for local communications
• C. 300 kHz to 3 MHz; limited range
• D. 3000 MHz to 30 GHz; line-of-sight only

Answer: (A)

HF encompasses roughly 3 to 30 MHz. Its defining feature is ionospheric propagation: radio waves in this range can be refracted by the ionosphere and return to Earth, allowing signals to travel long distances and, under favorable conditions, reach across continents or the globe. This skywave mechanism is what enables global reach, unlike higher bands that are mostly line-of-sight and limited to local or regional ranges. The other ranges correspond to propagation modes that don’t support global broadcasts in the same way: the 30–300 MHz range is typically line-of-sight VHF, the 300 kHz–3 MHz range relies more on groundwave with limited reach, and the microwave region (several GHz and up) is also primarily line-of-sight. So the description of 3–30 MHz with ionospheric bounce for global reach is the best fit.