What is the frequency range of HF?

The correct frequency range for High Frequency (HF) is from 3 to 30 Megahertz (MHz). This range is critical for various forms of communication, including long-distance radio broadcasts and amateur radio. HF radio waves are especially known for their ability to reflect off the ionosphere, which allows for communication over great distances, especially beyond the horizon.

The utility of this frequency range comes from the physics of radio wave propagation, where frequencies lower than this range, such as Very Low Frequency (VLF) or Low Frequency (LF), have different propagation characteristics and are typically limited to much shorter communication distances.

Understanding the distinction between MHz and kHz is also important, as MHz represents megahertz, where 1 MHz equals 1,000 kHz. The other choices do not accurately define HF, as they either fall outside the designated HF range or mistakenly represent the units involved, illustrating the necessity of precise terminology in radio frequency applications.