The frequency range 3-30 MHz. HF radio waves often propagate by bouncing off the ionosphere, allowing communication between continents. This tag may also be used for questions about the 160 meter band (1.8 MHz), which while not HF is often referred to as such due to its similar propagation.
Radio frequencies are commonly divided into ranges by frequency. Here are some of the ranges:
- Medium Frequency (MF), 300 kHz - 3 MHz
- High Frequency (HF), 3 - 30 MHz
- Very High Frequency (VHF), 30 - 300 MHz
HF frequencies have been used since the very earliest days of radio, and the HF bands remain very popular in amateur radio. HF radio signals often bounce off the ionosphere, allowing communication far beyond line-of-sight ranges; ham radio contacts between continents are common.
More information about HF is available at Wikipedia.