High-frequency

High-frequency (HF) is a term used to describe the range of radio frequency electromagnetic waves (radio waves) between 3 to 30 megahertz (MHz). It is also known as the decameter band or decameter wave as its wavelengths range from one to ten decameters (ten to one hundred meters). High-frequency radio waves are suitable for long-distance communication, by multiple skips off the ionosphere (skywave or "skip" propagation), thus including international broadcasts and communication with ships and aircraft.

Characteristics

High-frequency radio waves are used for a variety of purposes. They are used in shortwave broadcasting because they can be bounced off the ionosphere and travel great distances, even around the world. This makes them ideal for international broadcasting and communication with ships and aircraft.

High-frequency radio waves are also used in amateur radio, for emergency communications, and for certain types of radar systems. They can penetrate building walls and forests, but are absorbed by bodies of water and by heavy rainfall.

Propagation

High-frequency radio waves are propagated by skywave propagation, in which the waves are reflected or refracted back to Earth from the ionosphere, allowing communication around the curve of the Earth. This can be enhanced by layering of the ionosphere at night, which increases the distance that high-frequency radio waves can travel by skywave propagation.

Applications

High-frequency radio waves have many applications. They are used in shortwave broadcasting, amateur radio, and for emergency communications. They are also used in certain types of radar systems, and in some types of medical imaging and therapy.

See also

• Radio frequency
• Shortwave radio
• Amateur radio
• Ionosphere
• Skywave

References

High-frequency Resources
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