lyhytaallon

Lyhytaalto, the Finnish term for shortwave, refers to the high-frequency portion of the radio spectrum used for long-distance communication. This range roughly covers 1.6 to 30 megahertz. Shortwave signals can travel great distances because they are refracted or reflected by the Earth’s ionosphere, enabling reception far beyond line of sight.

Propagation depends on ionospheric conditions, time of day, season, and solar activity. Skywave propagation enables intercontinental reception, while higher frequencies are often used during daytime and lower frequencies may perform better at night, depending on conditions. Antennas, transmission power, and local interference influence the practical reach and quality of reception.

Common applications include international broadcasting, amateur radio, maritime and aviation communications, and emergency services. International broadcasters such as the BBC World Service, Voice of America, and Radio France Internationale have historically used shortwave to reach audiences worldwide. In addition, many hobbyists listen to shortwave (SWLs) and operate amateur radio stations on HF bands.

Although the rise of satellite and internet communications reduced its prominence in many regions, shortwave remains in use for distant broadcasts, remote areas, and disaster communications. Governments, international organizations, and broadcasters maintain HF services for redundancy and reach, while hobbyists continue to explore propagation, antenna technology, and portable reception.