lyhytaaltojen

Lyhytaaltojen refers to shortwave radio transmissions. These are radio waves with frequencies between 3 and 30 megahertz (MHz), corresponding to wavelengths between 10 and 100 meters. Shortwave radio is known for its ability to propagate over long distances, often thousands of kilometers, due to ionospheric reflection. This makes it suitable for international broadcasting, communication with ships and aircraft, and amateur radio. The ionosphere, a layer of Earth's upper atmosphere, reflects these radio waves back to the ground, allowing them to travel around the curvature of the Earth. The effectiveness of this reflection varies with the time of day, season, and solar activity. Different frequencies within the shortwave band are used for different purposes and are optimal at different times. International broadcasters like the BBC World Service, Voice of America, and Radio China International have historically used shortwave to reach audiences worldwide. While digital communication technologies have become more prevalent, shortwave radio remains an important medium for certain types of communication and for reaching areas with limited infrastructure.