Longwave

Diagram showing amplitude (a) and wavelength (b).

In radio, longwave (or long wave) refers to parts of the radio spectrum that has longer wavelengths. These are typically kilometer-sized or greater. The term is a historic one dating from the early 20th century. This was when the radio spectrum was considered to consist of long, medium and short wavelengths. Most modern radio systems and devices use wavelengths which would then have been called 'ultra-short'. For radio broadcasting is it the radio band between 30 kHz-299 kHz.

Longwaves have the advantage that diffraction helps them travel far.