Keskiaallot

Keskiaallot, also known as medium wave or simply MW, refers to a specific range of radio frequencies used for broadcasting. These frequencies typically fall between 300 kHz and 3 MHz on the radio spectrum. In many parts of the world, AM (Amplitude Modulation) radio stations broadcast within this band. The characteristic hum or static often associated with AM radio is a result of the way amplitude modulation encodes audio information onto a carrier wave.

The properties of medium waves make them suitable for medium-range broadcasting. During the day, signals tend to travel in a straight line from the transmitter to the receiver, with their range limited by the curvature of the Earth. However, at night, medium waves can bounce off the ionosphere, a layer of charged particles in the Earth's upper atmosphere. This phenomenon, known as skywave propagation, allows medium wave signals to travel much longer distances, sometimes thousands of kilometers, enabling reception of stations from far away.

The historical significance of medium waves is considerable. For much of the 20th century, it was the primary medium for public radio broadcasting, delivering news, entertainment, and music to widespread audiences. While FM (Frequency Modulation) broadcasting, with its generally superior audio quality and resistance to static, has become dominant for music, AM medium wave broadcasting remains relevant for talk radio, news, and in regions where its longer range and simpler receiver technology are advantageous. Interference from atmospheric conditions and other man-made electrical devices can affect the clarity of medium wave reception.