A radio station is a site configured for broadcasting sound. Traditionally, radio stations have broadcast through the air via radio waves, a form of electromagnetic radiation, but today many stations broadcast via cable, local wire networks, or the Internet as well or instead of atmospheric broadcasting. Often stations are linked in radio networks.
KDKA of Pittsburgh, Pennsylvania (owned by Westinghouse) started broadcasting as the first commercial radio station on November 2, 1920. The first broadcast was the results of the U.S. presidential election, 1920.
Radio stations are of a number of types. The best known are the AM and FM stations, both commercial and "public", or nonprofit.
AM stations occurred first. AM refers to amplitude modulation, a mode of broadcasting radio waves, and occurs on commercial US airwaves in the frequency range of 530 to 1600 KiloHertz (thousand cycles per second). FM refers to frequency modulation, and occurs on commercial US airwaves in the frequency range of 88 to 108 MegaHertz (million cycles per second).
FM stations are nowadays much more popular in the developed countries, such as Europe and United States today, especially since higher musical fidelity and stereo broadcasting is possible in this format.
The emerging Digital Radio stations have started their transmissions, first in Europe – the UK and Germany, and later in the United States. The European system is named DAB, for Digital Audio Broadcasting, and public. In the United States, the system is named HD Radio and owned by a private company. It is expected that for the next 10-20 years, all these systems will co-exist, while from 2015 – 2020, the main system, at least in the developed countries, will be the digital radio.
Many other types of radio stations exist. These include:
- base stations for police, fire and ambulance networks
- military base stations
- dispatch base stations for taxis, trucks, and couriers
- emergency broadcast systems