Broadcasting is the radio transmission of audio. It is a unidirectional broadcast transmission from a transmitter to all receiving equipment, the broadcast receivers or radios. The transmission can be analog, as in traditional broadcasting, but it can also be digital as digital broadcasting, Digital Audio Broadcast( DAB), and broadcast over terrestrial networks, cable distribution networks, and satellite.
Historically, terrestrial broadcasting of classical radio used the frequencies that were controllable at the time: long wave between 30 kHz and 300 kHz, medium wave between 300 kHz and 3 MHz, and short wave between 3 MHz and 30 MHz. In the frequency ranges mentioned, the audio signals are transmitted by means of amplitude modulation. VHF broadcasting, which was added later, uses the frequency range between 87.6 MHz and 108 MHz and transmits the signals in frequency modulation.
The transition from amplitude modulation in the LMK ranges (long, medium, short wave) to frequency modulation for VHF broadcasting was exclusively for qualitative reasons, which were due to the strong interference of AM modulation.
Common to all methods is the transmission technique, whereby the audio signal is modulated as a modulation signal of a higher transmission frequency. The audio signal itself can be a mono signal or a signal in stereophony. If several audio signals are transmitted, as in stereo, the carrier signal is modulated with the sum signal from the left and right channels and the difference signal is modulated onto a subcarrier.