Radiotransmission

Radiotransmission is the transmission of information through radio waves through space from a transmitter to a receiver without a physical medium. It is a fundamental form of wireless communication and forms the basis for most modern telecommunication systems.

In a typical radiotransmission system, an information signal is used to modulate a carrier wave produced by the transmitter. The modulated signal is amplified and radiated by an antenna. The receiver collects the signal with an antenna, removes the carrier, and restores the original information through demodulation. The performance depends on transmitter power, antenna design, and the propagation path.

Modulation methods include analog techniques such as amplitude modulation (AM), frequency modulation (FM), and phase modulation (PM), as well as digital schemes such as amplitude-shift keying (ASK), frequency-shift keying (FSK), phase-shift keying (PSK), and quadrature amplitude modulation (QAM). Modern systems often use combinations such as orthogonal frequency-division multiplexing (OFDM) and multiple-input multiple-output (MIMO).

Radiotransmission uses specific frequency bands allocated by governments and international bodies. Common bands include shortwave, VHF, UHF, microwave, and millimeter-wave ranges. Propagation is affected by frequency, atmospheric conditions, terrain, and obstacles. Line-of-sight limits range, while other modes such as ground wave or skywave extend reach beyond visual horizon.

Applications encompass broadcasting (radio and television), point-to-point links, mobile and cellular networks, wireless local area networks, satellite communications, radar, and remote sensing.

Regulation and standardization govern spectrum use, equipment certification, and interoperability. Organizations such as the International Telecommunication Union (ITU) coordinate international allocations, while national regulators issue licenses and enforce rules to manage interference and ensure efficient use of the radio spectrum.