radiosignal

A radio signal is an electromagnetic wave used to convey information over a distance. It is typically produced by modulating a carrier wave at a radio frequency with an information signal, such as sound, video, or data.

Transmitter chain includes an oscillator that generates the carrier, a modulator that imposes the information, a power amplifier, and an antenna. Common modulation methods include amplitude modulation (AM), frequency modulation (FM), and phase modulation (PM); digital schemes include PSK, QAM, FSK. The choice of modulation affects bandwidth, power efficiency, and robustness.

Radio signals propagate through space via line-of-sight, ground waves, or ionospheric reflection (skywave). Frequency bands from longwave to microwave exhibit different propagation characteristics. Higher frequencies offer higher data rates but shorter range and greater atmospheric attenuation. Bandwidth and spectral occupancy are regulated and allocated by authorities.

A receiver uses an antenna and front-end circuit to extract the modulated signal, then demodulates to recover the information. Radio link quality is described by signal strength, noise, interference, and signal-to-noise ratio. Practical systems use filters, error detection/correction, retransmission, and multiple access techniques.

Applications include radio broadcasting, point-to-point communications, mobile networks, Wi‑Fi and Bluetooth, satellite communications, radar, and telemetry.

Standards and regulation are managed by organizations such as the ITU, and national agencies allocate spectrum licenses and emission limits to avoid interference. Measurements use parameters such as carrier frequency, bandwidth, modulation type, SNR, and BER.