Radio

Radio is the radiation (wireless transmission) of electromagnetic signals through the atmosphere or free space at light speed

How Radio Works & Usages
Information is carried by systematically changing (modulating) some property of the radiated waves, such as their amplitude, frequency, phase, or pulse width. When radio waves strike an electrical conductor, the oscillating fields induce an alternating current in the conductor. The information in the waves can be extracted and transformed back into its original form.

Radio frequencies occupy the spectrum from 3 kHz to 300 GHz, although commercially important uses of radio use only a small part of this spectrum. These frequencies are used to transmit data for multiple uses. Uses include Audio, Telephony, Video, Navigation, Radar, Data (digital radio), Heating, Amateur radio service, Unlicensed radio services and Radio control (RC).

Disadvantages
Once generated, electromagnetic waves travel through space either directly, or have their path altered by reflection, refraction or diffraction. The intensity of the waves diminishes due to geometric dispersion (the inverse-square law); some energy may also be absorbed by the intervening medium in some cases. Noise will generally alter the desired signal; this electromagnetic interference comes from natural sources, as well as from artificial sources. Noise is also produced at every step due to the inherent properties of the devices used. If the magnitude of the noise is large enough, the desired signal will no longer be discernible; this is the fundamental limit to the range of radio communications. Radio is also “line of sight”, meaning that intervening objects (structures, mountains, planetary curvature) will weaken or block the signal.