Different types of unguided media include transmissions for radio, satellite, wireless computer networks and cellphones. In general, unguided media describes every kind of wireless communication, because these transmissions are achieved through the use of antennas between two sources of electromagnetic radiation.
Unguided media can be directional, meaning the transmission can be point-to-point focused beams using high frequencies. Electromagnetic beams that are omnidirectional use waves that propagate in all directions using signals with lower frequencies.
Broadcast radio is an example of an omnidirectional unguided medium because it goes out in every direction. Radio transmissions are usually between the frequencies of 30 megahertz and 1 gigahertz. These waves start from a central antenna, and then multitudes of receiving antennae pick up the transmission.
Microwave transmissions are often point-to-point transmissions because the frequencies are higher, and the transmissions are more exact. For instance, some satellite communications use microwave frequencies between 2 and 40 gigahertz. These transmissions start at a satellite dish on the ground, beam up to an orbiting satellite and are retransmitted back to another satellite dish on the Earth's surface. Terrestrial microwave transmissions occur between two antennae on the surface, since microwaves bend with the curvature of the Earth.
Unguided media can travel through air, water and the vacuum of space. Contrarily, guided media travels along a physical substance such as a wire, Internet cable or coaxial cable that provides direction for the transmission of information.