<P> Wireless communication uses electromagnetic waves to carry signals . These waves require line - of - sight , and are thus obstructed by the curvature of the Earth . The purpose of communications satellites is to relay the signal around the curve of the Earth allowing communication between widely separated points . Communications satellites use a wide range of radio and microwave frequencies . To avoid signal interference , international organizations have regulations for which frequency ranges or `` bands '' certain organizations are allowed to use . This allocation of bands minimizes the risk of signal interference . </P>
what type of energy do satellites generally use to communicate with earth
radio and microwave frequencies