Terrestrial microwave transmission is when microwaves are used to transmit data. Because of the curve of the Earth's surface, the repeaters must be constructed every 30 miles.
This type of transmission is used for both television and radio. In both cases the signal will originate from a large parabolic dish set as high up as possible. These transmissions are normally made in the spectrum from 2 GHz up to 24 GHz. This allows for multichannel transmissions and a high bandwidth. These positive elements of terrestrial microwave transmission make up for the expense of constructing the repeater stations every 30 miles and dealing with frequency regulations.