Microwave Communication - Spatial Diversity

A sharply defined beam of microwave transmissions means that separate signals can use the same range of frequencies without mutual interference if the paths are carefully planned. Lower radio-frequency assignments can accommodate fewer users because longer-wavelength signals cannot be confined to a narrow beam. A relative immunity to interference allows each microwave signal to use a very wide bandwidth. Wider bandwidths are required when more information per second is transmitted.

It is common practice to locate microwave receivers and transmitters atop high buildings when hilltops or mountain peaks are not available. The higher the antennas are raised, the further will be the distance to the radio horizon. It takes many ground-based relay "hops" to carry a microwave signal across a continent. Since the 1960s the United States has been spanned by a network of microwave relay stations.