The region covered by the useful range of a radiofrequency broadcast transmitter, such as a radio or television transmitter. The region is often represented pictorially on a service-area diagram.

The primary service area is the area within which satisfactory reception is possible, day or night, as a result of reception of the ground wave. The strength of the ground wave within this area is large compared to that of interference and indirect waves.

The secondary service area is the area within which satisfactory reception is possible using indirect waves. The strength of the ground wave within this area is attenuated to substantially less than the indirect waves.

The mush area is an area within which substantial fading or distortion of the received signal occurs. The unsatisfactory reception in this area results from interference either between waves from two or more synchronized transmitters or between direct and indirect waves from a single transmitter.