radio deadspot
With mobile radio, the radio link may be interrupted if there is no direct line of sight( LOS) between the transmitter and the receiving device.
Line of sight may be impaired by higher buildings or ground elevation. This is especially true if the structure is metal, such as a steel frame building. Under tunnels or bridges of steel structure construction also have the same effect, known as radio shadows or shadowing.
Shadowing also occurs in the studio when using wireless microphones, when the radio link between the transmitter and the wireless microphone is affected by walls or studio structures.