Line-of-sight communication means that there is no physical obstruction between the transmitter and the receiver. In such communications it is not necessary for the transmitting and receiving antennas to be at the same height. Height of the given antenna, h = 81 m
Radius of earth, R = 6.4 × 106 m
For range, d = 2Rh, the service area of the antenna is given by the relation:
