Is it necessary for a transmitting antenna to be at the same height as that of the receiving antenna for line-of-sight communication? A TV transmitting antenna is 81m tall. How much service area can it cover if the receiving antenna is at the ground level?
No, it is not necessary for a transmitting antenna and the receiving antenna to be at the same height. Because in this specific case of transmission there is no physical obstruction between the transmitter and the receiver.
(b) Height of the given antenna, h = 81 m
Radius of earth, R = 6.4 × 106 m
For range, d = (2Rh)1/2, the service area of the antenna is given by the relation:
A = π d2
= π (2Rh)
= 3.14 × 2 × 6.4 × 106 × 81 m2
= 3255.55 × 106 m2
~ 3256 km2
[As 1km = 103 m , so 1km2 = 106 m2]
4