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 81 m tall . How much service area can it cover if the receiving antenna is at the ground level ?

Explanation

No, it is not necessary for line of sight communication , the two antenna may not be at the same height .
Given, height of antenna h = 81 m
Radius of earth R = `6.4 xx 10^(6)` m .
Area `= pid^(2) ` , Range , d = `sqrt(2hR)`
`therefore` Service area = `pi xx 2h R = (22)/(7) xx 81 xx 2 xx 6.4 xx 10^(6) = 3258.5 km^(2)`.