The height of transmitting antenna and receiving antenna are 45 m and 80 m. If the radius of earth is $6.4 × 10^6m$. Then the maximum distance between the two antennas for satisfactory communication in LOS mode is:

56 Km

The correct answer is Option (1) → 56 Km

To calculate the maximum distance between two antennas for satisfactory line of sight (LOS) communication (d), we can use the formula for distance to the horizon.

$d=\sqrt{2RH_1}+\sqrt{2RH_2}$

where,

R, Radius of earth = $6.4×10^6m$

$h_1$, height of transmitting antenna = 45 m

$h_2$, height of receiving antenna = 80 m

$d=\sqrt{2×6.4×10^6×45}+\sqrt{2×6.4×10^6×80}$

$=\sqrt{576×10^6}+\sqrt{1024×10^6}$

$=24000m+32000m$

$=56000m=56km$