Question

Name the type of waves which are used for line of sight (LOS) communications. What is the range of their frequencies?
A transmitting antenna at the top of a tower has a height of 20 m and the height of the receiving antenna is 45 m. Calculate the maximum distance between them for satisfactory communication in LOS mode.(Radius of the Earth $=6.4\times {10}^{6}m$)

Answer 1

Space waves are used for the line of sight (LOS) communication.
The range of their frequencies is 40 MHz and above .
We have height of transmitting antenna.
$h_T=20m$ and height of receiving antenna, height of tower $h_R=45m$
Then, maximum distance between the two antennas
$dm=\sqrt{2R{h}_T}+\sqrt{2R{h}_R}$
$=\sqrt{2\times 6.4\times {10}^6\times 20}+\sqrt{2\times 6.4\times {10}^6\times 45}$
$=2\times 8\times {10}^3+3\times 8\times {10}^3$
$=40km$
Thus, the maximum distance between the antennas is $40km$.