Name the type of wave which are used for line of slight (LOS) communication. What is the range of their frequencies?
A transmitting antenna at the top of a tower has a hight 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 xx 10^(6)`m)

Explanation

These waves are space waves. The frequency range is from about 30 MHz to 300 MHz and higher.
The maximum distance between the two towers
`= 2sqrt(2R)(sqrt(H) + sqrt(h)) = sqrt(2 xx (6.4 xx 10^(6)))xx ( sqrt(20) + sqrt(45))`
= 40000 m = 40 km