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

Explanation

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)` = 45 m and Height of receiving antenna `h_(R)` = O m.
Then, maximum distance between the two antennas,
`dm = sqrt(2Rh_(T))+sqrt(2Rh_(R))" "dm = sqrt(2 xx 6.4 xx 10^(6) xx 45)+sqrt(2 xx 6.4 xx 10^(6) xx 0)=3 xx 8 xx 10^(3)+0 = 24 km`.
Thus, the maximum distance between the antennas is 24 km.