What is the line of sight communication? (ii) Why is it not possible to use sky waves for transmission of T.V. signals? Upto what distance can a signal be transmitted using an antenna of height h?

Explanation

(i) Line of sight communication is one in which
electromagnetic waves travel in straight path
between transmitting and receiving device.
Microwaves are propagated in this manner.
(ii) TV signals have frequency range of 54 MHz
to 890 MHz. They cannot be reflected by
ionosphere, rather they pass through the
ionosphere. that is why the TV signals can not
be transmitted via sky waves.
The coverage range of a TV signal transmitted
from an antenna of height `h_(T)` and received by a
receiving antenna of height `h_(R)` is
`d_(M) = sqrt(2Rh_(T)) + sqrt(2Rh_(R))`
where R is the radius of the earth.