Ground wave propagation:

The type of propagation in which radio waves propagate from transmitting antenna to receiving antenna following the surface of the earth is called ground wave propagation.

Electromagnetic waves which are vertically polarized can travel by this mode.

The intensity at the signal falls with the distance as radio waves induce current in the ground over which they pass. As the wave propagate, the corresponding angle of tilt goes on increasing after a certain time the wave dies out.

Frequency at which ground waves travel is up to 1500 KHZ.

c = f.λ

wavelength, λ = 200m

Used for local broadcasting, ship communication etc.

Space wave propagation :

Space wave propagation can be achieved in the following 2 ways:

1) LOS Communication

2) Satellite Communication

Consider a TV antenna OP of height h. The transmitted signal cannot be received beyond points $R_1$ and $R_2$.

$OR_1$ and $OR_2$ are maximum distance from the antenna.

let $OR_1 = OR_2 = d$

from $∆PCR_1$

$CP^2 = PR_1^2 + (CR_1)^2 \\ (R + h)^2 = PR^2 + R^2 \\ In ∆POR, \\ PR_1^2 = h^2 + dr^2 \\ (R + h)^2 = h^2 + dr^2 + R^2 \\ R^2 + 2hR + h^2 = h^2 + dr^2 + R^2 \\ dr =\sqrt{2 R h_r} \text{(for transmission)} \\ \text{Similarly,} d_R =\sqrt{2 R h_R} \\ d = dr + dR$