Question

What is space wave propagation? State the factors which limit its range of propagation. Derive an expression for the maximum line of sight distance between two antennas for space wave propagation.

Answer 1

When a wave propagates in a straight line, from the transmitting antenna to the receiving antenna, its 'mode of propagation' is called space wave communication.

Space waves are used for the Line of Sight (LOS) communication. Space wave communication involves the transmission from transmitter, traveling along a straight line in space, reaches to receiving antenna. The range of their frequencies is 40 MHz and above. The range of space wave propagation is limited by line of sight distance between transmission to receiver /repeater antenna.

From figure, the range of antenna PC is PA.

Using Pythagoras theorem

$(R+h{)}^2=P{A}^2+R^2$

$⟹PA=\sqrt{h^2+2Rh}$

$\approx \sqrt{2Rh}(h<<R)$