Electric field intensity at finite distance from transmitter Antenna

Let us derive the relation of electric field intensity at finite distance from transmitter Antenna

If a horizontal Hertzian dipole antenna is used as a transmitter antenna above the horizon, then energy will travel like a wave in free space. Therefore, the amplitude of electric field vector in the radiation field can be given as : Continue reading “Electric field intensity at finite distance from transmitter Antenna”


Today we will discuss a very important relation related to wave propagation. The equation is known as Friis free space equation.

As only a small fraction of radiated power is received at the receiver from an isotropic radiator in free space, but the received signals, must be 10-20 dB above the receiver noise to complete the link between transmitter (TX) and receiver (RX) antenna. The amount of received power depends on transmitted power, gains of transmitter and receiver antennas and separation between them, operating frequency and path attenuation. Thus in order to describe the characteristics of wave propagation, it is necessary to derive equation relating to these parameters. The expression relating these parameters is known as Friis free space wave equation. Continue reading “FRIIS FREE SPACE EQUATION”

Transmission of radio waves

When a radio wave is radiated from the transmitting antenna, it spreads in all directions with decrease in amplitude with increasing distance because of spreading of the electromagnetic energy through larger surface areas and it follows inverse square law. This law states that the intensity of the radiating waves is inversely proportional to the square of the distance from the radiator.

Electromagnetic wave in the frequency spectrum of 0.001 to 1016 Hertz are termed as radio waves, but broadly speaking by radio waves, in this chapter, mean that band of electromagnetic energy which covers the frequency range from few kHz.