Question

What is ground wave propagation? Discuss.

Hint:

Ground waves follow the Earth's curve for reliable, steady short-range communication. Sky waves bounce off the ionosphere for long-distance communication, while Space waves travel in straight lines-of-sight (VHF/UHF).

Answer 1

Step 1: Defining Ground Wave Propagation:
Ground wave propagation (also known as surface wave propagation) is a method of radio wave transmission where electromagnetic waves travel along the surface of the Earth, following its physical curvature.

Step 2: Analyzing the Propagation Mechanism:

• As the wave travels, it interacts with the Earth's surface, inducing electric currents in the ground. This conducting ground acts as a guide for the wave.
• Attenuation: Because the ground has electrical resistance, energy is absorbed from the wave as it travels. This causes ground waves to lose strength (attenuate) rapidly as distance increases, especially over dry, non-conducting surfaces like desert sand.

Step 3: Discussing Key Parameters and Applications:

• Frequency Limits: It is highly effective at Low Frequencies (LF) and Medium Frequencies (MF), typically ranging from $30\text{ kHz}$ to $3\text{ MHz}$. High frequencies are not propagated this way because they are quickly absorbed by the ground.
• Polarization Requirement: Vertically polarized antennas must be used. Horizontal polarization cannot be used because the electric field would be short-circuited by the Earth's surface.
• Use Cases: Widely used for local AM radio broadcasting, maritime communications (where salt water acts as an excellent conductor, extending the range), and tactical short-range military communications.