Wireless Propagation Modes Explained

This page describes wireless propagation modes, outlining the differences between Ground wave propagation, Sky wave propagation, and Line-of-Sight propagation.

Ground Wave Propagation

Ground Wave Propagation

Frequencies up to about 2 MHz fall into this category of propagation. Here, waves follow the contour/curvature of the Earth. This is due to electromagnetic (EM) waves inducing current in the Earth’s surface. This induced current causes the wavefront to bend towards the Earth, allowing it to follow and propagate along the Earth’s surface.

Typical applications include:

• AM radio broadcasting
• Direction finding
• Submarine communication
• Home control systems
• Analog telephone lines
• Long-range navigation

Sky Wave Propagation

Sky wave Propagation

Frequencies between 2 MHz and 30 MHz fall into this category of propagation. In this mode, the ionosphere above the Earth’s surface reflects the transmitted wave, enabling propagation due to reflection.

Typical applications include:

• Amateur radio
• CB radio
• International broadcasting
• Military communication
• Long-range aircraft/ship communication

Line-of-Sight (LOS) Propagation

Line of Sight Wave Propagation

Frequencies above 30 MHz fall into this category of propagation. Signals above 30MHz are generally not reflected by the ionosphere, and transmission relies on a line-of-sight concept.

For satellite applications, signals are transmitted from an earth station antenna to the satellite antenna. For ground-based wireless links, communication occurs when both the transmit (Tx) and receive (Rx) antennas are within each other’s line of sight.

Typical applications include:

• VHF/UHF television
• FM broadcast
• Optical communication
• Infrared LANs
• Terrestrial wireless links
• Radar
• Cellular telecom
• PCS (Personal Communications Service)
• WLL (Wireless Local Loop)