Radio line of sight (LoS) refers to the direct visual path between a transmitting
antenna and a receiving antenna without any obstacles blocking the signal. This
characteristic is crucial for the propagation of electromagnetic waves, particularly
at higher frequencies (above 30 MHz, such as VHF and UHF bands).
In line-of-sight propagation, the radio waves travel in a straight line from the
source to the receiver. Any obstruction, such as buildings, trees, or terrain, can
block or disrupt the signal. The farthest possible point of propagation in line-of-
sight communication is known as the "radio horizon.”
For optimal line-of-sight propagation, it is essential to keep the path between the
antennas clear of obstructions. Objects within the Fresnel zone, an elliptical area
around the direct line-of-sight path, can also disturb the signal even if they do not
block the geometric line between the antennas1. Raising the height of either or
both antennas can help reduce signal loss and improve communication range.
Line-of-sight propagation is commonly used in various applications, including
television broadcasting, mobile networks, and point-to-point communication
systems.