Ham Radio Extra Class Practice Test 2025 - Free Extra Class License Exam Questions and Study Guide

Diffraction is a phenomenon that occurs when a radio wave encounters an obstacle or an opening, allowing the wave to bend around it. Groundwave propagation is characterized by this diffraction effect, as it occurs along the surface of the Earth.

In the case of groundwave propagation, radio waves can take different paths due to obstacles such as buildings, trees, or hills. This bending enables the waves to follow the curvature of the Earth and reach receivers that may not be in a direct line-of-sight path from the transmitter.

This type of propagation is most commonly utilized for lower frequency signals, typically in the MF (Medium Frequency) and LF (Low Frequency) bands, where the groundwave can effectively travel over long distances.

The other types of propagation mentioned do not primarily rely on diffraction. Shortwave and skywave propagation typically involve reflections and refractions associated with the ionosphere, while spacewave propagation is focused on direct paths, such as line-of-sight communication, rather than bending around obstacles. Thus, the specific characteristics of groundwave propagation align naturally with the concept of diffraction.