Ham Amateur Radio Technician Practice Exam 2026 - Free Technician Practice Questions and Study Guide

A horizontal dipole HF antenna's height plays a crucial role in its radiation pattern, particularly regarding the elevation angles above 45 degrees. When the antenna is positioned less than 1/2 wavelength above the ground, the radiation pattern is close to omnidirectional, meaning it radiates equally in all directions in the horizontal plane. This omnidirectionality occurs because the antenna interacts more with the ground, causing the reflected waves to combine constructively across a wide azimuthal range.

As the height of the antenna increases, especially beyond 1/2 wavelength, the pattern begins to change and may exhibit directional properties at higher elevation angles, allowing for narrower and more effective radiation. However, the specific choice about omnidirectionality directly addresses the scenario when the antenna is less than 1/2 wavelength high, confirming that it radiates more uniformly across azimuthal angles in that configuration.

This principle underscores the relationship between antenna height and radiation patterns and explains why maintaining a specific height relative to wavelength can significantly influence performance and coverage in HF communications.