How does antenna height affect the azimuthal radiation pattern of a horizontal dipole HF antenna at elevation angles higher than about 45 degrees?

The height of a horizontal dipole above the ground significantly alters its radiation pattern due to ground reflections interacting with the direct radio wave. When a dipole is placed lower than 1/2 wavelength above the ground, much of the radiation is reflected straight up. At high elevation angles (above 45 degrees), this upward reflection creates an azimuthal pattern that is nearly omnidirectional. This effect is often exploited for Near Vertical Incidence Skywave (NVIS) communication, which provides reliable, omnidirectional regional coverage. If the antenna is raised to 1/2 wavelength or higher, this high-angle radiation decreases dramatically, and the classic broadside figure-eight pattern becomes much more distinct at lower takeoff angles.