Ham Radio General Class Practice Test

What is the low angle azimuthal radiation pattern of an ideal half-wavelength dipole antenna installed 1/2 wavelength high and parallel to the Earth?

1. It is a figure-eight at right angles to the antenna

2. It is a figure-eight off both ends of the antenna

3. It is a circle (equal radiation in all directions)

4. It has a pair of lobes on one side of the antenna and a single lobe on the other side

The correct answer is: It is a figure-eight at right angles to the antenna

The low angle azimuthal radiation pattern of an ideal half-wavelength dipole antenna installed at a height of half a wavelength and parallel to the Earth is characterized by a figure-eight shape at right angles to the antenna. This specific pattern arises because of the way the dipole radiates energy. When the dipole is oriented horizontally and elevated, it creates two main lobes of radiation on opposite sides of the antenna, corresponding to the areas directly perpendicular to the length of the dipole. The energy radiates most effectively in these directions, creating an area of low radiation directly above and below the antenna (the nulls). Thus, the pattern resembles a figure-eight when observed from above, with the lobes pointing outward in either direction from the ends of the dipole. In contrast, other options describe patterns that do not accurately reflect the dipole's behavior. A pattern described as a circle would imply equal radiation in all horizontal directions, which is not the case for a horizontally oriented dipole. The description of a figure-eight off both ends suggests a different orientation or configuration, while the mention of lobes on one side versus two on the other does not apply to a balanced half-wave dipole placed parallel to the ground. Understanding these principles of