ARRL Technician Practice Exam

In which direction is the radiation strongest from a half-wave dipole antenna in free space?

1. End fire to the antenna

2. Broadside to the antenna

3. Perpendicular to the axis of the antenna

4. Along the length of the antenna

The correct answer is: Broadside to the antenna

A half-wave dipole antenna is designed to radiate radio frequency energy efficiently. Its radiation pattern is key to understanding where the signal is strongest. The radiation is strongest broadside to the antenna, meaning that it radiates most intensely in a plane that is perpendicular to its length. This strong radiation occurs because of constructive interference of electromagnetic waves emitted from the two halves of the dipole. As you move perpendicular to the length of the antenna, these waves combine in such a way that they strengthen each other, resulting in higher intensity. Conversely, in the direction along the length of the antenna—sometimes referred to as the "end fire" direction—the waves tend to cancel out, leading to less radiation intensity. Therefore, a dipole antenna radiates more effectively and with greater strength when you are aligned broadside to it, allowing for optimal communication range in that direction.