ARRL Technician Practice Exam

How would you change a dipole antenna to make it resonant on a higher frequency?

1. Lengthen it

2. Shorten it

3. Change its orientation

4. Add a matching network

The correct answer is: Shorten it

To make a dipole antenna resonant at a higher frequency, you would shorten its length. The resonance frequency of a dipole antenna is inversely related to its physical length; as the length decreases, the frequency at which it resonates increases. This principle is rooted in the antenna's ability to effectively radiate electromagnetic waves, which is influenced by its size in relation to the wavelength of the signal. When shortening the dipole, you make it better suited to operate effectively at the desired higher frequency, thus maximizing its performance. Adjusting its length allows you to bring the resonant frequency of the antenna closer to the frequency of the signals you wish to transmit or receive. Changing the orientation of the antenna or adding a matching network wouldn’t inherently adjust the frequency at which the dipole is resonant; these options might affect radiation pattern or impedance matching, but would not directly address the core requirement of tuning the antenna to a higher frequency.