Which of the following is a basic resonant form of antennas?

Which of the following is a basic resonant form of antennas?

• A. Vertical
• B. Dipole
• C. Yagi
• D. Helical

Answer: (A)

A basic resonant radiator is a simple conductor length that supports a standing wave at the operating frequency. A vertical whip is the classic example: it’s essentially a quarter-wavelength monopole placed above a conductive surface. The ground plane acts as an image of the current, completing the circuit and allowing the system to resonate when the vertical length is about a quarter of the wavelength. This simple single-conductor form is the easiest to build and tune, and it radiates efficiently with vertical polarization, which is why it’s considered the basic resonant form. Dipoles are also resonant and fundamental, but they require two conductors and a different current distribution. A Yagi is a multi-element array built to direct energy, not a single resonant radiator. A helical antenna is a specialized form used for circular polarization and specific bandwidths.

A basic resonant radiator is a simple conductor length that supports a standing wave at the operating frequency. A vertical whip is the classic example: it’s essentially a quarter-wavelength monopole placed above a conductive surface. The ground plane acts as an image of the current, completing the circuit and allowing the system to resonate when the vertical length is about a quarter of the wavelength. This simple single-conductor form is the easiest to build and tune, and it radiates efficiently with vertical polarization, which is why it’s considered the basic resonant form.

Dipoles are also resonant and fundamental, but they require two conductors and a different current distribution. A Yagi is a multi-element array built to direct energy, not a single resonant radiator. A helical antenna is a specialized form used for circular polarization and specific bandwidths.