Question
Approximately how long is a Yagi’s driven element?
Answer Options
- A) 234 divided by frequency in MHz
- B) 1005 divided by frequency in MHz
- C) 1/4 wavelength
- D) 1/2 wavelength
Correct Answer: D
Explanation
A Yagi antenna is a linear array consisting of a driven element (the active radiator) and one or more parasitic elements (directors and reflectors). The driven element is the only part of the array that is directly connected to the feed line and must be resonant to function as the primary radiator.
Since the Yagi antenna operates on the principle of a resonant dipole, its driven element is approximately one-half wavelength long. This length ensures that the element resonates at the operating frequency and presents a manageable impedance (typically 50Ω to 75Ω at the feed point) to the transmission line.
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