What is the term for a straight electrical conductor measuring half a wavelength, fed at the center, and used as a basic balanced antenna?

What is the term for a straight electrical conductor measuring half a wavelength, fed at the center, and used as a basic balanced antenna?

• A. Yagi antenna
• B. Bluetooth antenna
• C. Wireless NIC
• D. Dipole antenna

Answer: (D)

A dipole antenna is a straight conductor about half a wavelength long that is fed at its center. This length makes it resonant at the operating frequency, causing currents to flow strongly in both halves in opposite directions. Because the feed is at the middle, the two arms form a balanced structure, so the feedline sees equal but opposite currents and, with a balun, tends to avoid unwanted currents on the outer conductor. Each arm is roughly a quarter-wavelength long, and the overall pattern is a donut-shaped radiation pattern around the wire, offering relatively broad radiation in the horizontal plane. The typical feed impedance in free space is near 73 ohms, which makes it a convenient standard radiator for many systems. Other options describe different things: a Yagi is a directional multi-element array, not the simple center-fed half-wavelength radiator; a Bluetooth antenna refers to a small, device-specific antenna for short-range comms; a wireless NIC is a network card, not an antenna type itself.

A dipole antenna is a straight conductor about half a wavelength long that is fed at its center. This length makes it resonant at the operating frequency, causing currents to flow strongly in both halves in opposite directions. Because the feed is at the middle, the two arms form a balanced structure, so the feedline sees equal but opposite currents and, with a balun, tends to avoid unwanted currents on the outer conductor.

Each arm is roughly a quarter-wavelength long, and the overall pattern is a donut-shaped radiation pattern around the wire, offering relatively broad radiation in the horizontal plane. The typical feed impedance in free space is near 73 ohms, which makes it a convenient standard radiator for many systems.

Other options describe different things: a Yagi is a directional multi-element array, not the simple center-fed half-wavelength radiator; a Bluetooth antenna refers to a small, device-specific antenna for short-range comms; a wireless NIC is a network card, not an antenna type itself.