Which of the following describes a simple dipole oriented parallel to Earth's surface?
The correct answer is B: A horizontally polarized antenna. A simple dipole oriented parallel to Earth's surface is a horizontally polarized antenna. Polarization refers to the orientation of the electric field of the radio wave. When a dipole is parallel to the ground (horizontal), it radiates horizontally polarized waves. For amateur radio operators, horizontal polarization is common for HF dipoles and many VHF/UHF antennas. Understanding polarization helps explain why antenna orientation matters and why matching polarization between transmit and receive antennas improves signal strength.
Exam Tip
Dipole parallel to ground = horizontally polarized. Think 'H'orizontal dipole = 'H'orizontally polarized. When the antenna is parallel to Earth's surface, the electric field is horizontal. Vertical polarization requires perpendicular orientation.
Memory Aid
"Dipole parallel to ground = horizontally polarized. Think 'H'orizontal dipole = 'H'orizontally polarized. Antenna parallel to Earth = horizontal polarization. Match polarization for best signal."
Real-World Application
You install a 20-meter dipole antenna with the wire running horizontally, parallel to the ground. This antenna is horizontally polarized - it radiates radio waves with horizontal electric fields. For best reception, the receiving antenna should also be horizontally polarized. If you used a vertical antenna, there would be polarization mismatch and signal loss.
Key Concepts
Why Other Options Are Wrong
Option A (Ground-wave antenna): Incorrect. Ground-wave refers to propagation along the Earth's surface, not antenna polarization. A horizontal dipole can be used for various propagation modes, not specifically ground-wave.
Option C (Travelling-wave antenna): Incorrect. A travelling-wave antenna is a specific antenna type (like a Beverage or long wire) where the wave travels along the antenna. A simple dipole is a standing-wave antenna, not a travelling-wave type.
Option D (Vertically polarized): Incorrect. A dipole parallel to the ground is horizontally polarized, not vertically polarized. Vertical polarization requires the antenna to be perpendicular to the ground.
题目解析
The correct answer is B: A horizontally polarized antenna. A simple dipole oriented parallel to Earth's surface is a horizontally polarized antenna. Polarization refers to the orientation of the electric field of the radio wave. When a dipole is parallel to the ground (horizontal), it radiates horizontally polarized waves. For amateur radio operators, horizontal polarization is common for HF dipoles and many VHF/UHF antennas. Understanding polarization helps explain why antenna orientation matters and why matching polarization between transmit and receive antennas improves signal strength.
考试技巧
Dipole parallel to ground = horizontally polarized. Think 'H'orizontal dipole = 'H'orizontally polarized. When the antenna is parallel to Earth's surface, the electric field is horizontal. Vertical polarization requires perpendicular orientation.
记忆口诀
Dipole parallel to ground = horizontally polarized. Think 'H'orizontal dipole = 'H'orizontally polarized. Antenna parallel to Earth = horizontal polarization. Match polarization for best signal.
实际应用示例
You install a 20-meter dipole antenna with the wire running horizontally, parallel to the ground. This antenna is horizontally polarized - it radiates radio waves with horizontal electric fields. For best reception, the receiving antenna should also be horizontally polarized. If you used a vertical antenna, there would be polarization mismatch and signal loss.
错误选项分析
Option A (Ground-wave antenna): Incorrect. Ground-wave refers to propagation along the Earth's surface, not antenna polarization. A horizontal dipole can be used for various propagation modes, not specifically ground-wave. Option C (Travelling-wave antenna): Incorrect. A travelling-wave antenna is a specific antenna type (like a Beverage or long wire) where the wave travels along the antenna. A simple dipole is a standing-wave antenna, not a travelling-wave type. Option D (Vertically polarized): Incorrect. A dipole parallel to the ground is horizontally polarized, not vertically polarized. Vertical polarization requires the antenna to be perpendicular to the ground.
知识点
Horizontal polarization, Dipole antennas, Antenna orientation, Polarization
Verified Content
Question from official FCC Technician Class question pool. Explanation reviewed by licensed amateur radio operators.