Deep Dive: T9A03
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.
Why Other Answers 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.
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 Example
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.
Source & Coverage
Question Pool: 2022-2026 Question Pool
Subelement: T9A
Reference: 2022-2026 Question Pool · T9 - Antennas and feed lines
Key Concepts
Verified Content
Question from the official FCC Technician Class pool. Explanation reviewed by licensed amateur radio operators and mapped to the T9A topic.