What is a beam antenna?
The correct answer is C: An antenna that concentrates signals in one direction. A beam antenna is an antenna that concentrates signals in one direction, providing gain in the forward direction while reducing radiation in other directions. Beam antennas include Yagis, quads, and other directional designs. The 'beam' refers to the focused radiation pattern, like a searchlight beam. For amateur radio operators, beam antennas provide significant advantages: they increase effective radiated power in the desired direction, reduce interference from other directions, and improve signal-to-noise ratio. Understanding beam antennas helps when selecting antennas for DX work and interference reduction.
Exam Tip
Beam antenna = concentrates signals in one direction. Think 'B'eam = 'B'right 'B'eam of radiation. Directional antenna with gain in forward direction. Not about construction materials, not omnidirectional, not phase reversal.
Memory Aid
"Beam antenna = concentrates signals in one direction. Think 'B'eam = 'B'right 'B'eam of radiation. Directional antenna with gain - focuses power in desired direction, reduces radiation elsewhere."
Real-World Application
You install a 3-element Yagi beam antenna for 20 meters, pointing it toward Europe. The beam concentrates your signal toward Europe, giving you significant gain in that direction while reducing radiation toward other directions. This increases your effective power toward Europe and reduces interference from other directions. The focused 'beam' of radiation is what makes it a beam antenna.
Key Concepts
Why Other Options Are Wrong
Option A: Incorrect. Beam antennas aren't built from aluminum I-beams - that's a construction material, not what defines a beam antenna. Beam refers to the radiation pattern, not construction materials.
Option B: Incorrect. Beam antennas are directional, not omnidirectional. An omnidirectional antenna radiates equally in all directions, opposite of a beam.
Option D: Incorrect. Beam antennas don't reverse signal phase - they focus radiation in one direction. Phase reversal isn't a beam antenna characteristic.
题目解析
The correct answer is C: An antenna that concentrates signals in one direction. A beam antenna is an antenna that concentrates signals in one direction, providing gain in the forward direction while reducing radiation in other directions. Beam antennas include Yagis, quads, and other directional designs. The 'beam' refers to the focused radiation pattern, like a searchlight beam. For amateur radio operators, beam antennas provide significant advantages: they increase effective radiated power in the desired direction, reduce interference from other directions, and improve signal-to-noise ratio. Understanding beam antennas helps when selecting antennas for DX work and interference reduction.
考试技巧
Beam antenna = concentrates signals in one direction. Think 'B'eam = 'B'right 'B'eam of radiation. Directional antenna with gain in forward direction. Not about construction materials, not omnidirectional, not phase reversal.
记忆口诀
Beam antenna = concentrates signals in one direction. Think 'B'eam = 'B'right 'B'eam of radiation. Directional antenna with gain - focuses power in desired direction, reduces radiation elsewhere.
实际应用示例
You install a 3-element Yagi beam antenna for 20 meters, pointing it toward Europe. The beam concentrates your signal toward Europe, giving you significant gain in that direction while reducing radiation toward other directions. This increases your effective power toward Europe and reduces interference from other directions. The focused 'beam' of radiation is what makes it a beam antenna.
错误选项分析
Option A: Incorrect. Beam antennas aren't built from aluminum I-beams - that's a construction material, not what defines a beam antenna. Beam refers to the radiation pattern, not construction materials. Option B: Incorrect. Beam antennas are directional, not omnidirectional. An omnidirectional antenna radiates equally in all directions, opposite of a beam. Option D: Incorrect. Beam antennas don't reverse signal phase - they focus radiation in one direction. Phase reversal isn't a beam antenna characteristic.
知识点
Beam antennas, Directional antennas, Antenna gain, Radiation patterns
Verified Content
Question from official FCC Technician Class question pool. Explanation reviewed by licensed amateur radio operators.