What is the primary function of antenna traps?
The correct answer is A: To enable multiband operation. The primary function of antenna traps is to enable multiband operation. Traps are resonant circuits that isolate parts of the antenna at different frequencies, allowing one antenna to work on multiple bands. For amateur radio operators, this is why trapped antennas are popular. Understanding this helps when using multiband antennas.
Exam Tip
Antenna trap function = enable multiband operation. Think 'T'rap = 'T'unes 'R'esonant 'A'ntenna 'P'arts. Traps are resonant circuits that isolate parts of antenna at different frequencies, allowing multiband operation. Not notching, not balanced impedance, not out-of-band prevention - just multiband operation.
Memory Aid
"Antenna trap function = enable multiband operation. Think 'T'rap = 'M'ultiband. Traps are resonant circuits that isolate parts of antenna at different frequencies, allowing multiband operation. Primary function of traps."
Real-World Application
A trapped antenna: Traps (LC resonant circuits) are placed along the antenna. At one frequency, a trap is high impedance, isolating the outer section. At another frequency, the trap is low impedance, allowing the full length to be used. This enables one antenna to work on multiple bands (e.g., 20m and 40m). This is the primary function of traps - multiband operation.
Key Concepts
Why Other Options Are Wrong
Option B: Incorrect. Traps don't notch spurious frequencies - they enable multiband operation, not filtering. Notching isn't the function.
Option C: Incorrect. Traps don't provide balanced feed point impedance - they enable multiband operation. Balanced impedance isn't the function.
Option D: Incorrect. Traps don't prevent out-of-band operation - they enable multiband operation. Out-of-band prevention isn't the function.
题目解析
The correct answer is A: To enable multiband operation. The primary function of antenna traps is to enable multiband operation. Traps are resonant circuits that isolate parts of the antenna at different frequencies, allowing one antenna to work on multiple bands. For amateur radio operators, this is why trapped antennas are popular. Understanding this helps when using multiband antennas.
考试技巧
Antenna trap function = enable multiband operation. Think 'T'rap = 'T'unes 'R'esonant 'A'ntenna 'P'arts. Traps are resonant circuits that isolate parts of antenna at different frequencies, allowing multiband operation. Not notching, not balanced impedance, not out-of-band prevention - just multiband operation.
记忆口诀
Antenna trap function = enable multiband operation. Think 'T'rap = 'M'ultiband. Traps are resonant circuits that isolate parts of antenna at different frequencies, allowing multiband operation. Primary function of traps.
实际应用示例
A trapped antenna: Traps (LC resonant circuits) are placed along the antenna. At one frequency, a trap is high impedance, isolating the outer section. At another frequency, the trap is low impedance, allowing the full length to be used. This enables one antenna to work on multiple bands (e.g., 20m and 40m). This is the primary function of traps - multiband operation.
错误选项分析
Option B: Incorrect. Traps don't notch spurious frequencies - they enable multiband operation, not filtering. Notching isn't the function. Option C: Incorrect. Traps don't provide balanced feed point impedance - they enable multiband operation. Balanced impedance isn't the function. Option D: Incorrect. Traps don't prevent out-of-band operation - they enable multiband operation. Out-of-band prevention isn't the function.
知识点
Antenna traps, Multiband operation, Resonant circuits, Frequency isolation
Verified Content
Question from official FCC General Class question pool. Explanation reviewed by licensed amateur radio operators.