What is the approximate length for a 1/2 wave dipole antenna cut for 3.550 MHz?
The correct answer is C: 132 feet. The approximate length for a 1/2 wave dipole antenna cut for 3.550 MHz is 132 feet. Length = 468/f (MHz) = 468/3.550 = 131.83 feet ≈ 132 feet. For amateur radio operators, this is a basic dipole length calculation. Understanding this helps when building dipoles.
Exam Tip
1/2 wave dipole at 3.55 MHz = 468/3.55 = 132 feet. Think 'D'ipole 'L'ength = '4'68/'F'requency. Length = 468/f (MHz) = 468/3.550 = 132 feet. Not 42 ft, not 84 ft, not 263 ft - just 132 feet.
Memory Aid
"1/2 wave dipole at 3.55 MHz = 132 feet. Think 'D'ipole 'L'ength = '4'68/'F'requency. Length = 468/f (MHz) = 132 feet. Standard dipole length formula for 80 meters."
Real-World Application
A 1/2 wave dipole for 3.550 MHz: Length = 468/3.550 = 131.83 feet ≈ 132 feet. This is the approximate length for a half-wave dipole at this frequency (80 meters). The formula 468/f (MHz) accounts for the velocity factor. This is a standard dipole length calculation.
Key Concepts
Why Other Options Are Wrong
Option A (42 feet): Incorrect. 42 feet is too short - that would be for about 11 MHz, not 3.55 MHz. Calculation error.
Option B (84 feet): Incorrect. 84 feet is too short - that would be for about 5.6 MHz, not 3.55 MHz. Calculation error.
Option D (263 feet): Incorrect. 263 feet is too long - that would be for about 1.78 MHz, not 3.55 MHz. Calculation error.
题目解析
The correct answer is C: 132 feet. The approximate length for a 1/2 wave dipole antenna cut for 3.550 MHz is 132 feet. Length = 468/f (MHz) = 468/3.550 = 131.83 feet ≈ 132 feet. For amateur radio operators, this is a basic dipole length calculation. Understanding this helps when building dipoles.
考试技巧
1/2 wave dipole at 3.55 MHz = 468/3.55 = 132 feet. Think 'D'ipole 'L'ength = '4'68/'F'requency. Length = 468/f (MHz) = 468/3.550 = 132 feet. Not 42 ft, not 84 ft, not 263 ft - just 132 feet.
记忆口诀
1/2 wave dipole at 3.55 MHz = 132 feet. Think 'D'ipole 'L'ength = '4'68/'F'requency. Length = 468/f (MHz) = 132 feet. Standard dipole length formula for 80 meters.
实际应用示例
A 1/2 wave dipole for 3.550 MHz: Length = 468/3.550 = 131.83 feet ≈ 132 feet. This is the approximate length for a half-wave dipole at this frequency (80 meters). The formula 468/f (MHz) accounts for the velocity factor. This is a standard dipole length calculation.
错误选项分析
Option A (42 feet): Incorrect. 42 feet is too short - that would be for about 11 MHz, not 3.55 MHz. Calculation error. Option B (84 feet): Incorrect. 84 feet is too short - that would be for about 5.6 MHz, not 3.55 MHz. Calculation error. Option D (263 feet): Incorrect. 263 feet is too long - that would be for about 1.78 MHz, not 3.55 MHz. Calculation error.
知识点
1/2 wave dipole, 3.550 MHz, 132 feet, Dipole length calculation
Verified Content
Question from official FCC General Class question pool. Explanation reviewed by licensed amateur radio operators.