Deep Dive: G9B11
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.
Why Other Answers 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.
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 Example
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.
Source & Coverage
Question Pool: 2023-2027 Question Pool
Subelement: G9B
Reference: 2023-2027 Question Pool · G9 - Antennas and Feed Lines
Key Concepts
Verified Content
Question from the official FCC General Class pool. Explanation reviewed by licensed amateur radio operators and mapped to the G9B topic.