Deep Dive: G9B10
The correct answer is D: 33 feet. The approximate length for a 1/2 wave dipole antenna cut for 14.250 MHz is 33 feet. Length = 468/f (MHz) = 468/14.250 = 32.84 feet ≈ 33 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 (8 feet): Incorrect. 8 feet is too short - that would be for much higher frequency. Calculation error. Option B (16 feet): Incorrect. 16 feet is too short - that would be for about 29 MHz, not 14.25 MHz. Calculation error. Option C (24 feet): Incorrect. 24 feet is too short - that would be for about 19.5 MHz, not 14.25 MHz. Calculation error.
Exam Tip
1/2 wave dipole at 14.25 MHz = 468/14.25 = 33 feet. Think 'D'ipole 'L'ength = '4'68/'F'requency. Length = 468/f (MHz) = 468/14.250 = 33 feet. Not 8 ft, not 16 ft, not 24 ft - just 33 feet.
Memory Aid
1/2 wave dipole at 14.25 MHz = 33 feet. Think 'D'ipole 'L'ength = '4'68/'F'requency. Length = 468/f (MHz) = 33 feet. Standard dipole length formula.
Real-World Example
A 1/2 wave dipole for 14.250 MHz: Length = 468/14.250 = 32.84 feet ≈ 33 feet. This is the approximate length for a half-wave dipole at this frequency. The formula 468/f (MHz) accounts for the velocity factor of wire in free space. 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.