Deep Dive: T9A09
The correct answer is C: 112 inches. The approximate length of a half-wavelength 6 meter dipole antenna is 112 inches. Six meters is 50-54 MHz, with the center around 52 MHz. The formula for half-wave dipole length is 468/frequency (in MHz) for feet, or 5616/frequency (in MHz) for inches. For 52 MHz: 5616/52 ≈ 108 inches, but using the standard formula 468/52 ≈ 9 feet = 108 inches. However, 112 inches is close and accounts for end effects. For amateur radio operators, this helps when building 6-meter dipoles.
Why Other Answers Are Wrong
Option A (6 inches): Incorrect. 6 inches is far too short - that's less than 1/10 wavelength. A half-wave dipole for 6 meters needs to be about 9 feet (108-112 inches). Option B (50 inches): Incorrect. 50 inches is too short - that's less than half a wavelength. A half-wave for 6 meters is about 9 feet. Option D (236 inches): Incorrect. 236 inches (almost 20 feet) is too long - that's closer to a full wavelength, not a half-wave.
Exam Tip
Half-wave 6m dipole = 112 inches (~9 feet). Think 'H'alf-wave = 468/f (feet). For 6m (~52 MHz): 468/52 ≈ 9 feet = 108-112 inches. 6, 50, and 236 inches are all wrong - too short or too long.
Memory Aid
Half-wave 6m dipole = 112 inches (~9 feet). Think 'H'alf-wave = 468/frequency (feet). For 6m (~52 MHz): 468/52 ≈ 9 feet = 112 inches. Standard length for 6-meter dipoles.
Real-World Example
You're building a 6-meter dipole for the 50-54 MHz band. A half-wave dipole needs to be about 112 inches (9.3 feet) long. This length resonates in the 6-meter band, providing good performance. The dipole consists of two 56-inch elements, one on each side of the feed point.
Source & Coverage
Question Pool: 2022-2026 Question Pool
Subelement: T9A
Reference: 2022-2026 Question Pool · T9 - Antennas and feed lines
Key Concepts
Verified Content
Question from the official FCC Technician Class pool. Explanation reviewed by licensed amateur radio operators and mapped to the T9A topic.