Deep Dive: T9A08
The correct answer is C: 19 inches. The approximate length of a quarter-wavelength vertical antenna for 146 MHz is 19 inches. The formula for quarter-wave length is 234/frequency (in MHz), giving length in feet, or 2808/frequency (in MHz) for inches. For 146 MHz: 2808/146 ≈ 19.2 inches. For amateur radio operators, this calculation helps when building or selecting antennas for 2-meter operation. Understanding antenna length calculations is fundamental to antenna work.
Why Other Answers Are Wrong
Option A (112 inches): Incorrect. 112 inches is approximately a half-wave for 2 meters, not a quarter-wave. A half-wave dipole for 146 MHz is about 38 inches total (19 inches per side). Option B (50 inches): Incorrect. 50 inches is too long for a quarter-wave - that's closer to 3/4 wave length. Option D (12 inches): Incorrect. 12 inches is too short - that's less than a quarter-wave. A quarter-wave for 146 MHz is about 19 inches.
Exam Tip
Quarter-wave for 146 MHz = 19 inches. Think 'Q'uarter-wave = 234/f (feet) or 2808/f (inches). For 146 MHz: 2808/146 ≈ 19 inches. 112 inches is half-wave, 50 and 12 inches are wrong lengths.
Memory Aid
Quarter-wave for 146 MHz = 19 inches. Think 'Q'uarter-wave = 2808/frequency (inches). For 146 MHz: 2808/146 ≈ 19 inches. Standard length for 2-meter mobile antennas.
Real-World Example
You're building a mobile antenna for 2 meters (146 MHz). A quarter-wave vertical needs to be about 19 inches long. This is a common length for mobile antennas - long enough to be efficient but short enough to be practical on a vehicle. The 19-inch length resonates at 146 MHz as a quarter-wave vertical.
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.