Deep Dive: E9E02
The correct answer is A: Gamma match. The gamma match is an antenna matching system that matches coaxial cable to an antenna by connecting the shield to the center of the antenna and the conductor a fraction of a wavelength to one side. This creates an impedance transformation. In a gamma match, the coaxial shield connects to the center of the antenna (or a symmetric point), and the center conductor connects to a point offset from center (a fraction of a wavelength to one side). This offset connection, combined with a series capacitor, creates the impedance transformation needed to match the antenna to 50-ohm coax. The gamma match is commonly used with Yagi antennas where the driven element can be connected to the boom (the shield connection). It's a popular matching method because it's relatively simple and works well.
Why Other Answers Are Wrong
Option B: Incorrect. Delta match is a different technique that uses a triangular connection, not the shield-to-center, conductor-to-side configuration described. Option C: Incorrect. T-match uses a different configuration with connections at different points, not the gamma match configuration. Option D: Incorrect. Stub match uses a parallel stub, not the series connection configuration of a gamma match.
Exam Tip
Gamma match = Shield to center, conductor to side. Remember: Gamma match connects coaxial shield to antenna center and conductor a fraction of wavelength to one side, with a series capacitor for impedance matching.
Memory Aid
**G**amma **M**atch = **S**hield **C**enter, **C**onductor **S**ide (think 'GM = SCCS')
Real-World Example
You're matching a Yagi to 50-ohm coax using a gamma match. You connect the coax shield to the center of the driven element (or to the boom if the element is connected). You connect the center conductor to a point offset from center (maybe 1/8 wavelength to one side). You add a series capacitor to complete the match. This transforms the antenna impedance to 50 ohms.
Source & Coverage
Question Pool: 2024-2028 Question Pool
Subelement: E9E
Reference: FCC Part 97.3
Key Concepts
Verified Content
Question from the official FCC Extra Class pool. Explanation reviewed by licensed amateur radio operators and mapped to the E9E topic.