*Question E9E02:
What antenna matching system 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?*  

*Correct Answer is  A: Gamma match*  

### AI Response: (may contain errors)  

The correct answer to the question is **A: Gamma match**. Here's a breakdown of why this is the case and why the other options are incorrect.

### Explanation of the Correct Answer: Gamma Match
- A **Gamma match** is an antenna matching system that connects the shield of the coaxial cable to the center of the antenna, while the center conductor is connected to a point that is a fraction of a wavelength away from the antenna's feed point. 
- This configuration allows for impedance matching by adjusting the length of the connecting element, which can help to minimize standing wave ratios (SWR) and improve power transfer.

### Why the Other Choices are Incorrect:
- **B: Delta match**
  - A Delta match typically involves a triangular configuration of elements and is not characterized by the specific connection method described in the question. It is more commonly used in Yagi antennas and does not connect the shield to the center of the antenna in the manner specified.

- **C: T-match**
  - A T-match uses a T-shaped configuration to connect the feed line to the antenna. It usually involves a matching network that can include capacitors or inductors, but it does not specifically connect the shield to the center of the antenna as described.

- **D: Stub match**
  - A Stub match uses a length of transmission line (the stub) connected to the feed line to create a matching network. It does not involve the direct connection of the coaxial shield to the antenna center conductor in the way the question describes.

### Useful Formulas and Rules of Thumb:
- **Impedance Matching**: The goal of any matching system is to ensure that the impedance of the antenna matches the impedance of the transmission line (usually 50 or 75 ohms). This can be expressed as:
  
  $$ Z_{in} = Z_{0} $$

  where:
  - $Z_{in}$ = input impedance of the antenna
  - $Z_{0}$ = characteristic impedance of the coaxial cable

- **SWR (Standing Wave Ratio)**: A lower SWR indicates better matching. The SWR can be calculated as:

  $$ SWR = \frac{1 + \Gamma}{1 - \Gamma} $$

  where $\Gamma$ is the reflection coefficient.

Understanding these concepts will help you grasp the purpose and function of different antenna matching systems, particularly the Gamma match.