*Question E9C08:
What is a folded dipole antenna?*  

*Correct Answer is  C: A half-wave dipole with an additional parallel wire connecting its two ends*  

### AI Response: (may contain errors)  

A folded dipole antenna is a specific type of dipole antenna with a unique structure that affects its impedance and bandwidth characteristics.

### Correct Answer: C
- **A half-wave dipole with an additional parallel wire connecting its two ends**:  
  This is the correct description of a folded dipole antenna. It consists of a standard half-wave dipole with an additional wire running parallel to it, connected at both ends. This configuration increases the antenna's impedance to approximately 300 ohms, which is useful for matching with certain types of transmission lines.

### Why Other Choices Are Incorrect:
- **Choice A: A dipole one-quarter wavelength long**:  
  A dipole that is one-quarter wavelength long is not a folded dipole. Instead, it is typically referred to as a "quarter-wave vertical" or "monopole" antenna, which requires a ground plane to function effectively.

- **Choice B: A center-fed dipole with the ends folded down 90 degrees at the midpoint of each side**:  
  This describes a "bent dipole" or "inverted V" antenna, not a folded dipole. Folding the ends down changes the radiation pattern and impedance but does not create the parallel wire structure characteristic of a folded dipole.

- **Choice D: A dipole configured to provide forward gain**:  
  This describes a directional antenna, such as a Yagi-Uda antenna, which uses additional elements to focus the signal in a particular direction. A folded dipole does not inherently provide forward gain; it is primarily used for impedance matching.

### Useful Information:
- **Impedance**:  
  The folded dipole's increased impedance (around 300 ohms) makes it suitable for use with 300-ohm twin-lead transmission lines, commonly used in TV antennas.

- **Bandwidth**:  
  The folded dipole typically has a wider bandwidth than a simple dipole, making it useful in applications where frequency agility is needed.

Understanding the structure and function of a folded dipole helps in recognizing its applications and advantages in various radio setups.