*Question E9C12:
Which of the following describes an extended double Zepp antenna?*  

*Correct Answer is  C: A center-fed 1.25-wavelength dipole antenna*  

### AI Response: (may contain errors)  

An extended double Zepp antenna is a specific type of dipole antenna with unique characteristics. Let's break down why the correct answer is a center-fed 1.25-wavelength dipole antenna and why the other choices are incorrect.

### Correct Answer: B: A center-fed 1.5-wavelength dipole antenna

1. **Why the correct answer is correct:**
   - The extended double Zepp antenna is traditionally a center-fed dipole that is 1.25 wavelengths long. This length provides a higher gain compared to a standard half-wave dipole.
   - The 1.25-wavelength length allows for a more focused radiation pattern, which is beneficial for certain communication needs.

2. **Why the other choices are incorrect:**
   - **A: An end-fed full-wave dipole antenna**
     - An end-fed antenna is not typically referred to as a Zepp or double Zepp. The Zepp design is center-fed, not end-fed.
   - **C: A center-fed 1.25-wavelength dipole antenna**
     - This is actually the correct description of an extended double Zepp antenna, not a 1.5-wavelength dipole.
   - **D: An end-fed 2-wavelength dipole antenna**
     - Similar to choice A, an end-fed design does not match the center-fed characteristic of a Zepp antenna. Additionally, a 2-wavelength length is not typical for a Zepp design.

### Useful Information:
- **Radiation Pattern:** The extended double Zepp has a more directional radiation pattern compared to a standard half-wave dipole, which can be advantageous for long-distance communication.
- **Gain:** The gain of an extended double Zepp is higher than that of a half-wave dipole, making it a popular choice for amateur radio operators looking to improve their signal reach.

Understanding these characteristics helps in identifying the correct description of an extended double Zepp antenna and differentiating it from other types of antennas.