*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)  

The correct answer to the question about the extended double Zepp antenna is:

**C: A center-fed 1.25-wavelength dipole antenna.**

### Explanation of the Correct Answer:
- An extended double Zepp antenna is essentially a dipole antenna that is longer than a standard half-wavelength dipole. Specifically, it is a center-fed dipole that is approximately 1.25 wavelengths long.
- The length of a dipole antenna can be calculated using the formula:

$$
L = \frac{468}{f}
$$

where:
- $L$ = length in feet
- $f$ = frequency in MHz

For a 1.25-wavelength dipole, the length would be:

$$
L = 1.25 \times \frac{468}{f}
$$

This makes it suitable for use in various amateur radio applications, providing a wider bandwidth and improved performance.

### Why the Other Choices are Incorrect:
- **A: An end-fed full-wave dipole antenna**
  - This describes a full-wave dipole, which is not the same as a 1.25-wavelength dipole. A full-wave dipole is typically 1 wavelength long, not 1.25 wavelengths.

- **B: A center-fed 1.5-wavelength dipole antenna**
  - This option describes a dipole that is longer than the extended double Zepp. A 1.5-wavelength dipole would have different characteristics and is not classified as an extended double Zepp.

- **D: An end-fed 2-wavelength dipole antenna**
  - This describes a dipole that is 2 wavelengths long, which is significantly longer than the extended double Zepp. It would also have different feedpoint impedance and radiation patterns.

### Summary:
- The extended double Zepp antenna is a center-fed dipole approximately 1.25 wavelengths long, making option C the correct choice. The other options describe antennas that do not fit this specific definition.