*Question E9C10:
Which of the following describes a Zepp antenna?*  

*Correct Answer is  B: An end-fed half-wavelength dipole*  

### AI Response: (may contain errors)  

A Zepp antenna is a type of antenna that is characterized by being an end-fed half-wavelength dipole. Let's break down why this is the correct answer and why the other choices are incorrect:

1. **Correct Answer: B - An end-fed half-wavelength dipole**
   - A Zepp antenna, short for Zeppelin antenna, is traditionally an end-fed half-wavelength dipole. It was originally used on airships like the Zeppelin, where the antenna was fed at one end and hung down from the airship. The key characteristic is that it is fed at the end, rather than the center, which is typical for most dipoles.

2. **Why the other choices are incorrect:**
   - **A: A horizontal array capable of quickly changing the direction of maximum radiation by changing phasing lines**
     - This describes a phased array antenna, not a Zepp antenna. Phased arrays use multiple elements and adjustable phase differences to steer the direction of radiation.
   - **C: An omni-directional antenna commonly used for satellite communications**
     - Omni-directional antennas radiate equally in all directions in a plane, which is not a characteristic of a Zepp antenna. Satellite communications often use dish antennas or other specialized designs, not Zepp antennas.
   - **D: A vertical array capable of quickly changing the direction of maximum radiation by changing phasing lines**
     - Similar to choice A, this describes a vertical phased array, which is not related to the Zepp antenna design.

3. **Useful Information:**
   - The Zepp antenna is often used in amateur radio for its simplicity and ease of deployment. It can be effectively used on multiple bands with the help of an antenna tuner.
   - The end-fed nature of the Zepp antenna can lead to high voltages at the feed point, so proper matching and insulation are important.

Understanding the basic characteristics of different antenna types is crucial for the exam, and recognizing the historical context of the Zepp antenna can help remember its unique design.