*Question E9C06:
What is the effect of adding a terminating resistor to a rhombic or long-wire antenna?*  

*Correct Answer is  B: It changes the radiation pattern from bidirectional to unidirectional*  

### AI Response: (may contain errors)  

When you add a terminating resistor to a rhombic or long-wire antenna, it primarily affects the antenna's radiation pattern.

### Correct Answer: 
**B: It changes the radiation pattern from bidirectional to unidirectional.**

- **Explanation**: 
  - A rhombic antenna is typically designed to be bidirectional, meaning it radiates equally well in two opposite directions. By adding a terminating resistor at the end of the antenna, you effectively absorb the energy that would otherwise be reflected back. This absorption reduces the radiation in the opposite direction, thus transforming the antenna's pattern to unidirectional. This is beneficial for focusing the signal in a specific direction, improving gain in that direction.

### Why the Other Choices are Incorrect:

- **A: It reflects the standing waves on the antenna elements back to the transmitter.**
  - This is incorrect because the purpose of the terminating resistor is to absorb energy rather than reflect it. A properly matched terminating resistor minimizes reflections, which helps to reduce standing waves.

- **C: It changes the radiation pattern from horizontal to vertical polarization.**
  - This is incorrect because adding a terminating resistor does not change the polarization of the antenna. The polarization is determined by the orientation of the antenna elements themselves, not by the termination.

- **D: It decreases the ground loss.**
  - This is also incorrect. While a terminating resistor can improve the efficiency of the antenna by reducing reflections, it does not directly decrease ground loss. Ground loss is influenced by the antenna's height above ground and the ground conductivity, not by the termination.

### Useful Concepts:
- **Antenna Patterns**: 
  - Bidirectional antennas radiate in two directions, while unidirectional antennas focus energy in one direction.
  
- **Termination**: 
  - A terminating resistor helps to absorb excess energy, reducing reflections and improving the overall efficiency of the antenna.

In summary, adding a terminating resistor to a rhombic or long-wire antenna changes its radiation pattern from bidirectional to unidirectional, enhancing its performance in a specific direction.