*Question G9B07:
How does the feed point impedance of a horizontal 1/2 wave dipole antenna change as the antenna height is reduced to 1/10 wavelength above ground?*  

*Correct Answer is  B: It steadily decreases*  

### AI Response: (may contain errors)  

The feed point impedance of a horizontal 1/2 wave dipole antenna is influenced by its height above ground. 

1. **Why the correct answer is correct (It steadily decreases):**  
   As the height of a horizontal 1/2 wave dipole antenna is reduced to 1/10 wavelength above ground, the feed point impedance decreases. This is primarily due to the increased interaction with the ground, which acts as a lossy medium. The impedance can drop significantly as the antenna approaches the ground, leading to lower values.

2. **Why the other choices are incorrect:**
   - **A: It steadily increases:** This is incorrect because as the antenna gets closer to the ground, the impedance does not increase; it decreases due to the ground's effect.
   - **C: It peaks at about 1/8 wavelength above ground:** While there is a point where the impedance can be maximized, it does not peak at 1/8 wavelength in a general sense. Instead, it continues to decrease as the height approaches 1/10 wavelength.
   - **D: It is unaffected by the height above ground:** This is incorrect because the height significantly affects the feed point impedance. The closer the antenna is to the ground, the more the impedance is influenced by the ground's properties.

3. **Useful formulas or rules of thumb:**  
   - The feed point impedance of a dipole antenna at a height of about 1/2 wavelength above ground is typically around 50-75 ohms. 
   - As the height decreases, especially below 1/4 wavelength, the impedance can drop to values as low as 20-30 ohms or even lower, depending on the ground conditions.

In summary, the feed point impedance of a horizontal 1/2 wave dipole antenna decreases as the height approaches 1/10 wavelength above ground due to increased ground interaction.