*Question G9B02:
Which of the following is a common way to adjust the feed point impedance of an elevated quarter-wave ground-plane vertical antenna to be approximately 50 ohms?*  

*Correct Answer is  B: Slope the radials downward*  

### AI Response: (may contain errors)  

To adjust the feed point impedance of an elevated quarter-wave ground-plane vertical antenna to be approximately 50 ohms, you can:

### Correct Answer: Slope the radials downward

1. **Why the correct answer is correct:**
   - **Sloping the radials downward**: By sloping the radials downward, you effectively lower the feed point impedance of the antenna. This adjustment can bring the impedance closer to 50 ohms, which is a common impedance for coaxial cables used in amateur radio. The downward slope changes the current distribution and mutual coupling between the radials and the vertical element, thus affecting the impedance.

### Why the other choices are incorrect:

2. **Slope the radials upward:**
   - Sloping the radials upward typically increases the feed point impedance rather than decreasing it. This would move the impedance further away from 50 ohms, making it less suitable for direct connection to 50-ohm coaxial cable.

3. **Lengthen the radials beyond one wavelength:**
   - Lengthening the radials beyond one wavelength is not practical for a quarter-wave ground-plane antenna. It would significantly alter the antenna's resonant frequency and radiation pattern, and it would not effectively adjust the impedance to 50 ohms.

4. **Coil the radials:**
   - Coiling the radials is not a standard method for adjusting feed point impedance. Coiling can introduce inductance, which may detune the antenna and affect its performance, but it does not specifically adjust the impedance to 50 ohms.

### Useful Rule of Thumb:

- **Impedance Matching**: For a quarter-wave vertical antenna with radials, the typical feed point impedance is around 36 ohms. Sloping the radials downward can increase this impedance to approximately 50 ohms, making it a better match for standard coaxial cables.