*Question E3C06:
How does the VHF/UHF radio horizon compare to the geographic horizon?*  

*Correct Answer is  A: It is approximately 15 percent farther*  

### AI Response: (may contain errors)  

The VHF/UHF radio horizon is influenced by the curvature of the Earth and the height of the antenna. Here's a breakdown of the correct answer and the reasoning behind it:

### Correct Answer: A - It is approximately 15 percent farther

1. **Why the correct answer is correct:**
   - The VHF/UHF radio horizon is typically about 15% farther than the geographic horizon due to the effects of radio wave propagation. This is because radio waves can travel beyond the line of sight, especially when transmitted from elevated antennas. The formula for calculating the radio horizon distance ($D$) in miles is given by:
   $$
   D \approx 1.414 \times \sqrt{h}
   $$
   where $h$ is the height of the antenna in feet. This formula shows that as the height increases, the distance to the radio horizon increases, allowing for a greater range compared to the geographic horizon.

### Why the other choices are incorrect:

2. **Choice B: It is approximately 20 percent nearer**
   - This choice is incorrect because the VHF/UHF horizon is not closer than the geographic horizon. In fact, it extends farther due to the propagation characteristics of radio waves.

3. **Choice C: It is approximately 50 percent farther**
   - This choice is also incorrect. While the VHF/UHF horizon does extend beyond the geographic horizon, it does not do so by as much as 50%. The 15% figure is a more accurate estimate based on typical propagation conditions.

4. **Choice D: They are approximately the same**
   - This choice is incorrect because it ignores the additional range provided by radio wave propagation. The VHF/UHF horizon is not the same as the geographic horizon; it is extended due to the ability of radio waves to bend slightly and travel beyond the visual line of sight.

### Summary:
- The VHF/UHF radio horizon is approximately 15% farther than the geographic horizon due to the effects of antenna height and radio wave propagation.
- Use the formula for radio horizon distance to understand how height affects range. 

This knowledge is crucial for understanding how to maximize communication range in amateur radio operations.