*Question E3A09:
Which of the following frequency ranges is most suited for meteor-scatter communications?*  

*Correct Answer is  C: 28 MHz - 148 MHz*  

### AI Response: (may contain errors)  

Meteor-scatter communications rely on the reflection of radio waves off the ionized trails left by meteors entering the Earth's atmosphere. The frequency range that is most effective for this type of communication is determined by the ability of the radio waves to reflect off these ionized trails.

### Correct Answer: 28 MHz - 148 MHz

1. **Why the correct answer is correct:**
   - The frequency range of 28 MHz to 148 MHz is ideal for meteor-scatter communications because it strikes a balance between the ability to reflect off meteor trails and the propagation characteristics of the radio waves. Frequencies in this range are high enough to efficiently reflect off the ionized trails but low enough to avoid excessive attenuation.

2. **Why the other choices are incorrect:**
   - **1.8 MHz - 1.9 MHz (Choice A):**  
     - These frequencies are too low for effective meteor-scatter communication. The ionized trails created by meteors are not dense enough to reflect such low-frequency radio waves efficiently.
   
   - **10 MHz - 14 MHz (Choice B):**  
     - While slightly better than the very low frequencies, this range is still not optimal. The reflection efficiency is lower compared to the 28 MHz - 148 MHz range, making it less suitable for meteor-scatter.
   
   - **220 MHz - 450 MHz (Choice D):**  
     - These frequencies are too high. At these frequencies, the radio waves tend to pass through the ionized trails rather than reflecting off them, reducing the effectiveness of meteor-scatter communication.

### Useful Rules of Thumb:
- **Frequency Range for Meteor-Scatter:**  
  - Typically, the VHF range (30 MHz to 300 MHz) is most effective, with the sweet spot being around 50 MHz to 144 MHz.
  
- **Reflection Efficiency:**  
  - The ability of a frequency to reflect off meteor trails decreases as the frequency moves outside the optimal range, either too low or too high.

Understanding these principles helps in selecting the appropriate frequency range for meteor-scatter communications, ensuring effective and reliable communication.