Which of the following frequencies will be suitable for beyond the horizon communication using sky waves?

Options

A. 10 kHz
B. 10 MHz
C. 1 GHz
D. 1000 GHz

Answer

To determine which frequency is suitable for beyond the horizon communication using sky waves, we need to analyze the properties of different frequency ranges and their interaction with the ionosphere.

### Step-by-Step Solution:

1. **Understanding Sky Wave Communication**:
- Sky wave communication relies on the reflection of radio waves off the ionosphere. This allows signals to travel beyond the horizon.

2. **Analyzing the Given Frequencies**:
- The options provided are:
- 10 kHz
- 10 MHz
- 1 GHz
- 1000 GHz

3. **Evaluating 10 kHz**:
- 10 kHz is a very low frequency. While it can be reflected by the ionosphere, it requires a large radiating antenna, making it less practical for communication.

4. **Evaluating 10 MHz**:
- 10 MHz is within the high frequency (HF) range. This frequency can be reflected by the ionosphere, making it suitable for sky wave communication. It allows for effective long-distance communication beyond the horizon.

5. **Evaluating 1 GHz and 1000 GHz**:
- Frequencies of 1 GHz and 1000 GHz fall into the microwave and millimeter wave ranges, respectively. These frequencies penetrate the ionosphere and do not get reflected, making them unsuitable for sky wave communication.

6. **Conclusion**:
- The only frequency that is suitable for beyond the horizon communication using sky waves is **10 MHz**.

### Final Answer:
The suitable frequency for beyond the horizon communication using sky waves is **10 MHz**.

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