The sky wave propagation is suitable for radiowaves of frequency

Options

A. up to 2 MHz
B. from 2 MHz to 20 MHz
C. from 2 MHz to 30 MHz
D. None of these

Answer

To determine the suitable frequency range for sky wave propagation, we need to analyze the characteristics of radio wave propagation methods. Here’s the step-by-step solution:

### Step 1: Understand the Types of Wave Propagation
There are three main types of radio wave propagation: ground wave, sky wave, and line-of-sight. Each type has its own frequency range and application.

### Step 2: Identify the Frequency Range for Sky Wave Propagation
Sky wave propagation is primarily used for long-distance communication. It occurs when radio waves are reflected off the ionosphere. The frequencies suitable for sky wave propagation typically range from about 3 MHz to 30 MHz.

### Step 3: Analyze the Options Given
The question provides four options regarding the frequency suitable for sky wave propagation:
1. Up to 2 MHz
2. From 2 MHz to 20 MHz
3. From 2 MHz to 30 MHz
4. None of these

### Step 4: Determine the Correct Option
Since sky wave propagation is effective for frequencies starting from about 3 MHz, we can eliminate option 1 (up to 2 MHz) as it is too low.

- Option 2 (from 2 MHz to 20 MHz) includes frequencies below 3 MHz, so it is not entirely suitable.
- Option 3 (from 2 MHz to 30 MHz) includes frequencies starting from 3 MHz, making it suitable for sky wave propagation.
- Option 4 (none of these) is incorrect since option 3 is valid.

### Conclusion
The correct answer is option 3: from 2 MHz to 30 MHz, as it encompasses the frequencies suitable for sky wave propagation.

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