The mode of propagation used by short wave broadcast services is

Options

A. space waveq
B. sky wave
C. ground wave
D. both and and c

Answer

To solve the question regarding the mode of propagation used by shortwave broadcast services, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Frequency Range**:
Shortwave broadcast services operate within a specific frequency range. This range is typically from a few megahertz up to 30 megahertz.

2. **Understand the Types of Propagation**:
There are three main types of radio wave propagation:
- **Ground Wave Propagation**: This occurs when signals travel along the surface of the Earth. It is effective for lower frequencies and is limited to short distances.
- **Sky Wave Propagation**: This involves signals that are transmitted towards the ionosphere, where they can be reflected back to Earth. This allows for long-distance communication.
- **Space Wave Propagation**: This occurs when signals travel directly through the atmosphere and can involve satellites. It is typically used for higher frequency transmissions.

3. **Relate Frequency to Propagation Type**:
Since shortwave broadcasts operate in the frequency range of a few megahertz to 30 megahertz, they are best suited for sky wave propagation. This is because the ionosphere can reflect these frequencies back to Earth, allowing signals to travel over long distances.

4. **Conclusion**:
Based on the frequency range and the characteristics of the different types of propagation, we conclude that the mode of propagation used by shortwave broadcast services is **sky wave propagation**.

### Final Answer:
The mode of propagation used by shortwave broadcast services is **sky wave propagation**.

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