*Question E3B12:
What is chordal-hop propagation?*  

*Correct Answer is  B: Successive ionospheric refractions without an intermediate reflection from the ground*  

### AI Response: (may contain errors)  

Chordal-hop propagation is a type of radio wave propagation that involves multiple refractions through the ionosphere without the waves touching the ground between hops. This allows signals to travel long distances with less attenuation compared to traditional multi-hop propagation, where each hop involves a ground reflection.

### Explanation:

1. **Correct Answer (B): Successive ionospheric refractions without an intermediate reflection from the ground**
   - In chordal-hop propagation, radio waves are refracted by the ionosphere multiple times in succession. This means the waves "hop" from one ionospheric layer to another without hitting the ground in between. This can result in lower signal loss and better signal quality over long distances.

2. **Why the Other Choices are Incorrect:**
   - **Choice A: Propagation away from the great circle bearing between stations**
     - This describes off-great-circle propagation, which is not related to chordal-hop propagation. Chordal-hop still follows the great circle path but involves multiple ionospheric refractions.
   - **Choice C: Propagation across the geomagnetic equator**
     - This describes trans-equatorial propagation, which is a different phenomenon where signals cross the geomagnetic equator. It is not related to the concept of chordal-hop propagation.
   - **Choice D: Signals reflected back toward the transmitting station**
     - This describes backscatter or back-reflection, where signals are reflected back to the source. Chordal-hop involves forward propagation through the ionosphere, not reflection back to the transmitter.

### Useful Concepts:

- **Ionospheric Refraction:** The bending of radio waves as they pass through the ionosphere, allowing them to travel beyond the horizon.
- **Great Circle Path:** The shortest path between two points on the surface of a sphere, which is the path radio waves typically follow for long-distance communication.

Understanding these concepts helps in recognizing how chordal-hop propagation allows for efficient long-distance communication by minimizing ground losses.