*Question G4B10:
Which of the following can be determined with a directional wattmeter?*  

*Correct Answer is  A: Standing wave ratio*  

### AI Response: (may contain errors)  

To understand why the correct answer is "Standing wave ratio" (SWR) and why the other options are incorrect, let's break it down:

### Correct Answer: A - Standing Wave Ratio (SWR)

- A directional wattmeter measures the forward and reflected power in a transmission line.
- The standing wave ratio is calculated using the formula:

$$
SWR = \frac{P_{forward}}{P_{reflected}}
$$

where:
- $P_{forward}$ = power traveling towards the antenna
- $P_{reflected}$ = power reflected back towards the transmitter

- By knowing both the forward and reflected power, you can determine the SWR, which indicates how well the antenna is matched to the transmission line.

### Why the Other Choices are Incorrect:

- **B: Antenna Front-to-Back Ratio**
  - This ratio measures the difference in gain between the front and back of a directional antenna. It is not something that can be directly measured with a directional wattmeter, as it requires knowledge of the antenna's radiation pattern rather than just power measurements.

- **C: RF Interference**
  - RF interference refers to unwanted signals that disrupt communication. A directional wattmeter does not measure interference; it only measures power levels in a specific direction. Identifying interference typically requires spectrum analyzers or other specialized equipment.

- **D: Radio Wave Propagation**
  - Radio wave propagation involves understanding how radio waves travel through different environments. This is a broader concept that cannot be determined by a wattmeter, which focuses solely on power measurements in a transmission line.

### Summary

- A directional wattmeter is specifically designed to measure forward and reflected power, allowing you to calculate the standing wave ratio (SWR).
- The other options involve concepts that require different types of measurements or analyses beyond what a wattmeter can provide. 

This understanding is crucial for effective antenna system design and troubleshooting in amateur radio.