*Question G9A08:
If the SWR on an antenna feed line is 5:1, and a matching network at the transmitter end of the feed line is adjusted to present a 1:1 SWR to the transmitter, what is the resulting SWR on the feed line?*  

*Correct Answer is  B: 5:1*  

### AI Response: (may contain errors)  

To understand the SWR (Standing Wave Ratio) in this scenario, let's break down the situation:

1. **Given Information**:
   - The SWR on the antenna feed line is 5:1.
   - A matching network at the transmitter end is adjusted to present a 1:1 SWR to the transmitter.

2. **Understanding SWR**:
   - SWR is a measure of how well the load (antenna) is matched to the transmission line. An SWR of 1:1 indicates a perfect match, while higher values indicate increasing levels of mismatch.

3. **Resulting SWR on the Feed Line**:
   - The matching network at the transmitter end can only affect the SWR seen at the transmitter. It does not change the SWR on the feed line itself.
   - Since the feed line still has an SWR of 5:1, the correct answer is **B: 5:1**.

### Explanation of Choices:
- **A: 1:1**: Incorrect because the matching network only presents a 1:1 SWR to the transmitter, not to the feed line. The feed line still has a mismatch of 5:1.
  
- **B: 5:1**: Correct. The SWR on the feed line remains 5:1 regardless of the matching network at the transmitter end.

- **C: Between 1:1 and 5:1 depending on the characteristic impedance of the line**: Incorrect. The characteristic impedance of the line does not change the SWR on the feed line; it remains at 5:1.

- **D: Between 1:1 and 5:1 depending on the reflected power at the transmitter**: Incorrect. The reflected power at the transmitter does not affect the SWR on the feed line, which remains at 5:1.

### Useful Formulas and Rules of Thumb:
- The relationship between the forward power ($P_f$) and reflected power ($P_r$) can be used to calculate SWR:
  
  $$SWR = \frac{P_f + P_r}{P_f - P_r}$$

- A matching network can improve the match at the transmitter but does not change the conditions on the feed line unless it is also adjusted to match the load.

In summary, the SWR on the feed line remains at 5:1, and the matching network only affects the SWR seen by the transmitter.