*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)  

When dealing with SWR (Standing Wave Ratio) on an antenna feed line, it's important to understand how matching networks affect the system.

1. **Correct Answer: 5:1**  
   - The SWR on the feed line itself remains unchanged at 5:1. The matching network at the transmitter end only affects the SWR seen by the transmitter, not the SWR on the feed line. The purpose of the matching network is to transform the impedance seen by the transmitter to 50 ohms, resulting in a 1:1 SWR at the transmitter. However, the actual SWR on the feed line remains at 5:1.

2. **Why Other Choices Are Incorrect:**
   - **A: 1:1**  
     - This choice is incorrect because the matching network does not change the SWR on the feed line itself; it only changes the SWR seen by the transmitter.
   - **C: Between 1:1 and 5:1 depending on the characteristic impedance of the line**  
     - This choice is incorrect because the characteristic impedance of the line does not affect the SWR on the line. The SWR is determined by the mismatch between the line and the load (antenna).
   - **D: Between 1:1 and 5:1 depending on the reflected power at the transmitter**  
     - This choice is incorrect because the reflected power at the transmitter is managed by the matching network, which does not alter the SWR on the feed line itself.

3. **Useful Concepts:**
   - **SWR Definition:**  
     The SWR is a measure of how well the load is matched to the transmission line. It is defined as:  
     $$ \text{SWR} = \frac{1 + |\Gamma|}{1 - |\Gamma|} $$  
     where $\Gamma$ is the reflection coefficient.
   - **Matching Network:**  
     A matching network is used to transform the impedance at one end of the line to match the desired impedance (usually 50 ohms for transmitters), but it does not change the SWR on the line itself.

Understanding these concepts helps clarify why the SWR on the feed line remains at 5:1 despite the matching network's adjustment at the transmitter end.