*Question E9E04:
What is the purpose of the series capacitor in a gamma match?*  

*Correct Answer is  B: To cancel unwanted inductive reactance*  

### AI Response: (may contain errors)  

The purpose of the series capacitor in a gamma match is to cancel unwanted inductive reactance.

### Explanation:

1. **Correct Answer (B): To cancel unwanted inductive reactance**

   - A gamma match is used to match the impedance of an antenna to the feed line. The antenna often has inductive reactance, which can cause a mismatch.
   - The series capacitor is used to cancel this inductive reactance. By doing so, it helps achieve a purely resistive impedance, which is easier to match to the feed line.
   - The cancellation occurs because capacitive reactance ($X_C$) is the opposite of inductive reactance ($X_L$). When they are equal in magnitude, they cancel each other out:
     $$X_C = -X_L$$

2. **Why the other choices are incorrect:**

   - **Choice A: To provide DC isolation between the feed line and the antenna**
     - While capacitors can provide DC isolation, this is not the primary purpose of the series capacitor in a gamma match. The main goal is impedance matching, not isolation.

   - **Choice C: To provide a rejection notch that prevents the radiation of harmonics**
     - A rejection notch is typically created using filters, not a single series capacitor. The series capacitor in a gamma match is not designed to filter harmonics.

   - **Choice D: To transform the antenna impedance to a higher value**
     - Impedance transformation in a gamma match is primarily achieved through the combination of the gamma rod and the series capacitor, but the capacitor itself is specifically for canceling reactance, not directly transforming impedance to a higher value.

By understanding the role of the series capacitor in canceling inductive reactance, you can see why choice B is the correct answer.