*Question E4B10:
Which of the following methods measures intermodulation distortion in an SSB transmitter?*  

*Correct Answer is  B: Modulate the transmitter using two AF signals having non-harmonically related frequencies and observe the RF output with a spectrum analyzer*  

### AI Response: (may contain errors)  

To measure intermodulation distortion (IMD) in a Single Sideband (SSB) transmitter, you need to understand how IMD products are generated and observed.

### Correct Answer:  
**B: Modulate the transmitter using two AF signals having non-harmonically related frequencies and observe the RF output with a spectrum analyzer**

#### Explanation:
1. **Intermodulation Distortion (IMD):**  
   - IMD occurs when two or more signals mix in a non-linear device, creating additional signals at frequencies that are sums and differences of the original frequencies.
   - For accurate measurement, the input signals should be audio frequencies (AF) that are not harmonically related. This ensures that any new frequencies observed are due to IMD and not harmonics.

2. **Spectrum Analyzer:**  
   - A spectrum analyzer is used to observe the RF output. It displays the frequency spectrum of the output signal, allowing you to see the IMD products.

### Why Other Choices Are Incorrect:

- **A: Modulate the transmitter using two RF signals having harmonically related frequencies and observe the RF output with a spectrum analyzer**  
  - Using RF signals that are harmonically related can confuse IMD products with harmonics, making it difficult to distinguish between them.

- **C: Modulate the transmitter using two AF signals having harmonically related frequencies and observe the RF output with a peak reading wattmeter**  
  - A peak reading wattmeter does not provide the frequency domain information needed to identify IMD products. It only measures power, not the specific frequencies present.

- **D: Modulate the transmitter using two RF signals having harmonically related frequencies and observe the RF output with a logic analyzer**  
  - A logic analyzer is not suitable for RF frequency analysis. It is typically used for digital signal analysis, not for observing RF spectra.

### Key Points:
- **Non-Harmonically Related Frequencies:**  
  - Ensures that any observed mixing products are due to intermodulation, not harmonics.
  
- **Spectrum Analyzer:**  
  - Essential for visualizing the frequency components of the RF output to identify IMD products.

By using two non-harmonically related AF signals and a spectrum analyzer, you can effectively measure and analyze intermodulation distortion in an SSB transmitter.