*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 an SSB transmitter, the correct method involves using two audio frequency (AF) signals that are non-harmonically related. Here's a breakdown of why this is the case:

### 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**: 
  - Intermodulation distortion occurs when two or more signals mix in a non-linear device, producing additional unwanted frequencies. 
  - Using non-harmonically related AF signals ensures that the resulting intermodulation products are distinct and can be effectively analyzed with a spectrum analyzer. 
  - The spectrum analyzer will display these products, allowing for a clear measurement of distortion.

### Why the 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.**
  - **Reason**: Using harmonically related RF signals can produce intermodulation products, but they will be at predictable harmonic frequencies. This makes it difficult to distinguish between the original signals and the distortion products, leading to less effective measurement of IMD.

- **C: Modulate the transmitter using two AF signals having harmonically related frequencies and observe the RF output with a peak reading wattmeter.**
  - **Reason**: While this method uses AF signals, harmonically related frequencies will also produce predictable intermodulation products. A peak reading wattmeter measures power but does not provide the frequency resolution needed to analyze distortion effectively.

- **D: Modulate the transmitter using two RF signals having harmonically related frequencies and observe the RF output with a logic analyzer.**
  - **Reason**: A logic analyzer is designed for digital signals and is not suitable for analyzing RF signals or intermodulation distortion. Additionally, using harmonically related RF signals limits the ability to measure IMD accurately.

### Summary:
To effectively measure intermodulation distortion in an SSB transmitter, use two non-harmonically related AF signals and analyze the output with a spectrum analyzer. This method provides the necessary resolution to identify and quantify distortion products.