*Question G8B02:
What is the term for interference from a signal at twice the IF frequency from the desired signal?*  

*Correct Answer is  B: Image response*  

### AI Response: (may contain errors)  

The correct answer to the question is **B: Image response**. 

### Explanation of the Correct Answer:
- **Image response** refers to the phenomenon where a signal at a frequency that is twice the intermediate frequency (IF) can interfere with the desired signal. This occurs in superheterodyne receivers, where the incoming signal is mixed with a local oscillator to produce an IF. If the local oscillator is set to a frequency that allows another signal (the image frequency) to also produce the same IF, it can cause interference.

### Why the Other Choices are Incorrect:
- **A: Quadrature response**: This term relates to the phase relationship in signals, particularly in quadrature amplitude modulation (QAM) and does not specifically refer to interference from an image frequency.
  
- **C: Mixer interference**: While this term could describe various types of interference in a mixer, it is not a standard term used to describe the specific issue of interference from an image frequency.

- **D: Intermediate interference**: This term is not commonly used in radio communications. It does not specifically describe the interference caused by signals at the image frequency.

### Useful Concepts:
- In a superheterodyne receiver, the image frequency ($f_{image}$) can be calculated as:
  
  $$f_{image} = f_{desired} + 2 \times f_{IF}$$

  where:
  - $f_{desired}$ is the frequency of the desired signal.
  - $f_{IF}$ is the intermediate frequency.

- To avoid image response interference, proper filtering and design techniques are employed in receiver circuits to ensure that only the desired signal is processed. 

Understanding these concepts will help you grasp the importance of image response in radio communications and prepare you for related questions on the Extra Class exam.