*Question E4D06:
What is the term for the reduction in receiver sensitivity caused by a strong signal near the received frequency?*  

*Correct Answer is  C: Desensitization*  

### AI Response: (may contain errors)  

**Correct Answer: Desensitization**

1. **Why the correct answer is correct:**

   - **Desensitization** refers to the reduction in a receiver's sensitivity due to a strong signal on a nearby frequency. This strong signal can overload the receiver's front-end, causing it to become less sensitive to weaker signals on the desired frequency. Essentially, the receiver is "desensitized" to the signals it is supposed to receive.

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

   - **Reciprocal mixing (A):** This occurs when the phase noise of a local oscillator mixes with a strong nearby signal, creating unwanted noise on the desired frequency. It is related to oscillator performance, not directly to receiver sensitivity reduction.

   - **Quieting (B):** This term is used in FM communications to describe the reduction of noise when a signal is strong enough to fully capture the receiver. It is not related to sensitivity reduction due to nearby strong signals.

   - **Cross modulation interference (D):** This happens when a strong signal modulates the desired signal, causing distortion. It is a form of interference but does not directly cause a reduction in sensitivity.

3. **Useful Concepts:**

   - **Receiver Sensitivity:** The minimum signal strength required for a receiver to detect a signal with a specified level of quality. Desensitization effectively raises this minimum level, making it harder to receive weak signals.

   - **Front-End Overload:** A condition where the receiver's initial stages are overwhelmed by a strong signal, leading to desensitization.

Understanding these concepts helps in identifying desensitization as the correct answer, as it specifically addresses the issue of reduced sensitivity due to strong nearby signals.