*Question E4C01:
What is an effect of excessive phase noise in an SDR receiver’s master clock oscillator?*  

*Correct Answer is  D: It can combine with strong signals on nearby frequencies to generate interference*  

### AI Response: (may contain errors)  

Excessive phase noise in a Software Defined Radio (SDR) receiver's master clock oscillator can significantly impact its performance. Let's break down the correct answer and the other choices.

### Correct Answer: D
**Explanation:**
- Excessive phase noise can cause the oscillator's output to fluctuate in frequency. This fluctuation can lead to the mixing of signals, especially when strong signals are present on nearby frequencies. 
- When these strong signals mix with the phase noise, they can create unwanted interference products, which can degrade the overall performance of the receiver. This is particularly problematic in crowded frequency environments.

### Why the Other Choices are Incorrect:
- **A: It limits the receiver’s ability to receive strong signals**
  - While phase noise can affect signal clarity, it does not inherently limit the ability to receive strong signals. Strong signals can still be received, but their quality may be compromised due to interference from phase noise.

- **B: It can affect the receiver’s frequency calibration**
  - Frequency calibration is primarily determined by the stability and accuracy of the oscillator. While excessive phase noise can introduce errors in signal processing, it does not directly affect the calibration of the receiver itself.

- **C: It decreases the receiver’s third-order intercept point**
  - The third-order intercept point (IP3) is a measure of a receiver's linearity and its ability to handle strong signals without distortion. Phase noise does not directly decrease the IP3; rather, it affects the quality of the received signals. IP3 is more influenced by the non-linear characteristics of the receiver's components.

### Summary
- **Phase Noise Impact:** Excessive phase noise can lead to interference by mixing with strong nearby signals.
- **Other Choices:** They either misinterpret the effects of phase noise or relate to different aspects of receiver performance.

Understanding these concepts will help you grasp the implications of phase noise in SDR systems and prepare effectively for the Extra Class exam.