*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 an SDR (Software-Defined Radio) receiver’s master clock oscillator can lead to interference issues. Here's why:

### Correct Answer: D
- **Interference Generation**: Excessive phase noise can cause the oscillator to produce signals that are not pure. These noisy signals can mix with strong signals on nearby frequencies, creating unwanted spurious signals or interference. This is known as reciprocal mixing, where the phase noise of the local oscillator degrades the receiver's ability to distinguish between closely spaced signals.

### Why Other Choices Are Incorrect:
- **Choice A**: "It limits the receiver’s ability to receive strong signals"  
  - Phase noise primarily affects the ability to distinguish between closely spaced signals, not the reception of strong signals. Strong signals are generally less affected by phase noise.

- **Choice B**: "It can affect the receiver’s frequency calibration"  
  - Frequency calibration is more related to frequency accuracy and stability, not phase noise. Phase noise affects signal purity, not the absolute frequency.

- **Choice C**: "It decreases the receiver’s third-order intercept point"  
  - The third-order intercept point (IP3) is a measure of linearity and dynamic range, not directly related to phase noise. Phase noise affects signal clarity and purity, not linearity.

### Key Concept:
- **Phase Noise**: It refers to the short-term frequency fluctuations of a signal, which can cause a spread of energy around the carrier frequency. This spread can interfere with nearby signals, especially in crowded frequency environments.

Understanding the impact of phase noise is crucial for ensuring that an SDR receiver can effectively separate and process signals in a dense signal environment.