*Question E4A02:
Which of the following parameters does a spectrum analyzer display on the vertical and horizontal axes?*  

*Correct Answer is  B: Signal amplitude and frequency*  

### AI Response: (may contain errors)  

A spectrum analyzer is a crucial tool in radio communications, and understanding its display parameters is essential for the Extra Class exam.

### Correct Answer: B: Signal amplitude and frequency

1. **Why the correct answer is correct:**
   - A spectrum analyzer displays the **signal amplitude** (usually in decibels, dB) on the vertical axis and **frequency** (in hertz, Hz) on the horizontal axis. This allows users to visualize the power of signals at different frequencies, which is vital for analyzing the frequency spectrum and identifying interference or signal quality.

2. **Why the other choices are incorrect:**
   - **A: Signal amplitude and time**  
     - This choice describes an oscilloscope, which displays signal amplitude over time, not frequency.
   - **C: SWR and frequency**  
     - SWR (Standing Wave Ratio) is a measure of impedance matching and is not typically displayed on a spectrum analyzer. Instead, it is often measured with a SWR meter.
   - **D: SWR and time**  
     - Similar to choice C, this option mixes parameters that are not relevant to a spectrum analyzer. SWR is not displayed in relation to time.

### Useful Concepts:
- **Signal Amplitude**: Often measured in dBm or dBW, indicating the power level of the signal.
- **Frequency Range**: Spectrum analyzers can cover a wide range of frequencies, allowing for the analysis of various signals within that range.

Understanding these parameters will help you effectively use a spectrum analyzer and interpret its readings in practical applications.