*Question E2B07:
Which types of modulation are used for amateur television DVB-T signals?*  

*Correct Answer is  B: QAM and QPSK*  

### AI Response: (may contain errors)  

To understand the modulation types used for amateur television DVB-T signals, let's break down the correct answer and the other choices.

### Correct Answer: B: QAM and QPSK

- **QAM (Quadrature Amplitude Modulation)**: This modulation technique combines both amplitude and phase variations to encode data. It is efficient for transmitting video signals, allowing for higher data rates, which is essential for television broadcasts.
  
- **QPSK (Quadrature Phase Shift Keying)**: This is a phase modulation technique that encodes data by changing the phase of the carrier signal. It is also efficient and allows for the transmission of two bits of data per symbol, making it suitable for DVB-T.

### Why the Other Choices are Incorrect:

- **A: FM and FSK**:
  - **FM (Frequency Modulation)**: While FM is used in analog television, it is not the primary modulation method for DVB-T, which is a digital standard.
  - **FSK (Frequency Shift Keying)**: This is typically used for data transmission rather than video signals. It is not suitable for the high data rates required for television.

- **C: AM and OOK**:
  - **AM (Amplitude Modulation)**: Similar to FM, AM is used in analog television but is not used in DVB-T, which relies on digital modulation techniques.
  - **OOK (On-Off Keying)**: This is a simple form of modulation used primarily for binary data transmission, not for video signals.

- **D: All these choices are correct**: Since only QAM and QPSK are used for DVB-T, this choice is incorrect.

### Summary

In summary, the correct modulation types for amateur television DVB-T signals are QAM and QPSK due to their efficiency in handling high data rates necessary for video transmission. The other options either pertain to analog methods or are not suitable for video broadcasting.

### Useful Rule of Thumb

- For digital television broadcasting, look for modulation schemes that efficiently utilize bandwidth and support high data rates, such as QAM and QPSK.