*Question T8A02:
What type of modulation is commonly used for VHF packet radio transmissions?*  

*Correct Answer is  A: FM or PM*  

### AI Response: (may contain errors)  

The correct answer to the question about the type of modulation commonly used for VHF packet radio transmissions is **A: FM or PM**. 

### Explanation of the Correct Answer:
- **FM (Frequency Modulation)** and **PM (Phase Modulation)** are both widely used for VHF packet radio because they provide better noise immunity and are more efficient for digital data transmission compared to other modulation types. 
- Packet radio typically involves sending digital data, and FM is particularly effective in maintaining signal integrity over varying conditions, which is crucial for reliable data communication.

### Why the Other Choices are Incorrect:
- **B: SSB (Single Sideband)**: 
  - SSB is primarily used for voice communications and is not suitable for digital data transmission like packet radio. It is more efficient for long-distance voice communication but does not handle the digital data format effectively.
  
- **C: AM (Amplitude Modulation)**: 
  - AM is less efficient for data transmission due to its susceptibility to noise and interference. It is mainly used for analog audio signals and is not ideal for the digital nature of packet radio.
  
- **D: PSK (Phase Shift Keying)**: 
  - While PSK is a digital modulation technique, it is not as commonly used for VHF packet radio as FM. PSK is more often associated with higher frequency digital communications and may not be as effective in the VHF range compared to FM.

### Useful Rules of Thumb:
- For digital data transmission, especially in VHF, **FM** is preferred due to its robustness against noise.
- When considering modulation types, remember that **FM** and **PM** are generally better for data, while **AM** and **SSB** are more suited for voice communications.

This understanding will help you choose the correct modulation type for various communication scenarios in amateur radio.