*Question E6B09:
What is a common use for point-contact diodes?*  

*Correct Answer is  C: As an RF detector*  

### AI Response: (may contain errors)  

Point-contact diodes are primarily used as RF detectors due to their ability to rectify high-frequency signals effectively. Here's a breakdown of the correct answer and why the other options are not suitable:

### Correct Answer: C - As an RF detector
- **Explanation**: Point-contact diodes are sensitive to high-frequency signals, making them ideal for detecting radio frequency (RF) signals. They can convert RF signals into a lower frequency that can be processed by other circuits, such as audio amplifiers. Their low capacitance allows them to operate efficiently at RF frequencies.

### Why the Other Choices are Incorrect:
- **A: As a constant current source**
  - Point-contact diodes do not inherently provide a constant current. They are primarily used for rectification and detection rather than for maintaining a steady current output.

- **B: As a constant voltage source**
  - Similar to the previous point, point-contact diodes do not function as constant voltage sources. They can exhibit a forward voltage drop, but this does not equate to providing a stable voltage under varying load conditions.

- **D: As a high-voltage rectifier**
  - While point-contact diodes can rectify signals, they are not typically used for high-voltage applications. Other types of diodes, such as silicon or Schottky diodes, are more suitable for high-voltage rectification due to their better voltage handling capabilities.

### Summary
- Point-contact diodes excel in RF detection due to their low capacitance and sensitivity to high frequencies.
- They are not suitable for constant current or voltage applications, nor are they ideal for high-voltage rectification.

This understanding will help you recognize the specific applications of different diode types in the context of amateur radio and electronics.