*Question T4A08:
Which of the following conductors is preferred for bonding at RF?*  

*Correct Answer is  D: Flat copper strap*  

### AI Response: (may contain errors)  

To understand why flat copper strap is preferred for bonding at RF, let's break down the options:

### Correct Answer: Flat Copper Strap
- **Why it's correct**: 
  - Flat copper strap has a large surface area, which reduces resistance and improves conductivity. 
  - It is effective at handling high-frequency signals due to its low inductance and ability to minimize skin effect, where RF currents tend to flow on the surface of conductors.
  - The flat shape allows for better contact with surfaces, enhancing the bonding effectiveness.

### Why the Other Choices are Incorrect:
- **A: Copper braid removed from coaxial cable**:
  - While copper braid is conductive, it is not as effective as a flat strap for RF bonding. The braid can have higher resistance due to its construction and may not provide as solid a connection as a flat strap.

- **B: Steel wire**:
  - Steel has a higher resistivity compared to copper, which means it is less effective for RF bonding. It can also corrode more easily, leading to poor electrical connections over time.

- **C: Twisted-pair cable**:
  - Twisted-pair cables are designed for data transmission and not for bonding. They have limited surface area for contact and are not suitable for RF applications where low resistance and high conductivity are critical.

### Summary
For RF bonding, the goal is to ensure a low-resistance, high-conductivity connection. Flat copper strap excels in this regard due to its physical properties, making it the preferred choice. 

### Rule of Thumb
- When selecting materials for RF bonding, prioritize materials with low resistivity and high surface area contact to minimize losses and improve performance.