*Question E9C05:
What is the purpose of feeding an off-center-fed dipole (OCFD) between the center and one end instead of at the midpoint?*  

*Correct Answer is  A: To create a similar feed point impedance on multiple bands*  

### AI Response: (may contain errors)  

Feeding an off-center-fed dipole (OCFD) between the center and one end instead of at the midpoint is primarily done to create a similar feed point impedance on multiple bands. Here's why:

### Correct Answer: A

- **Purpose**: By feeding the dipole off-center, the antenna can achieve a feed point impedance that is more consistent across multiple amateur radio bands. This is because the off-center feed point allows the antenna to operate as a multi-band antenna, taking advantage of harmonic resonances.
- **Impedance Matching**: At the off-center feed point, the impedance is typically higher than the 50 ohms found at the center of a half-wave dipole. This higher impedance can be closer to the impedance of the antenna at harmonic frequencies, making it easier to match with a standard 50-ohm coaxial cable across several bands.

### Why Other Choices Are Incorrect:

- **B: To suppress off-center lobes at higher frequencies**  
  Feeding the antenna off-center does not inherently suppress off-center lobes. The radiation pattern and lobes are more influenced by the physical length of the antenna relative to the wavelength and the height above ground.

- **C: To resonate the antenna across a wider range of frequencies**  
  While an OCFD can operate on multiple bands, the primary reason for off-center feeding is impedance matching, not necessarily to increase the range of resonant frequencies. The antenna's physical length and design determine its resonant frequencies.

- **D: To reduce common-mode current coupling on the feed line shield**  
  Common-mode currents are more effectively managed with proper balun use and feed line routing, rather than the feed point location. Off-center feeding does not inherently reduce common-mode currents.

### Useful Rule of Thumb:

- **Feed Point Impedance**: For a half-wave dipole, the center feed point impedance is approximately 50-75 ohms. Off-center feeding can result in impedances ranging from 200 to 600 ohms, which can be more suitable for multi-band operation with the use of a matching transformer or balun.

By understanding these principles, you can see why off-center feeding is a popular choice for multi-band dipole antennas.