*Question E9C09:
Which of the following describes a G5RV antenna?*  

*Correct Answer is  A: A wire antenna center-fed through a specific length of open-wire line connected to a balun and coaxial feed line*  

### AI Response: (may contain errors)  

The G5RV antenna is a popular multi-band wire antenna design, and understanding its characteristics is essential for the Extra Class exam.

### Correct Answer Explanation:
**A: A wire antenna center-fed through a specific length of open-wire line connected to a balun and coaxial feed line.**

- The G5RV antenna is indeed a center-fed dipole antenna that uses a specific length of open-wire transmission line (usually 450 ohm) to connect to a balun. 
- The balun then connects to a coaxial feed line, allowing the antenna to operate efficiently on multiple bands, typically from 20 meters to 10 meters.

### Incorrect Answer Explanations:
**B: A multi-band trap antenna.**  
- This is incorrect because a trap antenna uses inductors or capacitors (traps) to create resonant sections for different bands. The G5RV does not use traps; it relies on its length and feedline for multi-band operation.

**C: A phased array antenna consisting of multiple loops.**  
- This is incorrect as a phased array antenna consists of multiple antennas arranged in a specific geometric configuration to achieve directional radiation patterns. The G5RV is a single dipole antenna, not an array.

**D: A wide band dipole using shorted coaxial cable for the radiating elements and fed with a 4:1 balun.**  
- This is incorrect because the G5RV does not use shorted coaxial cable for its radiating elements. It is a dipole antenna fed with open-wire line and a balun, not a 4:1 balun specifically.

### Useful Formulas and Rules of Thumb:
- The length of a half-wave dipole antenna can be calculated using the formula:
  
  $$L = \frac{468}{f}$$

  where:
  - $L$ = length in feet
  - $f$ = frequency in MHz

- For the G5RV, the total length is typically around 102 feet, which is designed to be effective across multiple bands.

Understanding these characteristics will help you recognize the G5RV antenna's design and function, which is crucial for the Extra Class exam.