*Question E9H01:
When constructing a Beverage antenna, which of the following factors should be included in the design to achieve good performance at the desired frequency?*  

*Correct Answer is  D: It should be at least one wavelength long*  

### AI Response: (may contain errors)  

When constructing a Beverage antenna, the correct answer is:

**D: It should be at least one wavelength long.**

### Explanation of the Correct Answer:
- A Beverage antenna is a type of long wire antenna that is typically used for receiving low-frequency signals. 
- The effective length of a Beverage antenna should be at least one wavelength ($\lambda$) at the desired frequency to ensure good performance. This length allows the antenna to effectively capture the incoming radio waves and improve the signal-to-noise ratio.

### Why the Other Choices are Incorrect:
- **A: Its overall length must not exceed 1/4 wavelength**
  - This is incorrect because a Beverage antenna is designed to be longer than 1/4 wavelength. In fact, it is usually several wavelengths long to optimize reception.

- **B: It must be mounted more than 1 wavelength above ground**
  - This is not necessary for a Beverage antenna. While height can affect performance, it is typically recommended to be mounted just above ground level (often 1/10 to 1/4 wavelength) to minimize ground losses and maximize the antenna's effectiveness.

- **C: It should be configured as a four-sided loop**
  - This is incorrect because a Beverage antenna is not a loop antenna. It is a long, straight wire that is typically deployed in a straight line, not in a loop configuration.

### Useful Formulas and Rules of Thumb:
- The wavelength ($\lambda$) can be calculated using the formula:
  
  $$\lambda = \frac{c}{f}$$

  where:
  - $c$ = speed of light in meters per second (approximately $3 \times 10^8$ m/s)
  - $f$ = frequency in hertz (Hz)

- A common rule of thumb for the length of a Beverage antenna is:
  
  $$L \geq \lambda$$

  where $L$ is the length of the antenna. This ensures optimal performance for receiving signals. 

In summary, for a Beverage antenna to perform well, it should be at least one wavelength long, while the other options do not align with the design principles of this type of antenna.