*Question E9D11:
Why do most two-element Yagis with normal spacing have a reflector instead of a director?*  

*Correct Answer is  D: Higher gain*  

### AI Response: (may contain errors)  

In a two-element Yagi antenna, the choice between using a reflector or a director affects the antenna's performance characteristics. Here's why the correct answer is "Higher gain":

1. **Correct Answer: Higher gain (D)**
   - A two-element Yagi with a reflector typically has higher gain compared to one with a director. The reflector element, placed behind the driven element, helps to focus the energy in the forward direction, increasing the antenna's gain. This is because the reflector reflects energy back towards the driven element, reinforcing the forward radiation pattern.

2. **Why the other choices are incorrect:**
   - **Lower SWR (A):** The presence of a reflector or director does not inherently affect the standing wave ratio (SWR) of the antenna. SWR is more related to the impedance matching between the antenna and the transmission line.
   - **Higher receiving directivity factor (B):** While a reflector can improve directivity, the term "receiving directivity factor" is not commonly used in this context. The primary focus is on gain, which is a measure of directivity and efficiency.
   - **Greater front-to-side (C):** A reflector does improve the front-to-back ratio, but the question specifically asks about the choice of a reflector for gain, not the front-to-side ratio. The front-to-side ratio is more about reducing side lobes, which is not the primary reason for choosing a reflector.

In summary, the use of a reflector in a two-element Yagi is primarily to achieve higher gain by enhancing the forward radiation pattern.