Question
What is an advantage of vertically stacking horizontally polarized Yagi antennas?
Answer Options
- A) It allows quick selection of vertical or horizontal polarization
- B) It allows simultaneous vertical and horizontal polarization
- C) It narrows the main lobe in azimuth
- D) It narrows the main lobe in elevation
Correct Answer: D
Explanation
Stacking antennas is done to increase gain. When antennas are stacked vertically, the phasing of the two signals primarily affects the vertical radiation pattern (elevation angle). When the antennas are phased correctly, the horizontal pattern (azimuth) remains the same, but the vertical pattern is compressed.
Therefore, the advantage of vertically stacking Yagi antennas is that it narrows the main lobe in elevation. This concentration of energy into a flatter vertical angle (closer to the horizon) results in higher effective gain and is ideal for long-distance terrestrial communication.
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