Deep Dive: G9D05
The correct answer is D: It narrows the main lobe in elevation. An advantage of vertically stacking horizontally polarized Yagi antennas is that it narrows the main lobe in elevation. Stacking reduces the vertical beamwidth, concentrating energy in a narrower elevation angle. For amateur radio operators, this improves long-distance communication. Understanding this helps when designing antenna arrays.
Why Other Answers Are Wrong
Option A: Incorrect. Stacking doesn't allow quick selection of vertical or horizontal polarization - stacking is for elevation pattern, not polarization selection. Polarization selection isn't the advantage. Option B: Incorrect. Stacking doesn't allow simultaneous vertical and horizontal polarization - stacking is for elevation pattern, not dual polarization. Dual polarization isn't the advantage. Option C: Incorrect. Stacking doesn't narrow the main lobe in azimuth - it narrows in elevation, not azimuth. Azimuth narrowing isn't the advantage.
Exam Tip
Vertically stacked Yagis advantage = narrows main lobe in elevation. Think 'V'ertically 'S'tacked = 'V'ertical 'S'eparation = 'N'arrows 'E'levation. Stacking reduces vertical beamwidth, concentrating energy in narrower elevation angle. Not polarization selection, not dual polarization, not azimuth - just elevation narrowing.
Memory Aid
Vertically stacked Yagis advantage = narrows main lobe in elevation. Think 'V'ertically 'S'tacked = 'N'arrows 'E'levation. Stacking reduces vertical beamwidth, concentrating energy in narrower elevation angle. Improves long-distance communication.
Real-World Example
Two horizontally polarized Yagis stacked vertically: The vertical separation creates a narrower elevation pattern. Instead of a wide elevation beam, you get a narrower beam that concentrates energy at a specific elevation angle. This is ideal for long-distance communication - the narrower elevation beam improves performance. This is the advantage - narrows main lobe in elevation.
Source & Coverage
Question Pool: 2023-2027 Question Pool
Subelement: G9D
Reference: 2023-2027 Question Pool · G9 - Antennas and Feed Lines
Key Concepts
Verified Content
Question from the official FCC General Class pool. Explanation reviewed by licensed amateur radio operators and mapped to the G9D topic.