Question E9B06:
What is the elevation angle of peak response in the antenna radiation pattern shown in Figure E9-2?  

Choices:  
A: 45 degrees  
B: 75 degrees  
C: 7.5 degrees  
D: 25 degrees    

Correct Answer is  C: 7.5 degrees  

Answer: 7.5 degrees (Choice C)

Why this is correct:
- In Figure E9-2, the elevation (vertical) radiation pattern shows the main lobe extending farthest from the center at a very low angle above the horizon. Reading the angle grid, that peak aligns with $7.5^\circ$. This angle is the takeoff angle (TOA), i.e., the elevation angle of maximum radiation.

Why the other choices are incorrect:
- 25 degrees: Too high compared to the plotted main-lobe maximum; at this angle the pattern shows lower gain (often a sidelobe or below the main-lobe peak).
- 45 degrees: Mid-elevation; the figure shows much less gain here, not a peak.
- 75 degrees: High-angle region; the pattern is well inside the main-lobe radius, indicating low gain.

Useful rules of thumb:
- Takeoff angle (TOA) = elevation angle of peak response in the elevation pattern.
- On elevation polar plots: $0^\circ$ is the horizon; $90^\circ$ is straight up (zenith). The peak is where the pattern’s radius is largest.
- For HF DX, low TOA ($\approx 5^\circ$–$15^\circ$) is typically desirable; high angles ($>60^\circ$) favor short skip/NVIS.