Review Questions

1. Describe how radio energy is transmitted through space.

2. Distinguish between the induction field and the radiation field.

3. In what groups are radio frequencies sometimes classified?

4. What are the components of the ground wave?

5. Explain what is meant by diffraction, refraction, and absorption of radio waves.

6. What part does the ionosphere play in radio transmission?

7. What part does the troposphere play in radio transmission?

8. Describe how radio waves are reflected by the ionosphere.

9. What important ionospheric layers exist in summer? In winter? Does the E layer disappear completely at night?

10. What factors seem to influence the ionosphere?

11. What is virtual height, and how is it measured?

12. What is meant by penetration frequency? By maximum usable frequency?

13. What are the ordinary and extraordinary rays?

14. What is skip distance? Does the ground wave enter into determining it?

15. Discuss the phenomena that occur when radio waves strike the earth.

16. Define sky wave, ground wave, direct wave, and ground-reflected wave.

17. A vertically polarized wave is being propagated along the surface of the earth. Why must the wave front tilt forward slightly?

18. By what two paths does radio energy reach a distant receiving antenna?

19. What is fading, and how is it caused?

20. Describe direct-wave propagation.

21. Of what frequency are radio waves that are greatly affected by rain?

22. Distinguish between periodic and aperiodic antennas. By what names are they usually called?

23. Can the reactive component of the input impedance of an antenna be zero? Can the resistive component be zero?

24. At what frequencies is an antenna resonant? At all such frequencies is the input impedance the same value?

25. What important assumptions are made in determining ground-reflection factors?

26. Explain in simple terms how to find the radiation pattern for an antenna near the earth.

27. Define broadside array, end-fire array, collinear array.

28. What will be the phase relations in the vertical members of Fig. 22?

29. Why does a straight vertical antenna 0.53λ in length make an excellent radiator?

30. Why are vertical antennas used in amplitude-modulation broadcast?

31. Why are directional antennas used in these systems?

32. How are antennas arranged to produce directional patterns?

33. Why are the conductors of a frequency-modulation broadcast antenna horizontal?

34. What is the difference between antenna resistance and radiation resistance?

35. The rhombic antenna is what basic type? How does it operate?