Page:Electronics Technician - Volume 7 - Antennas and Wave Propagation - NAVEDTRA 14092.pdf/108

1-33. During the 27-day sunspotcycle, which ionospheric layer experiences the greatest fluctuations in density?

1. D
2. E
3. F1
4. F2

IN ANSWERING QUESTIONS 1-34 THROUGH 1-38, SELECT FROM THE FOLLOWING LIST THE DEFINITION OF THE INDICATED TERM.

A. Depends on the angle of the sun; refracts hf waves during the day, up to 20 MHz, to distances of 1200 miles; greatly reduced at night

B. Reflects vlf waves for long-range communications; refracts If and. mf for short-range communications; has little effect on. vhf and above; gone at night

C. Density depends on the angle of the sun; its main effect is absorption of hf waves passing through to the F2 layer

D. Provides long-range hf communications; very variable; height and density change with time of day, season, and sunspot activity

E. Structure and density depend. on the time of day and the angle of the sun; consists of one layer at night and two layers during the day

1-34. D layer.

1. A
2. B
3. C
4. D

1-3. E layer

1. A
2. B
3. C
4. D

1-36. F layer

1. B
2. C
3. D
4. E

1-37. F1 layer

1. A
2. B
3. C
4. D

1-38. F2 layer

1. A
2. C
3. D
4. E

1-39. During periods of maximum sunspot activity within the eleven-year cycle, critical frequencies for all layers increase.

1. True
2. False

1-40. Which of the following problems is NOT a negative side effect of the sporadic E layer?

1. Causes increased multipath problems
2. Provides additional absorption
3. Blanks out more favorable layers
4. Increased static in line of sight communications

1-41. When sudden ionospheric disturbances (SID) occurs, which ionospheric layer is affected the most?

1. D
2. E
3. F1
4. F2

1-42. What effect do ionospheric storms have on (a) the range of frequencies and (b) the working frequency used for communications?

1. (a) Increase (b) increase
2. (a) Decrease (b) decrease
3. (a) Increase (b) decrease
4. (a) Decrease (b) increase

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