1. Hf 2. Mf 3. Lf 4. Vlf 2-50. The density of what ionosphere layer increases because of a violent eruption on the surface of the sun? 1. D 2. E 3. F1 4. F2 2-51. Which irregular variation in ionospheric conditions can cause a waiting period of several days before communications return to normal? 1. Sporadic E 2. Ionospheric storms 3. Sudden ionospheric disturbance 4. Each of the above 2-52. For a radio wave entering the atmosphere of the earth at a given angle, the highest frequency at which refraction will occur is known by which of the following terms? 1. Usable frequency 2. Refraction frequency 3. Maximum usable frequency 4. Optimum working frequency 2-53. The most consistent communications can be expected at which of the following frequencies? 1. Critical frequency 2. Maximum usable frequency 3. Maximum working frequency 4. Optimum working frequency 2-54. If the optimum working frequency for a communications link is 4,250 kHz, what is the approximate maximum usable frequency? *diko lam formula* 1. 4,500 kHz 2. 5,000 kHz 3. 5,500 kHz 4. 6,000 kHz 2-55. In determining the success of radio transmission, which of the following factors is the LEAST predictable? 1. Antenna capabilities 2. Weather conditions along the path of communication 3. Density of ionized layers 4. Presence of ionized layers 2-56. At frequencies above 100 MHz, the greatest attenuation of rf energy from raindrops is caused by which of the following factors? 1. Ducting 2. Heat loss 3. Scattering 4. Absorption 2-57. Under certain conditions, such as ducting, line-of-sight radio waves often propagate for distances far beyond their normal ranges because of which of the following factors? 1. Low cloud masses 2. Ionospheric storms 3. Temperature inversions 4. Frequency fluctuations 2-58. When ducting is present in the atmosphere, multihop refraction of line-of-sight transmission can occur because of which of the following factors?
1. Operating frequency of the transmitter 2. Height of the transmitting antenna 3. Angle of incidence of the radio wave 4. Each of the above 2-59. A propagation technique used to extend uhf transmission range beyond the horizon uses which of the following propagation characteristics? 1. Ground reflection 2. Ionospheric scatter 3. Tropospheric scatter 4. Atmospheric refraction 2-60. Communications by tropospheric scatter can be affected by which of the following conditions? 1. Sunspot activity 2. Atmospheric conditions 3. Ionospheric disturbances 4. All of the above 2-61. What effect, if any, does the radiation angle of a transmitting antenna have on the reception of communications by tropospheric scatter? 1. The lower the angle, the weaker the signal 2. The lower the angle, the stronger the signal 3. The lower the angle, the more susceptible the signal is to distortion 4. None 2-62. Which of the following descriptions of tropospheric scatter signal reception is NOT true?
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- Spring '13
- Resistor, Harlem A. Agnote