57. Indicate the false statement. Modulation is used to
A. reduce the bandwidth used
B. separate differing transmissions
C. ensure that intelligence may be transmitted over long distances
D. allow the use of practicable antennas
58. One of the following is an indirect way of generating FM. This is the ?modulator.
A. reactance tube
B. varactor diode
D. reactance transistor
59. Diversity reception normally means
A. reception of diverse programmes
B. reception of programme from a transmitter through two receivers connected to two different aerial structures half wavelength apart.
C. reception of programme from a transmitter through two receivers connected to two different aerials situated a few wavelengths apart.
D. all the above
60. A carrier is simultaneously modulated by two sine waves with modulation indices of 0.3 and 0.4, the total modulation index
A. is 1
B. cannot be calculated unless the phase relations are known
C. is 0.5
D. is 0.7
61. In a pentode, the screen grid
A.reduces the plate grid capacitance
B.reduces the effect of secondary emission from plate
C. increases the trans-conductance of the tube
D. increase the power-handling capacity of the tube
62. One of the main functions of the RF amplifier in a superheterodyne receiver is to
A. provide improved tracking
B. permit better adjacent-channel rejection
C. increase the tuning range of the receiver
D. improve the rejection of the image frequency
63. In an FM receivet, the channel bandwidth is around ? kHz.
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