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1) Amplitude modulation is a. Change in amplitude of the carrier according to modulating signal b. Change in frequency of the carrier according to modulating signal c. Change in amplitude of the modulating signal according to carrier signal d. Change in amplitude of the carrier according to modulating signal frequency
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2) The ability of the receiver to select the wanted signals among the various incoming signals is termed as a. Sensitivity b. Selectivity c. Stability d. None of the above
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3) Emitter modulator amplifier for Amplitude Modulation a. Operates in class A mode b. Has a low efficiency c. Output power is small d. All of the above
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4) Super heterodyne receivers a. Have better sensitivity b. Have high selectivity c. Need extra circuitry for frequency conversion d. All of the above
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5) The AM spectrum consists of a. Carrier frequency b. Upper side band frequency c. Lower side band frequency d. All of the above
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6) Standard intermediate frequency used for AM receiver is a. 455 MHz b. 455 KHz c. 455 Hz d. None of the above
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7) In the TV receivers, the device used for tuning the receiver to the incoming signal is a. Varactor diode b. High pass Filter c. Zener diode d. Low pass filter
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8) The modulation technique that uses the minimum channel bandwidth and transmitted power is a. FM b. DSB-SC c. VSB d. SSB
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9) Calculate the bandwidth occupied by a DSB signal when the modulating frequency lies in the range from 100 Hz to 10KHz. a. 28 KHz b. 24.5 KHz c. 38.6 KHz d. 19.8 KHz
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10) In Amplitude Demodulation, the condition which the load resistor R must satisfy to discharge capacitor C slowly between the positive peaks of the carrier wave so that the capacitor voltage will not discharge at the maximum rate of change of the modulating wave (W is message bandwidth and ω is carrier frequency, in rad/sec) is a. RC < 1/W b. RC > 1/W c. RC < 1/ω d. RC > 1/ω
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11) A modulation index of 0.5 would be same as a. 0.5 of Modulation Depth b. 1/2% of Modulation Depth c. 5% of Modulation Depth d. 50% of Modulation Depth
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12) A 3 GHz carrier is DSB SC modulated by a signal with maximum frequency of 2 MHz. The minimum sampling frequency required for the signal so that the signal is ideally sampled is a. 4 MHz b. 6 MHz c. 6.004 GHz d. 6 GHz
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13) The function of multiplexing is a. To reduce the bandwidth of the signal to be transmitted b. To combine multiple data streams over a single data channel c. To allow multiple data streams over multiple channels in a prescribed format d. To match the frequencies of the signal at the transmitter as well as the receiver
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14) Aliasing refers to a. Sampling of signals less than at Nyquist rate b. Sampling of signals greater than at Nyquist rate c. Sampling of signals at Nyquist rate d. None of the above
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15) The amount of data transmitted for a given amount of time is called a. Bandwidth b. Frequency c. Noise d. Signal power
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16) An AM broadcast station transmits modulating frequencies up to 6 kHz. If the AM station is transmitting on a frequency of 894 kHz, the values for maximum and minimum upper and lower sidebands and the total bandwidth occupied by the AM station are: a. 900 KHz, 888 KHz, 12 KHz b. 894 KHz, 884 KHz, 12 KHz c. 894 KHz, 888 KHz, 6 KHz d. 900 KHz, 888 KHz, 6 KHz
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17) The total power in an Amplitude Modulated signal if the carrier of an AM transmitter is 800 W and it is modulated 50 percent. a. 850 W b. 1000.8 KW c. 750 W d. 900 W
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18) An un modulated AM signal produces a current of 5.4 A. If the modulation is 100 percent,
calculate (a) the carrier power, (b) the total power, (c) the sideband power when it is transmitted through an antenna having an impedance of 50Ω. a. 1458 W, 2187.5 W, 729.25 W b. 278 W, 2187.5 W, 1917.25 W c. 1438 W, 2187.5 W, 759.25 W d. 280 W, 2187.5 W, 750.25 W
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19) Calculate the depth of modulation when a transmitter radiates a signal of 9.8KW after modulation and 8KW without modulation of the signal. a. 80% b. 67% c. 50% d. 100%
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20) When AM signal is of 25KHz, calculate the number of channels required in Medium Frequency (MF) band of 300KHz-3000KHz. a. 94 b. 69 c. 85 d. 54
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