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1) De emphasis is a. is restoring of original signal power b. is done at the detector output of the receiver c. is the inverse process of Pre emphasis d. All of the above
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2) Pre emphasis is done before a. Before modulation b. Before transmission c. Before detection at receiver d. After detection at receiver
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3) What is the effect on the deviation d of an FM signal when it is passed through a mixer? a. Doubles b. Reduces c. Becomes half d. Remains unchanged
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4) Armstrong method is used for the generation of a. Direct FM b. Indirect FM c. SSB-SC d. DSB-SC
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5) The modulation index of FM is given by a. μ = frequency deviation/ modulating frequency b. μ = modulating frequency /frequency deviation c. μ = modulating frequency/ carrier frequency d. μ = carrier frequency / modulating frequency
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6) Disadvantages of FM over AM are a. Prone to selective fading b. Capture effect c. Poorer signal to noise ratio at high audio frequencies d. All of the above
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7) What is the required bandwidth according to the Carson’s rule, when a 100 MHz carrier is modulated with a sinusoidal signal at 1KHz, the maximum frequency deviation being 50 KHz. a. 1 KHz b. 50 KHz c. 102 KHz d. 150 KHz
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8) The audio signal having frequency 500Hz and voltage 2.6V, shows a deviation of 5.2KHz in a Frequency Modulation system. If the audio signal voltage changes to 8.6V, calculate the new deviation obtained. a. 17.2 KHz b. 19.6 KHz c. 25.6 KHz d. 14.6 KHz
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9) What is the change in the bandwidth of the signal in FM when the modulating frequency increases from 12 KHz to 24KHz? a. 40 Hz b. 58 Hz c. 24 Hz d. Bandwidth remains unaffected
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10) What is the maximum frequency deviation allowed in commercial FM broadcasting? a. 100 KHz b. 75 KHz c. 15 KHz d. 120 KHz
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11) What is the maximum modulating frequency allowed in commercial FM broadcastings? a. 40 KHz b. 75 KHz c. 15 KHz d. 120 KHz
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12) The ratio of actual frequency deviation to the maximum allowable frequency deviation is called a. Multi tone modulation b. Percentage modulation c. Phase deviation d. Modulation index
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13) The range of modulating frequency for Narrow Band FM is a. 30 Hz to 15 KHz b. 30 Hz to 30 KHz c. 30 Hz to 3 KHz d. 3 KHz to 30 KHz
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14) FM is advantageous over AM as a. The amplitude of FM is constant. So transmitter power remains unchanged in FM but it changes in AM b. The depth of modulation in FM can be changed to any value by changing the frequency deviation. So the signal is not distorted c. There is less possibility of adjacent channel interference due to presence of guard bands d. All of the above
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15) VCO is used to generate a. Direct FM b. Indirect FM c. SSB-SC d. DSB-SC
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16) Change in instantaneous phase of the carrier with change in amplitude of the modulating signal generates a. Direct FM b. Indirect FM c. SSB-SC d. DSB-SC
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17) Phase-locked loop can be used as a. FM demodulator b. AM demodulator c. FM receiver d. AM receiver
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18) The increase or decrease in the frequency around the carrier frequency is termed as a. Figure factor b. Frequency deviation c. Modulation index d. Frequency pectrum
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19) Carson's rule is used to calculate a. Bandwidth of FM signal b. Signal to noise ratio c. Modulation index d. Noise figure
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20) The ratio of maximum peak frequency deviation and the maximum modulating signal frequency is termed as a. Frequency deviation b. Deviation ratio c. Signal to noise ratio d. Frequency spectrum
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