If the bandwidth is increased by 2, the ?FM ?AM (where ? is the ratio of SNR of

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Question
If the bandwidth is increased by 2, the ?_FM ?_AM (where ? is the ratio of SNR of output to SNR at input, FM is frequency modulation and AM is amplitude modulation) is increased by a factor of
Options
A. 2
B. 3
C. 4
D. 6

Correct Answer

4

Explanation

Doubling of frequency increase SNR in frequency modulation by 4. It has no effect in AM.

Communication Systems problems

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2. Degaussing in a picture tube means
Options
A. Adding magnetism in mask and mounting frame
B. Removing residual magnetism in mask, shield etc...
C. Increasing resistance of coils to decrease time constant
D. Decreasing resistance of coils to increase time constant.

3. Which of the following has the highest input impedance?
Options
A. CE
B. CB
C. CC
D. Push pull

4. Frequency shift keying is used mostly in
Options
A. telegraphy
B. telephony
C. satellite communication
D. radio transmission

5. In colour TV receiver, varactor diode is used for
Options
A. detection
B. rectification
C. tuning
D. both (a) and (b)

6. When the channel is noisy, producing a conditional probability of error p = 0.5; the channel capacity and entropy function would be, respectively,
Options
A. 1 and 1
B. 1 and 0.5
C. 0.5 and 1
D. 0 and 1

7. c(t) and m(t) are used to generate an FM signal. If the peak frequency deviation of the generated FM signal is three times the transmission bandwidth of the AM signal, then the coefficient of the term cos [2p(1008 x 10³t)] in the FM signal (in terms of the Bessel Coefficients) is
Options
A. 5 J₄(3)
B. J₈(3)
C. J₈(4)
D. 5 J₄(6)

8. A carrier is simultaneously modulated by two sine waves having modulation indices of 0.4 and 0.3. The total modulation index will be
Options
A. 0.1
B. 0.7
C. 0.5
D. 0.35

10. In a fascimile reproduction time to scan one line is 2 ms. If it has 4% blanking, the visible trace time is
Options
A. 1.92 ms
B. 2.08 ms
C. 50 ms
D. 0.08 ms

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