Space wave may be a direct wave or wave reflected from earth. True False Strengt

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Question
Space wave may be a direct wave or wave reflected from earth.
Options
A. True
B. False

Correct Answer

False

Explanation

Strength of space wave depends on distance as it suffers attenuation.

Communication Systems problems

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1. 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.

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

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

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

5. Which of the following cannot be the Fourier series expansion of a periodic signal?
Options
A. x(t) = 2 cos t + 3 cos 3t
B. x(t) = 2 cos pt + 7 cos t
C. x(t) = cos t + 0.5
D. x(t) = 2 cos 1.5pt + sin 3.5 pt

6. 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

7. 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

8. 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)

9. 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

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