Frequency shift keying is used mostly in telegraphy telephony satellite communic

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

Correct Answer

telegraphy

Explanation

Frequency shift keying (FSK) is a system of frequency modulation used in telegraphy.

Communication Systems problems

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

2. 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

3. If C is capacity of noisy channel, (bits/s), ?f is bandwidth Hz and S/N is signal to noise ratio, then
Options
A.
B.
C.
D.

4. A 1000 kHz carrier is simultaneously modulated with 300 Hz, 800 Hz and 2 kHz audio sine waves. Which of the following frequency is least likely to be present in the output?
Options
A. 1002 kHz
B. 1000 kHz
C. 999.2 kHz
D. 998.0 kHz

5. Tracking of extra terrestrial objects requires
Options
A. high transmitting power
B. very sensitive receiver
C. fully steerable antenna
D. all of the above

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

7. 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.

9. 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

10. 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

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