162. Phase modulation is commonly used for data transmission mainly because
A. phase can be varied from +180? to ?180?
B. it is resistant to the effects of noise
C. demodulation is very easy
D. it gives highest data rates that can be transmitted over a given channel

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163. For satellite transmission, analog signals may be converted into digital form with the help of
A. modem
B. transponder
C. codec
D. compandor

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164. Orbital disturbances of a geosynchronous satellite are caused by the
A. Moon
B. Sun
C. Earth
D. all of the above

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165. The traffic-handling capacity of an Earth station on the up-link depends on
A. its EIRP
B. satellite antenna gain
C. noise associated with the satellite
D. all of the above

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166. The different access methods which permit many satellite users to operate in parallel through a single transponder without interfering with each other are
A. frequency division multiple access (FDMA)
B. time division multiple access (TDMA)
C. code division multiple access (CDMA)
D. all of the above

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167. A colour television signal having bandwidth of 4.6 MHz is digitised using 10 bits/sample. The digital bit rate used for its transmission with PCM would be kilobits/second.
A.92,000
B.920
C.23,000
D.230

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168. Which one of the following statements regarding compandor is FALSE?
A. it compresses the higher-amplitude parts of a signal before modulation and expands them back to normal again after demodulation.
B. it gives perferential treatment to the weaker parts of the signal
C. for weaker signals, it gives a poor ratio of signal strength to quantizing error
D. weaker signals traverse more quantum steps than they would do otherwise and so quantizing error is reduced

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