253.  Four signals each band-limited to 5 kHz are sampled at twice the Nyquist rate. The resulting PAM samples are transmitted over a single channel after time division multiplexing. The theoretical minimum transmission bandwidth of the channel should be equal to
A. 5 kHz
B. 20 kHz
C. 40 kHz
D. 80 kHz

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254.  Which one of the followingstatements regarding the following signal : x(t) = 5 sin (2n x 1030 sin(2n x 1060 is correct?
A. The upper side band frequency is 1001000
B. The lower side band frequency is 999000
C. x(t) is a DSB ? SC signal
D. All of these

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255.  In case a signal band limited to fm is sampled at a rate less than 2 fm, the constructed signal will be
A. distortionless
B. small in amplitude
C. having higher frequencies suppressed
D. distorted

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256.  An arbitrary signal m(t) has zero average value and it is band-limited to 3.2 kHz. It is sampled at the rate of 8k samples/s. The samples are passed through an ideal band-phass filter with centre frequency of 3.2 kHz and bandwidth of 6.4 kHz. The output of the band-pass filter is
A. AM-DSB signal with suppressed carrier
B. AM-DSB signal with carrier
C. AM-SSB signal with carrier
D. a sequence of exponentially decaying sine waves

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257. If the radiated power of AM transmitter is 10 kW, the power in thecarrier for modulation index of 0.6 is nearly
A. 8.24 kW
B. 8.47 kW
C. 9.26 kW
D. 9.6 kW

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258. One of the main functions of the RF amplifiers in a superheterodyne receiver is to
A. provide improved tracking
B. permit better adjacent channel rejection
C. increase the tuning range of the receiver
D. improve the reflection of the image frequency

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259. The phase shift method for generation of SSB signal is most suitable for
A. data signals
B. weak modulating signals
C. larger bandwidth modulating signals
D. smaller bandwidth modulating signals

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