127. Cosmic noise is caused by
A. distant stars
B. lightning discharge
C. solar eruptions
D. none of the above

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128. Probability density function of thermal noise is
A. Poisson
B. Binomial
C. Gaussian
D. None of the above

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129. The autocorrection function of the white noise is
A. impulse function
B. step function
C. constant
D. none of the above

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130. Frequency shift keying is used mostly in
A. telephony
B. telegraphy
C. radio transmission
D. none of the above .

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131. Thermal noise power is
A. proportional to B
B. proportional to 1/F3
C. proportional to 1/B2
D. proportional to B2

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132. If the sampling time is less than the Nyquist interval, then
A. guard time reduces
B. bandwidth increases
C. simpler filters may be used to obtain the original signal
D. channel capacity increases

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133. In order to get the original signal from the sampled signal, which of the following filters should be necessarily used?
A. Band stop filter
B. Low pass filter
C. High pass filter
D. Band pass filter

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