15. The noise equivalent temperature of a circuit having a noise figure of 11 with a reference temperature of 300?K is oK
A.3000
B.3300
C.30
D.3

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16. The noise figure of a circuit whose noise equivalent temperature and noise reference temperature are the same is
A.1
B.0
C.2
D. infinity

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17. The input signal-to-noise ratio for an envelope detector is90. If the modulation index for the incoming AM waves is 0.5, the output signal-to-noise ratio is
A.20
B.45
C.18
D.180

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18. If input signal-to-noise ratio of a synchronous detector is 100, the output signal-to-noise ratio is
A.50
B.25
C.200
D.400

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19. If maximum frequency deviation of a transmission system is 75 kHz and modulating frequency is 15 kHz, the improvement in the output S/N ratio due to FM over a comparable AM system with m = 1 is
A.25
B.75
C.90
D.225

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20. The minimum value of ms for an FM system required to produce a noticeable improvement in S/N ratio over a comparable AM system with m =1 is
A. ji
B.
C. it
D.1/./3

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21. The major source of thermal noise in a microwave system is
A. waveguide feeder
B. receiver mixer
C. TWT amplifier transmitter
D. FM demodulator

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