Exercise: Communication Systems

Questions for: Communication Systems

Two sinusoidal signals of same amplitude and frequencies 10 kHz and 10.1 kHz are added together. The combined signal is given to an ideal frequency detector. The output of the detector is
A:
0.1 kHz sinusoidal
B:
10.1 kHz sinusoidal
C:
a linear function
D:
a constant
Answer: B

Y(t) = A cos (2p x 104 t) + A cos (2p x 10.1 x 103 t)

when passed through high pass filter,

Output will be A cos (2p x 10.1 x 103 t) only.

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Some sources of TV programs are
  1. TV camera
  2. Telecine
  3. VTR
  4. External signal
Which of the above are actually present in a TV studio?
A:
1, 2, 3 and 4
B:
1, 2, 3
C:
1 and 3
D:
1 2 and 4
Answer: A

All these are present.

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An amplifier operating over a frequency range of 18 to 20 MHz has 10 kÎĐ input resistance. At a temperature of 27° C, the noise voltage at input of amplifier is (Boltzman constant k = 1.38 x 10-23 J/K)
A:
18.2 ΞV
B:
182 ΞV
C:
16.2 ΞV
D:
162 ΞV
Answer: A

Using Equation Va = (4 x 1.38 x 10-23 x 300 x 2 x 106 x 104)0.5 = 18.2 x 10-6 V.

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Graphic equaliser system in stereophonic systems generally have
A:
3 or 4 bands
B:
1 band
C:
more than 8 bands
D:
large number of bands
Answer: A

Stereo systems have 3 or 4 bands at 300 Hz, 1000 Hz, 10000 Hz etc. in graphic equaliser system.

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The frequency response of a microphone means
A:
bandwidth of frequencies having output with in Âą 1 dB of the output at 1000 Hz
B:
bandwidth of frequencies having output with in Âą 3 dB of the output at 1000 Hz
C:
bandwidth of frequencies having output with in Âą 1 dB of the output at 500 Hz
D:
bandwidth of frequencies having output with in Âą 3 dB of the output at 500 Hz
Answer: A

100 Hz is taken as standard for specifying the output.

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