Communication Systems MCQs with Answers 2027

Q121

In a superheterodyne receiver, rejection of the image signal can be achieved by using a

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Q122

In Amplitude Modulation, . . . . . . . . of total transmitted power is used for carrying message signal under best conditions.

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Q123

Open question

Consider the following:
1. Filter system
2. Phase-shift method
3. Third method
4. Balanced modulator
Which of these can be used to remove unwanted side-bands in SSB?

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Q124

Open question

x(t) = A cosωt + B sinωt, the BW of A cosωt is 10 kHz, BW of B sinωt is 15 kHz the BW of the signal x(t) is . . . . . . . .

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Q125

Open question

Which of the following is angle modulation

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Q126

Open question

The diagonal clipping in Amplitude Demodulation (using envelope detector) can be avoided if RC time-constant of the envelope detector satisfies the following condition, (here W is message bandwidth and ω is carrier frequency both in rad/sec)

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Q127

Open question

An antenna pointing in a certain direction has a noise temperature of 50 K. The ambient temperature is 290 K. The antenna is connected to a pre-amplifier that has a noise figure of 2 dB and an available gain of 40 dB over an effective bandwidth of 12 MHz. The effective input noise temperature T_e for the amplifier and the noise power P_a0 at the output of the preamplifier, respectively, are

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Q128

Open question

As the modulation index of an FM signal with sinusoidal modulation is increased from zero to three, the power in the carrier component will

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Q129

Open question

In an amplitude modulated system, if the total power is 600 W and the power in carrier is 400 W, then the modulation index is

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Q130

Open question

For an angle modulated signal x(t) = 3cos[2π10⁶t + 2sin(2π10³t)], what is the maximum frequency deviation?

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Q131

Open question

The input a coherent detector is DSB-SC signal plus noise. The noise at the detector output is

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Q132

Open question

The Foster-Seeley discriminator responds to the input FM signal's

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Q133

Open question

The auto-correlation function of an energy signal has

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Q134

Open question

The output of a transmitter is 100 kW with carrier unmodulated and 132 kW when carrier is modulated by a sinusoidal wave. Then the depth of modulation is

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Q135

Open question

Decoding, storage and interpretation are the process steps of . . . . . . . .

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Q136

Open question

Match List-I with List-II and select the correct answer using the options given below:

List-I	List-II
a. IF Noise	1. Ganged tunning
b. Image frequency	2. Spurious response
c. Station selector	3. Leaky filter capacitor
d. Excessive hum	4. Mixer stage

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Q137

Open question

A product modulator yields

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Q138

Open question

4(1 + 2cos200πt)cos400πt, for demodulation we are using which technique . . . . . . . .

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Q139

Open question

A carrier voltage is simultaneously modulated by two sine waves causing modulation indices of 0.4 and 0.3. The overall modulation index is

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Q140

Open question

A random variable X has

X

= 0 &

σ_{x}^{2}

= 1. Form a new random variable Y = 2X + 1. The values of

Y

&

σ_{y}^{2}

are:

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