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3
MCQ (Single Correct Answer)

A 1 kW signal is transmitted using a communication channel which provides attenuation at the rate of -2 dB per km . If the communication channel has a total length of 5 km , the power of the signal received is [gain in $\mathrm{dB}=10 \log \left(\frac{P_0}{P_i}\right)$ ]

A
900 W
B
100 W
C
990 W
D
1010 W
4
MCQ (Single Correct Answer)

A speech signal of 3 kHz is used to modulate a carrier signal of frequency 1 MHz , using amplitude modulation. The frequencies of the side bands will be

A
1.003 MHz and 0.997 MHz
B
3001 kHz and 2997 kHz
C
1003 kHz and 1000 kHz
D
1 MHz and 0.997 MHz
5
MCQ (Single Correct Answer)

A message signal of frequency $\omega_m$ is superposed on a carrier wave of frequency $\omega_c$ to get an Amplitude Modulated Wave (AM). The frequency of the AM wave will be

A
$\omega_m$
B
$\omega_c$
C
$\frac{\omega_c+\omega_m}{2}$
D
$\frac{\omega_c-\omega_m}{2}$
6
MCQ (Single Correct Answer)

I-V characteristics of four devices are shown in figure.

Identify devices that can be used for modulation

A
(i) and (iii)
B
only (iii)
C
(ii) and some regions of (iv)
D
All the devices can be used
7
MCQ (Single Correct Answer)

A male voice after modulation-transmission sounds like that of a female to the receiver. The problem is due to

A
poor selection of modulation index (selected $0< m< 1$ )
B
poor bandwidth selection of amplifiers
C
poor selection of carrier frequency
D
loss of energy in transmission.
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