Analog Communication System MCQs

Question 1

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

Accepted Answer

80

Answer

32

Answer

64

Answer

92

Question 2

If a 240-W carrier is simulataneously modulated by two sine waves with modulation indices of 0.3 and 0.4, its total modulation index is

Accepted Answer

0.5

Answer

0.7

Answer

0.12

Answer

0.75

Question 3

In an amplitude-modulated wave-form, the amplitude of side bands is

Accepted Answer

?2 x carrier amplitude x modulation index

Answer

independent of carrier amplitude

Answer

independent of modulation index

Answer

carrier amplitude x modulation index

Question 4

In the spectrum of an FM wave

Accepted Answer

amplitude of any sideband depends on the value of modulation index

Answer

total number of sidebands depends on the value of modulation index

Answer

carrier frequency can disappear if modulation index is high

Answer

carrier frequency cannot disappear whatever the modulation index

Question 5

When a signal with modulation index of m is passed through a frequency doubler, the output wave from the doubler will have a modulation index of

Accepted Answer

4m

Answer

m

Answer

I11/2

Answer

2m

Question 6

Modulated carrier power in FM

Accepted Answer

is independent of modulating signal power

Answer

increases with modulating signal power

Answer

decreases with modulating signal power

Question 7

For a PM signal, the modulating index depends upon

Accepted Answer

onyl the amplitude of the modulating signal

Answer

only the frequency of the modulating signal

Answer

both the amplitude and frequency of the modulating signal

Answer

the frequency of the carrier signal amongst other things

Question 8

Tick mark the false statement (s). In the spectrum of frequency-modulated wave

Accepted Answer

the carrier frequency disappears when the modulation index is large

Answer

the amplitude of any sideband depends on the modulation index

Answer

the total number of sidebands depends on the modulation index

Answer

the carrier frequency cannot disappear

Question 9

An FM signal with a modulation index m1 is passed through a frequency tripler. The wave in the output of the tripler will have a modulationindex of

Accepted Answer

3 mf

Answer

m1/3

Answer

mf

Answer

9 mf