A transmitting antenna is kept on the surface of the earth. The minimum height of receiving antenna required to receive the signal in line of sight at $4 km$ distance from it is $x \times 10^{- 2} m$ . The value of $x$ is __________.

(Let, radius of earth $R = 6400 km$ )

1.25

125

1250

12.5

Question 7.

A message signal of frequency $3 kHz$ is used to modulate a carrier signal of frequency $1.5 MHz$ . The bandwidth of the amplitude modulated wave is

6 MHz

6 kHz

3 MHz

3 kHz

Question 8.

A carrier wave of amplitude 15 V is modulated by a sinusoidal base band signal of magnitude 3 V. The ratio of maximum amplitude to minimum amplitude in an amplitude modulated wave is

\frac{3}{2}

Question 9.

The power radiated from a linear antenna of length $l$ is proportional to

(Given, $λ =$ Wavelength of wave):

{(\frac{l}{λ})}^{2}

\frac{l}{λ^{2}}

\frac{l^{2}}{λ}

\frac{l}{λ}

Question 10.

A TV transmitting antenna is $98 m$ high and the receiving antenna is at the ground level. If the radius of the earth is $6400 km$ , the surface area covered by the transmitting antenna is approximately:

4868 {km}^{2}

1240 {km}^{2}

3942 {km}^{2}

1549 {km}^{2}

Question 1.

For an amplitude modulated wave the minimum amplitude is $3 V$ , while the modulation index is $60 %$ . The maximum amplitude of the modulated wave is:

5 V

12 V

10 V

15 V

Question 2.

By what percentage will the transmission range of a TV tower be affected when the height of the tower is increased by $21 %$ ?

12%

15%

10%

14%

Question 3.

In an amplitude modulation, a modulating signal having amplitude of X Volt is superimposed with a carrier signal of amplitude Y Volt in first case. Then, in second case, the same modulating signal is superimposed with different carrier signal of amplitude 2Y Volt. The ratio of modulation index in the two cases respectively will be :

2 : 1

1 : 1

4 : 1

1 : 2

Question 4.

Which of the following frequencies does not belong to FM broadcast ?

106 MHz

89 MHz

64 MHz

99 MHz

Question 5.

Given below are two statements :

Statement I : For transmitting a signal, size of antenna ( $l$ ) should be comparable to wavelength of signal (at least $l = \frac{λ}{4}$ in dimension)

Statement II: In amplitude modulation, amplitude of carrier wave remains constant (unchanged).

In the light of the above statements, choose the most appropriate answer from the options given below

Statement I is incorrect but Statement II is correct

Both Statement I and Statement II are correct

Both Statement I and Statement II are incorrect

Statement I is correct but Statement II is incorrect

Question 6.

The amplitude of $15 \sin (1000 π t)$ is modulated by $10 \sin (4 π t)$ signal. The amplitude modulated signal contains frequency (ies) of

A. $500 Hz$

B. $2 Hz$

C. $250 Hz$

D. $498 Hz$

E. $502 Hz$

Choose the correct answer from the options given below:

B only

A only

A, D and E only

A and B only

Question 7.

Match List I with List II:

List I	List II
A. Attenuation	I. Combination of a receiver and transmitter.
B. Transducer	II. process of retrieval of information from the carrier wave at receiver
C. Demodulation	III. converts one form of energy into another
D. quad Repeater	IV. Loss of strength of a signal while propagating through a medium.

Choose the correct answer from the options given below:

A-I, B-II, C-III, D-IV

A-IV, B-III, C-I, D-II

A-IV, B-III, C-II, D-I

A-II, B-III, C-IV, D-I

Question 8.

A sinusoidal carrier voltage is amplitude modulated. The resultant amplitude modulated wave has maximum and minimum amplitude of $120 V$ and $80 V$ respectively. The amplitude of each sideband is :

15 V

20 V

5 V

10 V

Question 9.

The modulation index for an A.M. wave having maximum and minimum peak-to-peak voltages of 14 mV and 6 mV respectively is-

0.4

0.6

1.4

0.2

Question 10.

If the height of transmitting and receiving antennas are 80 m each, the maximum line of sight distance will be:

Given : Earth's radius $= 6.4 \times 10^{6}$ m

28 km

64 km

32 km

36 km

JEE Main Communication Systems Practice Questions With Solutions

JEE Main Physics Communication Systems Practice Questions

Question 1.

Question 2.

Question 3.

Question 4.

Question 5.

Question 6.

Question 7.

Question 8.

Question 9.

Question 10.

Question 1.

Question 2.

Question 3.

Question 4.

Question 5.

Question 6.

Question 7.

Question 8.

Question 9.

Question 10.

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