Communication Systems — JEE Previous Year Questions

Every Communication Systems question asked in JEE Main and JEE Advanced across the last 186 papers — 12 questions, each with its correct answer. Free to read, no account needed.

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11/186

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All 12 Communication Systems questions

Most recent papers first.

Q1·PhysicsSingle correctJEE Main 2019

In an amplitude modulator circuit, the carrier wave is given by,

C(t) = 4\sin(20000\pi t)

while modulating signal is given by,

m(t) = 2\sin(2000\pi t)

. The values of modulation index and lower side band frequency are:

(A)0.5 and 9 kHz
(B)0.3 and 9 kHz
(C)0.5 and 10 kHz
(D)0.4 and 10 kHz

Q2·PhysicsSingle correctJEE Main 2019

A message signal of frequency 100 MHz and peak voltage 100 V is used to execute amplitude modulation on a carrier wave of frequency 300 GHz and peak voltage 400 V. The modulation index and difference between the two side band frequencies are:

(A)4 ; $2 \times 10^{8}$ Hz
(B)4 ; $1 \times 10^{8}$ Hz
(C)0.25 ; $1 \times 10^{8}$ Hz
(D)0.25 ; $2 \times 10^{8}$ Hz

Q3·PhysicsSingle correctJEE Main 2019

Given below in the left column are different modes of communication using the kinds of waves given in the right column. From the options given below, find the most appropriate match between entries in the left and the right column.

Modes of Communication	Kinds of Waves
A.Optical Fibre Communication	P.Ultrasound
B.Radar	Q.Infrared Light
C.Sonar	R.Microwaves
D.Mobile Phones	S.Radio Waves

(A)A - S, B - Q, C - R, D - P
(B)A - Q, B - S, C - P, D - R
(C)A - R, B - P, C - S, D - Q
(D)A - Q, B - S, C - R, D - P

Q4·PhysicsSingle correctJEE Main 2019

A signal A cos

\omega

t is transmitted using

\nu_0

sin

\omega_0

t as carrier wave. The correct amplitude modulated (AM) signal is:

(A) $\nu_0\sin\left[\omega_0(1+0.01A\sin\omega t)t\right]$
(B) $\nu_0\sin\omega_0t+\frac{A}{2}\sin(\omega_0-\omega)t+\frac{A}{2}\sin(\omega_0+\omega)t$
(C) $\nu_0\sin\omega_0t+A\cos\omega t$
(D) $(\nu_0+A)\cos\omega t\sin\omega_0t$

Q5·PhysicsSingle correctJEE Main 2019

The physical sizes of the transmitter and receiver antenna in a communication system are:

(A)Proportional of carrier frequency
(B)Inversely proportional to modulation frequency
(C)Inversely proportional to carrier frequency
(D)Independent of both carrier and modulation frequency

Q6·PhysicsSingle correctJEE Main 2019

The wavelength of the carrier waves in a modern optical fiber communication network is close to:

(A)1500 nm
(B)600 nm
(C)2400 nm
(D)900 nm

Q7·PhysicsSingle correctJEE Main 2019

In a line of sight radio communication, a distance of about 50 km is kept between the transmitting and receiving antennas. If the height of the receiving antenna is 70m, then the minimum height of the transmitting antenna should be: (Radius of the Earth

= 6.4\times10^{6}

(A)32 m
(B)40 m
(C)51 m
(D)20 m

Q8·PhysicsSingle correctJEE Main 2019

To double the covering range of a TV transition tower, its height should be multiplied by :

(A) $\frac{1}{\sqrt{2}}$
(B)2
(C)4
(D) $\sqrt{2}$

Q9·PhysicsSingle correctJEE Main 2019

A 100 V carrier wave is made to vary between 160 V and 40 V by a modulating signal. What is the modulation index?

(A)0.3
(B)0.5
(C)0.6
(D)0.4

Q10·PhysicsSingle correctJEE Main 2019

An amplitude modulated signal is plotted below: Which one of the following best described the above signal?

(A) $(9+\sin(2.5\pi\times10^{5}t))\sin(2\pi+10^{4}t)$ V
(B) $(1+9\sin(2\pi\times10^{4}t))\sin(2.5\pi\times10^{5}t)$ V
(C) $(9+\sin(2\pi\times10^{4}t))\sin(2.5\pi\times10^{5}t)$ V
(D) $(9+\sin(4\pi\times10^{4}t))\sin(5\pi\times10^{5}t)$ V

Q11·PhysicsSingle correctJEE Main 2019

A TV transmission tower has a height of 140 m and the height of the receiving antenna is 40 m. What is the maximum distance upto which signals can be broadcasted from this tower in LOS (Line of Sight) mode? (Given : radius of earth

= 6.4 \times 10^{6}

m).

(A)65 km
(B)48 km
(C)80 km
(D)40 km

Q12·PhysicsSingle correctJEE Main 2019

In a communication system operating at wavelength 800 nm, only one percent of source frequency is available as signal bandwidth. The number of channels accommodated for transmitting TV signals of band width 6 MHz are (Take velocity of light c =

3 \times 10^{8}

m/s, h =

6.6 \times 10^{-34}

J-s)

(A)3.75 $\times$ 10 $^{6}$
(B)3.86 $\times$ 10 $^{6}$
(C)6.25 $\times$ 10 $^{5}$
(D)4.87 $\times$ 10 $^{5}$

Communication Systems — frequently asked

How many questions from Communication Systems appear in JEE?

Communication Systems has appeared in 11 of the last 186 JEE Main and JEE Advanced papers — about 6% of them — contributing 12 questions in total across those papers.

Is Communication Systems an important chapter for JEE?

Judged by how often it is actually tested, it appears in roughly 6% of papers. Chapters above about 50% are effectively guaranteed to show up every session, so they repay thorough preparation; lower-frequency chapters are better treated as targeted revision.

Where do these Communication Systems questions come from?

Every question is from an official JEE Main or JEE Advanced paper, transcribed from the original paper and tagged to this chapter. Answers follow the official answer key.

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