25. Communication Systems

If the carrier wave is given as c(t)=2sin‌(8πt) volts, the modulation index is :

[24-Jan-2023 Shift 1]

A modulating signal is a square wave, as shown in the figure.

If the carrier wave is given as c(t)=2sin‌(8πt) volts, the modulation index is :

[24-Jan-2023 Shift 1]

Q.2 Correct

Q.2 In-correct

Q.2 Unattempt

Match List I with List II

Choose the correct answer from the options given below:

[24-Jan-2023 Shift 2]

Match List I with List II

Choose the correct answer from the options given below:

[24-Jan-2023 Shift 2]

Q.3 Correct

Q.3 In-correct

Q.3 Unattempt

A message signal of frequency 5‌kHz is used to modulate a carrier signal of frequency 2 MHz. The bandwidth for amplitude modulation is:

[25-Jan-2023 Shift 1]

A message signal of frequency 5‌kHz is used to modulate a carrier signal of frequency 2 MHz. The bandwidth for amplitude modulation is:

[25-Jan-2023 Shift 1]

Q.4 Correct

Q.4 In-correct

Q.4 Unattempt

If the height of transmitting and receiving antennas are 80m each, the maximum line of sight distance will be :
Given : Earth's radius =6.4×106m.

[29-Jan-2023 Shift 1]

If the height of transmitting and receiving antennas are 80m each, the maximum line of sight distance will be :
Given : Earth's radius =6.4×106m.

[29-Jan-2023 Shift 1]

Q.5 Correct

Q.5 In-correct

Q.5 Unattempt

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

[29-Jan-2023 Shift 2]

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

[29-Jan-2023 Shift 2]

Q.6 Correct

Q.6 In-correct

Q.6 Unattempt

Match List I with List II :

Choose the correct answer from the options given below :

[30-Jan-2023 Shift 2]

Match List I with List II :

Choose the correct answer from the options given below :

[30-Jan-2023 Shift 2]

Q.7 Correct

Q.7 In-correct

Q.7 Unattempt

The amplitude of 15sin‌(1000πt) is modulated by 10sin‌(4πt) signal. The amplitude modulated signal contains frequency(ies) of
(A) 500‌Hz
(B) 2‌Hz
(C) 250‌Hz
(D) 498‌Hz
(E) 502‌Hz
Choose the correct answer from the options given below:

[31-Jan-2023 Shift 1]

The amplitude of 15sin‌(1000πt) is modulated by 10sin‌(4πt) signal. The amplitude modulated signal contains frequency(ies) of
(A) 500‌Hz
(B) 2‌Hz
(C) 250‌Hz
(D) 498‌Hz
(E) 502‌Hz
Choose the correct answer from the options given below:

[31-Jan-2023 Shift 1]

Q.8 Correct

Q.8 In-correct

Q.8 Unattempt

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=‌

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
[1-Feb-2023 Shift 1]

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=‌

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
[1-Feb-2023 Shift 1]

Q.9 Correct

Q.9 In-correct

Q.9 Unattempt

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

[1-Feb-2023 Shift 1]

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

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

[1-Feb-2023 Shift 2]

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

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

[6-Apr-2023 shift 1]

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

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

[6-Apr-2023 shift 2]

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

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

[8-Apr-2023 shift 1]

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

The power radiated from a linear antenna of length l is proportional to (Given, λ= Wavelength of wave):

[8-Apr-2023 shift 2]

The power radiated from a linear antenna of length l is proportional to (Given, λ= Wavelength of wave):

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

[10-Apr-2023 shift 1]

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

[10-Apr-2023 shift 1]

Q.16 Correct

Q.16 In-correct

Q.16 Unattempt

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

[10-Apr-2023 shift 2]

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

[10-Apr-2023 shift 2]

Q.17 Correct

Q.17 In-correct

Q.17 Unattempt

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 4‌km distance from it is x×10−2m. The value of x is (Let, radius of earth R=6400‌km )

[11-Apr-2023 shift 1]

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 4‌km distance from it is x×10−2m. The value of x is (Let, radius of earth R=6400‌km )

[11-Apr-2023 shift 1]

Q.18 Correct

Q.18 In-correct

Q.18 Unattempt

In satellite communication, the uplink frequency band used is:

[11-Apr-2023 shift 2]

In satellite communication, the uplink frequency band used is:

[11-Apr-2023 shift 2]

Q.19 Correct

Q.19 In-correct

Q.19 Unattempt

The amplitude of 15sin‌(100πt) is modulated by 10sin‌(4πt) signal. The amplitude modulated signal contains frequencies of
A. 500‌Hz
B. 2‌Hz
C. 250‌Hz
D. 498‌Hz
E. 502‌Hz
Choose the correct answer from the options given below :

[12-Apr-2023 shift 1]

The amplitude of 15sin‌(100πt) is modulated by 10sin‌(4πt) signal. The amplitude modulated signal contains frequencies of
A. 500‌Hz
B. 2‌Hz
C. 250‌Hz
D. 498‌Hz
E. 502‌Hz
Choose the correct answer from the options given below :

[12-Apr-2023 shift 1]

Q.20 Correct

Q.20 In-correct

Q.20 Unattempt

Match List - I with List - II

Choose the correct answer from the options given below:

[13-Apr-2023 shift 1]

Match List - I with List - II

Choose the correct answer from the options given below:

[13-Apr-2023 shift 1]

Q.21 Correct

Q.21 In-correct

Q.21 Unattempt

To radiate EM signal of wavelength λ with high efficiency, the antennas should have a minimum size equal to:

[13-Apr-2023 shift 2]

To radiate EM signal of wavelength λ with high efficiency, the antennas should have a minimum size equal to:

[13-Apr-2023 shift 2]

Q.22 Correct

Q.22 In-correct

Q.22 Unattempt

The height of transmitting antenna is 180m and the height of the receiving antenna is 245m. The maximum distance between them for satisfactory communication in line of sight will be: (given R=6400‌km )

[15-Apr-2023 shift 1]

The height of transmitting antenna is 180m and the height of the receiving antenna is 245m. The maximum distance between them for satisfactory communication in line of sight will be: (given R=6400‌km )

[15-Apr-2023 shift 1]

Q.23 Correct

Q.23 In-correct

Q.23 Unattempt

A baseband signal of 3.5‌MHz frequency is modulated with a carrier signal of 3.5‌GHz frequency using amplitude modulation method. What should be the minimum size of antenna required to transmit the modulated signal?

[24-Jun-2022-Shift-1]

A baseband signal of 3.5‌MHz frequency is modulated with a carrier signal of 3.5‌GHz frequency using amplitude modulation method. What should be the minimum size of antenna required to transmit the modulated signal?

[24-Jun-2022-Shift-1]

Q.24 Correct

Q.24 In-correct

Q.24 Unattempt

An antenna is placed in a dielectric medium of dielectric constant 6.25. If the maximum size of that antenna is 5.0‌mm, it can radiate a signal of minimum frequency of ____GHz
(Given µr=1 for dielectric medium)

[24-Jun-2022-Shift-2]

An antenna is placed in a dielectric medium of dielectric constant 6.25. If the maximum size of that antenna is 5.0‌mm, it can radiate a signal of minimum frequency of ____GHz
(Given µr=1 for dielectric medium)

[24-Jun-2022-Shift-2]

Q.25 Correct

Q.25 In-correct

Q.25 Unattempt

A signal of 100‌THz frequency can be transmitted with maximum efficiency by :

[25-Jun-2022-Shift-1]

A signal of 100‌THz frequency can be transmitted with maximum efficiency by :

[25-Jun-2022-Shift-1]

Q.26 Correct

Q.26 In-correct

Q.26 Unattempt

Choose the correct answer from the following options:

[25-Jun-2022-Shift-2]

Choose the correct answer from the following options:

[25-Jun-2022-Shift-2]

Q.27 Correct

Q.27 In-correct

Q.27 Unattempt

Choose the correct statement for amplitude modulation :

[26-Jun-2022-Shift-1]

Choose the correct statement for amplitude modulation :

[26-Jun-2022-Shift-1]

Q.28 Correct

Q.28 In-correct

Q.28 Unattempt

A sinusoidal wave y(t)=40‌sin(10×106πt) is amplitude modulated by another sinusoidal wave x(t)=20‌sin(1000πt). The amplitude of minimum frequency component of modulated signal is :

[26-Jun-2022-Shift-2]

A sinusoidal wave y(t)=40‌sin(10×106πt) is amplitude modulated by another sinusoidal wave x(t)=20‌sin(1000πt). The amplitude of minimum frequency component of modulated signal is :

[26-Jun-2022-Shift-2]

Q.29 Correct

Q.29 In-correct

Q.29 Unattempt

The height of a transmitting antenna at the top of a tower is 25m and that of receiving antenna is, 49m. The maximum distance between them, for satisfactory communication in LOS (Line-Of-Sight) is K√5×102m. The value of K is____
(Assume radius of Earth is 64×10+5m ) [Calculate upto nearest integer value]

[27-Jun-2022-Shift-1]

The height of a transmitting antenna at the top of a tower is 25m and that of receiving antenna is, 49m. The maximum distance between them, for satisfactory communication in LOS (Line-Of-Sight) is K√5×102m. The value of K is____
(Assume radius of Earth is 64×10+5m ) [Calculate upto nearest integer value]

[27-Jun-2022-Shift-1]

Q.30 Correct

Q.30 In-correct

Q.30 Unattempt

We do not transmit low frequency signal to long distances because-
(a) The size of the antenna should be comparable to signal wavelength which is unreal solution for a signal of longer wavelength.
(b) Effective power radiated by a long wavelength baseband signal would be high.
(c) We want to avoid mixing up signals transmitted by different transmitter simultaneously.
(d) Low frequency signal can be sent to long distances by superimposing with a high frequency wave as well.
Therefore, the most suitable option will be :

[27-Jun-2022-Shift-2]

We do not transmit low frequency signal to long distances because-
(a) The size of the antenna should be comparable to signal wavelength which is unreal solution for a signal of longer wavelength.
(b) Effective power radiated by a long wavelength baseband signal would be high.
(c) We want to avoid mixing up signals transmitted by different transmitter simultaneously.
(d) Low frequency signal can be sent to long distances by superimposing with a high frequency wave as well.
Therefore, the most suitable option will be :

[27-Jun-2022-Shift-2]

Q.31 Correct

Q.31 In-correct

Q.31 Unattempt

Match List-I with List-II

[28-Jun-2022-Shift-1]

Match List-I with List-II

[28-Jun-2022-Shift-1]

Q.32 Correct

Q.32 In-correct

Q.32 Unattempt

Amplitude modulated wave is represented by VAM=10[1+0.4‌cos(2π×104t)‌cos(2π×107t).. The total bandwidth of the amplitude modulated wave is :

[28-Jun-2022-Shift-2]

Amplitude modulated wave is represented by VAM=10[1+0.4‌cos(2π×104t)‌cos(2π×107t).. The total bandwidth of the amplitude modulated wave is :

[28-Jun-2022-Shift-2]

Q.33 Correct

Q.33 In-correct

Q.33 Unattempt

Only 2% of the optical source frequency is the available channel bandwidth for an optical communicating system operating at 1000‌nm. If an audio signal requires a bandwidth of 8‌kHz, how many channels can be accommodated for transmission :

[29-Jun-2022-Shift-1]

Only 2% of the optical source frequency is the available channel bandwidth for an optical communicating system operating at 1000‌nm. If an audio signal requires a bandwidth of 8‌kHz, how many channels can be accommodated for transmission :

[29-Jun-2022-Shift-1]

Q.34 Correct

Q.34 In-correct

Q.34 Unattempt

The TV transmission tower at a particular station has a height of 125m. For doubling the coverage of its range, the height of the tower should be increased by

[29-Jun-2022-Shift-2]

The TV transmission tower at a particular station has a height of 125m. For doubling the coverage of its range, the height of the tower should be increased by

[29-Jun-2022-Shift-2]

Q.35 Correct

Q.35 In-correct

Q.35 Unattempt

The required height of a TV tower which can cover the population of 6.03 lakh is h. If the average population density is 100 per square km and the radius of earth is 6400km, then the value of h will be

[25-Jul-2022-Shift-1]

The required height of a TV tower which can cover the population of 6.03 lakh is h. If the average population density is 100 per square km and the radius of earth is 6400km, then the value of h will be

[25-Jul-2022-Shift-1]

Q.36 Correct

Q.36 In-correct

Q.36 Unattempt

A radio can tune to any station in 6‌MHz to 10‌MHz band. The value of corresponding wavelength bandwidth will be:

[26-Jul-2022-Shift-1]

A radio can tune to any station in 6‌MHz to 10‌MHz band. The value of corresponding wavelength bandwidth will be:

[26-Jul-2022-Shift-1]

Q.37 Correct

Q.37 In-correct

Q.37 Unattempt

The maximum and minimum voltage of an amplitude modulated signal are 60V and 20V respectively. The percentage modulation index will be :

[26-Jul-2022-Shift-2]

The maximum and minimum voltage of an amplitude modulated signal are 60V and 20V respectively. The percentage modulation index will be :

[26-Jul-2022-Shift-2]

Q.38 Correct

Q.38 In-correct

Q.38 Unattempt

At a particular station, the TV transmission tower has a height of 100m. To triple its coverage range, height of the tower should be increased to

[27-Jul-2022-Shift-1]

At a particular station, the TV transmission tower has a height of 100m. To triple its coverage range, height of the tower should be increased to

[27-Jul-2022-Shift-1]

Q.39 Correct

Q.39 In-correct

Q.39 Unattempt

A square wave of the modulating signal is shown in the figure. The carrier wave is given by C(t)=5‌sin(8πt) Volt. The modulation index is :

[27-Jul-2022-Shift-2]

A square wave of the modulating signal is shown in the figure. The carrier wave is given by C(t)=5‌sin(8πt) Volt. The modulation index is :

[27-Jul-2022-Shift-2]

Q.40 Correct

Q.40 In-correct

Q.40 Unattempt

In the case of amplitude modulation to avoid distortion the modulation index (µ) should be:

[28-Jul-2022-Shift-1]

In the case of amplitude modulation to avoid distortion the modulation index (µ) should be:

[28-Jul-2022-Shift-1]

Q.41 Correct

Q.41 In-correct

Q.41 Unattempt

A FM Broadcast transmitter, using modulating signal of frequency 20‌kHz has a deviation ratio of 10 . The Bandwidth required for transmission is :

[28-Jul-2022-Shift-2]

A FM Broadcast transmitter, using modulating signal of frequency 20‌kHz has a deviation ratio of 10 . The Bandwidth required for transmission is :

[28-Jul-2022-Shift-2]

Q.42 Correct

Q.42 In-correct

Q.42 Unattempt

Find the modulation index of an AM wave having 8V variation where maximum amplitude of the AM wave is 9V.

[29-Jul-2022-Shift-1]

Find the modulation index of an AM wave having 8V variation where maximum amplitude of the AM wave is 9V.

[29-Jul-2022-Shift-1]

Q.43 Correct

Q.43 In-correct

Q.43 Unattempt

A modulating signal 2‌sin(6.28×106)‌t is added to the carrier signal 4‌sin(12.56×109)‌t for amplitude modulation. The combined signal is passed through a non-linear square law device. The output is then passed through a band pass filter. The bandwidth of the output signal of band pass filter will be _______ MHz.

[29-Jul-2022-Shift-2]

A modulating signal 2‌sin(6.28×106)‌t is added to the carrier signal 4‌sin(12.56×109)‌t for amplitude modulation. The combined signal is passed through a non-linear square law device. The output is then passed through a band pass filter. The bandwidth of the output signal of band pass filter will be _______ MHz.

[29-Jul-2022-Shift-2]

Q.44 Correct

Q.44 In-correct

Q.44 Unattempt

If the highest frequency modulating a carrier is 5kHz, then the number of AM broadcast stations accommodated in a 90kHz bandwidth are ......... .

[26 Feb 2021 Shift 2]

If the highest frequency modulating a carrier is 5kHz, then the number of AM broadcast stations accommodated in a 90kHz bandwidth are ......... .

[26 Feb 2021 Shift 2]

Q.45 Correct

Q.45 In-correct

Q.45 Unattempt

The maximum and minimum amplitude of an amplitude modulated wave is 16V and 8V, respectively. The modulation index for this amplitude modulated wave is ×10−2. The value of x is .......... .

[26 Feb 2021 Shift 1]

The maximum and minimum amplitude of an amplitude modulated wave is 16V and 8V, respectively. The modulation index for this amplitude modulated wave is ×10−2. The value of x is .......... .

[26 Feb 2021 Shift 1]

Q.46 Correct

Q.46 In-correct

Q.46 Unattempt

If a message signal of frequency fm is amplitude modulated with a carrier signal of frequency fc and radiated through an antenna, the wavelength of the corresponding signal in air is

[25 Feb 2021 Shift 2]

If a message signal of frequency fm is amplitude modulated with a carrier signal of frequency fc and radiated through an antenna, the wavelength of the corresponding signal in air is

[25 Feb 2021 Shift 2]

Q.47 Correct

Q.47 In-correct

Q.47 Unattempt

Given, below are two statements
Statement I A speech signal of 2kHz is used to modulate a carrier signal of 1MHz. The bandwidth requirement for the signal is 4kHz.
Statement II The side band frequencies are 1002kHz and 998kHz. In the light of the above statements, choose the correct answer from the options given below

[25 Feb 2021 Shift 1]

Given, below are two statements
Statement I A speech signal of 2kHz is used to modulate a carrier signal of 1MHz. The bandwidth requirement for the signal is 4kHz.
Statement II The side band frequencies are 1002kHz and 998kHz. In the light of the above statements, choose the correct answer from the options given below

[25 Feb 2021 Shift 1]

Q.48 Correct

Q.48 In-correct

Q.48 Unattempt

An audio signal vm=20‌sin‌2‌π(

1500

t

). amplitude modulates a carrier vc=80‌sin‌2‌π (100,000 t).
The value of percent modulation is

[24feb2021shift1]

An audio signal vm=20‌sin‌2‌π(

1500

t

). amplitude modulates a carrier vc=80‌sin‌2‌π (100,000 t).
The value of percent modulation is

If a message signal of frequency fm is amplitude modulated with a carrier signal of frequency fc and radiated through an antenna, the wavelength of the corresponding signal in air is

[25 Feb 2021 Shift 2]

If a message signal of frequency fm is amplitude modulated with a carrier signal of frequency fc and radiated through an antenna, the wavelength of the corresponding signal in air is

[25 Feb 2021 Shift 2]

Q.50 Correct

Q.50 In-correct

Q.50 Unattempt

A TV transmission tower antenna is at a height of 20m. Suppose that the receiving antenna is at
(i) ground level
(ii) a height of 5m.
The increase in antenna range in case (ii) relative to case (i) is n%.
The value of n, to the nearest integer, is

[18 Mar 2021 Shift 2]

A TV transmission tower antenna is at a height of 20m. Suppose that the receiving antenna is at
(i) ground level
(ii) a height of 5m.
The increase in antenna range in case (ii) relative to case (i) is n%.
The value of n, to the nearest integer, is

[18 Mar 2021 Shift 2]

Q.51 Correct

Q.51 In-correct

Q.51 Unattempt

For VHF signal broadcasting, ........ km2 of maximum service area will be covered by an antenna tower of height 30m, if the receiving antenna is placed at ground. Let radius of the Earth be 6400km. (Round off to the nearest integer).
(Take π as 3.14 )

[17 Mar 2021 Shift 1]

For VHF signal broadcasting, ........ km2 of maximum service area will be covered by an antenna tower of height 30m, if the receiving antenna is placed at ground. Let radius of the Earth be 6400km. (Round off to the nearest integer).
(Take π as 3.14 )

[17 Mar 2021 Shift 1]

Q.52 Correct

Q.52 In-correct

Q.52 Unattempt

Two identical antennas mounted on identical towers are separated from each other by a distance of 45km. What should nearly be the minimum height of receiving antenna to receive the signals in line of sight? (Assume, radius of earth is 6400km.)

[16 Mar 2021 Shift 2]

Two identical antennas mounted on identical towers are separated from each other by a distance of 45km. What should nearly be the minimum height of receiving antenna to receive the signals in line of sight? (Assume, radius of earth is 6400km.)

[16 Mar 2021 Shift 2]

Q.53 Correct

Q.53 In-correct

Q.53 Unattempt

A 25m long antenna is mounted on an antenna tower. The height of the antenna tower is 75m. The wavelength (in m ) of the signal transmitted by this antenna would be

[16 Mar 2021 Shift 1]

A 25m long antenna is mounted on an antenna tower. The height of the antenna tower is 75m. The wavelength (in m ) of the signal transmitted by this antenna would be

[16 Mar 2021 Shift 1]

Q.54 Correct

Q.54 In-correct

Q.54 Unattempt

What should be the height of transmitting antenna and the population covered if the television telecast is to cover a radius of 150km ? The average population density around the tower is 2000∕km2 and the value of Re=6.5×106m.

[22 Jul 2021 Shift 2]

What should be the height of transmitting antenna and the population covered if the television telecast is to cover a radius of 150km ? The average population density around the tower is 2000∕km2 and the value of Re=6.5×106m.

[22 Jul 2021 Shift 2]

Q.55 Correct

Q.55 In-correct

Q.55 Unattempt

A message signal of frequency 20 kHz and peak voltage of 20 volt is used to modulate a carrier wave of frequency 1 MHz and peak voltage of 20 volt. The modulation index will be :

[25 Jul 2021 Shift 2]

A message signal of frequency 20 kHz and peak voltage of 20 volt is used to modulate a carrier wave of frequency 1 MHz and peak voltage of 20 volt. The modulation index will be :

[25 Jul 2021 Shift 2]

Q.56 Correct

Q.56 In-correct

Q.56 Unattempt

The maximum amplitude for an amplitude modulated wave is found to be 12V while the minimum amplitude is found to be 3V. The modulation index is 0.6x where x is ______.

[27 Jul 2021 Shift 2]

The maximum amplitude for an amplitude modulated wave is found to be 12V while the minimum amplitude is found to be 3V. The modulation index is 0.6x where x is ______.

[27 Jul 2021 Shift 2]

Q.57 Correct

Q.57 In-correct

Q.57 Unattempt

The amplitude of upper and lower side bands of A.M. wave where a carrier signal with frequency 11.21 MHz, peak voltage 15 V is amplitude modulated by a 7.7 kHz sine wave of 5V amplitude are

V respectively. Then the value of

a

b

is ___________

[27 Jul 2021 Shift 1]

The amplitude of upper and lower side bands of A.M. wave where a carrier signal with frequency 11.21 MHz, peak voltage 15 V is amplitude modulated by a 7.7 kHz sine wave of 5V amplitude are

V respectively. Then the value of

a

b

is ___________

[27 Jul 2021 Shift 1]

Q.58 Correct

Q.58 In-correct

Q.58 Unattempt

In amplitude modulation, the message signal Vm(t)=10‌sin(2π×105t) volts and Carrier signal VC(t)=20‌sin(2π×107t) volts
The modulated signal now contains the message signal with lower side band and upper side band frequency, therefore the bandwidth of modulated signal is α kHz. The value of α is :

[25 Jul 2021 Shift 1]

In amplitude modulation, the message signal Vm(t)=10‌sin(2π×105t) volts and Carrier signal VC(t)=20‌sin(2π×107t) volts
The modulated signal now contains the message signal with lower side band and upper side band frequency, therefore the bandwidth of modulated signal is α kHz. The value of α is :

[25 Jul 2021 Shift 1]

Q.59 Correct

Q.59 In-correct

Q.59 Unattempt

A carrier wave VC(t)=160‌sin(2π×106t) volts is made to vary between Vmax=200V and Vmin=120V by a message signal Vm(t)=Am‌sin(2π×103t) volts. The peak voltage Am of the modulating signal is _______.

[20 Jul 2021 Shift 1]

A carrier wave VC(t)=160‌sin(2π×106t) volts is made to vary between Vmax=200V and Vmin=120V by a message signal Vm(t)=Am‌sin(2π×103t) volts. The peak voltage Am of the modulating signal is _______.

[20 Jul 2021 Shift 1]

Q.60 Correct

Q.60 In-correct

Q.60 Unattempt

A carrier signal C(t)=25‌sin‌left(2.512‌times‌1010‌t‌right) is amplitude modulated by a message signal m(t)=5‌sin‌left(1.57‌times‌108‌t‌right) and transmitted through an antenna. What will be the bandwidth of the modulated signal?

[17 Mar 2021 Shift 2]

A carrier signal C(t)=25‌sin‌left(2.512‌times‌1010‌t‌right) is amplitude modulated by a message signal m(t)=5‌sin‌left(1.57‌times‌108‌t‌right) and transmitted through an antenna. What will be the bandwidth of the modulated signal?

[17 Mar 2021 Shift 2]

Q.61 Correct

Q.61 In-correct

Q.61 Unattempt

An amplitude modulated wave is represented by Cm(t)=10(1+0.2‌cos‌12560‌t) sin(111×104t) V.
The modulating frequency in kHz will be ...... .

[26 Aug 2021 Shift 1]

An amplitude modulated wave is represented by Cm(t)=10(1+0.2‌cos‌12560‌t) sin(111×104t) V.
The modulating frequency in kHz will be ...... .

[26 Aug 2021 Shift 1]

Q.62 Correct

Q.62 In-correct

Q.62 Unattempt

A transmitting antenna at top of a tower has a height of 50m and the height of receiving antenna is 80m. What is range of communication for line of sight (LOS) mode?
[Use radius of Earth =6400‌km ]

[26 Aug 2021 Shift 2]

A transmitting antenna at top of a tower has a height of 50m and the height of receiving antenna is 80m. What is range of communication for line of sight (LOS) mode?
[Use radius of Earth =6400‌km ]

[26 Aug 2021 Shift 2]

Q.63 Correct

Q.63 In-correct

Q.63 Unattempt

An antenna is mounted on a 400m tall building. What will be the wavelength of signal that can be radiated effectively by the transmission tower upto a range of 44‌km?

[27 Aug 2021 Shift 2]

An antenna is mounted on a 400m tall building. What will be the wavelength of signal that can be radiated effectively by the transmission tower upto a range of 44‌km?

[27 Aug 2021 Shift 2]

Q.64 Correct

Q.64 In-correct

Q.64 Unattempt

If the sum of the heights of transmitting and receiving antennas in the line of sight of communication is fixed at 160m, then the maximum range of LOS communication is ...........km.
(Take, radius of Earth =6400‌km )

[31 Aug 2021 Shift 1]

If the sum of the heights of transmitting and receiving antennas in the line of sight of communication is fixed at 160m, then the maximum range of LOS communication is ...........km.
(Take, radius of Earth =6400‌km )

[31 Aug 2021 Shift 1]

Q.65 Correct

Q.65 In-correct

Q.65 Unattempt

An amplitude modulated wave is represented by the expression vm=5(1+0.6‌cos‌6280‌t)‌sin(211×104t) volts The minimum and maximum amplitudes of the amplitude modulated wave are, respectively:

[Sep. 02, 2020 (I)]

An amplitude modulated wave is represented by the expression vm=5(1+0.6‌cos‌6280‌t)‌sin(211×104t) volts The minimum and maximum amplitudes of the amplitude modulated wave are, respectively:

[Sep. 02, 2020 (I)]

Q.66 Correct

Q.66 In-correct

Q.66 Unattempt

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

[12 Jan. 2019 I]

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

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

[12 Jan 2019 II]

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

An amplitude modulated signal is given by V(t)=10[1+ 0.3‌cos(2.2×104t)]‌sin(5.5×105t). Here t is in seconds. The sideband frequencies (in kHz ) are, [ Given π=

An amplitude modulated signal is given by V(t)=10[1+ 0.3‌cos(2.2×104t)]‌sin(5.5×105t). Here t is in seconds. The sideband frequencies (in kHz ) are, [ Given π=

An amplitude modulated signal is plotted below:

Which one of the following best describes the above signal?

[11 Jan. 2019 II]

An amplitude modulated signal is plotted below:

Which one of the following best describes the above signal?

[11 Jan. 2019 II]

Q.70 Correct

Q.70 In-correct

Q.70 Unattempt

A TV transmission tower has a height of 140m and the height of the receiving antenna is 40m. What is the maximum distance upto which signals can be broadcasted from this tower in LOS (Line of Sight) mode? (Given : radius of earth =6.4×106m).

[10 Jan. 2019 I]

A TV transmission tower has a height of 140m and the height of the receiving antenna is 40m. What is the maximum distance upto which signals can be broadcasted from this tower in LOS (Line of Sight) mode? (Given : radius of earth =6.4×106m).

The modulation frequency of an AM radio station is 250 kHz, which is 10% of the carrier wave. If another AM station approaches you for license what broadcast frequency will you allot?

[10 Jan. 2019 I]

The modulation frequency of an AM radio station is 250 kHz, which is 10% of the carrier wave. If another AM station approaches you for license what broadcast frequency will you allot?

In a communication system operating at wavelength 800 nm, only one percent of source frequency is available as signal bandwidth. The number of channels accomodated for transmitting TV signals of band width 6MHz are (Take velocity of light c=3×108ms,h=6.6×10−34J−s)

[9 Jan. 2019 II]

In a communication system operating at wavelength 800 nm, only one percent of source frequency is available as signal bandwidth. The number of channels accomodated for transmitting TV signals of band width 6MHz are (Take velocity of light c=3×108ms,h=6.6×10−34J−s)

In an amplitude modulator circuit, the carrier wave is given by, C(t)=4‌sin(20000πt) while modulating signal is given by, m(t)=2‌sin(2000πt). The values of modulation index and lower side band frequency are :

[12 April 2019 II]

In an amplitude modulator circuit, the carrier wave is given by, C(t)=4‌sin(20000πt) while modulating signal is given by, m(t)=2‌sin(2000πt). The values of modulation index and lower side band frequency are :

[12 April 2019 II]

Q.74 Correct

Q.74 In-correct

Q.74 Unattempt

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

[10 April 2019 II]

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

[10 April 2019 II]

Q.75 Correct

Q.75 In-correct

Q.75 Unattempt

A signal A‌cos‌ω‌t is transmitted using v0‌sin‌ω0 t as carrier wave. The correct amplitude modulated (AM) signal is:

[9 April 2019 I]

A signal A‌cos‌ω‌t is transmitted using v0‌sin‌ω0 t as carrier wave. The correct amplitude modulated (AM) signal is:

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

[9 April 2019 II]

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

[9 April 2019 II]

Q.77 Correct

Q.77 In-correct

Q.77 Unattempt

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

[8 April 2019 I]

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

In a line of sight ratio communication, a distance of about 50km 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(Radius of the Earth =6.4×106m ).

[8 April 2019 II]

In a line of sight ratio communication, a distance of about 50km 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(Radius of the Earth =6.4×106m ).

[8 April 2019 II]

Q.79 Correct

Q.79 In-correct

Q.79 Unattempt

A telephonic communication service is working at carrier frequency of 10GHz. Only 10% of it is utilized for transmission. How many telephonic channels can be transmitted simultaneously if each channel requires a bandwidth of 5kHz ?

[2018]

A telephonic communication service is working at carrier frequency of 10GHz. Only 10% of it is utilized for transmission. How many telephonic channels can be transmitted simultaneously if each channel requires a bandwidth of 5kHz ?

[2018]

Q.80 Correct

Q.80 In-correct

Q.80 Unattempt

A carrier wave of peak voltage 14V is used for transmitting a message signal. The peak voltage of modulating signal given to achieve a modulation index of 80% will be:

[2018]

A carrier wave of peak voltage 14V is used for transmitting a message signal. The peak voltage of modulating signal given to achieve a modulation index of 80% will be:

[2018]

Q.81 Correct

Q.81 In-correct

Q.81 Unattempt

The number of amplitude modulated broadcast stations that can be accommodated in a 300kHz band width for the highest modulating frequency 15kHz will be:

[Online April 15, 2018]

The number of amplitude modulated broadcast stations that can be accommodated in a 300kHz band width for the highest modulating frequency 15kHz will be:

[Online April 15, 2018]

Q.82 Correct

Q.82 In-correct

Q.82 Unattempt

The carrier frequency of a transmitter is provided by a tank circuit of a coil of inductance 49µH and a capacitance of 2.5nF. It is modulated by an audio signal of 12kHz. The frequency range occupied by the side bands is:

[Online April 15, 2018]

The carrier frequency of a transmitter is provided by a tank circuit of a coil of inductance 49µH and a capacitance of 2.5nF. It is modulated by an audio signal of 12kHz. The frequency range occupied by the side bands is:

[Online April 15, 2018]

Q.83 Correct

Q.83 In-correct

Q.83 Unattempt

In amplitude modulation, sinusoidal carrier frequency used is denoted by ωc and the signal frequency is denoted byωm. The bandwidth (Δωm) of the signal is such that Δωm <ωc. Which of the following frequencies is not contained in the modulated wave?

[2017]

In amplitude modulation, sinusoidal carrier frequency used is denoted by ωc and the signal frequency is denoted byωm. The bandwidth (Δωm) of the signal is such that Δωm <ωc. Which of the following frequencies is not contained in the modulated wave?

[2017]

Q.84 Correct

Q.84 In-correct

Q.84 Unattempt

A signal is to be transmitted through a wave of wavelength lambda, using a linear antenna. The length 1 of the antenna and effective power radiated Peff will be given respectively as :
(K is a constant of proportionality)

[Online April 9, 2017]

A signal is to be transmitted through a wave of wavelength lambda, using a linear antenna. The length 1 of the antenna and effective power radiated Peff will be given respectively as :
(K is a constant of proportionality)

[Online April 9, 2017]

Q.85 Correct

Q.85 In-correct

Q.85 Unattempt

A signal of frequency 20kHz and peak voltage of 5 Volt is used to modulate a carrier wave of frequency 1.2MHz and peak voltage 25 Volts. Choose the correct statement.

[Online April 8, 2017]

A signal of frequency 20kHz and peak voltage of 5 Volt is used to modulate a carrier wave of frequency 1.2MHz and peak voltage 25 Volts. Choose the correct statement.

[Online April 8, 2017]

Q.86 Correct

Q.86 In-correct

Q.86 Unattempt

Choose the correct statement:

[2016]

Choose the correct statement:

[2016]

Q.87 Correct

Q.87 In-correct

Q.87 Unattempt

A modulated signal Cm(t) has the form Cm(t)=30‌sin‌300‌π‌t+10(cos‌200‌π‌t−cos‌400‌π‌t). The carrier frequency fc, the modulating frequency (message frequency) fω and the modulation indix µ are respectively given by:

[Online April 10, 2016]

A modulated signal Cm(t) has the form Cm(t)=30‌sin‌300‌π‌t+10(cos‌200‌π‌t−cos‌400‌π‌t). The carrier frequency fc, the modulating frequency (message frequency) fω and the modulation indix µ are respectively given by:

[Online April 10, 2016]

Q.88 Correct

Q.88 In-correct

Q.88 Unattempt

An audio signal consists of two distinct sounds: one a human speech signal in the frequency band of 200Hz to 2700Hz, while the other is a high frequency music signal in the frequency band of 10200Hz to 15200Hz. The ratio of the AM signal bandwidth required to send both the signals together to the AM signal bandwidth requried to send just the human speech is :

[Online April 9, 2016]

An audio signal consists of two distinct sounds: one a human speech signal in the frequency band of 200Hz to 2700Hz, while the other is a high frequency music signal in the frequency band of 10200Hz to 15200Hz. The ratio of the AM signal bandwidth required to send both the signals together to the AM signal bandwidth requried to send just the human speech is :

[Online April 9, 2016]

Q.89 Correct

Q.89 In-correct

Q.89 Unattempt

A signal of 5kHz frequency is amplitude modulated on a carrier wave of frequency 2MHz. The frequencies of the resultant signal is/are :

[2015]

A signal of 5kHz frequency is amplitude modulated on a carrier wave of frequency 2MHz. The frequencies of the resultant signal is/are :

Long range radio transmission is possible when the radio waves are reflected from the ionosphere. For this to happen the frequency of the radio waves must be in the range:

[Online April 19,2014]

Long range radio transmission is possible when the radio waves are reflected from the ionosphere. For this to happen the frequency of the radio waves must be in the range:

[Online April 19,2014]

Q.91 Correct

Q.91 In-correct

Q.91 Unattempt

For sky wave propagation, the radio waves must have a frequency range in between:

[Online April 12,2014]

For sky wave propagation, the radio waves must have a frequency range in between:

[Online April 12,2014]

Q.92 Correct

Q.92 In-correct

Q.92 Unattempt

A transmitting antenna at the top of a tower has height 32 m and height of the receiving antenna is 50m. What is the maximum distance between them for satisfactory communication in line of sight (LOS) mode?

[Online April 9,2014]

A transmitting antenna at the top of a tower has height 32 m and height of the receiving antenna is 50m. What is the maximum distance between them for satisfactory communication in line of sight (LOS) mode?

[Online April 9,2014]

Q.93 Correct

Q.93 In-correct

Q.93 Unattempt

A diode detector is used to detect an amplitude modulated wave of 60% modulation by using a condenser of capacity 250 picofarad in parallel with a load resistance 100 kilo ohm. Find the maximum modulated frequency which could be detected by it.

[2013]

A diode detector is used to detect an amplitude modulated wave of 60% modulation by using a condenser of capacity 250 picofarad in parallel with a load resistance 100 kilo ohm. Find the maximum modulated frequency which could be detected by it.

[2013]

Q.94 Correct

Q.94 In-correct

Q.94 Unattempt

Which of the following modulated signal has the best noise-tolerance?

[Online April 25, 2013]

Which of the following modulated signal has the best noise-tolerance?

[Online April 25, 2013]

Q.95 Correct

Q.95 In-correct

Q.95 Unattempt

Which of the following statement is NOT correct?

[Online April 23, 2013]

Which of the following statement is NOT correct?

[Online April 23, 2013]

Q.96 Correct

Q.96 In-correct

Q.96 Unattempt

This question has Statement- 1 and Statement- 2 . Of the four choices given after the Statements, choose the one that best describes the two Statements.
Statement-1: Short wave transmission is achieved due to the total internal reflection of the e-m wave from an appropriate height in the ionosphere.
Statement-2: Refractive index of a plasma is independent of the frequency of e-m waves.

[Online April 22, 2013]

This question has Statement- 1 and Statement- 2 . Of the four choices given after the Statements, choose the one that best describes the two Statements.
Statement-1: Short wave transmission is achieved due to the total internal reflection of the e-m wave from an appropriate height in the ionosphere.
Statement-2: Refractive index of a plasma is independent of the frequency of e-m waves.

[Online April 22, 2013]

Q.97 Correct

Q.97 In-correct

Q.97 Unattempt

If a carrier wave c(t)=A‌sin‌ωc‌t is amplitude modulated by a modulator signal m(t)=A‌sin‌ωm‌t then the equation of modulated signal [Cm(t)] and its modulation index are respectively.

[Online April 9, 2013]

If a carrier wave c(t)=A‌sin‌ωc‌t is amplitude modulated by a modulator signal m(t)=A‌sin‌ωm‌t then the equation of modulated signal [Cm(t)] and its modulation index are respectively.

[Online April 9, 2013]

Q.98 Correct

Q.98 In-correct

Q.98 Unattempt

A radar has a power of 1kW and is operating at a frequency of 10GHz. It is located on a mountain top of height 500m. The maximum distance upto which it can detect object located on the surface of the earth (Radius of earth =6.4×106m ) is :

[2012]

A radar has a power of 1kW and is operating at a frequency of 10GHz. It is located on a mountain top of height 500m. The maximum distance upto which it can detect object located on the surface of the earth (Radius of earth =6.4×106m ) is :

[2012]

Q.99 Correct

Q.99 In-correct

Q.99 Unattempt

A radio transmitter transmits at 830kHz. At a certain distance from the transmitter magnetic field has amplitude 4.82×10−11T. The electric field and the wavelength are respectively.

[Online May 26,2012]

A radio transmitter transmits at 830kHz. At a certain distance from the transmitter magnetic field has amplitude 4.82×10−11T. The electric field and the wavelength are respectively.

[Online May 26,2012]

Q.100 Correct

Q.100 In-correct

Q.100 Unattempt

Given the electric field of a complete amplitude modulated wave as

‌cos‌ωm‌t) cos‌ωc‌t
Where the subscript c stands for the carrier wave and m for the modulating signal. The frequencies present in the modulated wave are

[Online May 19, 2012]

Given the electric field of a complete amplitude modulated wave as

‌cos‌ωm‌t) cos‌ωc‌t
Where the subscript c stands for the carrier wave and m for the modulating signal. The frequencies present in the modulated wave are

[Online May 19, 2012]

Q.101 Correct

Q.101 In-correct

Q.101 Unattempt

A 10kW transmitter emits radio waves of wavelength 500 m. The number of photons emitted per second by the transmitter is of the order of

[Online May 12, 2012]

A 10kW transmitter emits radio waves of wavelength 500 m. The number of photons emitted per second by the transmitter is of the order of

[Online May 12, 2012]

Q.102 Correct

Q.102 In-correct

Q.102 Unattempt

This question has Statement -1 and Statement −2. Of the four choices given after the statements, choose the one that best describes the two statements.
Statement -1 : Sky wave signals are used for long distance radio communication. These signals are in general, less stable than ground wave signals.
Statement -2: The state of ionosphere varies from hour to hour, day to day and season to season.

[2011]

This question has Statement -1 and Statement −2. Of the four choices given after the statements, choose the one that best describes the two statements.
Statement -1 : Sky wave signals are used for long distance radio communication. These signals are in general, less stable than ground wave signals.
Statement -2: The state of ionosphere varies from hour to hour, day to day and season to season.

[2011]

Q.103 Correct

Q.103 In-correct

Q.103 Unattempt

Which of the following four alternatives is not correct?
We need modulation:

[2011 RS]

Which of the following four alternatives is not correct?
We need modulation:

[2011 RS]