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Communication System — JEE Main & Advanced Physics PYQs

139 previous year questions from Communication System with answers and solutions. Numbered list, year tags, and one-tap solutions — built for serious JEE / NEET practice.

139 questionsPhysicsSolutions on every page
1

The height of transmitting antenna is 180 m and the height of the receiving antenna is 245 m . The maximum distance between them for satisfactory communication in line of sight wil

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

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Match List-I with List-II List-I (Layer of atmosphere) List-II (Approximate height over earth's surface) ( A ) F 1 - Layer ( I ) 10 km B D - Layer II 170 - 190 km C Troposphere

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The amplitude of 15 sin ( 1000 π t ) is modulated by 10 sin ( 4 π t ) signal. The amplitude modulated signal contains frequencies of A. 500 Hz B. 2 Hz C. 250 Hz D. 498 Hz

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In satellite communication, the uplink frequency band used is:

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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 &#

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A massage 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

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

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

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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 antenn

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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:

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

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In an amplitude modulation, a modulating signal having amplitude of X V is superimposed with a carrier signal of amplitude Y V in first case. Then, in second case, the same modulat

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

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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). Sta

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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

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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 rece

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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

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

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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 × 10 6 m .

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

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Match List I with List II List-I List-II A AM Broadcast I 88 - 108 MHz B FM Broadcast II 540 - 1600 kHz C Television III 3 . 7 - 4 . 2 GHz D Satellite Communication IV 54 MHz - 590

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A modulating signal is a square wave, as shown in the figure. If the carrier wave is given as c t = 2 sin 8 π t volts, the modulation index is:

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A modulating signal 2 sin 6 . 28 × 10 6 t is added to the carrier signal 4 sin 12 . 56 × 10 9 t for amplitude modulation. The combined signal is passed through a non-line

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

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

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

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

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

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

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

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In AM modulation, a signal is modulated on a carrier wave such that maximum and minimum amplitude are found to be 6 V and 2 V respectively. The modulation index is

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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 6400 km , t

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

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Only 2 % of the optical source frequency is the available channel bandwidth for an optical communicating system operating at 1000 nm . If an audio signal requires a bandwidth of 8

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Amplitude modulated wave is represented by V AM = 10 1 + 0 . 4 cos 2 π × 10 4 t cos 2 π × 10 7 t . The total bandwidth of the amplitude modulated wave is

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Match List-I with List-II List-I List-II (A) Television signal I. 03 KHz (B) Radio signal II. 20 KHz (C) High Quality Music III. 02 MHz (D) Human speech IV. 06 MHz

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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 lon

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The height of a transmitting antenna at the top of a tower is 25 m and that of receiving antenna is, 49 m . The maximum distance between them, for satisfactory communication in LOS

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A sinusoidal wave y t = 40 sin 10 × 10 6 π t is amplitude modulated by another sinusoidal wave x t = 20 sin 1000 π t . The amplitude of minimum frequency component o

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Choose the correct statement for amplitude modulation

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Match List I with List II List I List II (A) Facsimile (I) Static Document Image (B) Guided media Channel (II) Local Broadcast Radio (C) Frequency Modulation (III) Rectangular wave

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

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An antenna is placed in a dielectric medium of dielectric constant 6 . 25 . If the maximum size of that antenna is 5 . 0 mm , it can radiate a signal of minimum frequency of _____

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A baseband signal of 3 . 5 MHz frequency is modulated with a carrier signal of 3 . 5 GHz frequency using amplitude modulation method. What should be the minimum size of antenna req

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A carrier wave with amplitude of 250     V is amplitude modulated by a sinusoidal base band signal of amplitude 150     V . The ratio of minimum amplitude to ma

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A bandwidth of 6 MHz is available for A . M . transmission. If the maximum audio signal frequency used for modulating the carrier wave is not to exceed 6 kHz . The number of statio

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If the sum of the heights of transmitting and receiving antennas in the line of sight of communication is fixed at 160 m , then the maximum range of LOS communication is _______ km

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

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A transmitting antenna has a height of 320 m and that of receiving antenna is 2000 m . The maximum distance between them for satisfactory communication in line of sight mode is d .

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A transmitting antenna at top of a tower has a height of 50 m , and the height of receiving antenna is, 80 m . What is the range of communication for the line of sight (LOS) mode?

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An amplitude-modulated wave is represented by, C m ( t ) = 10 ( 1 + 0 . 2 cos 12560 t ) sin 111 × 10 4 t V . The modulating frequency in kHz will be

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The maximum amplitude for an amplitude modulated wave is found to be 12 V while the minimum amplitude is found to be 3 V . The modulation index is 0 . 6 x where x is _____.

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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 5 V

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A message signal of frequency 20   kHz and peak voltage of 20 V is used to modulate a carrier wave of frequency 1   MHz and peak voltage of 20 V . The modulation index wi

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In amplitude modulation, the message signal V m ( t ) = 10 sin 2 π × 10 5 t volts and carrier signal V C t = 20 sin 2 π × 10 7 t volts. The modulated signal now

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What should be the height of transmitting antenna and the population covered if the television telecast is to cover a radius of 150 km ? The average population density around the t

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A carrier wave V C ( t ) = 160 sin 2 π × 10 6 t volts is made to vary between V max = 200   V and V min = 120   V by a message signal V m ( t ) = A m sin 2 &#96

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A TV transmission tower antenna is at a height of 20 m . Suppose that the receiving antenna is at. (i) ground level (ii) a height of 5 m . The increase in antenna range in case (ii

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Match List – I with List – II . List – I List – II (a) 10 km height over earth's surface (i) Thermosphere (b) 70 km height over earth's surface (ii)

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A carrier signal C ( t ) = 25 sin 2 . 512 × 10 10 t is amplitude modulated by a message signal m ( t ) = 5 sin 1 . 57 × 10 8 t and transmitted through an antenna. What wi

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For VHF signal broadcasting, _______ km 2 of maximum service area will be covered by an antenna tower of height 30 m , if the receiving antenna is placed at ground. Let radius of t

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Two identical antennas mounted on identical towers are separated from each other by a distance of 45 km . What should nearly be the minimum height of receiving antenna to receive t

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

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

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If a message signal of frequency f m is amplitude modulated with a carrier signal of frequency f c and radiated through an antenna, the wavelength of the corresponding signal in ai

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Given below are two statements: Statement I : A speech signal of 2 kHz is used to modulate a carrier signal of 1 MHz . The bandwidth requirement for the signal is 4 kHz . Statement

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A signal of 0 . 1 kW is transmitted in a cable. The attenuation of cable is - 5 dB per km and cable length is 20 km . The power received at the receiver is 10 - x W . The value of

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An audio signal v m = 20 sin 2 π 1500 t amplitude modulates a carrier v c = 80 sin 2 π 100 , 000 t . The value of percent modulation is

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An amplitude modulated waves is represented by expression v m = 5 1 + 0 . 6 cos 6280 t sin 211 × 10 4 t V . The minimum and maximum amplitudes of the amplitudes modulated wave

JEE Main 2020 Solution View → 71

Calculate how much population would be covered by T.V. broadcast if height of TV tower is 100 m and the average population density around the tower is 1000 km - 2 (Take radius of e

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In optical communication systems operating at 1200 nm , only 2 % of the source frequency is available for TV transmission having a bandwidth of 5 MHz . The number of TV channels th

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A carrier wave of peak voltage 12 V is used to transmit a message signal. The peak voltage of the modulating signal in order to have a modulation index of 75 % is

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The mode of propagation used by short wave broadcast services having a frequency range from a few MHz up to 30 MHz is

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The length of a dipole antenna for a carrier wave of frequency 6 × 10 8 Hz is ( take speed of EM wave 3 × 10 8 m s - 1 )

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Consider telecommunication through optical fibres. Which of the following statements is not true?

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Minimum length of antenna required to transmit a radio signal of frequency 10 MHz is equal to

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The maximum frequency for reflection of sky waves from a certain layer of the ionosphere is found to be f max = 9 ( N max ) 1 / 2 , where N max is the maximum electron density at t

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1 % of 10 12 Hz of a satellite link was used for telephony. The number of channels or subscribers if each channel is of 8 kHz are

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A radar sends waves towards a distant object and receives the signal reflected by the object. These waves are

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Amplitude modulation is the process of

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An amplitude modulated wave is as given in figure. Calculate the percentage modulation,

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A bandwidth of 10 M H z is available for A M transmission. If the maximum audio signal frequency used for modulating the carrier is not to exceed 5 kHz, how many stations can be br

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What is the modulation index of an FM signal having a carrier swing of 100 kHz when the modulating signal has a frequency of 8 kHz ?

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A TV tower has a height of 150 m . The area of the region covered by the TV broadcast is (radius of earth = 6.4 × 10 6 m )

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1000   kHz carrier wave is amplitude modulated by the signal frequency 200 - 4000   Hz . The channel width in this case is

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In optical communication system operating at 1200 nm , only 2 % of the source frequency is available for TV transmission having a bandwidth of 5 MHz . The number of TV channels tha

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If the height of TV tower is increased by 21 % , then the transmission range is enhanced by

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The glass of optical fibre has a refractive index 1 . 55 and cladding with another glass of refractive index 1 . 51 . When the surrounding medium is air, the numerical aperture wil

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The area of the region covered by the TV broadcast, by a TV tower of 100 m height is (Take, the radius of the earth, R e = 6.4 × 10 6 m )

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In optical communication systems operating at 1200 nm , only 2 % of the source frequency is available for TV transmission having a bandwidth of 5 MHz . The number of TV channels th

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A T.V. tower has a height of 100 m . The population covered by T.V. broadcast is, if the average population density around the tower is 1000 people km - 2 .

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The antenna current of an AM transmitter is 8 A when only the carrier is sent, but it increases to 8 . 93 A when the carrier is modulated by a single sine wave. Find the percentage

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A signal wave of frequency 12 kHz is modulated with a carrier wave of frequency 2.51 MHz. The upper and lower side band frequencies are respectively

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What is the value of frequency at which electromagnetic wave must be propagated for the D-region of atmosphere to have a refractive index of 0 . 5 ? Electron density for D-region i

NTA Abhyas JEE Main 2020 Solution View → 96

If the area to be covered for TV telecast is doubled, then the height of transmitting antenna (TV tower) will have to be

NTA Abhyas JEE Main 2020 Solution View → 97

The height of a TV antenna is 200 m . The population density is 4000 k m - 2 . Find the population benefited

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The antenna current of an AM broadcast transmitter which is modulated by 50 % is 11 A . The carrier current is

NTA Abhyas JEE Main 2020 Solution View → 99

The radius of the Earth is 6400 km . If the height of an antenna is 500 m , then its range is

NTA Abhyas JEE Main 2020 Solution View → 100

The maximum electron density in the ionosphere in the morning is 10 10 m - 3 . At noon time, it increases to 2 × 10 10 m - 3 . Find the ratio of critical frequency at noon and the

NTA Abhyas JEE Main 2020 Solution View → 101

In optical communication system operating at 1200 nm, only 2% of the source frequency is available for TV transmission having a bandwidth of 5 MHz. The number of TV channels that c

NTA Abhyas JEE Main 2020 Solution View → 102

If a carrier wave of 1000 kHz is used to carry the signal, the length of transmitting antenna will be at least equal to

NTA Abhyas JEE Main 2020 Solution View → 103

In a CE transistor amplifier, the audio signal voltage across the collector resistance of 2 kΩ is 2 V , if the base resistance is 1 kΩ and the current amplification of the transist

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A message signal of frequency 100 M H z and peak voltage 100 V is used execute amplitude modulation on a carrier wave of frequency 300 G H z and peak voltage 400 V . The modulation

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

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A signal A c o s ω t is transmitted using ν 0 s i n ω 0 t as carrier wave. The correct amplitude modulated ( A M ) signal is:

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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 70 m , then the

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

JEE Main 2019 Solution View → 109

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

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

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

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An amplitude modulated signal is given by V ( t )=10[1+0.3 . (2.2 10⁴ t ) ] (5.5 10⁵ t ) . Here t is in seconds. The sideband frequencies (in kHz ) are, [Given =22 / 7 ]

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The modulation frequency of an A M radio station is 250 k H z , which is 10 % of the carrier wave. If another A M station approaches you for license what broadcast frequency will y

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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 i

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In a communication system operating at wavelength 800 n m , only one percent of source frequency is available as signal bandwidth. The number of channels accommodated for transmitt

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

JEE Main 2018 Solution View → 117

The carrier frequency of a transmitter is provided by a tank circuit of a coil of inductance 49 H and a capactiance of 2.5 nF . It is modulated by an audio signal of 12 kHz . The f

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

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

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A telephonic communication service is working at a carrier frequency of 10 GHz . Only 10 % of it is utilized for transmission. How many telephonic channels can be transmitted simul

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