JEE Main
Physics
Communication Systems
Previous Years Questions

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...
Which of the following frequencies does not belong to FM broadcast.
Given below are two statements : Statement I : For transmitting a signal, size of antenna ( $l$ ) should be comparable to wavelength of signal (at lea...
The amplitude of $$15 \sin (1000 \pi \mathrm{t})$$ is modulated by $$10 \sin (4 \pi \mathrm{t})$$ signal. The amplitude modulated signal contains freq...
Match List I with List II: .tg {border-collapse:collapse;border-spacing:0;} .tg td{border-color:black;border-style:solid;border-width:1px;font-fami...
A sinusoidal carrier voltage is amplitude modulated. The resultant amplitude modulated wave has maximum and minimum amplitude of $$120 \mathrm{~V}$$ a...
The modulation index for an A.M. wave having maximum and minimum peak-to-peak voltages of 14 mV and 6 mV respectively is-
If the height of transmitting and receiving antennas are 80 m each, the maximum line of sight distance will be: Given : Earth's radius $$=6.4\times10^... A message signal of frequency 5 kHz is used to modulate a carrier signal of frequency 2 MHz. The bandwidth for amplitude modulation is : Match List I with List II .tg {border-collapse:collapse;border-spacing:0;} .tg td{border-color:black;border-style:solid;border-width:1px;font-family... A modulating signal is a square wave, as shown in the figure. If the carrier wave is given as$$\mathrm{c(t) = 2\sin(8\pi t)}$$volts, the modulation... Find the modulation index of an AM wave having$$8 \mathrm{~V}$$variation where maximum amplitude of the AM wave is$$9 \mathrm{~V}$$. A FM Broadcast transmitter, using modulating signal of frequency 20 kHz has a deviation ratio of 10. The Bandwidth required for transmission is :... In the case of amplitude modulation to avoid distortion the modulation index$$(\mu)$$should be : A square wave of the modulating signal is shown in the figure. The carrier wave is given by$$C(t)=5 \sin (8 \pi t)$$Volt. The modulation index is : ... At a particular station, the TV transmission tower has a height of 100 m. To triple its coverage range, height of the tower should be increased to... The maximum and minimum voltage of an amplitude modulated signal are$$60 \mathrm{~V}$$and$$20 \mathrm{~V}$$respectively. The percentage modulation... A radio can tune to any station in$$6 \,\mathrm{MHz}$$to$$10 \,\mathrm{MHz}$$band. The value of corresponding wavelength bandwidth will be :... In AM modulation, a signal is modulated on a carrier wave such that maximum and minimum amplitudes are found to be 6 V and 2 V respectively. The modul... A speech signal given by 11 sin(2200$$\pi$$t) V is used for amplitude modulation with a carrier signal given by 44 sin(6600$$\pi$$t) V. The minimum ... The TV transmission tower at a particular station has a height of 125 m. For doubling the coverage of its range, the height of the tower should be inc... Only 2% of the optical source frequency is the available channel bandwidth for an optical communicating system operating at 1000 nm. If an audio signa... Amplitude modulated wave is represented by$${V_{AM}} = 10\,[1 + 0.4\cos (2\pi \times {10^4}t)\cos (2\pi \times {10^7}t)$$. The total bandwidth of t... Match List-I with List-II .tg {border-collapse:collapse;border-spacing:0;} .tg td{border-color:black;border-style:solid;border-width:1px;font-family... We do not transmit low frequency signal to long distances because- (a) The size of the antenna should be comparable to signal wavelength which is unre... A sinusoidal wave y(t) = 40sin(10$$\times$$106$$\pi$$t) is amplitude modulated by another sinusoidal wave x(t) = 20sin (1000$$\pi$$t). The amplitu... Choose the correct statement for amplitude modulation : Match List I with List II .tg {border-collapse:collapse;border-spacing:0;} .tg td{border-color:black;border-style:solid;border-width:1px;font-family... A signal of 100 THz frequency can be transmitted with maximum efficiency by : A baseband signal of 3.5 MHz frequency is modulated with a carrier signal of 3.5 GHz frequency using amplitude modulation method. What should be the m... An antenna is mounted on a 400 m tall building. What will be the wavelength of signal that can be radiated effectively by the transmission tower upto ... A transmitting antenna at top of a tower has a height of 50 m and the height of receiving antenna is 80 m. What is range of communication for Line of ... In amplitude modulation, the message signalVm(t) = 10 sin (2$$\pi\times$$105t) volts and Carrier signalVC(t) = 20 sin(2$$\pi\times$$107 t)... What should be the height of transmitting antenna and the population covered if the television telecast is to cover a radius of 150 km? The average po... A carrier signal C(t) = 25 sin(2.512$$\times$$1010t) is amplitude modulated by a message signal m(t) = 5 sin(1.57$$\times$$108t) and transmitted t... A 25 m long antenna is mounted on an antenna tower. The height of the antenna tower is 75 m. The wavelength (in meter) of the signal transmitted by th... If a message signal of frequency 'fm' is amplitude modulated with a carrier signal of frequency 'fc' and radiated through an antenna, the wavelength o... Given below are two statements :Statement I : A speech signal of 2 kHz is used to modulate a carrier signal of 1 MHz. The bandwidth requirement for th... In an amplitude modulator circuit, the carrier wave is given by, C(t) = 4 sin(20000$$\pi $$t) while modulating signal is given by, m(t) = 2 sin (2000... A message signal of frequency 100 MHz and peak voltage 100 V is used to execute amplitude modulation on a carrier wave of frequency 300 GHz and peak v... Given below in the the left column are different modes of communication using the kinds of waves given the right column. .tg {border-collapse:collap... The physical sizes of the transmitter and receiver antenna in a communication system are :- A signal Acoswt is transmitted using v0 sin$$\omega $$0t as carrier wave. The correct amplitude modulated (AM) signal is In a line of sight radio communication, a distance of about 50 km is kept between the transmitting and receiving antennas. If the height of the receiv... The wavelength of the carrier waves in a modern optical fiber communication network is close to : To double the covering range of a TV transmittion tower, its height should be multiplied by : A 100 V carrier wave is made to vary between 160 V and 40 V by a modulating signal. What is the modulation index ? An amplitude modulated signal is plotted below : Which one of the following best describes the above signal ? ... An amplitude modulated signal is given by V(t) = 10[1 + 0.3cos(2.2$$ \times $$104 t)] sin(5.5$$ \times $$105 t). Here t is in seconds. The sideban... The modulation frequency of an AM radio station is 250 kHz, which is 10% of the carrier wave. If another AM station approaches you for license what br... A TV transmission tower has a height of 140 m and the height of the receiving antenna is 40 m. What is the maximum distance upto which signals can be ... In a communication system operating at wavelength 800 nm, only one percent of source frequency is available as signal bandwith. The number of channels... A carrier wave of peak voltage 14 V is used for transmitting a message signal. The peak voltage of modulating signal given to achieve a modulation ind... A telephonic communication service is working at carrier frequency of 10 GHz. Only 10% of it is utilized for transmission. How many telephonic channel... The carrier frequency of a transmitter is provided by a tank circuit of a coil of inductance 49$$\mu $$H and a capacitance of 2.5 nF. It is modulated... The number of amplitude modulted broadcast stations that can be accomodated in a$$300kHz$$band width for the highest modulating frequency$$15$... A signal is to be transmitted through a wave of wavelength $$\lambda$$, using a linear antenna. The length l of the antenna and effective power radia... A signal of frequency 20 kHz and peak voltage of 5 Volt is used to modulate a carrier wave of frequency 1.2 MHz and peak voltage 25 Volts. Choose the ... In amplitude modulation, sinusoidal carrier frequency used is denoted by $${\omega _c}$$ and the signal frequency is denoted by $${\omega _m}$$. The b... A modulated signal Cm(t) has the form Cm(t) = 30 sin 300 $$\pi$$t + 10 (cos 200 $$\pi$$t −cos 400 $$\pi$$t). The carrier frequency c, the modulatin... An audio signal consists of two distinct sounds : one a human speech signal in the frequency band of 200 Hz to 2700 Hz, while the other is a high freq... Choose the correct statement : A signal of $$5$$ $$kHz$$ frequency is amplitude modulated on a carrier wave of frequency $$2$$ $$MHz.$$ The frequencies of the resultant signal is/ar... A radar has a power of $$1kW$$ and is operating at a frequency of $$10$$ $$GHz.$$ It is located on a mountain top of height $$500$$ $$m.$$ The maximum... This question has Statement - $$1$$ and Statement - $$2$$. Of the four choices given after the statements, choose the one that best describes the two ... Consider telecommunication through optical fibres. Which of the following statements is not true? ## Numerical A modulating signal $$2 \sin \left(6.28 \times 10^{6}\right) t$$ is added to the carrier signal $$4 \sin \left(12.56 \times 10^{9}\right) t$$ for ampl... 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 $$\mat... The height of a transmitting antenna at the top of a tower is 25 m and that of receiving antenna is, 49 m. The maximum distance between them, for sati... An antenna is placed in a dielectric medium of dielectric constant 6.25. If the maximum size of that antenna is 5.0 mm, it can radiate a signal of min... A carrier wave with amplitude of 250 V is amplitude modulated by a sinusoidal base band signal of amplitude 150V. The ratio of minimum amplitude to ma... A bandwidth of 6 MHz is available for A.M. transmission. If the maximum audio signal frequency used for modulating the carrier wave is not to exceed 6... If the sum of the heights of transmitting and receiving antennas in the line of sight of communication is fixed at 160 m, then the maximum range of LO... A transmitting antenna has a height of 320 m and that of receiving antenna is 2000 m. The maximum distance between them for satisfactory communication... An amplitude modulated wave is represented by Cm(t) = 10(1 + 0.2 cos 12560t) sin(111$$\times$$104t) volts. The modulating frequency in kHz will be .... The maximum amplitude for an amplitude modulated wave is found to be 12V while the minimum amplitude is found to be 3V. The modulation index is 0.6x w... The amplitude of upper and lower side bands of A.M. wave where a carrier signal with frequency 11.21 MHz, peak voltage 15 V is amplitude modulated by ... A message signal of frequency 20 kHz and peak voltage of 20 volt is used to modulate a carrier wave of frequency 1 MHz and peak voltage of 20 volt. T... A carrier wave Vc(t) = 160 sin(2$$\pi\times$$106t) volts is made to vary between Vmax = 200 V and Vmin = 120 V by a message signal Vm(t) = Am si... A TV transmission tower antenna is at a height of 20 m. Suppose that the receiving antenna is at.(i) ground level(ii) a height of 5 m.The increase in ... For VHF signal broadcasting, ___________ km2 of maximum service area will be covered by an antenna tower of height 30 m, if the receiving antenna is p... If the highest frequency modulating a carrier is 5 kHz, then the number of AM broadcast stations accommodated in a 90 kHz bandwidth are _________. The maximum and minimum amplitude of an amplitude modulated wave is 16V and 8V respectively. The modulation index for this amplitude modulated wave is... A signal of 0.1 kW is transmitted in a cable. The attenuation of cable is$$-$$5 dB per km and cable length is 20 km. The power received at receiver i... An audio signal vm = 20 sin 2$$\pi$$(1500t) amplitude modulates a carrier vc = 80 sin 2$$\pi$\$(100,000t).The value of percent modulation is _________....
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