| The given block diagram shows general fornm of a Communication system (a) Idientifty the blocks X and Y (b) What is the difference between attenuation and amplification ? |
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| Previous Year Questions of March Examinations from 2010 to 2020 |
| Chapter Name: COMMUNICATION SYSTEMS |
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In amplitude modulation, which of the following will change? (a) Frequency (b) Phase (c) Amplitude (d) Wavelength ii) A message signal of frequency 10 KHz and peak voltage of 10 volts is used to modulate a carrier wave of frequency 1 MHz and peak voltage of 20 volts. Determine the modulation index and frequencies of side bands. |
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Television broadcast is done by space wave mode of propagation. a) What is the difference between sky wave and space wave modes of propagation? b) A TV transmission antenna is 81 m tall. How much service area can it cover if the receiving antenna is at the ground level? (Radius of earth is 6400km) |
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Spectrum allocations for communication are arrived at by an international agreement. a) Name the agency which administers the present system of frequency allocations. b) Draw block diagrams of an amplitude modulated i) Transmitter and ii) Receiver |
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Various propagation modes are used in communication a) Mention two communication systems that use space wave propagation b) Why modulation is necessary in communication? c) If a signal of frequency ωs is used to modulate a carrier wave of frequency ωc which are the frequencies contained in the modulated signal other than ωc |
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a) When a low flying aircraft passes over head, we sometimes notice a slight shaking of
the picture on our TV screen. Identify the optical phenomenon behind it b) In electromagnetic spectra, the wave length and frequencies are inversely related. A ratio can tune n to any station in the 7.5 MHz to 12MHz band. Determine the corresponding wave length band |
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In our daily life, modulation plays an important role a) Discuss the amplitude modulation b) Give a block diagram of a generalized communication system |
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a) Desribe how to detect an Amplitude Modulated Wave b) Sketch a neat diagram for a detector for AM signal |
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(A) Range of an electronic communication system is the (a) distance to the nearest TV station (b) distance to the nearest radio station (c) largest distance that the signal can travel (d) largest distance between a source and destination up to which the signal is received with sufficient strength (B) If the height of a TV transmitting antenna increases, its coverage increases. Why? |
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(a) A receiver in a communication system must have (i) Pick-up antenna (ii) demodulator (iii) amplifier (iv) all of these (b) Which of the following statement is wrong? (i) The attenuation of surface waves increases with increase in frequency (ii) The phenomenon involved in sky wave propagation is similar to total internal reflection (iii) Space wave mode of propagation is used in satellite communication (iv) Sky wave propagation is useful only in the range of frequencies 30 to 40 MHz |
| The given block diagram shows general fornm of a Communication system (a) Idientifty the blocks X and Y (b) What is the difference between attenuation and amplification ? |
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| What is the population covered by the transmission, if the average population density around the tower is 1200 km-2 The antenna height is 160 m. |
| In Amplitude Modulation, the amplitude of the carrier wave is varied in accordance with the information signal. (a) What is meant by modulation index ? (b) A message signal of frequency 10 kHz and peak value of 10 V used to modulate a carrier of frequency 1 MHz and peak voltage of 20 V. Determine the modulation index. (c) The block diagram of a transmitter is shown below. Identify the elements labeled X and Y. |
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| The given figure shows the various propagation modes of e.m. waves in communication. (a) Write the names of propagation modes in A, B, C. (b) Why transmission of TV signals via sky wave is not possible ? |
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In the broadcast of communication modulation is necessary. (a) What do you mean by modulation ? (b) Explain any two reason why modulation is necessary ? |