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प्रश्न
Write briefly any two factors which demonstrate the need for modulating a signal. Draw a suitable diagram to show amplitude modulation using a sinusoidal signal as the modulating signal.
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उत्तर
The need for modulation can be summarized as follows:
(1) The antenna needed for transmitting signals should have size at least λ/4, where, λ is the wavelength. The information signal, also known as baseband signal is of low frequency (and therefore the wavelength is high). If we need to transmit such a signal directly, the size of the antenna will be very large and impossible to build. Hence direct transmission is not practical.
(2) The radiated power by an antenna is inversely proportional to the square of the wavelength. So, if we use high frequency signals, the power radiated will be increased.
(3) If we transmit the baseband signals directly, the signals from different transmitters will get mixed up and the information will be lost. Because of these reasons, we use the technology of modulation, for transmitting message signals effectively for long distances.
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संबंधित प्रश्न
Frequencies in the UHF range normally propagate by means of:
(a) Ground waves.
(b) Sky waves.
(c) Surface waves.
(d) Space waves.
Digital signals
(i) Do not provide a continuous set of values,
(ii) Represent values as discrete steps,
(iii) Can utilize binary system, and
(iv) Can utilize decimal as well as binary systems.
Which of the above statements are true?
(a) (i) and (ii) only
(b) (ii) and (iii) only
(c) (i), (ii) and (iii) but not (iv)
(d) All of (i), (ii), (iii) and (iv).
Answer the following question :
Define 'bandwidth' and describe briefly its importance in communicating signals ?
Block diagram of a receiver is shown in the figure:
(a) Identify ‘X’ and ‘Y’.
(b) Write their functions.
Write any two factors which justify the need for modulating a signal ?
Draw a diagram showing an amplitude modulated wave by superposing a modulating signal over a sinusoidal carrier wave.
What do you mean by bandwidth of a signal? Give its importance.
The sound produced by a funning fark is a sort of:-
The audio frequency range is
Would sky waves be suitable for transmission of TV signals of 60 MHz frequency?
