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प्रश्न
Write three important factors which justify the need of modulating a message signal. Show diagrammatically how an amplitude modulated wave is obtained when a modulating signal is superimposed on a carrier wave.
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उत्तर
Three important factors which justify the need of modulating a message signal:
(i) Size of antenna or aerial: For communication within the effective length of the antennas, the transmitting frequencies should be high, so modulation is required.
(ii) Effective power which is radiated by antenna: Since the power radiated from a linear antenna is inversely proportional to the square of the transmitting wavelength. As high powers are needed for good transmission so, higher frequency is required which can be achieved by modulation.
(iii) The interference of signals from different transmitters: To avoid the interference of the signals there is need of high frequency which can be achieved by the modulation.
संबंधित प्रश्न
A modulating signal is a square wave, as shown
The carrier wave is given by `c(t) = 2 sin (8pit) "volts"`
(i) Sketch the amplitude modulated waveform
(ii) What is the modulation index?
Draw a schematic sketch showing how amplitude modulated signal is obtained by superposing a modulating signal over a sinusoidal carrier wave.
Solve the following question.
A message signal of frequency 20 kHz and peak voltage 10 V is used to modulate a carrier of frequency 2 MHz and peak voltage of 15 V. Calculate the modulation index. Why the modulation index is generally kept less than one?
In amplitude modulation ______.
A message signal of frequency ωm is superposed on a carrier wave of frequency ωc to get an amplitude modulated wave (AM). The frequency of the AM wave will be ______.
Identify the mathematical expression for amplitude modulated wave ______.
The maximum amplitude of an A.M. wave is found to be 15 V while its minimum amplitude is found to be 3 V. What is the modulation index?
An amplitude modulated wave is as shown in figure. Calculate
- the percentage modulation
- peak carrier voltage and
- peak value of information voltage.
The maximum and minimum voltage of an amplitude modulated signal are 60 V and 20 V respectively. The percentage modulation index will be ______.
A signal of 5 kHz frequency is amplitude modulated on a carrier wave of frequency 2 MHz. The frequencies of the resultant signal are ______.
