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प्रश्न
Why is a AM signal likely to be more noisy than a FM signal upon transmission through a channel?
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उत्तर
In AM, the carrier wave's instantaneous voltage is varied by modulating wave voltage. On transmission, noise signals can also be added and the receiver assumes noise is a part of the modulating signal.
However, in FM, the carrier frequency is changed as per modulating wave's instantaneous voltage. This can only be done at the mixing/ modulating stage and not while the signal is transmitting in a channel. Hence, noise doesn’t effect the FM signal.
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संबंधित प्रश्न
Explain any two factors that justify the need of modulating a low-frequency signal.
A signal of 5 kHz frequency is amplitude modulated on a carrier wave of frequency 2 MHz. What are the frequencies of the side bands produced?
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Define the term 'amplitude modulation'
Draw a schematic sketch showing how amplitude modulated signal is obtained by superposing a modulating signal over a sinusoidal carrier wave.
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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In amplitude modulation ______.
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Identify the mathematical expression for amplitude modulated wave ______.
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On radiating (sending out) an AM modulated signal, the total radiated power is due to energy carried by ωc, ωc – ωm and ωc + ωm. Suggest ways to minimise cost of radiation without compromising on information.
Draw the plot of amplitude versus ‘ω’ for an amplitude modulated wave whose carrier wave (ωc) is carrying two modulating signals, ω1 and ω2 (ω2 > ω1).
- Is the plot symmetrical about ωc? Comment especially about plot in region ω < ωc.
- Extrapolate and predict the problems one can expect if more waves are to be modulated.
- Suggest solutions to the above problem. In the process can one understand another advantage of modulation in terms of bandwidth?
An amplitude-modulated wave is represented by Cm(t) = 10(1 + 0.2 cos 12560t) × sin (111 × 104t) volts. The modulating frequency in kHz will be ______.
The maximum and minimum voltage of an amplitude modulated signal are 60 V and 20 V respectively. The percentage modulation index will be ______.
