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प्रश्न
Explain any two factors that justify the need of modulating a low-frequency signal.
उत्तर
Following are the factors that justify the need of modulating a low-frequency signal:-
(1) Size of the antenna: An antenna is required for both transmission and reception of the signal whose size (at least λ/4) should be comparable to the wavelength of the signal so that time variation of the signal can be properly sensed by the antenna. For a low-frequency signal, the wavelength is large, and an antenna of such a large required height is practically impossible to construct and operate. Thus, the need for high-frequency transmission arises.
(2) Mixing up of signals from various transmitters: When many transmitters are transmitting information signals simultaneously, they get mixed up and the information is lost. This gives rise to the need for high-frequency transmission and allotment of a band of frequencies to each transmitter to avoid mixing of signals.
(3) Higher energy: High-frequency signals have higher energy, and therefore, even after loss due to attenuation, the signals can be carried over long distances.
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?
Write two advantages of frequency modulation over amplitude modulation.
Why is frequency modulation preferred over amplitude modulation for transmission of music?
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?
Identify the mathematical expression for amplitude modulated wave ______.
In amplitude modulation, the modulation index m, is kept less than or equal to 1 because ______.
- m > 1, will result in interference between carrier frequency and message frequency, resulting into distortion.
- m > 1 will result in overlapping of both side bands resulting into loss of information.
- m > 1 will result in change in phase between carrier signal and message signal.
- m > 1 indicates amplitude of message signal greater than amplitude of carrier signal resulting into distortion.
Why is a AM signal likely to be more noisy than a FM signal upon transmission through a channel?
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.
An amplitude modulated wave is as shown in figure. Calculate
- the percentage modulation
- peak carrier voltage and
- peak value of information voltage.
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 ______.
