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Get Answers to all your Questions
(a) Give three reasons why modulation of a message signal is necessary for long distance transmission.
(b) Show graphically an audio signal, a carrier wave and an amplitude modulated wave.
Answers (1)
a) i) size of antenna or aerial:
The antenna used for transmission of signals should have a size comparable to the
the wavelength of the signal (at least in dimensions)
For low signals, if not practically possible to construct and operate such long antenna so there is a need for translating the information contained in air signal into high or radio frequency signal before transmission
ii) Mixing up of signals from different transmitters:
Suppose many transmitters are transmitting baseband information signals simultaneously. All these get signals will get mixed up.
So if the signal low-frequency baseband message or signal is translated to high-frequency wave, mixing up of signals can be avoided
iii) Effective power radiated by the antenna
The power radiated is proportional to where l is the length of antenna and
is the wavelength.
The effective power radiated by the long-wavelength signal is small. So converting baseband signal to high frequency is needed.
b) Amplitude modulation is the process of varying the magnitude of a carrier wave in accordance with instantaneous variation of the signal (Adio frequency wave).
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