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Answer Posted / muhammed abdhul rehman
Modulation is needed becuase of 3 reasons.
1.Low frequency signals are more immune to noise. So the
low frequency information signal should be mix up with high
frequency carrier to reduce noise affection
2.All sounds are with in the range from 20 Hz to 20 kHz. If
we send audio signal directly all signals from different
sources would be inseperably mixup.So it is necessary to
convert the information signal to different portions of the
electromagnetic spectrum
3.For efficient transmission and reception of Electro-
maganenic waves the Transmitting and Receiving antennas
should have lenths comparable to a quarter-wavelength of
the frequency used. This is 75 meters (75 m) at 1 magahertz
(1 MHz), but at 15 kHz it has incrased to 5000 m (5 Kilo
meter). A vertical antenna of this size is impracticable.
Because of above reasons modulation is needed for
transmitting Electro-magnetic Waves.
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