Answer / shiva krishna prasad

1. To reduce antenna height
2. To convert low freq signal to high freq
3. multiplexing of many signals through the same channel
4. To reduce noise& interference by modulation (means shifting
the signal to a place whr oise is less)
5. For narrow banding of signals
6. equipment limitation

Answer / shweta

modulation is needed to transfer the signal from
transmitter to reciever. As the signal passes from
transmmiter to reciever there are many external effects
such as noise and other factors which can degrade the
signal so there is a need of modulation so that the signal
cant become so much week that it cant reach the reciever.
If the signal is sent without modulating then it will get
degraded due to external effects.

Answer / m

1.For transmitting low frequancy signal over long range.
2 To reduce the height of antena
formula
wavelength = 7500000/frequancy

Answer / abdul quadir khumani

Modulation = the technique by some parameter of carrier are
varied in accordance with carrier frequency is called Modulation

There are mainly three need of Modulation

1. Multiplexing = many signals can be transmitted at once.
2. Narrow Banding = low bandwidth required.
3. Height of Antenna = small variation in height of antenna
while change in frequency of signals is considerable..

Answer / ashok

Let me explain with example.For example if you throw a paper
to some where,Then may be it will reach 20 mtrs.But if you
round that paper around a stone and throw it .Its going very
long distance.
Here i mean Paper=Message signal
Stone=Carrier signal

Both mixed and transmitted at transmitter side after
reaching the signal at receiver end we demodulate the
carrier signal ans using message signal

Answer / 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.

Answer / durga bhantana

modulation is necessary in communication system due to the
following reasons
1)for efficient radiation and reception the transmiting
reciving antennas most antennas have length equal to a
quarter wave length of the frequency used.
2)the energy of the wave depends upon frequency the greater
the frequency of the wave the greater the energy lossesed
by it as the audio signal frequencies are small
therefour ;these cannot be transmitted are larg distamces
it radiated directly into space. the only practical
solution is to modulated a high frequency carrier wave with
audio signal and permit the transmission fo occur of the
this high frequnecy
3)............

Answer / satyabrata panda

we all know that baseband signal is a less freqency
signal...as frequency directly propersonal to energy so it
is of low energy signal catagory for which it may
insufficient to travel from transmitter to far placed
receiver end...hence it will needed a high frequeny ...so a
high frequency carrier signal is superimposed on to baseband
signal which lead to a appropiate transmission to receiver
then demodulation made to get original less frequency
modulating signal

Answer / jash

for long distance communication.. transmission of digital
data by modulating it with carrier is known as passband
modulation

Answer / ali(kk)

it is used to strengthen weak signal which passing from
transmitter to receiver9 ( which has low frequency)

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