What is modulation why do we need modulation?

Answer 1

Sometimes we have to send low frequency information, like the tone of the voice of someone talking on a telephone, over a specific channel that only permits a specific high frequency, such as radio frequencies (RF). So how do we do that? One simple, cost effective, and bandwidth efficient method is to change, or modulate, a known RF signal a certain way. Some common ways of modulating such a high frequency signal are Amplitude Modulation and Frequency Modulation. Each of these modulation techniques has its own advantages and disadvantages and are therefore more useful in certain applications.

Answer 2

In simple terms, modulation is required to transmit signals from variuos sources simultaneously over a common channel by means of 'multiplexing'.For ex., the bandwidth of speech signals is 3.3KHz.,and transmitting N no.of speech signals simultaneously each of BW 3.3KHz causes interference.Hence,to overcome this problem, each speech signal is modulated onto one of N carriers of frequencies 60KHz,64KHz,68KHz etc...
Hope u got my answer
By modulation, we can reduce our antenna height as

Height=1/4 wavelength
and, wavelength=velocity of light/frequency

Answer 3

Modulation is the process of varying a particular characteristic(amplitude,phase,frequency) of a high frequency carrier signal according to the message signal.The need of modulation is as follows:-

1.Reduces the height of antenna :-The minimum height of antenna required for transmission or reception of RF signals is one forth the wavelenth i.e lower the frequency,higher the wavelenght ,greater the length of the antenna .eg.for wave of 15Khz,antenna height is 5km,which is impractical but for 1Mhz wave,height is 75 m.

2.Increases the range of communication:-At low frequencies,radiation is poor and signal gets attenuated.Modulation effectively increases the frequency of the message signal and thus signal can be transmitted over longer distance without attenuation.

3.Avoids mixing of signals and allows multiplexing of signals:-When many signals are transmitted simultaneously,they may get mixed and it becomes difficult to separate them at the receiver end.This can be avoided by modulating different signals with different carriers i.e. each signal is allocated a separate bandwidth.At the receiver end,required signal can be intercepted by the tuning the receiver to desired frenquency bandwidth.This allows multiplexing(i.e. transmission of more than one signal simultaneously over the same channel.)eg.channels on television

4.Improves the quality of reception:-Modulation techniques like frequency modulation reduce the effect of noise and improve the quality of reception.

Answer 4

Need of Modulation: To transfer the message signal from one site another site without any loss for that we are using modulation. Modulation classified in three types. 1.Amplitude modulation. 2.Frequency Modulation. 3.Phase Modulation.

Answer 5

• The baseband signal will not propagate far enough on its own.
• Multiple baseband signals would interfere, preventing more than one signal from being sent.