Explain the need for modulation.

Explanation

Need for modulation :
(1) Antenna lengths : The transmitting and receiving antenna can have convenient lengths comparable to a quarter of the carrier wavelength `lamda`.
(2) Transmission range : For smaller `lamda` (or higher frequency), the maximum power that cna be radiated from an anenna of a given length increases. This increases the transmission range.
(3) Frequency translation : Modulation of baseband signals onto a high frequency carrier confines the signals into a narrow frequency band. With the choice of appropriate carrier frequency and modulation technique, this frequency band can be suitably shifted into the passband of the intended communication channel.
(4) Multiplexing : Confining a message signal into a narrow frequency band allows sending multiple message signals at the same time over the shared communication channel by a technique called multiplexing.