Explain any two factors which justify the need for modulating a signal.

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> [!TLDR]
> Modulation is needed mainly for a practical antenna size and for effective radiated power (also to avoid interference between multiple transmitted signals).
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> Baseband message (audio) signals typically span the range 20 Hz to 20 kHz. Transmitting such low-frequency signals directly (without modulation) is impractical, for the following reasons:
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> **1. Size of the antenna (practicality):** For efficient transmission and reception, an antenna needs a length comparable to a quarter of the wavelength of the signal ($l\sim\lambda/4$) it must radiate. For an audio signal of, say, 20 kHz, the wavelength is
> $$\lambda = \dfrac{c}{
u} = \dfrac{3	imes10^8}{20	imes10^3} = 15\,	ext{km}$$
> requiring an antenna several kilometres long — physically impossible to build and erect. By modulating this signal onto a high-frequency carrier wave (MHz range), the required wavelength (and hence antenna length) shrinks to just a few metres, which is practical.
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Q.Explain any two factors which justify the need for modulating a signal.

Concept understanding — Need for Modulation

Q.Explain any two factors which justify the need for modulating a signal.

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