Question

Write two factors which justify the need of modulating a low frequency signal into high frequencies before transmission.

Answer 1

Hint:First let us see what modulation is:Modulation is the method of varying one or more properties of a continuous waveform, called the carrier signal, in electronics and telecommunications, with a modulating signal that usually includes information to be transmitted.

Complete step by step answer:
Modulation is called this method of placing an input signal on a carrier wave. In other words, the shape of a carrier wave shifts modulation to somehow encrypt the speech or data information we were involved in bringing.
The modulation helps one to transmit a signal over the frequency spectrum of a band pass. Allowing the use of a smaller antenna is another excuse to modulate a signal. A baseband (low frequency) signal will need a big antenna since the antenna has to be around ${\dfrac{1}{{10}}^{th}}$ the length of the wavelength to be effective.
The explanatory factors needed are-
(a) Low-frequency signal propagation requires an antenna $4 - 5\,km$ in height that cannot be installed. So we need to modulate the wave to reduce the antenna’s height.
(b) $P\alpha \dfrac{1}{{{\lambda ^2}}}$ would be the effective power radiated by the antenna. Therefore, the wave has to be modulated for efficient radiation by an antenna.
In radio communication, high frequency carrier frequencies are used because space is an insulator and one can only provide electric current in it to magnetise it if the source involves a voltage shift rate or a changing electric field.

Hence,the two factors are modulated waves and effective power radiated by antenna.

Note:Although high frequency signals are important, low frequency signals are also required because low frequency signals can travel long distances as they have low signal attenuation.