Briefly explain the three factors which justify the need of modulating low frequency signal into high frequencies

Explanation

Factors for justifying modulating signals are:
(i) energy (strength of signal) is low, so it can't be transmitted directly to large distance.
(ii) Height of singal antenna
(transmitter and receive) `= (lamda)/(4)`
(iii) Very high frequency signals can be transmitted without loss in air, only if the receiving antenna directly intercepts the signal from transmitting antenna. Also, there is fair chance of mixing up of signals from different transmitters.