State any two reason for necessity of modulation.

Explanation

Modulation: The process of attaching i.e., superimposing the message signal to a high frequency carrier wave for the purpose of long distance transmission is called modulation. The resulted obtained is called modulated wave
Necessity of modulation:
(i). Size of antenna:
Height of antenna`prop(1)/("frequency of signal")`
Low frequency signal cannot be transmitted as such because height of antenna is large. By attaching the signal with high frequency carrier wave, we can reduce the height of antenna.
(ii). Avoid mixing of signals:
If two message signals of similar frequency are transmitted as such then they can get mixed with each other. Hence, different transmission channels are allocating different carrier wave frequencies.
(iii). Power radiated:
Power radiated by an antenna is directly proportional to square of frequency.
power `propf`
Hence, higher is the frequency more is the power transmitted and signal travel a larger distance.