(a) A low frequency signal is modulation for the following purposes :
(i) It reduces the wavelength of transmitted signal and the minimum height of antenna for effective communication is λ / 4. Therefore height of antenna becomes practically achievable.
(ii) Power radiated into the space by an antenna is inversely proportional to 1.2. Therefore, the power radiated into the space increases and signal can travel larger distance.
(Give full credit of parts for any other correct answer)
(b) (i) High efficiency
(ii) Less noise
(iii) Maximum use of transmitted power
