question_answer

Give reasons for the following : (i) For ground wave transmission, size of antenna \[(l)\] should be comparable to wavelength of signal i.e., \[l=\lambda /4\]. (ii) Audio Signals, converted into an e .m. wave, are not directly transmitted as such. (iii) The amplitude of modulating signal is kept less than the amplitude of carrier wave.                

Answer:

                (i) When the size of the antenna is com- parable to wavelength of the signal, the time variations of the signal are properly sensed by the antenna. (ii) An e. m. wave, of audio signal frequency, would have a very high wavelength. It would, therefore, need an antenna, whose size would be practically unattainable. (iii) The amplitude of modulating signal is kept less than the amplitude of carrier wave to avoid distortion.