Significance of modulation index in AM transmission
It is used to determine the strength and quality of transmitted signal. If the modulation index is small, then the amount of variation in the carrier amplitude is small. Thus, the audio signal transmitted will not be strong. The greater the degree of modulation, die stronger and clearer will be the audio signal during reception.
Effect of modulation index on AM wave
i) m < 1
If m < 1 or if the percentage of modulation is less than 100% the this type of modulation is known as under modulation The amplitude of modulating signal less than carrier amplitude, no distortion will occur.
ii) m = 1
If m = 1 or percentage of modulation is 100 this type modulation is 100% modulation The ideal condition for AM is m =1, since this will produce the greatest output at the receiver with no distortion.
If m > 1 or if the percentage of modulation is greater than 100% the this type of modulation is known as over modulation the modulating signal being of greater amplitude part of its information is lost in the process of modulation which is undesirable.