Numerial - Change in transmission power with change in modulation index

Q.  What is the effect on the transmitted power of AM signal when the modulation index changes from 0.8 to 1?
- Published on 13 Oct 15

a. 0.1364
b. 0.3856
c. 1.088
d. 0.5

ANSWER: 0.1364
 
The total power in an AM is given by
Pt = Pc (1 + m2/2)
Where Pc is the carrier power and m is the modulation index.

Therefore,

Pt1 = Pc (1 + 0.82/2) = 1.32 Pc
Pt2 = Pc ( 1 + 12/2) = 1.5 Pc
Increase in power = (1.5 Pc - 1.32 Pc)/ 1.32 Pc
= 0.1364

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