Question

An ECE student decided to replace his radio transmitter and design a new one. He soon found out that the antenna current of his new transmitter, which is modulated to a depth of 72% by an audio signal, is equal to 14 A. It increase to 16.08 A as a result of simultaneous modulation by another audio signal. What is the modulation index of the second audio signal?

Answer 1

* We know, page-1 It = Icllt er It - Antenna current when Am is transmitted into free space. Ic - Antenna Curxent before modulation. Case (1): M= 72 100 0.72 It = 14A we know, It = Ic 42 It = Ic fit 2 Vit (0.722 14 = Ic Z 14 = Ic 1+0.2592 14 = Ic V1.2592 14 = Ic (1.122140810) 14 Ic 1.122140811) Ic =12.4 761526018 A

page-2 from Case()), Ic = 12.4761526018 A Case(2): New It is, It = 16.08 A 16-08 = 1204761526018 Vitara * Here U is resultant of two two Modulation incides. 1.2888588745 = - Vit einem Square on both sides, 1•6611571984 = 1+ us? 2 42 0.6611571984 2 2 U=1.3223143968 M, ² + 1 ² = 1.3223143968 0-723+ M2 = 1.3223143968 0-5184 + M2 ² = 1.3223143968 M2² = 0.8039143968

M2=/0. 80.8039143968 page-3 M2=0.8966127351 - * Hence, Modulation index of Second Audio signal is, Ug = 0.8966127351