• # question_answer The antenna current of an AM transmitter is 8A when only the carrier is sent, but it increases to 8 -93A when the carries is modulated by single sine wave. Find the modulation index. A)  0.601                    B)  0.701    C)  0.801                    D)  0.501

Let ${{E}_{C}}\And m{{E}_{C}}$ are amplitude volt of carrier wave & modulated wave respectively, than ${{P}_{C}}=\frac{E_{C}^{2}}{2R}$Power of transmitted wave, ${{P}_{T}}={{P}_{C}}+{{P}_{S}}=\frac{E_{C}^{2}}{2R}+\frac{{{m}^{2}}E_{C}^{2}}{4R}$where ${{P}_{S}}$ is the power of side bands. $\frac{{{P}_{T}}}{{{P}_{C}}}=1+\frac{{{m}^{2}}}{2}$ $\Rightarrow$${{\left( \frac{{{I}_{T}}}{{{I}_{C}}} \right)}^{2}}=1+\frac{{{m}^{2}}}{2}$$\Rightarrow$${{\left( \frac{8.93}{8} \right)}^{2}}=1+\frac{{{m}^{2}}}{2}$ $\Rightarrow$$m=0.701$