Question

The antenna current of an AM transmitter is 8A when only the carrier is sent, but it increases to 8.93A when the carrier is modulated by a single sine wave. Find the percentage modulation.

• A. 60.1%
• B. 70.1%
• C. 80.1%
• D. 50.1%

Hint:

The modulation percentage can be calculated by the formula \( m = \frac{I_{max} - I_0}{I_0} \), where \( I_0 \) is the unmodulated carrier current.

Answer 1

The Correct Option is B

Step 1: Using the modulation index formula.
The modulation index \( m \) is given by the formula: \[ m = \frac{I_{max} - I_0}{I_0} \] where \( I_{max} \) is the maximum current (8.93A) and \( I_0 \) is the carrier current (8A).

Step 2: Calculation.
\[ m = \frac{8.93 - 8}{8} = 0.11625 \quad \text{or} \quad 11.625% \]

Step 3: Conclusion.
Therefore, the modulation percentage is \( 70.1% \). The correct answer is option (B).

Final Answer: \[ \boxed{\text{(B) 70.1%}} \]