Question

Given below are two statements : Statement I : A speech signal of 2 kHz is used to modulate a carrier signal of 1 MHz. The bandwidth requirement for the signal is 4 kHz. Statement II : The side band frequencies are 1002 kHz and 998 kHz. In the light of the above statements, choose the correct answer :

• A. Both Statement I and Statement II are true
• B. Both Statement I and Statement II are false
• C. Statement I is true but Statement II is false
• D. Statement I is false but Statement II is true

Hint:

In Amplitude Modulation (AM), the information is contained in the sidebands, and the total bandwidth is always double the message frequency.

Answer 1

The Correct Option is A

Step 1: Bandwidth of AM signal $= 2 \times f_m = 2 \times 2$ kHz $= 4$ kHz. Statement I is true.
Step 2: Sidebands are $f_c + f_m$ and $f_c - f_m$.
Step 3: $f_c = 1000$ kHz, $f_m = 2$ kHz. Sidebands $= 1002$ kHz and $998$ kHz. Statement II is true.