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A message signal of frequency 100 MHz and peak voltage 100 V is used to execute amplitude modulation on a carrier wave of frequency 300 GHz and peak voltage 400 V. The modulation index and difference between the two side band frequencies are:(A) 4 ; 2 × 10⁸ Hz (B) 4 ; 1 × 10⁸ Hz(C) 0.25 ; 1 × 10⁸ Hz (D) 0.25 ; 2 × 10⁸ Hz |
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Answer» •According to the question, amessage signal of frequency 100 MHz and peak voltage 100 V is used to execute amplitude modulation on a carrier wave of frequency 300 GHz and peak voltage 400 V. • So,Fm = 100MHZ = 10^8 MHz (Vm)o = 100V , ( Ve)o =400 V So the modulation index = (Vm)o /( Ve)o = 100/400 = 1/4 = 0.25 UBF or Upper Band Frequency = FE + Fm LBF or Lower Band Frequency= Fe – Fm so,the difference between the two SIDE band frequencies are [UBF — LBF] = 2Fm = 2× 10 ^8 Hz So, the ANSWER is (D) 0.25 ; 2 × 10⁸ Hz
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