SarkariPYQ

SSC CPO 2025 PYQ — Question 83

SSC CPO - 9 Dec 2025 - Shift 1 • General Awareness • Q83

Back to paper

Read the following statements regarding different modulation techniques:
1. In Amplitude Modulation (AM), the bandwidth of the modulated signal is twice the modulating signal frequency.
2. Frequency Modulation (FM) typically consumes less power than AM for the same coverage area.
3. Phase Modulation (PM) is equivalent to Frequency Modulation (FM) when the modulating signal is integrated before applying to the phase modulator.
Which of the above statements are correct?

Show answer & explanation

Correct answer: C

Explanation

Correct Answer: 1 and 3 are only

Analysis of Statements:

  • Statement 1 (True): In Amplitude Modulation (AM), the generated bandwidth is twice the maximum frequency (fₘ) of the message signal. Mathematically, BW = 2fₘ. It consists of the carrier wave along with two sidebands (USB and LSB).
  • Statement 2 (False): To achieve the same coverage area as Frequency Modulation (FM), AM requires 3 times more power and significantly greater bandwidth. However, while FM is more resistant to noise and offers superior quality, its power consumption and complexity are higher than those of AM.
  • Statement 3 (True): This is a fundamental principle of modulation. If we integrate the modulating signal and then apply it to a Phase Modulator (PM), the resulting output signal is identical to an FM signal. Consequently, PM is frequently utilized to generate FM signals.

Comparative Table:

Feature — Amplitude Modulation (AM) — Frequency Modulation (FM)

• Bandwidth — Low (2fₘ) — High (According to Carson's Rule)

• Noise — Highly Affected — Minimally Affected

• Applications — Radio Broadcasting (MW/SW) — High-Quality Radio, TV Audio

• Efficiency — Low — High

Important Questions for Upcoming Examinations:

  • • Question: Which modulation technique offers the best signal quality (Fidelity)?
  • Answer: Frequency Modulation (FM)
  • • Question: For which modulation technique is Carson's Rule used to calculate bandwidth?
  • Answer: FM (Frequency Modulation)
  • • Question: Which modulation technique is used for the video signal in TV broadcasting?
  • Answer: VSB (Vestigial Sideband Modulation) – a variant of AM.