# Analog Communications Questions and Answers – Chopper Circuit

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This set of Analog Communications Multiple Choice Questions & Answers (MCQs) focuses on “Chopper Circuit”.

1. What is the full form of PEP in communication?
a) Peak Efficiency Power
b) Peak Envelope Power
c) Peak Efficiency Product
d) Peak Envelope Power

Explanation: PEP in communication stands for Peak Envelope Power. It is the highest envelope power that is transmitted to antenna transmission line by a transmitter. It is used to measure the power of varying signals.

2. Only audio can be sent using Amplitude Modulation.
a) True
b) False

Explanation: Amplitude modulation has the capability to send audio, video and digital data using different amplitude modulation techniques. So the statement that only audio signal can be sent by amplitude modulation is wrong.

3. What is the total modulation index, if one wave has a modulation index of m1 and other wave has a modulation index of m2?
a) m1 + m2
b) $$\frac{m_1+m_2}{2}$$
c) $$\sqrt{(m_1 \times m_2) + (m_1 \times 2m_2)}$$
d) $$\sqrt{(m_1 \times m_1) + (m_2 \times m_2)}$$

Explanation: Modulation index tells us the amount by which the carrier wave is varied with respect to the message signal. The total modulation index of two waves having modulation index m1 and m2 is $$\sqrt{(m_1 \times m_1) + (m_2 \times m_2)}$$.
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4. How many sidebands is produced with a single tone in an amplitude modulated system?
a) One
b) Two
c) Three
d) Four

Explanation: Single tone modulation is that in which the modulation is carried out with a message signal having single frequency component. Thus, the modulated wave has two sidebands.

5. If we compared to the USB, the information in LSB is ________
a) different to USB
b) twice of USB
c) same as USB
d) half of USB

Explanation: The two bands i.e. upper sideband and lower sideband generally contains same information. They also has same power.
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6. In amplitude modulated system, total sideband power is ________ than the carrier power.
a) always less
b) always more
c) sometimes more
d) sometimes less

Explanation: If we take the total power, then it is the sum of the carrier power and power of all the sidebands produced in the modulated signal. Thus, the total power is always more than the carrier power.

7. An amplitude modulated system requires less bandwidth than single side band system.
a) True
b) False

Explanation: In Single Sideband transmission, the carrier is suppressed and only either of the two sidebands is transmitted. Thus, it reduces the total power consumption and also reduces the bandwidth required. The two sidebands carries exactly the same information and thus removing a sideband does not have any effect on the signal.

8. In SC in DSB-SC stands for _________
a) suppressed-carrier
b) single-carrier
c) sideband-carrier
d) super-carrier

Explanation: DSB-SC stands for Double Side Band- Suppressed Carrier. In SBSC, the carrier is suppressed and only the two sidebands are transmitted. In DSB-SC all the frequencies produced by amplitude modulation are symmetrically arranged above and below the carrier frequency.

9. What is the correct statement about FM modulation index?
a) increases with both modulation frequency and deviation
b) decreases with modulation frequency and increases with deviation
c) it increase with modulation frequency and decreases with deviation
d) it is equal to twice the deviation

Explanation: Modulation index tells us the amount by which the carrier wave is varied with respect to the message signal. In FM, modulation index is the ratio of frequency deviation and modulating frequency. Frequency modulated modulation index increases as deviation increase. It also decreases with modulation frequency.

10. Which mathematically term is used for calculating FM bandwidth?
a) Bessel functions
b) Trigonometry
c) Taylor series
d) Fractals

Explanation: Bessel function are the solution of Bessel differential equation which are non-singular at the origin. In communication it is used to calculate FM bandwidth.

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