Analog Communications Questions and Answers – Average Power For Sinusoidal AM

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This set of Analog Communications Multiple Choice Questions & Answers (MCQs) focuses on “Average Power For Sinusoidal AM”.

1. A 1000KHz carrier is modulated by 100Hz and 200Hz waves, then which of the following frequencies cannot be present at the output?
a) 1000.1KHz
b) 999.9KHz
c) 1000.2KHz
d) 999.7KHz
View Answer

Answer: d
Explanation: Frequencies present at output will be 1000 ± 0.1 KHz = 1000.1KHZ and 999.9KHz and 1000 ± 0.2 KHz = 1000.2KHZ and 999.8KHz. Therefore, Only, 999.7KHz is out of the range.

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2. Aspect ratio is the ratio of ________
a) width to height
b) height to width
c) power to width
d) width to power
View Answer

Answer: a
Explanation: Aspect ratio, being one of the crucial attributes in image projection, describes the varying relationship between the width of the image and it’s height. Thus, Aspect ratio is the ratio of width to the height of image (screen).

3. If the levels in PCM are transmitted in 10 unit code having sampling frequency equals to 20KHz. What is its bandwidth?
a) 150KHz
b) 125KHz
c) 100KHz
d) 110KHz
View Answer

Answer: c
Explanation: PCM bandwidth is half of Bit rate.
Bit Rate = 10 X 20 = 200
Bandwidth = 200/2 = 100 KHz.
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4. Carrier frequency is given by the formula ________
a) \(\frac{1}{2 \pi \sqrt{LC}}\)
b) \(\frac{1}{2 \pi \sqrt{L}}\)
c) \(\frac{1}{2 \pi \sqrt{C}}\)
d) \(\frac{1}{\pi \sqrt{LC}}\)
View Answer

Answer: a
Explanation: Carrier wave is a high frequency signal whose certain characteristics, like amplitude, phase and frequency, are varied with respect to the instantaneous amplitude of the baseband signal (message signal). This variation is called modulation. Carrier frequency is given by the formula, fc = \(\frac{1}{2 \pi \sqrt{LC}}\) where L is inductance and C is Capacitance.

5. Among all amplifiers, Common Collector has highest power gain.
a) True
b) False
View Answer

Answer: b
Explanation: An amplifier is an electronic device that increases the voltage, current, or power of a signal. Amplifiers are used in wireless communications and broadcasting, and in audio equipment of all kinds. It is common emitter which has highest power gain. Common emitter has a very high voltage gain and also has good amount of current, so its power gain is high.
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6. Find the carrier frequency if the inductance and capacitance are 30μH and 10nF respectively?
a) 244KHz
b) 523KHz
c) 290KHZ
d) 300KHz
View Answer

Answer: c
Explanation: Carrier frequency is a waveform (usually sinusoidal) that is modulated (modified) with an input signal for the purpose of conveying information. The carrier frequency is 290KHZ if inductance & capacitance are 30μH & 10nF

7. Helical antenna is used to obtain ________ polarization.
a) elliptical
b) circular
c) linear
d) perpendicular
View Answer

Answer: b
Explanation: A helical antenna is an antenna made of one or more conducting wires wound in the form of a helix. It produces circular polarization, because of which it is highly used in radio telemetry.
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8. What is number of possible outputs if there is 6 line digital input?
a) 64
b) 32
c) 16
d) 128
View Answer

Answer: a
Explanation: Total possible outputs will be 2n = 26 which is equal to 64.

9. Push pull amplifier is a class B amplifier.
a) True
b) False
View Answer

Answer: a
Explanation: A push pull amplifier is an amplifier which has an output stage that can drive a current in either direction through through the load. Push pull amplifier uses a pair of active devices that alternately supply current to a connected load and also absorb current from a connected load. It is a class B amplifier.
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10. For removing unwanted signals we should use ________
a) mixing method
b) filter method
c) modulation method
d) detecting method
View Answer

Answer: b
Explanation: Filteration method is used to remove unwanted components from the signal. It is mainly used to eliminate noise.

Sanfoundry Global Education & Learning Series – Analog Communications.

To practice all areas of Analog Communications, here is complete set of 1000+ Multiple Choice Questions and Answers.

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Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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