# Analog Communications Questions and Answers – Average Power For Sinusoidal AM

«
»

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

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.

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

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

Explanation: PCM bandwidth is half of Bit rate.
Bit Rate = 10 X 20 = 200
Bandwidth = 200/2 = 100 KHz.
Sanfoundry Certification Contest of the Month is Live. 100+ Subjects. Participate Now!

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) $$\frac{1}{\pi \sqrt{LC}}$$

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

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.

6. Find the carrier frequency if the inductance and capacitance are 30μH and 10nF respectively?
a) 244KHz
b) 523KHz
c) 290KHZ
d) 300KHz

Explanation: Carrier frequency is a waveform (usually sinusoidal) that is modulated (modified) with an input signal for the purpose of conveying information.

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

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.

8. What is number of possible outputs if there is 6 line digital input?
a) 64
b) 32
c) 16
d) 128

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

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.

10. For removing unwanted signals we should use ________
a) mixing method
b) filter method
c) modulation method
d) detecting method

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.