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Seat No.: Enrolment
GUJARAT TECHNOLOGICAL UNIVERSITY
DIPLOMA ENGINEERING SEMESTER -III• EXAMINATION SUMMER 2017
Subject Code: 331104 Date: 05 05 2017
Subject Name: Communication Engineering- I
Time: 02:30 PM TO 05:00 PM Total Marks: 70
Instructions:
1. Attempt all questions.
2. Make Suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.
4. Use of programmable Communication aids are strictly prohibited.
5. Use of only simple calculator is permitted in Mathematics.
6. English version is authentic.
Q.1

What is Modulation? Define AM, FM and PM with necessary waveforms.
07


AM, FM


Define Noise. Explain types of noise in detail.
07



Q.2

Define modulation Index for AM wave. Explain different methods used to
measure it and draw the waveforms for m>1 for each method.
07


AM m>1


Compare High Level Modulation with Low Level Modulation.
07



OR

The total power of AM wave is 600W. Determine the percentage modulation of the signal if each of the sidebands contains 75W.
07

AM 600W

Q.3

List advantages, disadvantages and applications of FM.
07





Draw and explain the block diagram of FM Transmitter using Armstrong
method of FM generation.
07

FM FM

OR
Q.3

Explain pre-emphases and de-emphases circuit.
07





Explain the circuit diagram for FM generation using varactor diode.
07

FM

Q.4

Explain different characteristics of Radio receiver.
07
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Explain balance slope detector circuit used for FM detection.
07



OR
Q.4

What is heterodyne? Draw and explain the block diagram of Super heterodyne AM radio receiver.
07


AM


Explain phase-shift discriminator circuit used in FM receiver.
07

FM discriminator

Q.5

Explain the Yagi-Uda antenna with neat diagram.
07





What is fading? Explain different Diversity techniques used to combat the
effect of fading.
07



OR
Q.5

Explain the Log-Periodic antenna with neat diagram
07





Explain the following term in brief: MUF, Fading.
07

MUF,