COMMUNICATION SYSTEM-1 (paper no. 2) by SURESH KUMAR.....sureshkumarthegreat@yahoo.com

COMMUNICATION SYSTEM-1

PAPER NO. 2

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                                               EC-309
                               COMMUNICATION SYSTEM-1
                                  (B.Tech 5th Semester,2052)
Time : 3 Hours                                                                                        Maximum Marks : 60
NOTE:- This paper consist of Three Sections. Section A is compulsory. Do any Four questions from
                 Section B and any two questions from Section C

                                     Section-A                                         Marks : 20

1(a) Differentiate between Deterministic and Random Signals.
(b) What do you understand by orthogonal signals?
(c) List various types of internal noise.
(d) A broadcast AM transmitter radiates 50 kW of carrier power. What will be the radiated power at 85% modulation ?
(e) Where vestigial side-band modulation is used ?
(f) What is de-emphasis ?
(g) What is a tank circuit ? What is its purpose ?
(h) What is simple AGC ? What are its functions ?
(i) Define pulse position modulation, and explain with waveforms how is it derived from PWM ?
(j) Why are FM broadcarters made on VHF and UHF bands ?

                                              Section-B                                          Marks:5 Each

2. The antenna current of an AM broadcast transmitter, modulated to a depth of 40% by an audio sine wave, is 11 amperes. It increses to 12 amperes as a result of simultaneous modulation by another audio sine wave. What is the modulation index due to this second wave ?
3. Using a circuit diagram, explain the working of ring modulator.
4. Define and describe independent side band transmission.
5. Explain the generation of FM by any one of the indirect methods.
6. A 25 MHz carrier is modulated by a 400 Hz audio sine wave. If the carrier voltage is 4 volts and the maximum deviation is 4 volts and the maximum devation is 10 kHz, write the equation of this modulated wave for FM. If the modulating frequency is now changed to 2 kHz, all else remainig constant, write a new equation for FM.

                                               Section-C                                        Marks : 10 Each

7. Draw the block diagram of a superhetrodyne AM reciever. Explain the function of each block.
8. With the help of a circuit diagram, explain the operation of radio detector. Also explain how amplitude limiting is done by Ratio Detector ?
9. Using a block diagram, explain the working of a suppressed carrier reciever.

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