Code: DE18                                                                   Subject: TELEVISION ENGINEERING

Time: 3 Hours                                                                                                     Max. Marks: 100

NOTE: There are 9 Questions in all.

· Question 1 is compulsory and carries 20 marks. Answer to Q. 1. must be written in the space provided for it in the answer book supplied and nowhere else.

· Out of the remaining EIGHT Questions answer any FIVE Questions. Each question carries 16 marks.

· Any required data not explicitly given, may be suitably assumed and stated.

Q.1       Choose the correct or best alternative in the following:                                         (2x10)

a. Persistance of vision helps in fixing  

(A)  Horizontal scanning                       (B)  Blanking Period

(C)   Video frequency                          (D)  Vertical frame frequency

b. If the aspect ratio is 4:3 in a conventional TV system, what would be the width and height in cms for a 100 cm screen?

(A) 80, 60                                           (B) 87, 49

(C) 60, 45                                           (D) 30, 40

             c.   Loss of Horizontal synchronization causes

(A) Picture tear                                   (B)  No Video

(C)  Rolling of Picture                          (D)  Smearing

             d.   Vertical sync pulses are also called

(A)  Equalising Pulses                         (B)  Serrated Pulses

(C)  Vertical Blanking Pulses               (D)  Sync Burst     

             e.   In CCIR-B the video bandwidth is

(A) 4.5 MHz                                      (B)  5.5 MHz

(C)  5.0 MHz                                      (D)  6.0 MHz

             f.    Halo-effect takes place in

(A) Image Orthicon                            (B)  Plumbicon

(C)  Vidicon                                        (D)  Trinitron

             g.   The usual take-off point for synchronising signal in a monochrome receiver is

(A) the output of the IF stage              (B) the output of the video detector stage

(C) the output of the mixer stage          (D) the output of video amplifier stage

             h.   The most used picture tube in present day colour TV receivers is the

(A)  Delta-gun tube                              (B) PIL tube

(C)  Image orthicon tube                      (D)  Plumbicon

             i.    An acoustic delay line is used in:

(A) PAL receiver                                (B) NTSC receiver

(C) Monochrome receiver                   (D) PAL transmitter

             j.    Most of the remote systems use

(A) Ultrasonic carrier                          (B)  Radio Frequency carrier

(C)  Infrared carrier                             (D) Microwave carrier

Answer any FIVE Questions out of EIGHT Questions.

Each question carries 16 marks.

Q.2     a.   What is the need of scanning, explain the principle of interlaced scanning with an illustration show that it reduces flickering.                                (8)

             b.   Calculate the Video bandwidth of a 625 line system, with a Kell factor of 0.64 and aspect ratio 4:3. Assume interlaced scanning with two fields per frame and frame frequency of 25Hz.                        (8)

Q.3     a.   Draw composite video signal for a chess board pattern and indicate percentage amplitudes and timings of

                   (i)  Blanking level                                 (ii)  Sync. Pulse level

                   (iii) Time from the start of one line to the start of next line in microsecond             (8)

             b.   What is meant by D-C component of the video signal? How DC restoration is achieved.                (8)

Q.4     a.   What is compatibility? Why and how luminance and chrominance signals are generated in colour transmission?                                       (8)

b.   Why weighting is required in building chrominance signal? Draw video color composite signal with weighting.                                                           (8)

Q.5     a.   What is automatic frequency tuning, explain the principle of working of AFT.                      (8)

     b.   What are the disadvantages of non-keyed AGC, explain the principle of keyed AGC.                     (8)

  Q.6     a. How sound takes-off is obtained, explain the working of sound section.              (8)

             b.   Explain the principle of working of Trinitron picture tube.                                    (8)

Q.7     a.   How sync separation is achieved, how AFC is achieved.                                    (8)

b.   Give the merits and demerits of negative modulation in TV transmission.             (8)

Q.8     a.   Design a five element Yagi-Uda antenna for channel VII of CCIR and draw its diagram.                 (8)

             b.   What is a Booster, how does it work? Explain with schematic.                            (8)

Q.9           Write short notes on:

(i) SECAM encoder

(ii) PLL control

(iii) Dipole antenna with reflector and director

(iv) Color killer                                                                                         (4 x 4)