Code: D-18                                                                    Subject: TELEVISION ENGINEERING

Time: 3 Hours                                                             Flowchart: Alternate Process: December 2005                                        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.       The horizontal resolution in lines of a typical low-cost US monochrome receiver having a video bandwidth of 3 MHz is 

 

                   (A)  200 lines.                                     (B)  240 lines.

(C)    100 lines.                                     (D)  150 lines.

       

b.      In monochrome receivers, at the final anode of the picture tube

 

                   (A) 10 to 11 KV EHT supply is required.                                                                        

                   (B)  No EHT supply is required.

                   (C) 20 to 25 KV EHT supply is required. 

                   (D) 1 to 10 KV EHT supply is required.

            

             c.   The exact value of the color sub carrier frequency chosen in the PAL system is

                  

(A)    4.4382157 MHz                          (B)  4.4339789 MHz

(C)  4.43361875 MHz.                       (D)  4.43387958 MHz

 

             d.   To produce a good quality picture, the peak signal-to-r.m.s. noise ratio that is generally considered adequate is around 

 

(A)    10 dB.                                        (B)  70 dB.

(C)  45 dB.                                         (D)  100 dB.         

 

             e.   The RF carrier power output of commonly used VHF TV transmitters varies from

                  

(A)     4 to 8 KW                                   (B)  100 to 150 KW

(C)  10 to 50 KW                               (D)  2 to 8 MW

 

 

 

 

 

 

 

             f.    While designing any Yagi antenna array for calculating the spanning between the reflector and dipole in meter, as a starting point, the formula used is

 

(A)                                              (B) 

(C)                                             (D) 

 

                   Where ‘f’ is the centre frequency of the channel in MHz.

 

             g.   The pattern of scanning lines in a video system is called

 

(A)    Retrace.                                       (B) Resolution.

(C) Raster.                                          (D) Interlace.

 

             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.    The PAL system was developed in

 

(A)   Japan.                                          (B) USA.

(C) South Africa.                                 (D) The Federal Republic of Germany.

 

             j.    The bandwidth allowed for the colour difference quadrature signals after modulation is about

 

(A)  0.99 MHz.                                   (B)  2 MHz.

(C)  1.3 MHz.                                     (D) 0.6 MHz.

 

 

Answer any FIVE Questions out of EIGHT Questions.

Each question carries 16 marks.

 

  Q.2     a.   Explain the principle of interlaced scanning with an illustration.                             (8)

       

             b.   Briefly describe the following:

(i)                  the effect of interlaced scanning on bandwidth.

(ii)                The effect of field frequency on bandwidth.                                 (8)

 

  Q.3     a.   List the characteristics to be possessed by a camera tube in order to be called the eye of a TV system.  Explain briefly the term ‘VIEWING DISTANCE’ as applied to a TV camera.    (6)

 

             b.   Name the two cameras which are variations of the standard vidicon and briefly explain each one of them.                                                               (10)                                                           

 

 

 

 

 

  Q.4     a.   With a neat sketch, illustrate the field synchronising pulse trains of the 625 line TV system at the end of the first field.  What is the purpose served by

(i)                  serrating the vertical sync pulses?

(ii)                Providing pre and post equalising pulses?                                              (10)

 

             b.   For the 525 line system, calculate the percentage (total) of the signal time that is occupied by

                   (i)   horizontal blanking                         (ii)  vertical blanking

                   (iii) active video.                                                                                                 (6)

 

  Q.5     a.   Distinguish between a monochrome picture tube and a colour picture tube.          (4)

       

             b.   With a neat sketch explain the elements of a monochrome picture tube employing low voltage electrostatic focussing and magnetic deflection.        (12)

 

  Q.6     a.   What type of colour mixing is employed in colour television?  Explain the principle involved in the technique used.  State Grassman’s Law.              (7)

 

             b.   What are the characteristics to be possessed by any colour to specify its visual information?  An RGB video signal has normalised values of R=0.2, G=0.4 and B=0.8.  Find values of the luminance signal, the in-phase component of colour signal and the quadrature component of the colour signal.                   (9)

 

  Q.7     a.   What do you mean by positive modulation and negative modulation?  Make a comparison of the above techniques on the following aspects:

(i)                  effect of noise interference on picture signal.

(ii)                Peak power available from transmitter.                                                 (13)

 

             b.   In the colour system, why is the sub carrier frequency is chosen to be an odd multiple of one-half the horizontal frequency?                           (3)

 

  Q.8     a.   With necessary illustrations explain how an FET can be used as a horizontal sync separator.                                                                       (11)

 

             b.   What is the function of the Chroma bandpass amplifier?  Name the parts of this amplifier.                (5)

 

  Q.9     a.   What is a colour bar pattern generator?  What are the checks to be carried out to align a new monochrome TV set before proceeding with the alignment of RF and IF sections of the receiver?  Indicate the sequence to be followed to carry out receiver alignment.                                                        (9)

 

             b.   What is the use of remote control facility?  With a schematic, explain a basic remote control system.                                                                       (7)