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. Aspect ratio of a picture is
(A) Height to width ratio. (B) Width to height ratio.
(C) Diagonal length ratio. (D) Depth to height ratio.
b. Contrast of a picture is
(A) Sharpness. (B) Amount of light.
(C) Difference between intensities. (D) Average light intensity.
c. Dark current in a camera is
(A) When there is no picture. (B) When there is no light.
(C) When contrast is zero. (D) When current is zero.
d. The purpose of Dichroic mirror is to
(A) filter specific wavelength. (B) reflect light into lens.
(C) reflect specific wavelength. (D) act as relay lens.
e. Degaussing helps in
(A) alignment of electrons. (B) removing magnetic flux.
(C) producing electrostatic focus. (D) remove ghost image.
f. Serrated pulses give information of
(A) equalizing lines. (B) vertical synchronisation.
(C) horizontal synchronization. (D) end of vertical period.
g. Chrominance signal is generated from
(A) R, G, B (B) B-Y, G-Y
(C) R-Y, G-Y (D) R-Y, B-Y
h. Differential Phase error is because of
(A) Change in phase of chrominance signal.
(B) Change in phase of Luminance signal.
(C) Change in phase of Sub-carrier.
(D) Change in amplitude of chrominance signal.
i. A single horizontal line on the picture tube screen is because of
(A) Failure of focusing circuit. (B) Failure of de-gaussing.
(C) Failure of horizontal scan circuit.(D) Failure of Vertical scan circuit.
j. In PAL the video bandwidth is
(A) 4.5 MHz. (B) 5.5 MHz.
(C) 5.0 MHz. (D) 6.0 MHz.
Answer any FIVE Questions out of EIGHT Questions.
Each question carries 16 marks.
Q.2 a. Define and explain the effect of following on the reproduction of picture.
(i) Brightness.
(ii) Contrast.
(iii) Resolution. (9)
b. A video standard uses interlacing of 2:1 with 819 scanning lines. if 15% of lines are lost during retrace, if vertical frequency is 50Hz, calculate
(i) Horizontal line period.
(ii) Element period.
(iii) Bandwidth for aspect ratio 4:3. (7)
Q.3 a. Explain how silicon diode array is used to convert optical image to electrical video signal. (8)
b. Explain the construction of deflection yoke and show how these assist in vertical and horizontal movement of electron beam in a picture tube. (8)
Q.4 a. What are the basic components of a composite video signal? Draw such a signal for two lines of vertical bars containing grey scale of seven starting from white. Indicate the 625-B timings and relative amplitudes. (10)
b. What is the need of incorporating pre-equalising and post-equalising pulses? (6)
Q.5 a. What is compatibility? Why and how luminance and chrominance signals are generated in colour transmission? (8)
b. Explain the advantages of using VSB instead of SSB transmission. Draw the transmitted spectrum in UK standard for Channel-2 VHF. (8)
Q.6 a. What is the basic difference between CCIR-PAL and SECAM chrominance processing, explain. (8)
b. If there is phase error of 15 degrees in a chrominance signal that was transmitted at 55 degrees, what would be its effect in an NTSC system and PAL system. Show drawing phasor diagrams. (8)
Q.7 a. What is meant by vestigial side band correction & how is it achieved in the receiver? (8)
b. Why AGC is required in a TV receiver, explain a typical scheme of keyed AGC? (8)
Q.8 a. Spell out the drawbacks of PAL-S (simple). How is it overcome in PAL-D (delay line), explain using schematic. (10)
b. What is the role of colour killer in a colour receiver? Why it is not required in a monochrome receiver? (6)
Q.9 a. Explain the principle of tuning in a digital R.F. tuner. (8)
b. Why AFT is required in a receiver, draw a typical AFT circuit and explain. (8)