Jkp Constable Telecommunication Telecommunication Mcqs Jkp Constable (1089 MCQs) | JKSSB & SSC Quiz

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Practice Questions

1089 Total
Question 11 Discuss
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Why is Vestigial Sideband (VSB) modulation used in analog TV video transmission?

A
To eliminate the need for an audio carrier
B
To save bandwidth while preserving low-frequency content
C
To increase the transmit power efficiency
D
To prevent interference from FM radio

Answer & Explanation

Correct Option: B

VSB transmits one full sideband and a trace (vestige) of the other, saving bandwidth compared to DSB while being easier to filter than SSB.
Question 12 Discuss
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What is the purpose of interlaced scanning in a television system?

A
To increase horizontal resolution
B
To reduce bandwidth requirements
C
To reduce flicker without increasing the video bandwidth
D
To improve color saturation

Answer & Explanation

Correct Option: C

Interlaced scanning divides each frame into two fields drawn sequentially, effectively doubling the refresh rate and reducing flicker without needing extra bandwidth.
Question 13 Discuss
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In a composite video signal, what is the function of the blanking pulses?

A
To synchronize the horizontal oscillator
B
To carry color burst information
C
To turn off the electron beam during retrace periods
D
To amplify the weak video signals

Answer & Explanation

Correct Option: C

Blanking pulses suppress the electron beam so the retrace lines are not visible on the screen when the beam moves back.
Question 14 Discuss
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A half-wave dipole antenna is designed to operate at 300 MHz. What is its approximate physical length?

A
0.25 meters
B
0.475 meters
C
0.5 meters
D
1.0 meters

Answer & Explanation

Correct Option: B

Wavelength (lambda) = c/f = 300Mm/300MHz = 1m. Theoretical half-wave = 0.5m. Practical length uses an end effect factor (approx 0.95), yielding 0.475m.
Question 15 Discuss
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Which component in a Yagi-Uda antenna acts to narrow the beamwidth and increase forward gain?

A
Reflector
B
Director
C
Driven element
D
Balun

Answer & Explanation

Correct Option: B

Directors are placed in front of the driven element to focus the radiation pattern in the forward direction, increasing gain.
Question 16 Discuss
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An antenna has a radiation resistance of 70 ohms and a loss resistance of 10 ohms. What is its directivity if its power gain is 14?

A
12.25
B
14.0
C
16.0
D
18.5

Answer & Explanation

Correct Option: C

Efficiency = Rr / (Rr + Rl) = 70 / 80 = 0.875. Gain = Efficiency * Directivity. Directivity = 14 / 0.875 = 16.
Question 17 Discuss
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The characteristic impedance of a standard coaxial cable used for television receivers is typically:

A
50 ohms
B
75 ohms
C
300 ohms
D
600 ohms

Answer & Explanation

Correct Option: B

Standard TV coaxial cables (like RG-6 or RG-59) have a characteristic impedance of 75 ohms for optimal power transfer and low loss.
Question 18 Discuss
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In the standard CCIR 625-line TV system, what is the standard intermediate frequency (IF) for the picture carrier?

A
10.7 MHz
B
33.4 MHz
C
38.9 MHz
D
45.5 MHz

Answer & Explanation

Correct Option: C

In standard 625-line systems, the picture IF is 38.9 MHz, while the sound IF is typically 33.4 MHz.
Question 19 Discuss
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What is the theoretical input impedance of a standard folded dipole antenna?

A
73 ohms
B
150 ohms
C
288 ohms
D
600 ohms

Answer & Explanation

Correct Option: C

A folded dipole has four times the impedance of a standard half-wave dipole (4 * 72 ohms = 288 ohms).
Question 20 Discuss
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Compared to progressive scanning, interlaced scanning requires:

A
Double the bandwidth
B
Half the bandwidth
C
The same bandwidth
D
Four times the bandwidth

Answer & Explanation

Correct Option: B

By transmitting half the image lines per field, interlaced scanning halves the necessary bandwidth compared to a progressive scan at the same frame rate.
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