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

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Practice Questions

1089 Total
Question 1 Discuss
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If an AM signal has a carrier power of 100W and a modulation index of 0.8, what is the total transmitted power?

A
132 W
B
164 W
C
150 W
D
180 W

Answer & Explanation

Correct Option: A

Total Power Pt = Pc(1 + m^2/2) = 100(1 + 0.64/2) = 100(1.32) = 132 W.
Question 2 Discuss
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Which layer of the ionosphere is mainly responsible for long-distance high-frequency night-time sky wave propagation?

A
D layer
B
E layer
C
F1 layer
D
F2 layer

Answer & Explanation

Correct Option: D

The F2 layer remains highly ionized at night and facilitates long-distance HF radio wave reflection.
Question 3 Discuss
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Calculate the bandwidth of an FM signal if the maximum frequency deviation is 75 kHz and the modulating signal frequency is 15 kHz.

A
90 kHz
B
120 kHz
C
150 kHz
D
180 kHz

Answer & Explanation

Correct Option: D

By Carson's Rule, Bandwidth = 2(Delta f + fm) = 2(75 + 15) = 2(90) = 180 kHz.
Question 4 Discuss
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In a superheterodyne receiver, if the received signal frequency is 1000 kHz and the intermediate frequency is 455 kHz, what is the image frequency?

A
1455 kHz
B
1910 kHz
C
545 kHz
D
2000 kHz

Answer & Explanation

Correct Option: B

Image frequency = fs + 2(IF) = 1000 + 2(455) = 1000 + 910 = 1910 kHz.
Question 5 Discuss
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Which of the following techniques is primarily used in FM transmitters to improve the signal-to-noise ratio at higher modulating frequencies?

A
De-emphasis
B
Pre-emphasis
C
Amplitude Limiting
D
Companding

Answer & Explanation

Correct Option: B

Pre-emphasis artificially boosts high-frequency signals at the transmitter to overcome high-frequency noise.
Question 6 Discuss
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What is the primary advantage of a Ratio Detector over a Foster-Seeley discriminator in FM demodulation?

A
It provides higher output voltage
B
It is intrinsically insensitive to amplitude variations
C
It has a simpler circuit design
D
It requires less bandwidth

Answer & Explanation

Correct Option: B

A Ratio Detector rejects amplitude modulation (AM) variations inherently, negating the need for a separate limiter stage.
Question 7 Discuss
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What is the total power saved if the carrier and one sideband are suppressed in an AM transmission with a 100% modulation index?

A
50.0%
B
66.6%
C
83.3%
D
100.0%

Answer & Explanation

Correct Option: C

At m=1, carrier power is 66.6% and each sideband is 16.6%. Suppressing carrier + one sideband saves 66.6 + 16.6 = 83.3%.
Question 8 Discuss
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Ground wave propagation is most effective and primarily used in which of the following frequency ranges?

A
VHF
B
UHF
C
SHF
D
VLF and MF

Answer & Explanation

Correct Option: D

Ground wave propagation follows the earth's contour and works best at lower frequencies like VLF, LF, and MF.
Question 9 Discuss
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Calculate the approximate line-of-sight distance between a transmitting antenna of height 16m and a receiving antenna of height 9m.

A
21 km
B
29 km
C
35 km
D
45 km

Answer & Explanation

Correct Option: B

d = 4.12(sqrt(Ht) + sqrt(Hr)) = 4.12(sqrt(16) + sqrt(9)) = 4.12(4 + 3) = 4.12(7) = 28.84 km, approx 29 km.
Question 10 Discuss
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Fading in sky wave communication is primarily caused by which phenomenon?

A
Multipath interference
B
Ground reflection
C
Thermal noise
D
Antenna mismatch

Answer & Explanation

Correct Option: A

Fading occurs because the signal reaches the receiver via multiple paths with different phases, causing constructive and destructive interference.
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