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1

JEE Main 2021 (Online) 27th August Evening Shift

MCQ (Single Correct Answer)
An antenna is mounted on a 400 m tall building. What will be the wavelength of signal that can be radiated effectively by the transmission tower upto a range of 44 km?
A
37.8 m
B
605 m
C
75.6 m
D
302 m

Explanation

h : height of antenna

$$\lambda$$ : wavelength of signal

h < $$\lambda$$

$$\lambda$$ > h

$$\lambda$$ > 400 m
2

JEE Main 2021 (Online) 26th August Evening Shift

MCQ (Single Correct Answer)
A transmitting antenna at top of a tower has a height of 50 m and the height of receiving antenna is 80 m. What is range of communication for Line of Sight (LoS) mode?

[use radius of earth = 6400 km]
A
45.5 km
B
80.2 km
C
144.1 km
D
57.28 km

Explanation



$${d_t} = \sqrt {2R{h_1}} + \sqrt {2R{h_2}} $$

$$ = \sqrt {2R} \left( {\sqrt {{h_1}} + \sqrt {{h_2}} } \right)$$

$$ = {(2 \times 6400 \times {10^3})^{1/2}}(\sqrt {50} + \sqrt {80} )$$

$$ = 3578(7.07 + 8.94)$$

$$ = 57.28$$ km
3

JEE Main 2021 (Online) 25th July Morning Shift

MCQ (Single Correct Answer)
In amplitude modulation, the message signal

Vm(t) = 10 sin (2$$\pi$$ $$\times$$ 105t) volts and

Carrier signal

VC(t) = 20 sin(2$$\pi$$ $$\times$$ 107 t) volts

The modulated signal now contains the message signal with lower side band and upper side band frequency, therefore the bandwidth of modulated signal is $$\alpha$$ kHz. The value of $$\alpha$$ is :
A
200 kHz
B
50 kHz
C
100 kHz
D
0

Explanation

Bandwidth = 2 $$\times$$ fm

= 2 $$\times$$ 105 HZ = 200 KHZ
4

JEE Main 2021 (Online) 22th July Evening Shift

MCQ (Single Correct Answer)
What should be the height of transmitting antenna and the population covered if the television telecast is to cover a radius of 150 km? The average population density around the tower is 2000/km2 and the value of Re = 6.5 $$\times$$ 106 m.
A
Height = 1241 m

Population covered = 7 $$\times$$ 105
B
Height = 1731 m

Population covered = 1413 $$\times$$ 105
C
Height = 1800 m

Population covered = 1413 $$\times$$ 108
D
Height = 1600 m

Population covered = 2 $$\times$$ 105

Explanation

$$d = \sqrt {2{R_e}h} $$

Area covered = $$\pi$$d2

$$h = {{{d^2}} \over {2{R_e}}}$$ = 1731 m

Population covered = 2000 $$\times$$ $$\pi$$(d2)

Questions Asked from Communication Systems

On those following papers in MCQ (Single Correct Answer)
Number in Brackets after Paper Indicates No. of Questions
JEE Main 2022 (Online) 24th June Evening Shift [ Memory Based ] (1)
JEE Main 2021 (Online) 27th August Evening Shift (1)
JEE Main 2021 (Online) 26th August Evening Shift (1)
JEE Main 2021 (Online) 25th July Morning Shift (1)
JEE Main 2021 (Online) 22th July Evening Shift (1)
JEE Main 2021 (Online) 17th March Evening Shift (1)
JEE Main 2021 (Online) 16th March Morning Shift (1)
JEE Main 2021 (Online) 25th February Evening Shift (1)
JEE Main 2021 (Online) 25th February Morning Shift (1)
JEE Main 2019 (Online) 12th April Evening Slot (1)
JEE Main 2019 (Online) 10th April Morning Slot (2)
JEE Main 2019 (Online) 9th April Evening Slot (1)
JEE Main 2019 (Online) 9th April Morning Slot (1)
JEE Main 2019 (Online) 8th April Evening Slot (1)
JEE Main 2019 (Online) 8th April Morning Slot (1)
JEE Main 2019 (Online) 12th January Evening Slot (1)
JEE Main 2019 (Online) 12th January Morning Slot (1)
JEE Main 2019 (Online) 11th January Evening Slot (1)
JEE Main 2019 (Online) 11th January Morning Slot (1)
JEE Main 2019 (Online) 10th January Evening Slot (1)
JEE Main 2019 (Online) 10th January Morning Slot (1)
JEE Main 2019 (Online) 9th January Evening Slot (1)
JEE Main 2018 (Online) 16th April Morning Slot (1)
JEE Main 2018 (Offline) (1)
JEE Main 2018 (Online) 15th April Evening Slot (1)
JEE Main 2018 (Online) 15th April Morning Slot (1)
JEE Main 2017 (Online) 9th April Morning Slot (1)
JEE Main 2017 (Online) 8th April Morning Slot (1)
JEE Main 2017 (Offline) (1)
JEE Main 2016 (Online) 10th April Morning Slot (1)
JEE Main 2016 (Online) 9th April Morning Slot (1)
JEE Main 2016 (Offline) (1)
JEE Main 2015 (Offline) (1)
AIEEE 2012 (1)
AIEEE 2011 (1)
AIEEE 2003 (1)

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