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?
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)
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