Communication Systems

A transmitting antenna is kept on the surface of the earth. The minimum height of receiving antenna required to receive the signal in line of sight at 4km distance from it is \(x\times {10}^{-2}\mathrm{m}\). The value of x is (Let. radius of earth R= \(6400\mathrm{km}\) )

[JEE Main 2023, 11 Apr (Shift 1)]

The modulation index of an A.M. wave having maximum and minimum peak to peak voltages of \(14 mV\) and \(6 mV\) respectively is:

[JEE Main 2023, 29 Jan (Shift 2)]

In satellite communication, the uplink frequency band used is:

[JEE Main 2023, 11 Apr (Shift 2)]

The amplitude of \(15 \sin (1000 \pi t)\) is modulated by \(10 \sin (4 \pi t)\) signal. The amplitude modulated signal contains frequency(ies) of
A. \(500 Hz\)
B. \(2 Hz\)
C. \(250 Hz\)
D. \(498 Hz\)
E. \(502 Hz\)

Choose the correct answer from the options given below:

[JEE Main 2023, 12 Apr (Shift 1)]

If the height of transmitting and receiving antennas are \(80 m\) each, the maximum line of sight distance will be:
Given: Earth's radius \(=6.4 \times 10^6 m\)

[JEE Main 2023, 29 Jan (Shift 1)]

The modulation index of an A.M. wave having maximum and minimum peak to peak voltages of \(14\mathrm{mV}\) and \(6\mathrm{mV}\) respectively is:

[JEE Main 2023, 29 Jan (Shift 2)]

Given below are two statements
Statement-I: For transmitting a signal, size of antenna (l) should be comparable to wavelength of signal (at least \(l=\frac{\lambda }{4}\) in dimension).
Statement-II: In amplitude modulation, amplitude of carrier wave remains constant (unchanged).
In the light of the above statements, choose the most appropriate answer from the options given below.

[JEE Main 2023, 31 Jan (Shift 2)]

By what percentage will the transmission range of a TV tower be affected when the height of the tower is increased by 21 % ?

[JEE Main 2023, 6 Apr (Shift 1)]

For an amplitude modulated wave the minimum amplitude is 3 V, while the modulation index is 60 %. The maximum amplitude of the modulated wave is:

[JEE Main 2023, 6 Apr (Shift 2)]

If the height of transmitting and receiving antennas are 80 m each, the maximum line of sight distance will be:Given: Earth's radius \(=6.4\times {10}^{6}\mathrm{m}\)

[JEE Main 2023, 29 Jan (Shift 1)]

A message signal of frequency \(5 kHz\) is used to modulate a carrier signal of frequency \(2 MHz\). The bandwidth for amplitude modulation is:

[JEE Main 2023, 25 Jan (Shift 1)]

The height of transmitting antenna is \(180\mathrm{m}\)and the height of the receiving antenna is \(245\mathrm{m}\). The maximum distance between them for satisfactory communication in line of sight will be: (given \(R=6400\mathrm{km}\) )

[JEE Main 2023, 15 Apr (Shift 1)]

In an amplitude modulation, a modulating signal having amplitude of X V is superimposed with a carrier signal of amplitude Y V in first case. Then, in second case, the same modulating signal is superimposed with different carrier signal of amplitude \(2\mathrm{YV}\). The ratio of modulation index in the two case respectively will be:

[JEE Main 2023, 1 Feb (Shift 2)]

In an amplitude modulation, a modulating signal having amplitude of \(X V\) is superimposed with a carrier signal of amplitude \(YV\) in first case. Then, in second case, the same modulating signal is superimposed with different carrier signal of amplitude \(2 Y V\). The ratio of modulation index in the two case respectively will be:

[JEE Main 2023, 1 Feb (Shift 2)]

A \(25\mathrm{m}\) long antenna is mounted on an antenna tower. The height of the antenna tower is \(75\mathrm{m}\). The wavelength (in meter) of the signal transmitted by this antenna would be:

[JEE Main 2021, 16 Mar (Shift 1)]

By what percentage will the transmission range of a TV tower be affected when the height of the tower in increased by 21%?

[JEE Main 2023, 6 Apr (Shift 1)]

In Amplitude Modulation, the message signal \({V}_{m}\left(t\right)\)\(=10\sin \left(2\pi \times {10}^{5}t\right)\) volts and carrier signal \({V}_{C}(t)=20\) \(\sin \left(2\pi \times {10}^{7}t\right)\) 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 \(\alpha \mathrm{kHz}\). The value of \(\alpha\) is:

[JEE Main 2021, 25 Jul (Shift 1)]

A carrier wave of amplitude \(15\mathrm{V}\) is modulated by a sinusoidal base band signal of amplitude\(3\mathrm{V}\). The ratio of maximum amplitude to minimum amplitude in an amplitude modulated wave is:

[JEE Main 2023, 10 Apr (Shift 1)]

A transmitting antenna at top of a tower has a height of \(50\mathrm{m}\) and the height of receiving antenna is \(80\mathrm{m}\). What is the range of communication for Line of Sight (LoS) mode? [use radius of earth \(=6400\mathrm{km}\) ]

[JEE Main 2021, 26 Aug (Shift 2)]

To radiate EM signal of wavelength \(\lambda\) with high efficiency, the antennas should have a minimum size equal to:

[JEE Main 2023, 13 Apr (Shift 2)]

Which of the following frequencies does not belong to FM broadcast.

[JEE Main 2023, 1 Feb (Shift 1)]

A message signal of frequency \(3\mathrm{kHz}\) is used to modulate a carrier signal of frequency \(1.5\mathrm{MHz}\). The bandwidth of the amplitude modulated wave is

[JEE Main 2023, 10 Apr (Shift 2)]