Communication Systems

A TV transmitting antenna is \(98 \mathrm{~m}\) high and the receiving antenna is at the ground level. If the radius of the earth is \(6400 \mathrm{~km}\), the surface area covered by the transmitting antenna is approximately:

The power radiated from a linear antenna of length \(l\) is proportional to
(Given, \(\lambda=\) Wavelength of wave):

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

For an amplitude modulated wave the minimum amplitude is \(3 \mathrm{~V}\), while the modulation index is \(60 \%\). The maximum amplitude of the modulated wave is:

The amplitude of \(15 \sin (1000 \pi \mathrm{t})\) is modulated by \(10 \sin (4 \pi \mathrm{t})\) signal. The amplitude modulated signal contains frequency (ies) of
A. \(500 \mathrm{~Hz}\)
B. \(2 \mathrm{~Hz}\)
C. \(250 \mathrm{~Hz}\)
D. $$...

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...

A sinusoidal carrier voltage is amplitude modulated. The resultant amplitude modulated wave has maximum and minimum amplitude of \(120 \mathrm{~V}\) and \(80 \mathrm{~V}\) respectively. The amplitude of each sideband is :

Match List I with List II:


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If the height of transmitting and receiving antennas are 80 m each, the maximum line of sight distance will be:
Given : Earth's radius \(=6.4\times10^6\) m

The modulation index for an A.M. wave having maximum and minimum peak-to-peak voltages of 14 mV and 6 mV respectively is-

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

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A modulating signal is a square wave, as shown in the figure.

If the carrier wave is given as \(\mathrm{c(t) = 2\sin(8\pi t)}\) volts, the modulation index is :

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

In an amplitude modulation, a modulating signal having amplitude of X Volt is superimposed with a carrier signal of amplitude Y Volt in first case. Then, in second case, the same modulating signal is superimposed with different carrier sign...

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 $\mathrm{R}=6400 \mathrm...

Match List - I with List - II

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

The amplitude of \(15 \sin (1000 \pi \mathrm{t})\) is modulated by \(10 \sin (4 \pi \mathrm{t})\) signal. The amplitude modulated signal contains frequencies of
A. \(500 \mathrm{~Hz}\)
B. \(2 \mathrm{~Hz}\)
C. \(250 \mathrm{~Hz}\)
D. $$498 ...

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 \(4 \mathrm{~km}\) distance from it is \(x \times 10^{-2} \mathrm{~m}\). The value of $$x...

In satellite communication, the uplink frequency band used is :

A carrier wave of amplitude 15 V is modulated by a sinusoidal base band signal of magnitude 3 V. The ratio of maximum amplitude to minimum amplitude in an amplitude modulated wave is

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

A speech signal given by 11 sin(2200 \(\pi\)t) V is used for amplitude modulation with a carrier signal given by 44 sin(6600 \(\pi\)t) V. The minimum amplitude of modulated wave will be :

Only 2% of the optical source frequency is the available channel bandwidth for an optical communicating system operating at 1000 nm. If an audio signal requires a bandwidth of 8 kHz, how many channels can be accommodated for transmission :

The TV transmission tower at a particular station has a height of 125 m. For doubling the coverage of its range, the height of the tower should be increased by

Find the modulation index of an AM wave having \(8 \mathrm{~V}\) variation where maximum amplitude of the AM wave is \(9 \mathrm{~V}\).

A modulating signal \(2 \sin \left(6.28 \times 10^{6}\right) t\) is added to the carrier signal \(4 \sin \left(12.56 \times 10^{9}\right) t\) for amplitude modulation. The combined signal is passed through a non-linear square law device. Th...

Match List-I with List-II

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Amplitude modulated wave is represented by \({V_{AM}} = 10\,[1 + 0.4\cos (2\pi \times {10^4}t)]\cos (2\pi \times {10^7}t)\). The total bandwidth of the amplitude modulated wave is :

In the case of amplitude modulation to avoid distortion the modulation index \((\mu)\) should be :

A FM Broadcast transmitter, using modulating signal of frequency 20 kHz has a deviation ratio of 10. The Bandwidth required for transmission is :

The height of a transmitting antenna at the top of a tower is 25 m and that of receiving antenna is, 49 m. The maximum distance between them, for satisfactory communication in LOS (Line-Of-Sight) is K\(\sqrt5\) \(\times\) 102 m. The value o...

We do not transmit low frequency signal to long distances because-
(a) The size of the antenna should be comparable to signal wavelength which is unreal solution for a signal of longer wavelength.
(b) Effective power radiated by a long wave...

At a particular station, the TV transmission tower has a height of 100 m. To triple its coverage range, height of the tower should be increased to

A square wave of the modulating signal is shown in the figure. The carrier wave is given by \(C(t)=5 \sin (8 \pi t)\) Volt. The modulation index is :

Choose the correct statement for amplitude modulation :

A sinusoidal wave y(t) = 40sin(10 \(\times\) 106 \(\pi\)t) is amplitude modulated by another sinusoidal wave x(t) = 20sin (1000 \(\pi\)t). The amplitude of minimum frequency component of modulated signal is :

A radio can tune to any station in \(6 \,\mathrm{MHz}\) to \(10 \,\mathrm{MHz}\) band. The value of corresponding wavelength bandwidth will be :

The maximum and minimum voltage of an amplitude modulated signal are \(60 \mathrm{~V}\) and \(20 \mathrm{~V}\) respectively. The percentage modulation index will be :

A signal of 100 THz frequency can be transmitted with maximum efficiency by :

Match List I with List II

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The required height of a TV tower which can cover the population of \(6.03\) lakh is \(h\). If the average population density is 100 per square \(\mathrm{km}\) and the radius of earth is \(6400 \mathrm{~km}\), then the value of \(h\) will b...

In AM modulation, a signal is modulated on a carrier wave such that maximum and minimum amplitudes are found to be 6 V and 2 V respectively. The modulation index is :

A baseband signal of 3.5 MHz frequency is modulated with a carrier signal of 3.5 GHz frequency using amplitude modulation method. What should be the minimum size of antenna required to transmit the modulated signal?

An antenna is placed in a dielectric medium of dielectric constant 6.25. If the maximum size of that antenna is 5.0 mm, it can radiate a signal of minimum frequency of __________ GHz.
(Given \(\mu\)r = 1 for dielectric medium)

If the sum of the heights of transmitting and receiving antennas in the line of sight of communication is fixed at 160 m, then the maximum range of LOS communication is ___________ km. (Take radius of Earth = 6400 km)

A bandwidth of 6 MHz is available for A.M. transmission. If the maximum audio signal frequency used for modulating the carrier wave is not to exceed 6 kHz. The number of stations that can be broadcasted within this band simultaneously witho...

The amplitude of upper and lower side bands of A.M. wave where a carrier signal with frequency 11.21 MHz, peak voltage 15 V is amplitude modulated by a 7.7 kHz sine wave of 5V amplitude are \({a \over {10}}V\) and \({b \over {10}}V\) respec...