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If a, b, c, d are inputs to a gate and x is its output, then, as per the following time graph, the gate is :
Option: 1 NOT
Option: 2 AND
Option: 3 OR
Option: 4 NAND
\

The output of OR gate is 0 when all inputs are 0 and output is 1 when at least one of the input is 1.

Observing output x it is 0 when all inputs are 0 and it is 1 when at least one of the inputs is 1
therefore, the gate is OR

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Posted by

Ritika Jonwal

The amplitude of upper and lower side bands of A.M. wave where a carrier signal with frequency 11.21 \mathrm{MHz}, peak voltage 15 \mathrm{~V} is amplitude modulated by a 7.7 \mathrm{kHz} sine wave of 5 \mathrm{~V} amplitude are \frac{\mathrm{a}}{10} \mathrm{~V}$ and $\frac{\mathrm{b}}{10} \mathrm{~V} respectively. Then the value of \frac{a}{b} is______
 

\begin{gathered} f_{c}=11.21 \times 10^{6} \mathrm{~Hz} \\ A_{c}=15 \\ f_{m}=7.7 \times 10^{3} \mathrm{~Hz} \\ A_{m}=5 \mathrm{~V} \end{gathered}

\begin{aligned} \frac{a}{10}=\frac{b}{10} &=\frac{\mu A_{c}}{2} \\ \frac{a}{b} &=1 \end{aligned}

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Posted by

vishal kumar

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The maximum amplitude for an amplitude modulated wave is found to be 12V while the minimum amplitude is found to be 3V. The modulation index is 0.6x where x is ______.
 

\begin{aligned} &\text { Maximum \: amplitude}=V_{\text {max }}=12\\ \end{aligned}

\begin{aligned} &\text { Minimum amplitude }=V_{\text {min }}=3\\ \end{aligned}

\begin{aligned} &\mu =\frac{V_{\max }-V_{\min }}{V_{\max }+V_{\min }}=\frac{9}{15}\\ &\mu =0.6\\ &\therefore x=1 \end{aligned}

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Posted by

vishal kumar

An amplitude modulated wave is represented by  C_{m}\left ( t \right )= 10\left ( 1+0\cdot 2\cos 12560t \right )\sin \left ( 111\times 10^{4}t \right ) volts. The modulating frequency in kHz will be -----------------------.
 

C_{m}\left ( t \right )= 10\left ( 1+0\cdot 2\cos 12560t \right )\sin \left ( 111\times 10^{4}t \right )
\omega _{m}= 12560= 2\pi f
12560= 6\cdot 28\times f
f= \frac{12560}{6\cdot 28}
= 2\cdot 0\, kHz
f= 2\, kHz 

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Posted by

vishal kumar

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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 the range of communication for Line of Sight (LoS) mode?
[use radius of earth = 6400 km]
Option: 1 80.2 km
Option: 2 144.1 km
Option: 3 57.28 km
Option: 4 45.5 km

Range\; of\: communication = \sqrt{2h_{T}R}+\sqrt{2h_{R}R}
                                                         = \sqrt{2\times 50\times 6400\times 10^{3}}+\sqrt{2\times 80\times 6400\times 10^{3}}
=10\times 80\times 10\sqrt{10}+40\times 80\times 10
=800\left ( 10\sqrt{10}+40 \right )
=800\left ( 31\cdot 62+40 \right )
Range=57\cdot 28\times 10^{3}m= 57\cdot 28\, km
The correct option is (3)

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Posted by

vishal kumar

A transmitting antenna has a height of 320 \mathrm{~m} and that of receiving antenna is 2000 \mathrm{~m}. The maximum distance between them for satisfactory communication in line of sight mode is 'd'. The value of ' d ' is ________\mathrm{km}.
 

Range\, of\, communication= \sqrt{2h_{T}R}+\sqrt{2h_{R}R}
                                                        = \sqrt{2\times 320\times 6400\times 10^{3}}+\sqrt{2\times 2000\times 6400\times 10^{3}}
=80\times 80\times 10+200\times 80\times 10
=64000+160000
=224000 \, m
=224 \, km

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Posted by

vishal kumar

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An antenna is mounted on a 400 \mathrm{~m} tall building. What will be the wavelength of signal that can be radiated effectively by the transmission tower upto a range of 44 \mathrm{~km} ?
Option: 1 605\: m
Option: 2 302\: m
Option: 3 37.8\: m
Option: 4 75.6\: m

Range of Transmission = \sqrt{2hR}

Height of transmission tower = h= h_{building }+h_{antenna}

44000= \sqrt{2\times h\times 6400\times10^{3}}

44000\times 44000= 2h\times 6400\times10^{3}

h_{min}= 151.25

\lambda = 4h= 605m

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Posted by

vishal kumar

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

Range of LOS communication = \sqrt{2h_{T}R}+\sqrt{2h_{R}R}
                 h_{T}+h_{R}=160\, m
For maximum range ,
h_{T}=h_{R}
\therefore h_{T}=h_{R}= 80 m
    = 2\sqrt{2h_{T}R}
    = 2\times \sqrt{2\times 80\times 6400\times 10^{3}}
    = 2\times \sqrt{160\times 6400\times 10^{3}}
   = 2\times80\times 40\times 10
\Rightarrow Range= 64000 m= 64\, km 

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Posted by

vishal kumar

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A bandwidth of 6 \mathrm{MHz} is available for A.M. transmission. If the maximum audio signal frequency used for modulating the carrier wave is not to exceed 6 \mathrm{kHz}. The number of stations that can be broadcasted within this band simultaneously without interfering with each other will be_________. Given 27
 

Signal Bandwidth =2f_{m}

\because f_{m}=6KHz

\therefore Signal Bandwidth =12KHz

No of stations that can be broadcast is let say N

N=\frac{6MHz}{12KHz}=\frac{6000}{12}=500

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Posted by

vishal kumar

A carrier wave with amplitude of 250 \mathrm{~V} is amplitude modulated by a sinusoidal base band signal of amplitude 150 \mathrm{~V}. The ratio of minimum amplitude to maximum amplitude for the amplitude modulated wave is 50: x, then value of x is____________.
 

A_{max}= A_{c}+A_{m}= 250+150= 400
A_{min}= A_{c}-A_{m}= 250-150= 100
\frac{A_{min}}{A_{max}}= \frac{100}{400}= \frac{1}{4}= \frac{50}{200}
x= 200

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Posted by

vishal kumar

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