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प्रश्न
The process of superimposing a low frequency signal on a high frequency wave is_______ .
पर्याय
detection
mixing
modulation
attenuation
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उत्तर
modulation
The process of superimposing a low frequency signal on a high frequency wave is known as modulation.
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संबंधित प्रश्न
Define modulation and transducer
Define modulation index.
State three important factors showing the need for translating a low frequency signal into a high frequency wave before transmission
How are side bands produced?
A carrier wave of peak voltage 12 V is used to transmit a message signal. What should be the peak voltage of the modulating signal in order to have a modulation index of 75%?
Due to economic reasons, only the upper sideband of an AM wave is transmitted, but at the receiving station, there is a facility for generating the carrier. Show that if a device is available which can multiply two signals, then it is possible to recover the modulating signal at the receiver station.
Explain the need for modulation related to the size of antenna (aerial).
Why is Modulation index kept low?
What is the role of a bandpass filter?
The carrier wave is represented by
Define the term modulation. Draw a block diagram of a simple modulator for obtaining AM signal ?
In the block diagram of a simple modulator for obtaining an AM signal, shown in the figure, identify the boxes A and B. Write their function.
In the given block diagram of a receiver, identify the boxes labeled as X and Y and write their functions.
Given modulation index physical significance .For an amplitude modulated wave, the maximum amplitude is found to be 10 V while the minimum amplitude is 2 V. Determine the modulation index μ ?
Answer the following question.
Why a signal transmitted from a TV tower cannot be received beyond a certain distance? Write the expression for the optimum separation between the receiving and the transmitting antenna.
A 100 m long antenna is mounted on a 500 m tall building. The complex can become a transmission tower for waves with λ.
A speech signal of 3 kHz is used to modulate a carrier signal of frequency 1 MHz, using amplitude modulation. The frequencies of the sidebands will be ______.
I-V characteristics of four devices are shown in Figures.
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| (i) | (ii) | (iii) | (iv) |
Identify devices that can be used for modulation.
An audio signal of 15kHz frequency cannot be transmitted over long distances without modulation because ______.
- the size of the required antenna would be at least 5 km which is not convenient.
- the audio signal can not be transmitted through sky waves.
- the size of the required antenna would be at least 20 km, which is not convenient.
- effective power transmitted would be very low, if the size of the antenna is less than 5 km.
A TV transmission tower antenna is at a height of 20 m. How much service area can it cover if the receiving antenna is (i) at ground level, (ii) at a height of 25 m? Calculate the percentage increase in area covered in case (ii) relative to case (i).
A 25 m long antenna is mounted on an antenna tower. The height of the antenna tower is 75 m. The wavelength (in meter) of the signal transmitted by this antenna would be ______.
A carrier wave Vc(t) = 160 sin(2π × 106t) volts is made to vary between Vmax = 200 V and Vmin = 120 V by a message signal Vm(t) = Am sin(2π × 103t) volts. The peak voltage Am of the modulating signal is ______.
