Digital Waves

Q.

The maximum and minimum amplitude of an amplitude-modulated wave is $16V,8V$respectively. The modulation index for this amplitude modulated wave is$x\times {10}^{–2}.$ The value of$x$ is

Q.

What is full form SBC?

Q.

What is modulation factor?

Q. A signal of frequency $10\text{kHz}$ and peak voltage of $10\text{V}$ is used to modulate a carrier of frequency $800\text{kHz}$ and peak voltage of $20\text{V}$. What is the amplitude modulation index?

1. $0.5$
2. $1.0$
3. $2.5$
4. $2.0$

Q. Difference between modulation and demodulation

Q. Indicate which one of the following system is digital?

1. Pulse width modulation
2. Pulse position modulation
3. Pulse code modulation
4. Pulse amplitude modulation

Q. Digital signals(i) do not provide a continuous set of values, (ii) represent values as discrete steps, (iii) can utilize binary system, and(iv) can utilize decimal as well as binary systems.Which of the above statements are true?(a) (i) and (ii) only(b) (ii) and (iii) only(c) (i), (ii) and (iii) but not (iv)(d) All of (i), (ii), (iii) and (iv).

Q.

The binary system uses powers of ________ for positional values.

1. $2$

2. $8$

3. $10$

4. $16$

Q.

What is the role of amplitude limiter in FM receiver?

Q. Write the functions of the following in communications system :

(i) Transmitter

(ii) Modulator

Q.

Suppose the amplitude of a modulated wave is equal to the signal amplitude. Then modulation is

1. $10\%$

2. $25\%$

3. $50\%$

4. $100\%$

Q. Define modulation index. Why is its value kept, in practice, less than one?
A carrier wave frequency $1.5MHz$ and amplitude $50V$ is modulated by a sinusoidal wave of frequency $10kHz$ producing $50$% amplitude modulation. Calculate the amplitude of the AM wave and frequencies of the side bands produced.

Q.

What is the modulation index?

Q. A message signal of peak voltage $20V$ is used to modulate a carrier wave of peak voltage $30V$. Determine the modulation index.

Q. (a) How is amplitude modulation achieved?
(b) The frequencies of two side bands in an AM wave are $640$ kHz and $660$ kHz respectively. Find the frequencies of carrier and modulating signal. What is the bandwidth required for amplitude modulation?

Q. Define amplitude modulation in communication system.

Q. In amplitude modulation, bandwidth is ________ the audio signal frequency

1. Thrice
2. Four times
3. Twice
4. None of the above

Q. In amplitude modulation, the bandwidth is :

1. Equal to the signal frequency
2. Thrice the signal frequency
3. Twice the signal frequency
4. Four times the signal frequency

Q. A signal of $5kHz$ frequency is amplitude modulated on a carrier wave of frequency $2MHz$. Frequencies of the resultant signal is/are

1. $2MHz$ only
2. $2005kHz$, $2000kHz$ and $1995kHz$
3. $2005kHz$ and $1995kHz$
4. $2000kHz$ and $1995kHz$

Q.

Suggest a possible communication channel for the transmission of a message signal

Q. A signal of 5 kHz frequency modulates a carrier of frequency 1 MHz and peak voltage 25 V. If the amplitude at the sidebands of the amplitude modulated signal is 5 V, then the modulation index is

1. 0.8
2. 0.6
3. 0.5
4. 0.2
5. 0.4

Q. What type of modulation is employed in India for radio transmission ?

1. Amplitude modulation
2. Frequency modulation
3. Pulse modulation
4. None of these

Q. A digital signal can utilize decimal as well as binary systems.

1. True
2. False

Q. A message signal of frequency ${\omega }_m$ is superposed on a carrier wave of frequency ${\omega }_e$ to get an amplitude mediated wave (AM). The frequency of the AM wave will be

1. ${\omega }_m$
2. ${\omega }_e$
3. $\frac{{\omega }_e+{\omega }_m}{2}$
4. $\frac{{\omega }_e-{\omega }_m}{2}$

Q. Define modulation factor in amplitude modulation.

Q. An example of an analog communication method is -

1. Voice grade telephone line
2. microwave
3. All of the above
4. Laser beam

Q. In amplitude modulation , the modulation index $\mu$, is kept less than or equal to 1 because

Q. Indicate which one of the following system is digital :

1. Pulse position modulation
2. Pulse code modulation
3. Pulse width modulation
4. Pulse amplitude modulation

Q. The waves used in telecommunication are

1. Cosmic rays
2. Infrared
3. Microwaves
4. Ultraviolet

Q. A carrier wave of amplitude A is used to modulate (amplitude) the signal. Modulated signal amplitude swings from 0.1A to 1.9A, calculate modulation index

1. 1.8
2. 0.9
3. 0.75
4. 0.5