Short Questions and Answers on Introduction to Analog Communication System
Q.1. What is meant by radio communication?
Ans. It is the type of communication which uses free space as communication medium. The signal is transmitted in the form of electromagnetic waves.
Q.2. What are the various transducers used in communication systems?
Ans. Microphones, loudspeakers, TV camera tube (to convert light into electrical signal), picture tube are some of the transducers used in communication systems.
Q.3. What do you understand by the term baseband signal?
Ans. The electrical equivalent of the original message signal (i.e., sound, picture, computer data) is called as baseband signal.
Q.4. List the drawbacks of baseband transmission.
Ans. (i) Excessively large antenna heights (ii) Signals get mixed up (iii) Poor quality of reception (iv) Short range of communication (v) Multiplexing is not possible.
Q.5. Define a communication channel and name different types of communication channels.
Ans. Communication channel is the medium used for transmission of electronic signal from one place to the other place. Communication channels can be conducting wires, cables, optical fibres or free space.
Q.6. Why is modulation used?
Ans. Modulation is used for its following advantages: (i) Reduction in antenna height (ii) Avoids mixing of signals (iii) Increases the range of communication (iv) Multiplexing is possible (v) Improves quality of reception
Q.7. What is the channel bandwidth for TV transmission in India?
Ans. 7 MHz.
Q.8. What is the function of a carrier in a modulation system?
Ans. The carrier is supposed to carry the message signal or information from the transmitter to receiver.
Q.9. Define the bandwidth of a baseband signal.
Ans. Bandwidth of a baseband signal is defined as its frequency range.
Q.10. What is meant by line communication?
Ans. Line or wire communication is the type of communication where transfer of signal takes place through medium such as wires, cables or optical fibres (i.e., physical connection).
Q.11. What are the bandwidths of the following baseband signals? (i) TV signal (picture), (ii) Voice signal (Telephoney), (iii) Music signal
Ans. (i) 5 MHz, (ii) 3100 Hz, (iii) Approximately 15 kHz
Q.12. What is meant by channel bandwidth?
Ans. The channel bandwidth may be defined as the range of frequencies in which a communication channel can allow the signal to travel with uniform attenuation and zero phase change (ideally). Signal distortion can take place if the channel bandwidth is not adequately large.
Q.13. Name the communication channels used for the following systems: (i) Cable TV Network, (ii) TV and radio broadcasting, (iii) Satellite communication, (iv) Closed circuit TV (CTV).
Ans. (i) Shielded coaxial cable or optical fibre, (ii) Free space, (ii) Free space, (iv) Shielded coaxial cable.
Q.14. List different types of analog modulation systems?
Ans. Amplitude modulation (AM), frequency modulation (FM) and phase modulation (PM) are the types of continuous wave analog modulation systems whereas PAM, PWM and PPM are the pulse analog modulation systems.
Q.15. Duplex communication is ……………
Ans. Simultaneous two way communication.
Q.16. Two way communication with each transmitter transmitting one by one (not simultaneously) is ………
Ans. Half duplex communication.
Q.17. Why is PCM system called digital modulation system?
Ans. As its output is a train of binary bits i.e., 0s and 1s, the amplitude, frequency, phase, position, width etc., are constant.
Q.18. State common sources of information.
Ans. The common sources of information are sound, picture and text.
Q.19. One way communication is known as …………..
Ans. Simplex communication.
Q.20. Recovery of the original transmitted signal is called as ……………
Ans. Detection or demodulation.
Q.21. Give examples of simplex, half duplex and duplex systems.
Ans. Simplex: Radio, TV broadcasting Half duplex: Walky talky Duplex: Telephone.
Q.22. Putting voice, video or digital signal directly onto the communication medium is called as ……
Ans. Baseband transmission.
Q.23. Give an example of baseband communication.
Ans. Telephone and Intercom communication are examples of baseband communication.
Q.24. Frequency range of human voice is………
Ans. 30 to 3200 Hz.
Q.25. Frequency range of human hearing is……..
Ans. 20 Hz to 20 KHz ideally.
Q.26. Signals that travel through free space for long distance are called as……….
Ans. Electromagnetic waves.
Q.27. Electromagnetic waves are made up of …..
Ans. Electric and magnetic fields.
Q.28. What is the wavelength of a signal with a frequency of 10 MHz.
Ans. The wavelength is given by λ = c/f = 3 × 108/ 10 × 106 = 30 m.
Q.29. Frequency of ac mains is …..
Ans. 50 Hz.
Q.30. The frequencies above 1 GHz are called…
Q.31. One micron is equal to ….. m.
Ans. 10-6 m.
Q.32. AM broadcast takes place in the frequency range……….
Ans. 535 to 1605 kHz.
Q.33. One angstrom is equal to… µm.
Ans. 10-4 µm.
Q.34. Angstrom is a unit to measure….
Ans. Wavelength of light.
Q.35. State the types of transmission lines.
Ans. Co axial cable and parallel wire lines.
Q.36. The wired medium which is not affected by external magnetic field is…..
Ans. Optical fibers.
Q.37. The shielding in co axial cable helps to….
Ans. Reduce the electromagnetic interference.
Q.38. The medium used to carry light signals is….
Ans. Optical fibers.
Q.39. The SHF and EHF are used for…. applications.
Ans. Satellite and RADAR communications.
Q.40. The spectrum space occupied by a signal is called….
Q.41. The tools for analyzing frequency domain behaviour of a signal are….
Ans. Fourier series and Fourier transform.
Q.42. List the various communication channels.
Ans. Transmission lines, waveguides, free space, optical fibers.
Q.43. The L, C, R and G components shown in the equivalent circuit of a transmission line are…
Ans. Distributed components.
Q.44. One of the applications of parallel wire transmission line is….
Ans. In connecting TV receiving antenna to TV receiver.
Q.45. The EM waves travel through the waveguides due to….
Ans. Internal reflections.
Q.46. State the applications of infrared light in communication.
Ans. Remote control, optical fiber communication.
Q.47. Are the X rays and gamma rays used for communication?
Ans. No, these rays are not used for communication.
Q.48. Which frequency band is used for the TV transmission?
Ans. VHF and UHF bands are used for the TV transmission.