Steel Authority of India Limited (SAIL)
Management Trainee Exam
Electronics & Communication Model Paper
Q.1. In a communication system, noise is most likely to get into the system
- at the transmitter
- in the channel
- in the information source
- at the destination
Q.2. When modulation frequency is doubled, the modulation index is halved, and the modulating voltage remains constant, the modulation system is
- amplitude modulation
- phase modulation
- frequency modulation
- angle modulation
Q.3. Impedance inversion may be obtained with
- a short – circuited stub
- an open – circuited stub
- a quarter – wave line
- a half – wave line
Q.4. HIGH frequency waves are
- observed by the F2 layer
- reflected by D layer
- capable of use for long-distance communication on the moon
- affected by the solar cycle
Q.5. Which one of the following terms does not apply to the Yagi-uda array
- Good band width
- Parasitic elements
- Folded dipole
- High gain
Q.6. A duplexer is used
- to couple two different antennae to a transmitter without mutual interference
- to allow one antenna to be used for reception or transmission without mutual interference
- to prevent interference between two antennae when they are connected to receiver
- to increase the speed of the pulses in pulsed radar
Q.7. Indicate which of the following system is digital
- Pulse – Position modulation
- Pulse – Code modulation
- Pulse – Width modulation
- Pulse – Frequency modulation
Q.8. A forward error correcting code corrects errors only
- requiring partial retransmission of the signal
- requiring retransmission of entire signal
- using parity to correct to errors in all cases
- requiring no part of the signal to be transmitted
Q.9. A typical signal strength received from a geosynchronous communication satellite is of the order of
- a few milli watts
- kilo watts
- watts
- few pico watts
Q.10. Telephone traffic is measured
- with echo canceller's
- by the relative congestion
- in terms of the grade of service
- in erlangs
Q.11. Positive logic in a logic circuit is one in which
- logic 0 and 1 are represented by 0 and positive voltage respectively
- logic 0 and 1 are represented by negative and positive voltages respectively
- logic 0 voltage level in higher than logic 1 voltage level
- logic 0 voltage level is lower than logic 1 voltage level
Q.12. A half-adder can be made from
- two NAND gates
- a NOT gate and an OR gate
- an AND gate and an OR gate
- an AND gate and an X-OR gate
Q.13. Which of the following devices has its characteristics very close to that of an ideal current source.
- Field effect transistor
- Transistor in common base mode
- Zener diode
- MOSFET
Q.14. The main use of a common base transistor amplifier is
- as voltage amplifier
- current amplifier
- for matching a high source impedance to a low load impedance
- for rectification of a.c. signal
Q.15. A class-B amplifier is biased
- Just at cut-off
- nearly twice cut-off
- at mid point of load line
- so that IB equals jut IC
Q.16. If the peak transmitted power in a radar system is increased by a factor of 16, the maximum range will be increased by a factor of
Q.17. A high PRF will (indicate the false statement)
- make the returned echoes easier to distinguish from noise
- make target tracking easier with conical scanning
- increase the maximum range
- have no effect of the range resolution
Q.18. A solution to the “blind speed” problem in a radar system is to
- change the Doppler frequency
- vary the PRF
- use mono pulse
- use MTI
Q.19. The number of active picture elements in a television image depends on
- fly back time
- CRT screen size
- received band width
- FB ratio of receiver antenna
Q.20. In a colour TV, the three primary colours are
- red, orange and blue
- red, blue and green
- red, green and yellow
- red, orange and green
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