EKT Question of ELECTRONICS AND COMMUNICATIONS

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