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 dipole
(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 the 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
doubt
(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 doubt
(A) A few milli watts
(B) Kilo watts
(C) Watts
(D) Few pico watts
10. Telephone traffic is measured doubt
(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 doubt
(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?doubt
(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-> CE
(B) Current amplifier (CB for HF applications)
(C) For matching a high source impedance to a low load
impedance ->CC
(D) For rectification of a.c. signal -> any confi but
generally CE
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) doubt
(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 color TV, the three primary colors are
(A) Red, orange and blue
(B) Red, blue and green
(C) Red, green and yellow
(D) Red, orange and green
