Que. 1 Equalising pulses in TV are placed during the
A vertical blanking preiod
B horizontal blanking
C serrations
D horizontal retrace
Que. 2 The noise figure of an amplifier is 3 dB its noise temp. will be about
A 145k
B 290k
C 580k
D 870k
Que. 3 To prevent loading in the last I.F. amplifier in a superhet receiver is
to
A provide better tracking
B provide excellent adjacent channel selectivity
C improve image freq. rejection
D increase the tuning range of the receiver
Que. 4 4volt peak audio modulating signal changes thecarrier freq. from 200khz
to 210khz the freq. deviation is
A 5khz
B 10khz
C 15khz
D 20khz
Que. 5 If each stage had a gain of 10dB,and noise figure of 10dB,then the overall
noise figure of two stage cascade amplifier will be
A 10
B 1.09
C 1.0
D 10.9
Que. 6 If the transmission bandwith is doubled in FM,then the SNR is
A also doulded
B improved four fold
C dcreased by one fourth
D unaffected
Que. 7 A 1000khz carrier is simultaneously modulated with 300hz,800hz and 2khz
audio sine wave the freq. present in the output will be
A 1000khz,300hz,800hz and 2khz
B 1300khz,1800hz,2100hz and 4100khz
C 300khz,500hz,1200hz and 998khz
D 998khz,999.2khz,999.7khz,1000.3khz,10008khz and 1002.0khz
Que. 8 In the high power AM transmission,modulation is done at
A buffer stage
B RF power stage
C oscillator stage
D IF stage
Que. 9 A PLL can be used to demodulate
A PAM signal
B PCM signal
C FM signal
D DSB-SC signal
Que. 10 An analog signal within +/-0.5% of the peak to peak full scale value is
transmitted by PCM system then how many binary digits must each sample
contain?
A 5
B 6
C 7
D 8
Que. 11 Two dissimaliar antennas having their maximum directivities equal,
A must have their beam widthes also equal
B cannot have their beam widthes also equal because they are dissimaliar
antennas
C may not necessarily have their maximum power gains equal
D must have their effective aperture areas also equal
Que. 12 The autocorrelation function of an energy signal has
A no symmetry
B conjugate symmetry
C odd symmetry
D even symmetry
Que. 13 The image channel rejection in a superhetrodyne receiver comes from
A IF stage only
B RF stage only
C detector and RF stage only
D detector IF and RF stage
Que. 14 the maximum power efficiency of an AM modulator is
A 25%
B 50%
C 75%
D 100%
Que. 15 The depth of velocity modulation in two cavity klystron amplifier can
be increased by increasing the
A amplitudde of applided signal voltage
B beam coupling coefficient
C cavity gap transit angle
D catcher d.c. voltage
Que. 16 for a narrow band noise with gaussian gradrature components, the probability
density function of its envelope will be
A uniform
B gaussian
C exponential
D rayleigh
Que. 17 a 1 kHZ signal is flatop sampled at the rate of 1800 samples sec and
samples are applided to an ideal rectangular LPF with cutoff frequency
of 1100 hz then the output of filter contains
A only 800 Hz components
B 800Hz and 900 Hz components
C 800Hz and 1000 Hz components
D 800Hz, 900Hz and 1000 Hz components
Que. 18 the total number of memory accesses involved (inclusive of the op-code
fetch) when an 8085 processor executes the instruction LDA 2003 is
A 1
B 2
C 3
D 4
Que. 19 An FM signal with a modulation index 9 is applied to a frequency tripler
the modulation index in the output signal will be
A 0
B 3
C 9
D 27
Que. 20 Quadrature multiplexing is
A the same as FDM
B the same as TDM
C the combination of FDM and TDM
D quite difference between FDM and TDM
Que. 21 Compression in PCM refers to relative compression of
A higher signal amplitude
B lower signal amplitude
C lower signal frequencies
D higher signal frequencies
Que. 22 At a given probalility of error, binary coherent FSK is inferior to binary
coherent PSK by
A 6 DB
B 3 DB
C 2 DB
D 0 DB
Que. 23 the number of memory cycles required to execute the following 8085 instruction
(I) LDA 3000 H (II) LXI, FOF 1 H would be
A 2 for (I) and 2 for (II)
B 4 for (I) and 3 for (II)
C 3 for (I) and 3 for (II)
D 3 for (I) and 4 for (II)
Que. 24 (D)the speech signal is being sampled at the Nyquest rate
A the input to the modulator is essentially constant
B the modulator is going through slope overload
C the accumulator is in saturation
D the speech signal is being sampled at the Nyquest rate
Que. 25 Frequencies in UHF range propagate by means of
A ground waves
B sky waves
C space waves
D surface waves
Que. 26 In air a lossless transmission line of length of 50cm with L=10 micro.H/m
is operated at 25 mhz.Its electrical length is
A 2.0m
B (lemda)m
C (pi)/2radian
D 180 egree
Que. 27 In a twice wire transmission line in air. the adjacent voltage maximum
are at 12.5cm and 27.5cm the operating freq. is
A 300mhz
B 1Ghz
C 2Ghz
D 6.28Ghz
Que. 28 Two events A and B are stastically indepndent and mutually exclusive.
The probability P(AB) is:
A 0
B 1
C infinite
D none of these
Que. 29 A lossless line of 50 ohms is terminated in a load of 100 ohms resistive.The
VSWR is
A 1:2.5
B 2:1
C 4:1
D 3:4
Que. 30 Ques:short term fading in microwave communication links can be over come
buy
A incresing the transmitted power
B changing the antenna
C changing themodulation scheme
D diversity reception and transmission
Que. 31 FM broadcast band lies in
A VHF band
B UHF band
C SHF band
D HF band
Que. 32 Which one of the following microphones doesnot have a flat freq. response?
A carbon microphone
B condenser microphone
C Ribon microphone
D Crystal microphone
Que. 33 The intermediate freq. of the superhet receiver is 450khz if it is tuned
to 1200khz, the image freq. will be
A 750khz
B 900khz
C 1600khz
D 2100khz
Que. 34 Microwave link repeaters are typically 50 km apart in TV transmission
because
A of atmospheric attenuation
B of output power tube limitations
C microwave transmission is through surface wave whic attenuation faster
D of earth's curvature
Que. 35 The balance output the local oscillator noise at the input to the intermediate
freq. or to IF amplifier is superheterodyne receivers, the microwave
ckt used is
A balabced amplifier
B balabced isolator
C balabced phase shifter
D balabced microwave mixer
Que. 36 In a 100 line exchange with 10 first selectors,the number of line finders
required
A is 10
B is 100
C would depend upon the traffic flow
D is busy hour calling rate
Que. 37 A satellite carrying antenna system,transmitter,receiver and power supply
is known as
A geostationary satellite
B orbital satellite
C avtive satellite
D passive satellite
Que. 38 The smallest change in sound intensity that can be detected
A 1dB
B 3dB
C 10dB
D 20dB
Que. 39 At very high freq. earth acts as a
A dielectric
B conductor
C perfect conductor
D perfect dielectric
Que. 40 compading is used
A to protect small signal in PCM from quantizing distortion
B to overcome quantized noise in PCM
C to overcome the impulse noise
D none of these
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