Technical Officer, SCERT • 2025 • Paper-III
In microwave transmission using digital radio, what causes most intersymbol interference?
A)
Delayed spreading
B)
Rayleigh fading
C)
Random Doppler shift
D)
Slow fading
Option A is correct: Delayed spreading.
Technical Officer, SCERT • 2025 • Paper-III
In a Magic Tee, if a signal is input through the E-arm, then-
A)
power is divided equally in the other three arms with equal phase
B)
power divided equally only in the collinear arms with opposite phase
C)
power divided equally only in the collinear arms with equal phase
D)
power goes to the H-arm with 90° phase shift
Option B is correct: power divided equally only in the collinear arms with opposite phase.
Technical Officer, SCERT • 2025 • Paper-III
A 1 MHz carrier is amplitude modulated by a 5 kHz signal with a modulation index of 0.8. The bandwidth of the AM signal is-
A)
5kHz
B)
10 kHz
C)
15kHz
D)
20kHz
Option B is correct: 10 kHz.
Technical Officer, SCERT • 2025 • Paper-III
What is the maximum transmission efficiency?
A)
33.33%
B)
75%
C)
50.10%
D)
67.88%
Option A is correct: 33.33%.
Technical Officer, SCERT • 2025 • Paper-III
What is the typical wavelength range used for optical fiber communication?
A)
200-400 nm
B)
400-700 nm
C)
800-1600 nm
D)
2000-3000 nm
Option C is correct: 800-1600 nm.
Technical Officer, SCERT • 2025 • Paper-III
What is the typical uplink frequency range in C-band satellite communication?
A)
3.7 -4.2 GHz
B)
5.925 - 6.425 GHz
C)
7.9 - 8.4 GHz
D)
12.75 - 13.25 GHz
Option B is correct: 5.925 - 6.425 GHz.
Technical Officer, SCERT • 2025 • Paper-III
TDM link has 20 signal channels and each channel is sampled at 8 KHz. Each sample is represented by 7 bits and contains an additional bit for synchronization. The total bit rate for TDM link is-
A)
1128 Kbps
B)
1180 Kbps
C)
1280 Kbps
D)
128 Mbps
Option C is correct: 1280 Kbps.
Technical Officer, SCERT • 2025 • Paper-III
The formula used to calculate the entropy of a source in information theory is-
A)
H(X)=-p(x) log, p(x)
B)
HEX) = Xp(x) log, p(x)
C)
H(X) = Xp) log, 2p(x)
D)
HX) =-3 ps) log, p(x)
Option A is correct: H(X)=-p(x) log, p(x).
Technical Officer, SCERT • 2025 • Paper-III
The power spectral density of White noise over the entire frequency range is-
A)
flat
B)
Gaussian
C)
Rician
D)
Rayleigh
Option A is correct: flat.
Technical Officer, SCERT • 2025 • Paper-III
Modulation is done in
A)
Transmitter
B)
Receiver
C)
Among transmitter and radio receiver
D)
Transducer
Option A is correct: Transmitter.
Technical Officer, SCERT • 2025 • Paper-III
One of the following cannot be used to remove the unwanted side band in SSB.
A)
Filter system
B)
Phase shift method
C)
Third method
D)
Balance modulator
Option D is correct: Balance modulator.
Technical Officer, SCERT • 2025 • Paper-III
The frequency range for the broadcast satellite service is-
A)
2 GHz to 7 GHz
B)
4GHzto 9.5 GHz
C)
9.5 GHz to 12.5 GHz
D)
12.5 GHz to 26.5 GHz
Option D is correct: 12.5 GHz to 26.5 GHz.
Technical Officer, SCERT • 2025 • Paper-III
Which feeding system is not used for microstrip patch antenna?
A)
Coaxial feed
B)
Proximity feed
C)
Aperture coupled feed
D)
Cassegrain feed
Option D is correct: Cassegrain feed.
Technical Officer, SCERT • 2025 • Paper-III
Which of the following is a special-purpose register of microprocessor?
A)
Accumulator
B)
Program counter
C)
Temporary register
D)
Instruction register
Option B is correct: Program counter.
Technical Officer, SCERT • 2025 • Paper-III
The modes of wave propagation that a parallel plate waveguide can support are:
A)
TM, TE modes
B)
TEM, TE modes
C)
TEM,TM modes
D)
TEM, TE, TM modes
Option D is correct: TEM, TE, TM modes.
Technical Officer, SCERT • 2025 • Paper-III
Which one is an Avalanche Transit Time Diode?
A)
Gunn diode
B)
Schottky diode
C)
IMPATT diode
D)
Tunnel diode
Option C is correct: IMPATT diode.
Technical Officer, SCERT • 2025 • Paper-III
The number of semiconductor layers in IMPATT diode is-
A)
2
B)
3
C)
4
D)
5
Option C is correct: 4.
Technical Officer, SCERT • 2025 • Paper-III
Faraday effect occurs mostly in-
A)
high frequency transmission
B)
simple radio transmission
C)
transionospheric transmission
D)
tropospheric transmission
Option C is correct: transionospheric transmission.
Technical Officer, SCERT • 2025 • Paper-III
If modulation index of an AM wave is increased from 1.5 to 2, then the transmitted power
A)
increases by 41%
B)
increases by 11%
C)
increases by 27%
D)
remains same
Option A is correct: increases by 41%.
Technical Officer, SCERT • 2025 • Paper-III
Which of the following is not a status flag in microprocessor?
A)
Overflow flag
B)
Direction flag
C)
Interrupt flag
D)
Index flag
Option D is correct: Index flag.
Technical Officer, SCERT • 2025 • Paper-III
In microwave communications systeni, for a carrier frequency of 6 GHz and a distance of 40 kin, determine the free-space path loss in dB.
A)
150dB
B)
140 dB
C)
160 dB
D)
170 dB
Option B is correct: 140 dB.
Technical Officer, SCERT • 2025 • Paper-III
The electrodes of a GUNN diode are made of-
A)
GaAs
B)
Gold
C)
Molybdenum
D)
Diamond
Option B is correct: Gold.
Technical Officer, SCERT • 2025 • Paper-III
The 8-bit two’s complement representation of -45 is-
A)
10101101
B)
11010011
C)
11010100
D)
10101100
Option B is correct: 11010011.
Technical Officer, SCERT • 2025 • Paper-III
Repeaters inside communications satellites are known as :
A)
Transponders
B)
Transducers
C)
TWT
D)
Transceivers
Option A is correct: Transponders.
Technical Officer, SCERT • 2025 • Paper-III
GaAs is used in the fabrication of GUNN diodes because:
A)
Less forbidden energy gap
B)
Ithas low conduction band electrons
C)
GaAs is cost effective
D)
Itless temperature sensitive
Option B is correct: Ithas low conduction band electrons.
