Vikram Sarabhai Space Centre Technical Assistant Electronics Paper 2017
VSSC Technical Assistant/Scientific Assistant/Library Assistant exam is scheduled to be conducted on 30th July 2023 in Thiruvananthapuram. If you are the aspirants of the said exam, then you must read this question paper for practice.
| 1 | Assume worst case SNR of a 10 bit ADC is 57 dB. If the resolution is increased by 2 bits, the resulting SNR will be approximately
(a) 67 dB (b) 69 dB (c) 45 dB (d) 42 dB |
| 2 | In optical communication using silica optical fiber, 1 nm spectral width at 1300 nm corresponds to a bandwidth of (assume refractive index of silica optial fiber = 1.5)
(a) 150 GHz (b) 120 GHz (c) 80 GHz (d) 90 GHz |
| 3 | Graded index fiber is used to
(a) Reduce absorption and resulting power loss (b) Reduce dispersion and thereby increase data rate (c) Establish secure communication (d) Increase numerical aperture |
| 4 | The range of numbers represented by an 8-bit tow’s complement representation is
(a) -128 to + 127 (b) -127 to + 128 (c) -128 to + 128 (d) 0 to 255 |
| 5 | An inductor of 3.3 mH with a series resistance of 12.5 ohms is connected to a 5V dc supply. When the supply is switched off, the circuit current decay to zero to 60 micro seconds. What is the value of back e.m.f generated?
(a) – 66 V (b) – 33.3 V (c) – 22 V (d) – 30 V |
| 6 | In an 8 bit two’s compliment number system, inversion of all 8 bits occur during code transition
(a) -127 to – 128 (b) 0 to + 127 (c) + 126 to + 127 (d) – 1 to 0 |
| 7 | The dielectric constant of material used in a transmission line is 2. What is the velocity factor of this line, if its characteristic impedance is 300 Ohms?
(a) 70.7% (b) 75% (c) 1.414 (d) 150 |
| 8 | In a broadcast super heterodyne receiver, having no RF amplifier, the IF=455 kHz. What is the image frequency if the receiver is tuned to 1000 kHz?
(a) 1455 kHz (b) 1910 kHz (c) 545 kHz (d) 2455 kHz |
| 9 | A stationary CW radar is operating at 5 GHz. What is the Doppler frequency, if the target is moving at 108 km/hr speed?
(a) 3.6 kHz (b) 1000 Hz (c) 500 Hz (d) 1800 Hz |
| 10 | Bandwidth efficiency is expressed in units of
(a) Hz/bits/sec (b) Hz/watts (c) Bits/sec/Hz (d) It has no dimension |
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