30-03-2013, 04:41 PM
SELF EVALUATION TEST - 28
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1. A ground receiver station is receiving a signal at (i) 5 MHz
and transmitted from a ground transmitter at a height of
300 m, located at a distance of 100 km from the receiver
station. The signal is coming via. Radius of earth = 6.4 ×
106 m. Nmax of isosphere = 1012 m3
(a) Space wave (b) Sky wave propagation
© Satellite transponder (d) All of these
2. The impedance of coaxial cable, when its inductance is
0.40 μH and capacitance is 1 × 10–11 F, can be
(a) 2 × 102 (b) 100
© 3 × 103 (d) 3 × 10– 2
3. A wave is represented as
10 sin(10 6 sin 1250 ) 8 e = t + t
then the modulating index is
(a) 10 (b) 1250
© 108 (d) 6
4. An optical fibre communication system works on a
wavelength of 1.3 μm. The number of subscribers it can
feed if a channel requires 20 kHz are
(a) 2.3 × 1010 (b) 1.15 × 1010
© 1 × 105 (d) None of these
5. In an FM system a 7 kHz signal modulates 108 MHz
carrier so that frequency deviation is 50 kHz. The carrier
swing is
(a) 7.143 (b) 8
© 0.71 (d) 350
6. In a radio receiver, the short wave and medium wave
stations are tuned by using the same capacitor but coils of
different inductance Ls and Lm respectively then
(a) Ls > Lm (b) Ls < Lm
© Ls = Lm (d) None of these
7. The electron density of E, F1, F2 layers of ionosphere is 2 ×
1011, 5 × 1011 and 8 × 1011 m–3 respectively. What is the
ratio of critical frequency for reflection of radiowaves
(a) 2 : 4 : 3 (b) 4 : 3 : 2
© 2 : 3 : 4 (d) 3 : 2 : 4
8. A carrier is simultaneously modulated by two sine waves
with modulation indices of 0.4 and 0.3. The resultant
modulation index will be
(a) 1.0 (b) 0.7
© 0.5 (d) 0.35
9. Mean optical power launched into an 8 km fibre is 120
μW and mean output power is 4 μW, then the overall
attenuation is (Given log 30 = 1.477)
(a) 14.77 dB (b) 16.77 dB
© 3.01 dB (d) None of these