Bharat Electronics Limited (BEL) Question Bank continued from Part 2…
Q-14. If bandwidth of an amplifier is decreased, what is the effect on thermal noise?
A : On decreasing bandwidth, the thermal noise would also decrease.
Q-15. What is a geostationary satellite? Why is it called geostationary? Name an Indian one.
A : Geostationary satellite is a type of satellite that has equatorial plane, a correct altitude of 35786 Km (from earth’s surface) and a time period of 24 hrs due to which it appears stationary with respect to earth and thus called geo-stationary. INSAT (Indian Navigational SATellite System) is one of them.
Q-16. Which type of modulation is employed in picture and sound transmission in TV?
A : Picture transmission in TV employs Vestigial Side Band (VSB) modulation and sound transmission employs Frequency Modulation (FM).
Q-17. In AM wave, if Vmax is 10 V and Vmin is 5 V, what is the % modulation?
A : % modulation is given by, (Vmax – Vmin) / (Vmax + Vmin) = 5/15 = 1/3 or 33.3%.
Q-18. What do you mean by free-running? To which device is it associated with?
A : Free-running is associated with Astable multi-vibrator in which the circuit keeps on switching from one state to other and is stable in neither of them. Free-running means that it alternates between two different voltage levels during its ON time and the output remains at each level for a definite amount of time.
Q-19. How is communication between satellite and ground station done?
A : The communication between satellite and ground station is achieved through Line Of Sight (LOS) propagation.
(Continued to Part 4…)