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Communication systems
1-Dont try to cram or spend more time here just read it fast and cover syllabus then practice MCQ's cheptor of same topic to check your progress. . |
2-Wrong options are also given but dont concentrate there, Right answer is in bold format. |
Q41 ⇒ In TV transmitter, visual exciter may consist of
1, 2, 3, 4 and 5 [other wrong options] [Discuss in forum] 1, 2 and 3 2, 3 and 4 1, 2, 3 and 4 |
Q42 ⇒ Why does a FM radio station perform better than and AM station radiating the same actual power? Capture effects appears in FM. [other wrong options] [Discuss in forum] FM is immune to noise AM has only two sidebands while FM has more FM uses larger bandwidth for large modulation depth. |
Q43 ⇒ Push pull amplifier is class B [other wrong options] [Discuss in forum] class A class C Class A or Class C |
Q44 ⇒ The sampling frequency in CD is 10 kHz. TRUE [other wrong options] [Discuss in forum] FALSE |
Q45 ⇒ An angle modulated signal is given by s(t) = cos 2p (2 x 106t + 30 sin 150t + 40 cos 150t). The maximum frequency and phase deviations of s(t) are 7.5 kHz, 100p rad [other wrong options] [Discuss in forum] 10.5 kHz, 140p rad 6 kHz and 80p rad 10.5 kHz, 100p rad |
Q46 ⇒ Modulation index of a AM wave is measured using oscilloscope. The display on the CRO is as shown in figure it can be concluded t the output wave is distorted [other wrong options] [Discuss in forum] the output wave is under modulated the modulation index is 100% the modulation index is 50% |
Q47 ⇒ A 1000 kHz carrier wave modulated 40% at 40000 Hz is applied to a resonant circuit tuned to a carrier frequency and having Q = 140. What is the degree of modulator after transmission through the circuit? 0.27 [other wrong options] [Discuss in forum] 0.4 0.2 0.54 |
Q48 ⇒ Limiter is not essential in the following detector ratio detector [other wrong options] [Discuss in forum] foster-Seeley balanced none of the above |
Q49 ⇒ In a TV receiver there is no raster, no picture and no sound. The most likely defective stage is power supply unit [other wrong options] [Discuss in forum] video output circuit horizontal oscillator balun |
Q50 ⇒ The oscillator frequency is set for best picture [other wrong options] [Discuss in forum] max. sound min. sound sound in picture |
Q51 ⇒ A 5000 W signal is attenuated by - 196 dB. The resultant signal strength is 1.26 x 10-16 W [other wrong options] [Discuss in forum] 1.26 x 106 W 1.26 x 10-2 W 1.26 x 10-8 W |
Q52 ⇒ In an AM system, doubling of modulation index doubles the antenna current. The system is single side band suppressed carrier [other wrong options] [Discuss in forum] single side band full carrier vestigial side band double side band full carrier |
Q53 ⇒ To separate channels in FDM receiver we have to use band pass filter [other wrong options] [Discuss in forum] integration AND gate differentiation |
Q54 ⇒ Under identical conditions, for a single modulating frequency, FM and PM are indistinguishable. Now if the modulating frequency is reduced, then phase modulation index will remain constant whereas frequency modulation index will increase [other wrong options] [Discuss in forum] phase modulation index as well as frequency modulation index decrease phase modulation index as well as frequency modulation index increase phase modulation index will decrease whereas frequency modulation index will remain constant |
Q55 ⇒ Noise which assumes great importance at high frequencies is transit-time noise [other wrong options] [Discuss in forum] flicker noise Johnson noise shot noise |
Q56 ⇒ FM broadcast is used in both VHP and UHF range [other wrong options] [Discuss in forum] VHP range UHF range MF range |
Q57 ⇒ A pure tone at 1000 Hz has a dB level of 40 dB. If the required dB level is 100, the number of such tones is 106 [other wrong options] [Discuss in forum] 2.5 60 104 |
Q58 ⇒ In amplitude modulation, the magnitude of side bands is ma/2 times the carrier amplitude, Ec [other wrong options] [Discuss in forum] ma times the carrier amplitude, Ec 2ma times the carrier amplitude, Ec 4ma times the carrier amplitude, Ec |
Q59 ⇒ In FM, as the modulating frequency decreases and the modulating voltage amplitude remains constant, the modulation index increases [other wrong options] [Discuss in forum] increases, the modulation index increases decrease, the modulation index increases remains constant, the modulation index decreases |
Q60 ⇒ Which of the following pulse communication system is inherently immune to noise? PCM [other wrong options] [Discuss in forum] PPM PWM PAM |
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