MCQOPTIONS
Saved Bookmarks
MCQOPTIONS
This section includes 1362 Mcqs, each offering curated multiple-choice questions to sharpen your Electronics & Communication Engineering knowledge and support exam preparation. Choose a topic below to get started.
| 1201. |
Modulation system used for video-modulation in television broadcast is |
| A. | SSB AM with carrier |
| B. | SSB with carrier suppressed |
| C. | DSB AM with carrier |
| D. | a modified form of SSB with carrier called vestigial sideband |
| Answer» E. | |
| 1202. |
Which of the following is an indirect method of generating FM? |
| A. | Reactance BJT modulator |
| B. | Armstrong modulation |
| C. | Varactor diode modulation |
| D. | Reactive FM modulator |
| Answer» C. Varactor diode modulation | |
| 1203. |
The number of channels in a stereophonic system is |
| A. | 8 |
| B. | 4 |
| C. | 2 |
| D. | 1 |
| Answer» D. 1 | |
| 1204. |
Which of the following is invariably found in SSB? |
| A. | Tuned modulator |
| B. | Class B, RF amplifier |
| C. | Class C, audio amplifier |
| D. | All of the above |
| Answer» B. Class B, RF amplifier | |
| 1205. |
Assertion (A): In AM carrier component remains constant in amplitude and frequency.Reason (R): In AM the two side bands are images of each other. |
| A. | Both A and R are correct and R is correct explanation of A |
| B. | Both A and R are correct but R is not correct explanation of A |
| C. | A is correct but R is wrong |
| D. | A is wrong but R is correct |
| Answer» C. A is correct but R is wrong | |
| 1206. |
When modulation index of an AM wave is increased from 0.5 to 1, the transmitted power |
| A. | remains the same |
| B. | increases by 25% |
| C. | increases by 33.3% |
| D. | increases by 50% |
| Answer» D. increases by 50% | |
| 1207. |
The sampling frequency in CD is 10 kHz. |
| A. | 1 |
| B. | |
| C. | radio transmission |
| D. | television transmission |
| Answer» B. | |
| 1208. |
Frequency modulation consists in |
| A. | varying the frequency and amplitude of the carrier in accordance with the instantaneous value of modulating signal |
| B. | varying the amplitude of the carrier in accordance with the instantaneous value of the modulating voltage |
| C. | varying the frequency of the carrier voltage in accordance with the instantaneous value of the modulating voltage |
| D. | vary the frequency of the carrier voltage |
| Answer» D. vary the frequency of the carrier voltage | |
| 1209. |
Some possible disadvantages of high level modulation in TV transmitters are Video monitor has to supply high video voltages upto several hundred volts into highly capacitive loads drawing high current at video frequenciesThe grid modulated stage presents a varying load to its driverThe linearity and high video driving power present design problems Out of above which are true? |
| A. | 1 only |
| B. | 1 and 2 only |
| C. | 1, 2 and 3 |
| D. | 2 and 3 only |
| Answer» D. 2 and 3 only | |
| 1210. |
A TV remote control works on the principle of |
| A. | pulse code modulated ultra violet light |
| B. | pulse code modulated infrared light |
| C. | demodulation |
| D. | either (a) or (b) |
| Answer» C. demodulation | |
| 1211. |
In TV transmitter some possible advantages of IF modulation are The modulator section and visual exciter can be solid state devicesVSB filter can be introduced at low power levelThe subsequent stages following VSB filter can be tuned permanently for wideband linear operationIt is economical which of the above are true? |
| A. | 1 and 2 |
| B. | 1, 2 and 3 |
| C. | 2, 3 and 4 |
| D. | 1, 2, 3 and 4 |
| Answer» E. | |
| 1212. |
The number of repeaters in a coaxial cable link depends on |
| A. | system bandwidth |
| B. | separation of equalizers |
| C. | the number of coaxial cables in the tube |
| D. | none of the above |
| Answer» B. separation of equalizers | |
| 1213. |
The message carrying efficiency is best in |
| A. | AM |
| B. | FM |
| C. | AM-SC |
| D. | Phase modulation |
| Answer» D. Phase modulation | |
| 1214. |
Which of the following microphones has lowest output impedance? |
| A. | Moving coil |
| B. | Ribbon |
| C. | Crystal |
| D. | Condenser |
| Answer» C. Crystal | |
| 1215. |
Assertion (A): In India we use CCIR-B standardReason (R): Video signals are frequency modulated. |
| A. | Both A and R are correct and R is correct explanation of A |
| B. | Both A and R are correct but R is not correct explanation of A |
| C. | A is correct but R is wrong |
| D. | A is wrong but R is correct |
| Answer» D. A is wrong but R is correct | |
| 1216. |
If e = 10 sin(108 t + 3 sin 104 t) then carrier frequency is |
| A. | 0.159 MHz |
| B. | 1.59 MHz |
| C. | 15.9 MHz |
| D. | 159 MHz |
| Answer» D. 159 MHz | |
| 1217. |
The bandwidth of DSB suppressed carrier modulation system when the modulating frequency varies between 500 Hz and 5 kHz is |
| A. | 555 kHz |
| B. | 505 kHz |
| C. | 500 kHz |
| D. | 9 kHz |
| Answer» E. | |
| 1218. |
In a tape recorder the output from RF oscillator is given to |
| A. | only erase head coil |
| B. | only record head coil |
| C. | coils of both erase head and record head |
| D. | none of the above |
| Answer» B. only record head coil | |
| 1219. |
Microwave link repeaters are typically 50 km apart in TV transmission due to |
| A. | atmosphere attenuation |
| B. | output power tube limitations |
| C. | attenuation of surface wave |
| D. | earth's curvature |
| Answer» E. | |
| 1220. |
Which of the following types of noise assumes greater importance at high frequencies? |
| A. | Transit time noise |
| B. | Shot noise |
| C. | Impulse noise |
| D. | Random noise |
| Answer» B. Shot noise | |
| 1221. |
When ωm is the modulation frequency in frequency modulation, the modulation index is proportional to |
| A. | ωm |
| B. | ω2m |
| C. | 1/ωm |
| D. | 1/ω2m |
| Answer» D. 1/œâ2m | |
| 1222. |
In an AM system, doubling of modulation index doubles the antenna current. The system is |
| A. | single side band full carrier |
| B. | vestigial side band |
| C. | single side band suppressed carrier |
| D. | double side band full carrier |
| Answer» D. double side band full carrier | |
| 1223. |
Two sinusoidal signals of same amplitude and frequencies 10 kHz and 10.1 kHz are added together. The combined signal is given to an ideal frequency detector. The output of the detector is |
| A. | 0.1 kHz sinusoidal |
| B. | 10.1 kHz sinusoidal |
| C. | a linear function |
| D. | a constant |
| Answer» C. a linear function | |
| 1224. |
Space wave may be a direct wave or wave reflected from earth. |
| A. | 1 |
| B. | |
| Answer» C. | |
| 1225. |
An FM signal is modulated by an 8 kHz sine wave and has maximum and minimum frequencies of 100.05 MHz and 99.95 MHz respectively. Its deviation frequency is |
| A. | 100 kHz |
| B. | 100 MHz |
| C. | 500 kHz |
| D. | 108 kHz |
| Answer» E. | |
| 1226. |
In AM the amplitude of carrier components ... while in FM it |
| A. | remains constant, does not remain constant |
| B. | does not remain constant ... remains constant |
| C. | remains constant... also remains constant |
| D. | does not remain constant, also does not remain constant |
| Answer» B. does not remain constant ... remains constant | |
| 1227. |
The range of a cordless telephone is about |
| A. | 1000 m |
| B. | 500 m |
| C. | 100 m |
| D. | 10 m |
| Answer» D. 10 m | |
| 1228. |
In a system an input resistance of 20 kΩ causes a noise voltage of 15μV. If two such input resistances each of 20 kΩ are used in parallel, the total noise voltage will be about |
| A. | 15 μV |
| B. | 30 μV |
| C. | 7.5 μV |
| D. | 10.6 μV |
| Answer» E. | |
| 1229. |
If aspect ratio is and number of lines in each frame is 625, the number of picture elements in one frame is |
| A. | x 625 |
| B. | (625)2 |
| C. | 6252 |
| D. | (625)2 |
| Answer» C. 6252 | |
| 1230. |
In TV system in India, each frame is divided into |
| A. | 625 horizontal lines |
| B. | 525 horizontal lines |
| C. | 425 horizontal lines |
| D. | 325 horizontal lines |
| Answer» B. 525 horizontal lines | |
| 1231. |
c(t) and m(t) are used to generate an FM signal. If the peak frequency deviation of the generated FM signal is three times the transmission bandwidth of the AM signal, then the coefficient of the term cos [2p(1008 x 103t)] in the FM signal (in terms of the Bessel Coefficients) is |
| A. | 5 J4(3) |
| B. | J8(3) |
| C. | J8(4) |
| D. | 5 J4(6) |
| Answer» E. | |
| 1232. |
To relay outdoor remotely located live programs, TV transmitter use |
| A. | microwave links |
| B. | coaxial cable link |
| C. | open wire link |
| D. | either (b) or (c) |
| Answer» B. coaxial cable link | |
| 1233. |
If the bandwidth is increased by 2, the γFM γAM (where γ is the ratio of SNR of output to SNR at input, FM is frequency modulation and AM is amplitude modulation) is increased by a factor of |
| A. | 2 |
| B. | 3 |
| C. | 4 |
| D. | 6 |
| Answer» D. 6 | |
| 1234. |
If each short element of signal occupies 20 ms, the speed is |
| A. | 20 bauds |
| B. | 50 bauds |
| C. | bauds |
| D. | 0.05 bauds |
| Answer» C. bauds | |
| 1235. |
In case of low level amplitude modulation system, the amplifiers following the modulated stage must be |
| A. | class C amplifiers |
| B. | linear devices |
| C. | non-linear devices |
| D. | harmonic devices |
| Answer» C. non-linear devices | |
| 1236. |
To couple a coaxial line to a parallel line wire it is best to use |
| A. | slotted line |
| B. | balun |
| C. | directional coupler |
| D. | transformer |
| Answer» C. directional coupler | |
| 1237. |
Consider the following statements as regards SAW filter The centre frequency is determined by the pitch of IDT comb shaped electrodesThe response can be modified shaping the overlap of comb electrodesThe response is maximum when acoustic wave has its wavelength equal to pitchWhen a number of identical electrodes are arranged at the same pitch, the frequency characteristics of the filter is expressed by (sin x)/x Which of the above statements are correct? |
| A. | 1, 2, 3, 4 |
| B. | 1, 2, 3 only |
| C. | 1, 2, 4 only |
| D. | 2, 3, 4 only |
| Answer» D. 2, 3, 4 only | |
| 1238. |
In amplitude modulation the rms value of radio frequency voltage after 40% modulation is 60 mV. If modulation is 80% the rms value after modulation will be about |
| A. | 50 mV |
| B. | 60 mV |
| C. | 66 mV |
| D. | 80 mV |
| Answer» D. 80 mV | |
| 1239. |
When the length of antenna is a whole wavelength |
| A. | the radiation at right angles is zero |
| B. | the radiation at right angles is maximum |
| C. | the radiation is zero in all directions |
| D. | the radiation is maximum in all directions |
| Answer» B. the radiation at right angles is maximum | |
| 1240. |
For an ideal 3000 Hz channel, Nyquist rate is |
| A. | 3000 bps |
| B. | 6000 bps |
| C. | 9000 bps |
| D. | 12000 bps |
| Answer» C. 9000 bps | |
| 1241. |
The PAM Signal can be detected by |
| A. | Band pass filter |
| B. | Band stop filter |
| C. | High pass filter |
| D. | Low pass filter |
| Answer» E. | |
| 1242. |
Non-coherently detection is not possible for |
| A. | PSK |
| B. | ASK |
| C. | FSK |
| D. | both (a) and (c) |
| Answer» B. ASK | |
| 1243. |
In VHS format each video head is tilted from azimuth by |
| A. | 20° |
| B. | 10° |
| C. | 6° |
| D. | 1° |
| Answer» D. 1¬∞ | |
| 1244. |
Which of the following can be used to convert PPM into PWM? |
| A. | Integrator |
| B. | Astable multivibrator |
| C. | Bistable multivibrator |
| D. | Monostable multivibrator |
| Answer» D. Monostable multivibrator | |
| 1245. |
How can the quantizing noise be reduced? |
| A. | By using de-emphasis circuit |
| B. | By using RF amplifier in the receiver |
| C. | By increasing the number of quantization levels |
| D. | By sending sloping pulses |
| Answer» D. By sending sloping pulses | |
| 1246. |
The percentage saving in power when the carrier and one of the sidebands are suppressed in an AM wave modulated to a depth of 100% will be nearly |
| A. | 0.5 |
| B. | 0.66 |
| C. | 0.75 |
| D. | 0.83 |
| Answer» E. | |
| 1247. |
An AM signal is detected using an envelope detector, the carrier frequency and modulating signal frequency are 1 MHz and 2 kHz respectively. An appropriate value for the time constant of the envelope detector is |
| A. | 500 μ sec |
| B. | 20 μ sec |
| C. | 0.2 μ sec |
| D. | 1 μ sec |
| Answer» C. 0.2 Œº sec | |
| 1248. |
Assertion (A): Free space does not interfere with normal radiation and propagation of radio wavesReason (R): Free space has no magnetic or gravitational fields. |
| A. | Both A and R are correct and R is correct explanation of A |
| B. | Both A and R are correct but R is not correct explanation of A |
| C. | A is correct but R is wrong |
| D. | A is wrong but R is correct |
| Answer» B. Both A and R are correct but R is not correct explanation of A | |
| 1249. |
Energy content of atmospheric noise |
| A. | does not depend on frequency |
| B. | decreases as frequency is increased |
| C. | increases as frequency is increased |
| D. | either (a) or (c) depending on the temperature |
| Answer» C. increases as frequency is increased | |
| 1250. |
For telegraphy the most commonly used modulation system is |
| A. | FSK |
| B. | two tone modulation |
| C. | PCM |
| D. | single tone modulation |
| Answer» B. two tone modulation | |