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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.
| 1251. |
In audio cassettes the width of each recording track is |
| A. | 5 mm |
| B. | 2.5 mm |
| C. | 1.5 mm |
| D. | 1 mm |
| Answer» C. 1.5 mm | |
| 1252. |
As EM waves travel in free space they get |
| A. | reflected |
| B. | refracted |
| C. | attenuated |
| D. | absorbed |
| Answer» D. absorbed | |
| 1253. |
For a plate-modulated class C amplifier the plate supply voltage is E. The maximum plate cathode voltage could be almost high as |
| A. | 2E |
| B. | 3E |
| C. | 4E |
| D. | 6E |
| Answer» D. 6E | |
| 1254. |
AM amplifier having noise figure of 20 dB and available power gain of 15 dB is followed by a mixer circuit having noise figure of 9 dB. The overall noise figure as referred to input in dB is |
| A. | 10.44 |
| B. | 11.07 |
| C. | 21.52 |
| D. | 0.63 |
| Answer» B. 11.07 | |
| 1255. |
Assertion (A): A video monitor does not need RF tuner and IF amplifier Reason (R): The picture tube in TV is basically a CRT. |
| 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 | |
| 1256. |
Johnson noise is |
| A. | white for all Practical application |
| B. | always white |
| C. | depends on temperature |
| D. | never white |
| Answer» B. always white | |
| 1257. |
Probability of error in DPSK is less than PSK |
| A. | 1 |
| B. | |
| C. | equal |
| D. | depend upon noise |
| Answer» B. | |
| 1258. |
In equally tampered scale, frequency of each tone equals the frequency of lower adjacent tone multiplied by |
| A. | (2)1/7 |
| B. | (2)1/12 |
| C. | (2)1/6 |
| D. | (2)1/5 |
| Answer» C. (2)1/6 | |
| 1259. |
In asynchronous TDM, for n signal sources, each frame contains m slots, where m is usually |
| A. | Less than n |
| B. | 2n |
| C. | n |
| D. | greater than 2n |
| Answer» E. | |
| 1260. |
Which of the following is not advantage of FM over AM? |
| A. | Noise immunity |
| B. | Capture effect |
| C. | Fidelity |
| D. | Spluttering effect |
| Answer» E. | |
| 1261. |
At FM demodulator output noise power density |
| A. | increases with frequency |
| B. | decreases with frequency |
| C. | remains unaltered |
| D. | none of the above |
| Answer» B. decreases with frequency | |
| 1262. |
In an FM signal, the modulating frequency is 2 kHz and maximum deviation is 10 kHz. The bandwidth requirement is |
| A. | 2 kHz |
| B. | 10 kHz |
| C. | 5 kHz |
| D. | 32 kHz |
| Answer» C. 5 kHz | |
| 1263. |
In MTI radar, clutter means |
| A. | echos from moving targets |
| B. | echos from stationary targets |
| C. | atmospheric noise |
| D. | thermal noise |
| Answer» C. atmospheric noise | |
| 1264. |
Fields are said to be circularly polarised if their magnitudes are |
| A. | equal and they are in phase |
| B. | equal but they differ in phase by ± 90° |
| C. | unequal and differ in phase by ± 90° |
| D. | unequal but are in phase |
| Answer» C. unequal and differ in phase by ¬± 90¬∞ | |
| 1265. |
A Marconi antenna |
| A. | is a grounded antenna with a length equal to λ/4 |
| B. | is an ungrounded antenna with a length equal to λ/4 |
| C. | has a length equal to 1 |
| D. | has a length equal to λ/2 |
| Answer» B. is an ungrounded antenna with a length equal to Œª/4 | |
| 1266. |
The number of noise sources in a BJT are |
| A. | 3 |
| B. | 2 |
| C. | 1 |
| D. | 4 |
| Answer» B. 2 | |
| 1267. |
In a certain '12 channel TDM' system it is found that channel no. 3 and channel no. 8 are connected to the same input signal. This technique |
| A. | wastes the channel capacity |
| B. | takes care of different sampling rate |
| C. | is required when different bandwidth signals are to be transmitted |
| D. | reduces noise |
| Answer» C. is required when different bandwidth signals are to be transmitted | |
| 1268. |
In TV signals colour burst is used |
| A. | to maintain colour sequence |
| B. | to ensure I and Q phase correctly |
| C. | to synchronise colours |
| D. | for interlacing of horizontal lines |
| Answer» C. to synchronise colours | |
| 1269. |
In the television system in India, the odd and even fields are scanned |
| A. | 25 times each |
| B. | 25 times each but alternately |
| C. | 50 times each |
| D. | 50 times each but alternately |
| Answer» C. 50 times each | |
| 1270. |
The orbital period of a geostationary communication satellite is |
| A. | 12 hours |
| B. | 24 hours |
| C. | 36 hours |
| D. | 48 hours |
| Answer» C. 36 hours | |
| 1271. |
Foster Seeley discriminator uses a |
| A. | single tuned circuit |
| B. | double tuned circuit with primary and secondary tuned to the same frequency |
| C. | double tuned circuit with primary and secondary tuned to the different frequency |
| D. | none of the above |
| Answer» B. double tuned circuit with primary and secondary tuned to the same frequency | |
| 1272. |
UHF range is |
| A. | 3 to 30 MHz |
| B. | 30 to 300 MHz |
| C. | 300 to 3000 MHz |
| D. | 3000 to 30000 MHz |
| Answer» D. 3000 to 30000 MHz | |
| 1273. |
In a phase discriminator fc, is the IF to which primary circuit is tuned. Consider the following statements: The primary and secondary voltages are exactly 90° out of phase when input frequency is fcmore than 90° out of phase when input frequency is higher than fcless than 90° out of phase when input frequency is lower than fc Which of the above statements is correct? |
| A. | 1 only |
| B. | 1 and 2 |
| C. | 1, 2 and 3 |
| D. | 2 and 3 |
| Answer» B. 1 and 2 | |
| 1274. |
A remote control of TV uses a 10 bit word. The maximum number of total commands it can transmit is |
| A. | 64 |
| B. | 256 |
| C. | 512 |
| D. | 1024 |
| Answer» E. | |
| 1275. |
Which of the following microphones has highest output impedance? |
| A. | Carbon |
| B. | Ribbon |
| C. | Crystal |
| D. | Condenser |
| Answer» E. | |
| 1276. |
Which one of the following statements is wrong. The radar cross-section of a target? |
| A. | depends on frequency |
| B. | may be reduced by special coating of non-spherical target |
| C. | depends on the aspect of target if it is non-spherical |
| D. | is equal to actual cross-sectional area for small targets |
| Answer» E. | |
| 1277. |
A carrier wave carries information. |
| A. | 1 |
| B. | |
| Answer» C. | |
| 1278. |
In a 4-ary FSK, the frequencies are separated by fs. Then they are |
| A. | in phase |
| B. | in phase opposition |
| C. | orthogonal |
| D. | none of the above |
| Answer» D. none of the above | |
| 1279. |
LCD uses |
| A. | nematic crystals |
| B. | sematic crystals |
| C. | cholesteric crystals |
| D. | twisted nematic crystal |
| Answer» E. | |
| 1280. |
In FM, which one is correct? |
| A. | The total power is equal to carrier power at 100% modulation and diminish thereafter. |
| B. | The carrier disappears at 100% modulation |
| C. | The total power is times the carrier power at 100% modulation |
| D. | The total power of the carrier and sidebands is equal to the carrier power at any modulation index. |
| Answer» E. | |
| 1281. |
Degaussing in a picture tube means |
| A. | Adding magnetism in mask and mounting frame |
| B. | Removing residual magnetism in mask, shield etc... |
| C. | Increasing resistance of coils to decrease time constant |
| D. | Decreasing resistance of coils to increase time constant. |
| Answer» C. Increasing resistance of coils to decrease time constant | |
| 1282. |
The baud rate is |
| A. | always equal to the bit transfer rate |
| B. | equal to twice the bandwidth of an ideal channel |
| C. | not equal to the signalling rate |
| D. | equal to one half the bandwidth of ideal channel |
| Answer» C. not equal to the signalling rate | |
| 1283. |
In telephone systems the relation between load r, number of calls initiated during a specified interval λ and average duration of a call (h) is |
| A. | r = λh |
| B. | r = λh2 |
| C. | λ = rh |
| D. | h = λr |
| Answer» B. r = Œªh2 | |
| 1284. |
In SSB generation, the most commonly used filter is |
| A. | low pass |
| B. | RC |
| C. | LC |
| D. | mechanical |
| Answer» E. | |
| 1285. |
Assertion (A): The maximum range of a radar is proportional to fourth root of the peak transmitted pulse power.Reason (R): Radar signals are subjected twice to inverse square law. |
| 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 | |
| 1286. |
The F.T. of {e-1 ‚à™(t)} is equal to . Therefore is |
| A. | ef ‚à™ (f) |
| B. | e-f ‚à™ (f) |
| C. | ef ‚à™ (-f) |
| D. | e-f ‚à™ (-f) |
| Answer» D. e-f ‚à™ (-f) | |
| 1287. |
In a colour TV receiver, PAL Dematrix consists of |
| A. | chroma detector to separate the three primary colours |
| B. | delay line and PAL matrix to give U and V signals |
| C. | delay line and PAL matrix to give RGB colours |
| D. | none of the above |
| Answer» C. delay line and PAL matrix to give RGB colours | |
| 1288. |
In CCIR-B system, the time between start of one H syn. pulse and next is |
| A. | 64 μs |
| B. | 6.4 μs |
| C. | 640 μs |
| D. | 0.64 μs |
| Answer» B. 6.4 Œºs | |
| 1289. |
The name modem is a contraction of terms modulator demodulator. |
| A. | 1 |
| B. | |
| C. | halves the bandwidth required for transmission |
| D. | does not affect the bandwidth for transmission |
| Answer» B. | |
| 1290. |
Transistor T1 operates at 30 kHz and T2 operates at 300 Hz. The flicker noise is |
| A. | not depend on frequency |
| B. | T1 > T2 |
| C. | T1 = T2 |
| D. | T1 < T2 |
| Answer» E. | |
| 1291. |
The smallest change in sound intensity that can be detected by human ear is __________ dB. |
| A. | 1 |
| B. | 3 |
| C. | 10 |
| D. | 20 |
| Answer» C. 10 | |
| 1292. |
Some types of traps used in video IF amplifier of colour TV are |
| A. | shunt traps |
| B. | series traps |
| C. | absorption traps |
| D. | all of the above |
| Answer» E. | |
| 1293. |
The velocity of sound waves in air |
| A. | is constant at all temperatures |
| B. | varies directly as temperature |
| C. | varies inversely as absolute temperature |
| D. | varies directly as square root of absolute temperature |
| Answer» E. | |
| 1294. |
To prevent overloading in the last IF amplifier one should use |
| A. | variable sensitivity |
| B. | squelch |
| C. | double conversion |
| D. | variable selectivity |
| Answer» B. squelch | |
| 1295. |
In FM modulation pre-emphasis is done for |
| A. | high frequency components |
| B. | low frequency components |
| C. | middle frequency components |
| D. | both (a) and (b) |
| Answer» B. low frequency components | |
| 1296. |
Consider the following statements as regards DPSK and DEPSK DPSK demodulator requires a device which operates at carrier frequency and provides a delay of bit time TbIn DPSK, synchronous demodulation recovers the signal b(t) and the decoding of b(t) to generate d(t) is done at base bandIn both DPSK and DEPSK errors always occur in pairs Which of the above statements are correct? |
| A. | 1 and 3 |
| B. | 1 and 2 |
| C. | 2 and 3 |
| D. | 1, 2 and 3 |
| Answer» C. 2 and 3 | |
| 1297. |
An angle modulated signal is expressed by fa(t) = cos (2 x 108 pt) + 75 sin (2 x 103 pt). The peak frequency deviation of the carrier is |
| A. | 1 kHz |
| B. | 7.5 kHz |
| C. | 75 kHz |
| D. | 100 MHz |
| Answer» D. 100 MHz | |
| 1298. |
Which of the following statement regarding the advantages of the phase discriminator over the slope detector is false? |
| A. | Better linearity |
| B. | Fewer tuned circuits |
| C. | Much easier alignment |
| D. | Greater limiting |
| Answer» B. Fewer tuned circuits | |
| 1299. |
In PAL system |
| A. | phase of U signal is reversed on alternating lines |
| B. | phase of V signal is reversed on alternating lines |
| C. | phases of both U and V signals are reversed on alternating lines |
| D. | none of the above |
| Answer» C. phases of both U and V signals are reversed on alternating lines | |
| 1300. |
If D is mouth diameter of a paraboloid reflector, its directivity is proportional to |
| A. | D |
| B. | D2 |
| C. | D |
| D. | D3 |
| Answer» C. D | |