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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.
| 401. |
Super high frequency means more than 3000 MHz. |
| A. | 1 |
| B. | |
| C. | half wave line |
| D. | a short circuited stub |
| Answer» B. | |
| 402. |
In a transmission line, losses due to dielectric heating are |
| A. | proportional to voltage and inversely proportional to Z0 |
| B. | proportional to voltage and proportional to Z0 |
| C. | proportional to current and proportional to Z0 |
| D. | proportional to current and inversely proportional to Z0 |
| Answer» B. proportional to voltage and proportional to Z0 | |
| 403. |
FM broadcast is used in |
| A. | MF range |
| B. | both VHP and UHF range |
| C. | a few watts |
| D. | about 500 W |
| Answer» E. | |
| 404. |
The service area of a TV transmitter is a little beyond radio horizon. |
| A. | 1 |
| B. | |
| C. | P |
| D. | mP |
| Answer» B. | |
| 405. |
In a TV studios, flying spot scanner is a device for |
| A. | mixing video and audio signals |
| B. | telecasting feature films |
| C. | live telecast of outdoor programs |
| D. | telecast of indoor music programs |
| Answer» C. live telecast of outdoor programs | |
| 406. |
Speeds of sound and radio waves are equal. |
| A. | 1 |
| B. | |
| C. | Pt = 1.5 Pc |
| D. | Pt = 2.5 Pc |
| Answer» C. Pt = 1.5 Pc | |
| 407. |
Companding is used in PCM to |
| A. | reduce bandwidth |
| B. | increasing S/N ratio |
| C. | get almost uniform S/N ratio |
| D. | increase bandwidth |
| Answer» D. increase bandwidth | |
| 408. |
Assertion (A): Radio transmission is by sky wavesReason (R): Waves having frequencies higher than 30 MHz penetrate the atmosphere and do not return to earth. |
| 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 | |
| 409. |
24 telephone channels, each band limited to 3.4 kHz, are to be time division multiplexed by using PCM, calculate the bandwidth of PCM system for 128 quantization levels and an 8 KHz sampling frequency |
| A. | 192 kHz |
| B. | 2 MHz |
| C. | 1.299 MHz |
| D. | 1.54 MHz |
| Answer» E. | |
| 410. |
BFO stands for |
| A. | Beat Frequency Oscillator |
| B. | Broad Frequency Oscillator |
| C. | Blocking Frequency Oscillator |
| D. | Ballistic Frequency Oscillator |
| Answer» B. Broad Frequency Oscillator | |
| 411. |
In a telephone system, the grade of service means |
| A. | the quality of sound reception at the receiver telephone |
| B. | the probability that a called for connection is established |
| C. | the type of wires cables used for the system |
| D. | none of the above |
| Answer» C. the type of wires cables used for the system | |
| 412. |
In Modulation, "carrier" is |
| A. | resultant wave |
| B. | speech voltage to be transmitted |
| C. | voltage with constant frequency, phase or amplitude |
| D. | voltage for which frequency, phase or amplitude is varied |
| Answer» E. | |
| 413. |
In FM and AM the ratio of signal to noise ratio at the detector output least depends upon |
| A. | bandwidth |
| B. | transmission |
| C. | carrier frequency |
| D. | modulating frequency |
| Answer» D. modulating frequency | |
| 414. |
The signal plate of vidicon tube is coated with tin oxide. |
| A. | 1 |
| B. | |
| C. | 100 μ sec |
| D. | 50 μ sec |
| Answer» B. | |
| 415. |
The equation v(t) = A cos [ωct + φ(t)] where A and ωc are constant and φ(t) is a function of base signal represents Phase modulationAmplitude modulationAngle modulationFrequency modulation Which of the above are true? |
| A. | 3 only |
| B. | 1, 3 and 4 |
| C. | 1, 2, 3, 4 |
| D. | 3 and 4 only |
| Answer» C. 1, 2, 3, 4 | |
| 416. |
The positive peak of an AM wave is 16 V and the minimum value is 4 V Assuming single tone modulation, the modulation index is |
| A. | 0.6 |
| B. | 0.25 |
| C. | 4 |
| D. | 0.36 |
| Answer» B. 0.25 | |
| 417. |
In amplitude modulation, the magnitude of side bands is |
| A. | 2ma times the carrier amplitude, Ec |
| B. | 4ma times the carrier amplitude, Ec |
| C. | fs + fi |
| D. | fs ± fi |
| Answer» E. | |
| 418. |
A narrow band noise show |
| A. | AM only |
| B. | AM and FM |
| C. | FM |
| D. | PCM |
| Answer» C. FM | |
| 419. |
At f = 7 GHz, a 120 cm dish antenna gives a gain of about |
| A. | 50 |
| B. | 500 |
| C. | 5000 |
| D. | 50000 |
| Answer» E. | |
| 420. |
A transmitter power of 5 W is increased by 20 dB. The effective radiated power is |
| A. | 25 W |
| B. | 500 W |
| C. | 100 |
| D. | 75 |
| Answer» E. | |
| 421. |
Assertion (A): In SSB, carrier is suppressed by about 45 dB Reason (R): SSB is standard form for radio communication |
| 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 | |
| 422. |
If the average power of radar transmitters is 2 kW and the peak power of the transmitter is 1000 kW, what will be the duty cycle? |
| A. | 0.002 |
| B. | 0.02 |
| C. | 0.001 |
| D. | 0.01 |
| Answer» B. 0.02 | |
| 423. |
The generally used value of EHV supply in TV receivers is |
| A. | 1 kV per diagonal cm |
| B. | 1 kV per diagonal inch |
| C. | 0.5 kV per diagonal cm |
| D. | 0, 5 kV per diagonal inch |
| Answer» C. 0.5 kV per diagonal cm | |
| 424. |
Troposphere is the portion of atmosphere |
| A. | nearest to ground |
| B. | between 50 to 90 km above ground |
| C. | between 110 to 220 km above ground |
| D. | between 250 to 350 km above ground |
| Answer» B. between 50 to 90 km above ground | |
| 425. |
A balanced modulator circuit uses |
| A. | two identical diodes with same V-I characteristics |
| B. | two triodes with different V-I characteristics |
| C. | two diodes with different V-I characteristics |
| D. | a diode and a triode |
| Answer» B. two triodes with different V-I characteristics | |
| 426. |
A buffer amplifier is |
| A. | a double-tuned amplifier |
| B. | a high gain D.C. amplifier |
| C. | a cathode follower stage |
| D. | none of the above |
| Answer» C. a cathode follower stage | |
| 427. |
Loudness control gives |
| A. | high boost to bass and little boost to treble |
| B. | equal boost to bass and treble |
| C. | less boost to bass and more boost to treble |
| D. | less boost to both bass and treble |
| Answer» B. equal boost to bass and treble | |
| 428. |
A 400 W carrier is modulated to a depth of 75 percent. The total power in modulated wave will be |
| A. | 38.5 W |
| B. | 400 W |
| C. | 512.5 W |
| D. | 615.5 W |
| Answer» D. 615.5 W | |
| 429. |
The modulation index of an AM wave is measured using a CRO. The waveform is as shown in figure, the modulation index is nearly |
| A. | 0.43 |
| B. | 0.3 |
| C. | 0.23 |
| D. | 0.17 |
| Answer» B. 0.3 | |
| 430. |
In a AM wave the carrier and one of the side bands is suppressed. If m = 0.5, the percentage saving in power is |
| A. | 0.5 |
| B. | 0.833 |
| C. | 0.944 |
| D. | 1 |
| Answer» D. 1 | |
| 431. |
Which colour picture tube uses slotted aperture mask? |
| A. | Trinitron |
| B. | Shadow mask tube |
| C. | PIL |
| D. | None of the above |
| Answer» D. None of the above | |
| 432. |
In the stabilized reactance modulators AFC system |
| A. | the discriminator frequency must not be too low, or the system will fail |
| B. | phase modulation is converted into FM by the equalizer circuit |
| C. | 1500 Ω |
| D. | 150 Ω |
| Answer» E. | |
| 433. |
In PCM, the biggest disadvantage as compared to AM is |
| A. | larger bandwidth |
| B. | larger noise |
| C. | inability to handle analog signals |
| D. | incompatibility with time division multiplex systems |
| Answer» B. larger noise | |
| 434. |
The advantage of pulse modulation is |
| A. | the transmitted power can be concentrated into short bursts |
| B. | the time intervals between pulses can be filled with sample values from other message |
| C. | pulse wave may obtain appreciable D.C. and low frequency content |
| D. | all of the above |
| Answer» E. | |
| 435. |
An antenna operates effectively when its dimensions are |
| A. | of the order of magnitude of wavelength to be transmitted |
| B. | very small than the magnitude of wavelength to be transmitted |
| C. | very large than the magnitude of wavelength to be transmitted |
| D. | either (a) or (b) |
| Answer» B. very small than the magnitude of wavelength to be transmitted | |
| 436. |
The trapezoidal pattern of figure is obtained when examining an AM wave by an oscilloscope. Modulation factor of the wave is |
| A. | 0.33 |
| B. | 0.5 |
| C. | 2 |
| D. | 1 |
| Answer» C. 2 | |
| 437. |
A trigonometric function is synonyms to |
| A. | singular function |
| B. | none of the above |
| Answer» C. | |
| 438. |
A balun provides an impedance transformation of |
| A. | 0.66736111111111 |
| B. | 0.33402777777778 |
| C. | 0.16736111111111 |
| D. | 0.084027777777778 |
| Answer» D. 0.084027777777778 | |
| 439. |
A shadow zone does not receive any space wave |
| A. | 1 |
| B. | |
| C. | Push pull amplifier |
| D. | Wideband amplifier |
| Answer» B. | |
| 440. |
To select one out of N equally probable events, the number of bits required is |
| A. | log2 N |
| B. | log10 N |
| C. | loge N |
| D. | N |
| Answer» B. log10 N | |
| 441. |
RF choke used for suppressing interference in TV is generally |
| A. | honey comb wound coil |
| B. | iron core coil |
| C. | single layer coil |
| D. | multilayer coil |
| Answer» C. single layer coil | |
| 442. |
Assertion (A): A Smith chart can be used for a number of calculations of a transmission lineReason (R): Smith chart is basically a polar impedance diagram. |
| 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 | |
| 443. |
The most noise resistant modulation system is |
| A. | PCM |
| B. | SSB suppressed carrier |
| C. | FM |
| D. | pulse position modulation |
| Answer» B. SSB suppressed carrier | |
| 444. |
During day time ionosphere can be considered to be consisting of |
| A. | D, E, F1 and F2 layers |
| B. | D, E, F1 layers |
| C. | D, E, F2 layers |
| D. | D and E layers |
| Answer» B. D, E, F1 layers | |
| 445. |
Consider the following statements about Rhombic antenna It is non resonantIt is a broad band antennaIt is ideally suited for HF transmission Which of the above are correct? |
| A. | 1, 2, 3 |
| B. | 1, 3 only |
| C. | 2, 3 only |
| D. | 1 only |
| Answer» B. 1, 3 only | |
| 446. |
Audio frequency range lies between |
| A. | 20 Hz and 20 kHz |
| B. | 20 kHz and 20 MHz |
| C. | 2 MHz and 20 MHz |
| D. | 20 MHz and 200 MHz |
| Answer» B. 20 kHz and 20 MHz | |
| 447. |
Public address systems generally use electret microphones. |
| A. | 1 |
| B. | |
| C. | raised-cosine |
| D. | flat |
| Answer» B. | |
| 448. |
In a pulsed RADAR typical value of pulse duration and pulse frequency respectively are |
| A. | 1 μs and 50 Hz |
| B. | 1 μs and 500 Hz |
| C. | 4 μs and 50 Hz |
| D. | 4 μs and 500 Hz |
| Answer» C. 4 Œºs and 50 Hz | |
| 449. |
The open loop gain of an amplifier is 50 but is likely to change by 20%. If negative feedback with β = 0.1 is used, the change in gain will be about |
| A. | 0.2 |
| B. | 0.1 |
| C. | 0.04 |
| D. | 0.0005 |
| Answer» D. 0.0005 | |
| 450. |
The reactance of coupling capacitors, for DC quantities, is |
| A. | zero |
| B. | low |
| C. | infinite |
| D. | zero or low |
| Answer» D. zero or low | |