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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.
| 651. |
An S/N ratio of 3 expressed in db is |
| A. | 4.8 dB |
| B. | 2.4 dB |
| C. | 0.48 dB |
| D. | 0.24 dB |
| Answer» B. 2.4 dB | |
| 652. |
Assertion (A): In FM the frequency of the carrier is varied by the modulating voltageReason (R): FM and PM are two forms of angle modulation. |
| 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 | |
| 653. |
The unit of loudness is |
| A. | phon |
| B. | sone |
| C. | decibel |
| D. | mel |
| Answer» D. mel | |
| 654. |
Which of the following is unlikely to happen when quantising noise is decreased in PCM? |
| A. | Increased bandwidth |
| B. | Increased channel noise |
| C. | Increased number of standard levels |
| D. | All of the above |
| Answer» E. | |
| 655. |
In an amplitude modulated waveform, the amplitude of the sideband is |
| A. | independent of the carrier amplitude |
| B. | independent of the modulation index |
| C. | carrier amplitude x modulation index |
| D. | 1/2 carrier amplitude x modulation index |
| Answer» E. | |
| 656. |
A noiseless 3 kHz channel can't transmit binary bit at the rate |
| A. | 12000 bps |
| B. | 1000 bps |
| C. | 6000 bps |
| D. | 3000 bps |
| Answer» B. 1000 bps | |
| 657. |
A RADAR can be used to |
| A. | aim a gun at an aircraft |
| B. | to direct guided missiles |
| C. | to search submarines |
| D. | all of the above |
| Answer» E. | |
| 658. |
If the variance σx2 of d(n) = x(n) - x(n - 1) is one-tenth the variance σx2 of a stationary zero mean discrete time signal x(n), then the normalized autocorrelation function Rxx(x)/σx2 at k = 1 is |
| A. | 0.95 |
| B. | 0.9 |
| C. | 0.1 |
| D. | 0.05 |
| Answer» D. 0.05 | |
| 659. |
The IF bandwidth of a radar receiver is inversely proportional to |
| A. | pulse interval |
| B. | pulse width |
| C. | PRF |
| D. | none of the above |
| Answer» C. PRF | |
| 660. |
In major diatonic musical scale, an octave is divided into |
| A. | 12 intervals |
| B. | 10 intervals |
| C. | 7 intervals |
| D. | 5 intervals |
| Answer» D. 5 intervals | |
| 661. |
In free space, line of sight propagation case, the transmission losses between transmitter and receiver increase with frequency (f) as |
| A. | f |
| B. | f2 |
| C. | f4 |
| D. | f1/2 |
| Answer» D. f1/2 | |
| 662. |
Which of the following is very useful as multiband HF receiving antenna? |
| A. | Square loop |
| B. | Conical horn |
| C. | Folded dipole |
| D. | Log-periodic |
| Answer» E. | |
| 663. |
For FM, which of the following statement is not true? |
| A. | The bandwidth increases as modulation index is increased |
| B. | The total power remains constant with respect to modulation index |
| C. | The carrier never becomes zero |
| D. | All of the above |
| Answer» D. All of the above | |
| 664. |
If the target area is small compared to wavelength of radar the situation is called |
| A. | resonance region |
| B. | Rayleigh region |
| C. | optical region |
| D. | binomial region |
| Answer» C. optical region | |
| 665. |
QAM stands for |
| A. | Quasi-Amplitude Modulation |
| B. | Quadrature Angle Modulation |
| C. | Quadrature Amplitude Modulation |
| D. | None of the above |
| Answer» D. None of the above | |
| 666. |
In which frequency range is the noise figure in a transistor independent of frequency |
| A. | intermediate frequencies |
| B. | high frequency |
| C. | low frequencies |
| D. | both low and high frequencies |
| Answer» B. high frequency | |
| 667. |
PIL tube means |
| A. | Picture in Line Tube |
| B. | Precision in Line Tube |
| C. | Pairing in Line Tube |
| D. | Pattern in Line Tube |
| Answer» C. Pairing in Line Tube | |
| 668. |
In band III of TV, distant reception (beyond line of sight range) is possible due to |
| A. | tropospheric bending by refraction |
| B. | reflection of waves |
| C. | ionospheric scattering |
| D. | none of the above |
| Answer» B. reflection of waves | |
| 669. |
VLF waves are sometimes used because |
| A. | they penetrate the ionosphere easily |
| B. | they are very reliable |
| C. | they require low power |
| D. | they require transmitting antennas of convenient sizes |
| Answer» C. they require low power | |
| 670. |
The inductance of connecting leads can be a source of |
| A. | low frequency parasitics |
| B. | high frequency parasitics |
| C. | carrier frequency parasitics |
| D. | none of the above |
| Answer» C. carrier frequency parasitics | |
| 671. |
An FM signal with a deviation is passes through the mixer, and has its frequency reduced five fold. The deviation in the output of the mixer is |
| A. | Δ |
| B. | 5Δ |
| C. | Δ/5 |
| D. | indeterminant |
| Answer» B. 5Œî | |
| 672. |
In practical commercial AM system channel bandwidth is |
| A. | 150 kHz |
| B. | 100 kHz |
| C. | 15 kHz |
| D. | 200 kHz |
| Answer» D. 200 kHz | |
| 673. |
Circuit switching, Message switching and Packet Switching Network belong to which of the following systems? |
| A. | Computer communication system |
| B. | Electromechanical communication system |
| C. | PBX system |
| D. | EPBX system |
| Answer» B. Electromechanical communication system | |
| 674. |
In a picture tube, the video signal is applied to |
| A. | cathode |
| B. | grid |
| C. | any anode |
| D. | either cathode or grid |
| Answer» B. grid | |
| 675. |
A 300 Hz sound wave of intensity 20 dB is transmitted by a 1500 kHz radio wave by frequency modulation. It is seen that instantaneous frequency varies between 1500.2 kHz and 1499.8 kHz, 300 times a second. If the intensity of sound wave is 100 dB. |
| A. | The instantaneous frequency variations will be between 1500.2 and 1499.8 kHz, 1500 times a second |
| B. | The instantaneous frequency variations will be between 1501 and 1499 kHz, 1500 times a second |
| C. | The instantaneous frequency variations will be between 1501 and 1499 kHz, 300 times a second |
| D. | The instantaneous frequency variations will be between 1501 and 1499 kHz, 60 times a second |
| Answer» D. The instantaneous frequency variations will be between 1501 and 1499 kHz, 60 times a second | |
| 676. |
The power to the portable unit of a cordless telephone is provided by |
| A. | pencil cells |
| B. | dry cells |
| C. | rechargeable cells |
| D. | AC mains |
| Answer» D. AC mains | |
| 677. |
For a parallel two wire line with both conductors touching each other, the characteristic impedance is about |
| A. | 300 Ω |
| B. | 200 Ω |
| C. | 80 Ω |
| D. | 24 Ω |
| Answer» D. 24 Œ© | |
| 678. |
Which type of modulator amplifier is used in AM transmitter? |
| A. | Class A |
| B. | Class B |
| C. | Classes AB |
| D. | Class C with negative feedback |
| Answer» E. | |
| 679. |
Bandwidth for practical PCM system is (where n is no. of channels, N length of PCM codes) |
| A. | 2n N fm Hz |
| B. | 4n fm Hz |
| C. | 2n fm |
| D. | (N + 1)fm |
| Answer» B. 4n fm Hz | |
| 680. |
ARQ stands for |
| A. | Automatic Repeat Quest |
| B. | Analog Repeat Request |
| C. | Automatic Repeat Request |
| D. | None Of the above |
| Answer» D. None Of the above | |
| 681. |
For an RC low pass filter, the relation between noise bandwidth BN and 3-dB bandwidth B3dB is |
| A. | |
| B. | BN = B3-dB |
| Answer» B. BN = B3-dB | |
| 682. |
Limiter is not essential in the following detector |
| A. | foster-Seeley |
| B. | ratio detector |
| C. | balanced |
| D. | none of the above |
| Answer» C. balanced | |
| 683. |
The intermediate frequencies in VCR are |
| A. | video 38.9 MHz and audio 33.4 MHz |
| B. | 38.9 MHz for both video and audio |
| C. | 33.4 MHz for both video and audio |
| D. | 33.4 MHz for video and 38.9 MHz for audio |
| Answer» B. 38.9 MHz for both video and audio | |
| 684. |
The highest modulating frequency typically used in AM systems is |
| A. | 1 kHz |
| B. | 5 kHz |
| C. | 20 kHz |
| D. | 50 kHz |
| Answer» C. 20 kHz | |
| 685. |
The image frequency of a superheterodyne receiver is |
| A. | created within the receiver itself |
| B. | not rejected by IF tuned circuits |
| C. | independent of the frequency of tuning |
| D. | due to insufficient adjacent channel rejection |
| Answer» C. independent of the frequency of tuning | |
| 686. |
Oscillator crystal is made of |
| A. | silicon |
| B. | germanium |
| C. | diamond |
| D. | quartz |
| Answer» E. | |
| 687. |
A channel has a SNR of 7 and BW 4 kHz. Keeping the channel capacity (BPS) same, the BW is reduced to accommodate more channels. The SNR |
| A. | decreases |
| B. | increases |
| C. | remains same |
| D. | partially affected |
| Answer» C. remains same | |
| 688. |
In telecast |
| A. | video and audio signals are frequency modulated |
| B. | video signals are frequency modulated but audio signals are amplitude modulated |
| C. | both audio and video signals are amplitude modulated |
| D. | video signals are amplitude modulated and audio signals are frequency modulated |
| Answer» E. | |
| 689. |
Which stage generates RF carrier? |
| A. | Amplifier |
| B. | Oscillator |
| C. | Power supply |
| D. | All of the above |
| Answer» C. Power supply | |
| 690. |
In radar system which of the following is called A scope |
| A. | deflection modulation of CRT |
| B. | intensity modulation of CRT |
| C. | computer display |
| D. | none of the above |
| Answer» B. intensity modulation of CRT | |
| 691. |
In AM receiver the oscillator frequency is |
| A. | always equal to signal frequency |
| B. | always equal to 455 kHz |
| C. | always higher than signal frequency |
| D. | always lower than signal frequency |
| Answer» D. always lower than signal frequency | |
| 692. |
If fh(t) is Hilbert transform of f(t), then Hilbert transform of fh(t) is |
| A. | #NAME? |
| B. | #NAME? |
| C. | f2(t) |
| D. | f(t) |
| Answer» B. #NAME? | |
| 693. |
In a communication receiver, a squelch circuit is normally inserted |
| A. | before detector |
| B. | after detector |
| C. | before mixer |
| D. | after power amplifier |
| Answer» C. before mixer | |
| 694. |
For a low level AM system, the amplifiers modulated stage must be |
| A. | linear devices |
| B. | harmonic devices |
| C. | class C amplifiers |
| D. | non-linear devices |
| Answer» B. harmonic devices | |
| 695. |
Telecine equipment in a TV studio consists of |
| A. | projector telecine |
| B. | flying spot telecine |
| C. | digital CCD telecine |
| D. | none of the above |
| Answer» E. | |
| 696. |
Full duplex operation-permits transmission in both directions at the same time. |
| A. | 1 |
| B. | |
| Answer» B. | |
| 697. |
The filter circuit for feeding tweeter has |
| A. | an inductance in series and a capacitance in parallel |
| B. | a capacitance in series and an inductance in parallel |
| C. | a resistance in series and a capacitance in parallel |
| D. | a capacitance in series and a resistance in parallel |
| Answer» C. a resistance in series and a capacitance in parallel | |
| 698. |
Line of sight transmission is used in |
| A. | radio frequencies below 1 MHz |
| B. | VHF only |
| C. | audio signals only |
| D. | VHF and UHF |
| Answer» E. | |
| 699. |
SSB stands for |
| A. | Single Side Band |
| B. | Suppressed Side Band |
| C. | Single Sound Band |
| D. | Single Sky Band |
| Answer» B. Suppressed Side Band | |
| 700. |
A 1 MHz sinusoidal carrier is amplitude modulated by a symmetrical square wave of period 100 μ sec. Which of the following frequencies will not be in the modulated signal? |
| A. | 990 kHz |
| B. | 1010 kHz |
| C. | 1020 kHz |
| D. | 1030 kHz |
| Answer» D. 1030 kHz | |