ECE Noise Q&A

1. What is a non-continuous noise of irregular pulses or spikes of short duration with high amplitudes?
A. Wander
(B) Jitter
C. Hits
D. Singing
2. What theorem sets a limit on the maximum capacity of a channel with a given noise level?
A. Nyquist theorem
B. Hartley law
(C) Shannon-Hartly theorem
D. Shannon theorem
3. Quanting noise occurs in
(A) PCM
B. PLM
C. PDM
D) PAM
4. Noise always affect the signal in a communication system at the ______.
A. transmitter
(B) channel
C. information
D. destination
5. A particular circuit that rids FM of noise.
A. Detector
B. Discriminator
C. Phase shifter
(D) Limiter
6. Unwanted radio signal on assigned frequency.
A. Spatter
B. RFI
(C) Noise
D. EMI
7. Which standard recommends crosstalk limits?
A. CCITT G. 152
B. CCITT G. 150
(C) CCITT G. 151
D. CCITT G. 161
8. What is the reference frequency of CCITT phosphometric noise measurement?
(A) 800 Hz
B. 1000 Hz
C. 1500 Hz
D. 3400 Hz
9. Reference temperature used in noise analysis.
A. 75 K
B. 250 K
(C) 290 K
D. 300 K
10. Man-made noise is usually from ______.
(A) Transmission over power lines and by ground wave
B. sky-wave
C. space-wave
D. troposphere
11. External noise fields are measured in term of _____.
A. rms values
B. dc values
C. average values
(D) peak values
12. Form of interference caused by rain or dust storms.
(A) Precipitation static
B. Shot-noise
C. Gallactic noise
D. Impulse noise
13. Is the interference coming from other communication channels.
A. Jiller
(B) Crosstalk
C. RFI
D. EMI
14. What is the unit of noise power of psophometer?
(A) pWp
B. dBa
C. dBm
D. dBrn
15. Atmospheric noise is known as ____ noise.
(A) static
B. cosmic
C. solar
D. lunar
16. If bandwidth is doubled, the signal power is _____.
(A) not changed
B. quadrupled
C. tripled
D. doubled
17. The difference between signal strength at a given point and a reference level is _____.
A. power
B. dBm
(C) level
D. ratio
18. F1A weighting refers to _____.
A. -90 dBm
B. dBrnc0
C. dBrnc
(D) F1A handset
19. Reading a 58 dBrn, at a+7 test point is equal to _____ dBa0.
A. 26
B. 65
C. 51
(D) 46
20. What is the reference tone level for dBrn?
(A) -90 dBm
B. -82 dBm
C. -67 dBm
D. -85 dBm
21. Atmospheric noise becomes less severe at frequencies
(A) above 30 MHz
B. below 30 MHz
C. Above 3000 kHz
D. below 3000 kHz
22. Which of the following is not a source of industrial noise?
A. Automobile ignition
(B) Sun
C. Electric motors
D. Leakage from high voltage line
23. The value of the resistor creating thermal noise is doubled. The noise power generated is therefore
A. halved
B. quadrupled
C. doubled
(D) unchanged
24. Which of the following is not a source of external noise?
(A) Thermal agitation
B. Auto ignition
C. The sun
D. Fluorescent light
25. Noise at the input to a receiver can be as high as several
(A) microvolts
B. millivolts
C. volts
D. kilovolts
26. Which noise figure represents the lowest noise?
(A) 1.6 dB
B. 2.1 dB
C. 2.7 dB
D. 3.4 dB
27. The transiror with the lowest noise figure in the microwave region is a
A. MOSFET
B. Dual-gate MOSFET
C. JFET
(D) MESFET
28. The solar cycle repeats the period of great electrical disturbance approximately every
(A) 11 years
B. 10 years
C. 9 years
D. 8 years
29. Noise consisting of irregular pulses of short duration and relatively high amplitude.
A. Quantizing noise
B. Tone interference
(C) Impulse noise
D. Crosstalk
30. Noise that occurs via capacitive or inductive coupling in a cable
(A) Crosstalk
B. Quantizing noise
C. Reference noise
D. Tone interference

ECE Modulation Q&A

1.____ is the maximum sideband suppression value using filter system?
(A) 50 dB
B.60 dB
C. 40 dB
D. 30 dB
2. ___ determine the number of sideband components in FM
A. Carrier frequency
B. Modulation frequency
(C) Modulation index
D. Deviation ratio
3. One of the following transmits only one sideband
(A) H3E
B. R3E
C.A3E
D. B8E
4. What produces the sidebands on FM?
A. Signal amplitude
B. Carrier harmonics
(C) Baseband frequency
D. Broadband frequency
5. Which test instrument displays the carrier and the sidebands amplitude with frequency to frequency?
A. Oscilloscope
(B) Spectrum analyzer
C. Frequency analyzer
D. Amplitude
6 Mixer is also known as a _____.
A. modulator
B. suppressor
(C) converter
D) beater
7. Which one of the following emission transmit the lower sideband and half of the upper sideband.
A. A5C
B. J3E
C. A3J
(D) A3H
8. An FM receiver signal _____.
A. vary in amplitude with modulation
(B) vary in frequency with modulation
C. vary in frequency and amplitude with wideband modulation
D. is not immune to noise
9. The process of impressing intelligence on the carrier is called
(A) modulation
B. defection
C. mixing
D. impression
10. ____ is an electronic instrument used to show both the carrier and the sidebands of a modulated signal in the frequency domain.
(A) Spectrum analyzer
B. Oscilloscope
C. Digital counter
D. Frequency counter
11. What part of the carrier is varied by the intelligence during modulation in an AM system?
A. Phase
B. Frequency
(C) Amplitude
D) Phase and amplitude
12. The difference between the RF carrier and the modulating signal frequencies is called the
A. USB
(B) LSB
C. Sideband
D. Carrier frequency
13. What stage in a radio transmitter isolates the oscillator from the load?
A. Oscillator
(B) Buffer
C. Separator
D. Mixer
14. The frequency of the unmodulated carrier in FM system is
A. modulating frequency
(B) center frequency
C. carrier frequency
D. deviation frequency
15. The radio of maximum deviation modulating frequency is called
A. carrier swing
(B) deviation ratio
C. modulation factor
D. modulation index
16. A carrier signal has
A. constant amplitude
(B) a frequency of 20 kHz and above
C. a varying amplitude
D. the information content
17. Which of the following is considered as an indirect method of generating FM?
A. Reactance modulator
B. Balance modulator
C. Varactor diode modulator
(D) Armstrong system
18. To generate an SSB or DSB signal one must use a circuit known as
A. Filter modulator
B. ring modulator
(C) balanced modulator
D. reactance modulator
19. Which is the first radio receiver?
A. TRF receiver
B. Superheterodyne receiver
(C) Crystal radio receiver
D. Heterodyne receiver
20. Single sideband reduced carrier emission type.
A. H3E
(B) R3E
C. J3E
D. B8E
21. Independent sideband emission type.
A. H3E
B. R3E
C. J3E
(D) B3E
22. Which one is not an advantage of SSB over AM?
A. Power saving
B. Requires haft the bandwidth
C. Wider area of reception
D. Better fidelity
23. The advantage of a low-modulated AM transmitter is
(A) less audio power required
B. better fidelity
C. higher value of operating power
D. less distortion
24. ____ is the bad effect caused by overmodulation in AM transmission
A. Increase in noise
B. Deviation in the operating frequency
(C) Interference to other radio services
D. Decrease in the output power
25. Which characteristic of a radio receiver refers to its ability to reject an unwanted signal signal?
A. Sensitivity
(B) Selectivity
C. Fidelity
D. Quality
26. AM transmission power increase with _____.
A. frequency
B. source
C. load
(D) Modulation
27. The modulation system inherently more resistant to noise
A. Single sideband suppressed carrier
(B) Frequency modulation
C. Pulse-position modulation
D. Amplitude shift keying
28. Subcarriers that are arranged so that the channels occupying adjacent frequency bands with some frequency space between them is known as
(A) guard bands
B AM bands
C. band gap
D. void band
29.Modulation of an RF carrier results in
A. multiple channels
B. smaller antennas
C. directional propagation
(D) all of the above
30. A process which occurs in the transmitter
A. Mixing
(B) Modulation
C. Heterodyning
D. Demodulation

ECE Acoustics Q&A

1. When waves bend away from straight lines of travel, it is called _______.
A. reflection
B. defraction
C. rarefraction
(D) refraction
2. Required time for any sound to decay to 60 dB.
A. Echo time
B. Delay time
(C) Reverberation time
D. Transient time
3. The intensity needed to produce an audible sound varies with _________.
(A) frequency
B. noise
C. amplitude
D. tone
4. Sound that vibrates at frequency too high for the human ear to hear (over 20 kHz).
A. Subsonic
B. Transonic
(C) Ultrasonic
D. Stereo
5. The thin springy sheet or bakelite or metal that permits the voice coil in a dynamic
loudspeaker to move back and forth along the core of its magnet.
A. Vibrator
B. Diaphragm
C. Hypex
(D) Spider
6. What is the dB SPL of an auditorium with contemporary music?
A. 90
(B) 85 – 90
C. 95 – 100
D. 100 – 105
7. Intensity can also be called as
A. volume
(B) loudness
C. sharpness
D. strength
8. The loudness of a sound depends upon the energy of motion imparted to
__molecules of the medium transmitting the sound.
A. transmitting
B. running
C. moving
(D) vibrating
9.__________is affected by the distance between the listener and the source of
the sound and its intensity varies inversely with the square of this distance.
A. volume
B. bass
C. treble
(D) loudness
10. If the distance between the listener and the source of the sound is doubled, the
intensity is reduced to
A. ½
B. 1/3
C. 2/3
(D) ¼
11. An instrument designed to measure a frequency-weighted value of the sound
pressure level.
(A) Sound level meter.
B. Transducer
C. Sound pressure meter
12. A unit of noisiness related to the perceived noise level
(A) Noy
B. Sone
C. dB
D. Phon
13. An agreed set of empirical curves relating octave-band sound pressure level to
the center frequency of the octave bands.
A. C-message weighting curve
B. Psophometric curve
(C) Noise rating curves
D. F1A weighting curve
14. The frequency of a free vibration.
A. Resonant frequency
(B) Natural frequency
C. Center frequency
D. Normal frequency
15. The transmission of sound from one room to an adjacent room, via common
walls, floors or ceilings.
(A) Flanking transmission
B. Refraction
C. Reflection
D. Reverberation
16. The measure of threshold of hearing, expressed in decibels relative to a specified
standard of normal hearing.
A. Hearing loss
B. Sensation level
(C) Hearing level
D. Sound pressure level
17. Velocity of sound in air.
A. 300 m/s
(B) 330 m/s
C. 1130 m/s
D. 344 m/s
18. Speaker is a device that
A. converts sound waves into current and voltage
(B) converts current variation into sound waves
C. converts electrical energy to mechanical energy
D. converts electrical energy into electromagnetic energy
19. Which type of microphone operates on the principle that the electrical
resistance of carbon granules varies as the pressure on the granules vary?
A. Dynamic
B. Crystal
(C) Carbon
D. Ribbon-type
20. Bass response is
A. maximum high frequency response
B. emphasizing the high audio frequencies
(C) bypassing high audio frequencies
D. bypassing low audio frequencies
21. Pure tone of sound used as standard on testing.
A. 1 Hz
B. 10 Hz
C. 100 Hz
(D) 1000 Hz
22. _______ is early reflection of sound.
(A) Echo
B. Reverberation
C. Pure sound
D. Intelligible sound
23. Noise reduction system used for him sound in movie.
(A) dolby
B. dBa
C. dBx
D. dBk
24. What is the sound energy per unit area at right angles to the propagation
direction per unit time?
A. Loudness
B. Coherence
C. Sound pressure
(D) Sound intensity
25. _________ is the unit of loudness level of a sound.
A. Sone
B. Decibel
C. Mel
(D) Phon
26. _________ is the average rate of transmission of sound energy in a given
Direction through a cross-section area of 1 sq. m. at right angles to the direction.
A. Sound pressure
B. Loudness
(C) Sound intensity
D. Pressure variation
27. What is the unit of pitch?
A. Sone
B. Phon
C. Decibel
(D) Mel
28. A measure of the intensity of sound in comparison to another sound intensity.
A. Phon
(B) Decibel
C. Pascal
D. Watts
29. Sound wave has two main characteristics which are
A. highness and loudness
B. tone and loudness
(C) pitch and loudness
D. rarefraction and compression
30. Which type of microphone operated by electromagnetic induction that
generates an output signal voltage?
A. Carbon
(B) Dynamic
C. Crystal
D. Condenser

ECE Transmission Fundamentals Q&A

1. What is the opposition to the transfer of energy which is consider the dominant
Characteristics of a cable or circuit that emanates from its physical structure?
A. Conductance
B. Resistance
C. Reactance
(D) Impedance
2. When load impedance equal to Zo of the line, it means that the load
____ all the power.
A. reflects
(B) absorbs
C. attenuates
D. radiates
3. Impedance matching radio of a coax balun.
A. 1:4
(B) 4:1
C. 2:1
D. 3:2
4. Which stands for dB relative level?
A. dBm
B. dBa
(C) dBr
D. dBx
5. Standard test tone used for audio measurement.
A. 800 Hz
B. 300 Hz
C. 100 Hz
(D) 1000 Hz
6. When VSWR is equal to zero, this means
(A) that no power is applied
B. that the load is purely resistive
C. that the load is a pure reactance
D. that the load is opened
7. Transmission line must be matched to the load to ____.
A. transfer maximum voltage to the load
(B) transfer maximum power to the load
C. reduce the load current
D. transfer maximum current to the load
8. Which indicate the relative energy loss in a capacitor?
A. Quality factor
B. Reactive factor
(C) Dissipation factor
D. Power factor
9. What is the standard test tone?
A. 0 dB
B. 0 dBW
(C) 0 dBm
D. 0 dBrn
10 The energy that neither radiated into space nor completely transmitted
A. Reflected waves
B. Captured waves
C. Incident waves
(D) Standing waves
11. Why is it impossible to use a waveguide at low radio frequencies?
(A) Because of the size of the waveguide
B. Due to severe attenuation
C. Due to too much radiation
D. All of these
12. ____ is the transmission and reception of information
A. Modulation
(B) Communications
C. Radiation
D. Emission
13. What is the loss of the circuit in dB if the power ratio of output is 0.01?
(A) 20
B. -20
C. 40
D. -40
14. Transmission lines are either balanced or unbalanced with respect to
A. negative terminal
B. reference
(C) ground
D. positive terminal
15. The standing wave ratio is equal to ___ if the load is properly matched
With the transmission line.
A. infinity
B. 0
C. -1
(D) 1
16. ___ is the advantage of the balanced transmission line compared to unbalance line.
(A) Low attenuation
B. Easy installation
C Low radiaton loss
D. Tensile strength
17 ____ is the method of determining the bandwidth of any processing system.
A. Fourier series
(B) Spectral analysis
C. Frequency analysis
D. Bandwidth analysis
18. What causes the attenuation present in a waveguide?
A. The air dielectric filling the guide
B. The coating of silver inside
(C) Losses in the conducting wall of the guide
D. Radiation loss
19. What device that converts a balanced line to an unbalanced line of a transmission line
A. Hybrid
B. Stub
C. Directional coupler
(D) Balun
20. What is the average power rating of RG-58 C/u?
A. 25 W
(B) 50 W
C. 75 W
D. 200 W
21. The velocity factor of the transmission line
(A) depends on the dielectric constant of the material used
B. increases the velocity along the transmission line
C. is governed by the skin effect
D. is higher for a solid dielectric than for air
22. One of the following is not a bounded media.
A. Coaxial line
B. Two-wire line
C. Waveguide
(D) Ocean
23. The impedance measured at the input of the transmission line when its length is
Infinite.
A. Input impedance
B. Open circuit impedance
(C) Characteristic impedance
D. Short circuit impedance
24. The following are considered primary line constant except
A. conductance
B. resistance
C. capacitance
(D) complex propagation constant
25. The dielectric constants of materials commonly used in transmission line
Range from about
(A) 1.2 to 2.8
B. 2.8 to 3.5
C. 3.5 to 5.2
D. 1.0 to 1.2
26. The concept used to make one Smith chart universal is called
A. ionization
(B) normalization
C. rationalization
D. termination
27. What are the basic elements of communication system?
A). Source, transmission channel, transmitter
(B) Transmitter, receiver, transmission, channel
C. Information, transmission channel receiver
D. Sender and receiver
28. ____ is the transmission of printed material over telephone lines.
A) Internet
B) Data communication
C) Telegraphy
(D) Facsimile
29. ____ is a continuous tone generated by the combination of two frequencies of 350 Hz
And 440 Hz used in telephone sets.
A) DC tone
B) Ringing tone
C) Dial tone
(D) Call waiting tone
30. If the SWR is infinite, what type of load transmission line has?
(A) Purely reactive
B. Purely resistive
C. Purely capacitive
D. Purely inductive