1. 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-Hartley theorem
d. Shannon theorem
2. Noise always affects the signal in a communications system at the ______
a. Transmitter
b. Channel
c. Information source
d. Destination
3. _____ is the random and unpredictable electric signals from natural causes, both internal and
external to the system.
a. Interference
b. Attenuation
c. Distortion
d. Noise
4. Noise from random acoustic or electric noise that has equal energy per cycle over a specified
total frequency band.
a. Gaussian noise
b. White nose
c. Thermal noise
d. All of the above
5. What is the reference noise temperature in degrees Celsius?
a. 17
b. 273
c. 25
d. 30
6. Man-made noise is usually from _____.
a. Transmission over power lines and by ground wave
b. Sky-wave
c. Space-wave
d. Troposphere
7. NIF Stands for
a. Non-intrinsic figure
b. Noise improvement factor
c. Narrow intermediate frequency
d. Noise interference figure
8. Industrial noise frequency is between ____.
a. 0 to 10kHz
b. 160 MHz to 200 MHz
c. 15 to 160MHz
d. 200 to 3000 MHz
9. External noise fields are measured in terms of ____.
a. RMS values
b. DC values
c. Average values
d. Peak values
10. ____is an electric noise produced by thermal agitation of electrons in conductor and
semiconductor
a. External noise
b. Internal noise
c. Thermal noise
d. Flicker
11. Three identical circuits having 10 dB signal noise-to-noise ratio each are connected in tandem
with each other, what is the overall S/N?
a. 5.23 dB
b. 14.77 dB
c. 30 dB
d. 40 dB
12. What is the reference noise level?
a. 10 pW
b. 0 dBm
c. 1 mW
d. - 90 dBm
13. A large emission of hydrogen from the sun that affects communications.
a. Solar flare
b. Cosmic disturbance
c. Ballistic disturbance
d. Solar noise
14. Atmospheric noise is known as noise.
a. Static
b. Cosmic
c. Solar
d. Lunar
15. Absolute temperature in Kelvin.
a. °C + 273
b. °C + 75
c. °C + 19
d. °C + 290
16. If bandwidth is doubled, the signal power is___
a. Not changed
b. Quadrupled
c. Tripled
d. Doubled
17. Name one or more sources of noise bearing on electronic communications.
a. Steam boiler
b. Galaxies
c. Internal combustion engine
d. Both B and C
18. Interfering effect of noise, C message anti-noise weighted, is
a. dBa
b. dBm
c. dBrnc
d. dB
19. Reference noise Is
a. a 1000 Hz, -90 dBm tone
b. a noise that creates the same interfering effect as a 1000 Hz, -90 dBm tone
c. a noise than creates zero dBrn in a voice channel
d. B and C above
20. Indicate the noise whose sources are in category different from that of the other three?
a. Solar noise
b. Cosmic noise
c. Atmospheric noise
d. Galactic noise
21. Indicate the false statement.
a. Industrial noise is usually of the impulse type
b. Static is caused by lightning discharges in thunderstorms and other natural electric
disturbances occurring in the atmosphere
c. Distant stars are another source of man-made noise
d. Fluorescent lights are another source of man-made noise
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. One of the following is not a useful quantity for comparing the noise performance of receivers.
a. Input noise voltage
b. Equivalent noise resistance
c. Noise temperature
d. Noise figure
24. Most internal noise comes from
a. Shot noise
b. Transit-time noise
c. Thermal agitation
d. Skin effect
25. Which of the following is not a source of external noise?
a. Thermal agitation
b. Auto ignition
c. The sun
d. Fluorescent lights
26. Noise can be reduced by
a. Widening the bandwidth
b. Narrowing the bandwidth
c. Increasing temperature
d. Increasing transistor current levels
27. Noise at the input to a receiver can be as high as several
a. Microvolts
b. Millivolts
c. Volts
d. Kilovolts
28. Which circuit contributes most of the noise in a receiver?
a. IF amplifier
b. Demodulator
c. AF amplifier
d. Mixer
29. Which noise figure represents the lowest noise?
a. 1.6 dB
b. 2.1 dB
c. 2.7 dB
d. 3.4 dB
30. The transistor with the lowest noise figure in the microwave region is a
a. MOSFET
b. Dual-gate MOSFET
c. JFET
d. MESFET
31. Which of the following types of noise becomes of great importance at high frequencies?
a. Shot noise
b. Random noise
c. Impulse noise
d. Transit-time noise
32. The solar cycle repeats the period of great electrical disturbance approximately every
a. 11 years
b. 10 years
c. 9 years
d. 8 years
33. The square of the thermal noise voltage generated by a resistor is proportional
a. Its resistance
b. Its temperature
c. The bandwidth over which it is measured
d. All of the above
34. Noise occurring in the presence of signal resulting from a mismatch between the exact value of
an analog signal and the closest available quantizing step in a digital coder.
a. Quantizing noise
b. Thermal noise
c. Impulse noise
d. Crosstalk
35. Noise that occurs via capacitive or inductive coupling in a cable.
a. Crosstalk
b. Quantizing noise
c. Reference noise
d. Tone interference
36. External noise originating outside the solar system
a. Cosmic noise
b. Solar noise
c. Thermal noise
d. Lunar noise
37. A noise whose source is within the solar system
a. Solar noise
b. Thermal noise
c. Cosmic noise
d. Johnson noise
38. The total noise power present in a 1-Hz bandwidth
a. Noise density
b. Noise figure
c. Noise limit
d. Noise intensity
39. Which of the following is not a way of minimizing if not eliminating noise?
a. Use redundancy
b. Increase transmitted power
c. Reduce signaling rate
d. Increase channel bandwidth
40. What is the primary cause of atmospheric noise?
a. Thunderstorm
b. Lightning
c. Thunderstorm and lightning
d. Weather condition
41. What do you call the noise coming from the sun and stars?
a. Black-body noise
b. Space noise
c. Galactic noise
d. All of these
42. The major cause of atmospheric or static noise are
a. Thunderstorms
b. Airplanes
c. Meteor showers
d. All of these
43. Which of the following low noise transistors is commonly used at microwave frequencies?
a. MOSFET
b. GASFET
c. MESFET
d. JFET
44. Crosstalk due to incomplete suppression of sidebands or to intermodulation of two or more
frequency-multiplexed channels which is unintelligible is classified as
a. Impulse noise
b. Thermal noise
c. Quantizing noise
d. Miscellaneous noise
45. An amplifier operating over the frequency range of 455 to 460 kHz has a 200 kg input resistor.
What is the RMS noise voltage at the input to this amplifier if the ambient temperature is 17°С?
a. 40μV
b. 4.0 μV
c. 400 μV
d. 4.0 mV
46. The front-end of a television receiver, having a bandwidth of 7 MHz, and operating at a
temperature of 27°C, consists of an amplifier having a gain of 15, followed by a mixer whose gain
is 20. The amplifier has a 300Ω input resistor and a shot noise equivalent resistance of 500Ω ; for
the mixer, these values are 2.2 kΩ and 13.5 kΩ, respectively, and the load resistance of the mixer
is 470 kΩ. Calculate the equivalent noise resistance for this television receiver.
a. 8760 Ω
b. 875 Ω
c. 8.76 Ω
d. 0.876 Ω
47. Calculate the noise figure of the amplifier whose Req equals 2518Ω (R+= 600Ω ) if it's driven by a
generator whose output impedance is 50Ω.
a. 39.4
b. 3.94
c. 394
d. 0.394
48. Calculate the noise figure of the receiver whose RF amplifier has an input resistance of 1000Ω
and an equivalent shot-noise resistance of 2000 Ω, a gain of 25 and a toad resistance of 125 kΩ.
Given that the bandwidth is 1.0 MHz and the temperature is 20°C, and that the receiver is
connected to an antenna with an impedance of 75Ω
a. 30.3
b. 3.03
c. 303
d. 0.303
49. A receiver connected to an antenna whose resistance is 50 Ω has an equivalent noise resistance
of 30Ω. Calculate its equivalent noise temperature if the noise figure is equal to 1.6.
a. 17.4 K
b. 174 K
c. 1.74 K
d. 17 K
50. What is the noise voltage across 300 input resistance to a TV set with a 6 MHz bandwidth and
temperature of 30°C?
a. 2.3μV
b. 3.8 μV
c. 5.5 μV
d. 6.4 μV