NOISE1. What is the non-continuous noise of irregular pulses or spikes of 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-Hartley theorem D. Shannon theorem

3. Quantizing noise occurs inA. PCM B. PLM C. PDM D. PAM

4. Noise always affects the signal in a communications systems at the ________.A. transmitter B. channel C. information source D. destination

5. _________ 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

6. Noise from random acoustic or electric noise that has equal energy per cycle over a specified total frequency band.A. Gaussian noise B. Whiter noise C. Thermal noise D. All of the above

7. Which causes a quantization noise in PCM system?A. Serial transmission errors B. The approximation of the quantized signal C. The synchronization between encoder and decoder D. Binary coding techniques

8. A particular circuit that rids FM of noiseA. Detector B. Discriminator C. Phase Shifter D. Limiter

9. What is the reference noise temperature in degrees Celsius?A. 17 B. 273 C. 25 D. 30

10. Unwanted radio signal on assigned frequency.A. Splatter B. RFI C. Noise D. EMI

11. What is the reliable measurement for comparing amplifier noise characteristics?A. Thermal agitation noise B. Noise factor C. Noise margin D. Signal-to-noise

12. _________ is measured on a circuit when it is correctly terminated but does not have any traffic.A. White noise B. Galactic noise C. Impulse noise D. Atmospheric noise

13. Which standard recommends crosstalk limits?A. CCIT G.152 B. CCIT G.150 C. CCIT G.151 D. CCIT G.161

14. Which standard is utilized in intermodulation noise rates on PCM audio channels?A. CCIT Rec. G.151 B. CCIT Rec. G.172 C. CCIT Rec. G.190 D. CCIT Rec. G.190

15. What is the reference frequency of CCIT phosphomeric noise measurement?A. 800 Hz B. 1000 Hz C. 1500 Hz D. 3400 Hz

16. Reference temperature use in noise analysisA. 75 K B. 250 K C. 290 K D. 300 K

17. Which noise is produced by lighting discharges in thunderstorms?A. White noise B. Extraterrestrial noise C. Industrial noise D. Atmospheric noise

18. Man-made noise is usually from _______.A. transmission over power lines and by ground wave B. sky-wave C. space-wave D. troposphere

19. nif stands forA. Non-intrinsic figure B. Noise improvement factor C. Narrow intermediate frequency D. Noise interference figure

20. Industrial noise frequency is between _____.A. 0 to 10 KHz B. 160 MHz to 200 MHz C. 15 to 160 MHz D. 200 to 3000 MHz

21. External noise fields are measured in terms of _______.A. rms values B. dc values C. average values D. peak values

22. Form of interference caused by rain or dust storms.A. Precipitation static B. Shot-noise C. Galactic noise D. Impulse noise

23. At 17 C, the noise voltage generated by 5k resistor, operating over a bandwidth of 20KHz isA. 1.3 nV B. 1.3 V C. 1.3 pV D. 1.3 mV

24. ________ 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

25. 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. 14.77dB C. 30 dB D. 40 dB

26. The noise figure of the first circuit in tandem connection is 10.5 dB while its power gain is 15, what is the over all noise figure if the second circuit has a noise figure of 11 dB?A. 11.59 dB B. 11.23 dB C. 10.79 dB D. 10.5 dB

27. Is the interference coming from other communications channels?A. Jitter B. Crosstalk C. RFI D. EMI

28. What is the reference noise level?A. 10 pW B. 0 dBm C. 1mW D. -90 dBm

29. What is the unit of noise power of psophometer?A. pWp B. dBa C. dBm D. dBrn

30. A large emission of hydrogen from the sun that affects communications.A. Solar flare B. Cosmic disturbance C. Ballistic disturbance D. Solar noise

31. Atmospheric noise is known as _______noise.A. static B. cosmic C. solar D. lunar

32. Standard design reference for environmental noise temperature.A. 300 K B. 290 K C. 32 F D. 212F

33. Absolute temperature in Kelvin.A. C + 273 B. C + 75 C. C + 19 D. C + 290

34. If bandwidth is doubled, the signal power is _________.A. not changed B. quadrupled C. tripled D. doubled

35. 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

36. The transmitter technique adopted to reduce the noise effect of the preceding question is calledA. noise masking B. anitnoise C. noise killing D. preemphasis

37. Deemphasis in the receiver in effect attenuates modulating signal components and noise in what frequency range?A. dc B. low C. intermediate D. high

38. Atmospheric noise or static is not a great problemA. at frequencies below 20 MHz B. at frequencies below 5 MHz C. at frequencies above 30 MHz D. at frequencies above 1 MHz

39. What is the proper procedure for suppressing electrical noise in a mobile station?A. Apply shielding and filtering where necessary B. Insulate a all plain sheet metal surfaces from each other C. Apply anti-static spray liberally to all nonmetallic D. Install filter capacitors in series with all dc wiring

40. Where is the noise generated that primarily determines the signal-to-noise ratio in a VHF (150MHz) marine-band receiver?A. Man-made noise B. In the atmosphere C. In the receiver front end D. In the ionosphere

41. The difference between signal strength at a given point and a reference level is________.A. power B. dBm C. level D. ratio

42. Interfering effect of noise, C message weighted, is _________.A. dBa B. dBm C. dBmc D. dB

43. F1A weighting refers to ___________.A. -90 dBm B. dBrnc0 C. dBrnc D. F1A handset

44. Reading a 58 dBrnC on your Western Electric 3A test set at a +7 test point is equal to ______ dBrnc0.A. 58 B. 51 C. 65 D. 27

45. Reading a 58 dBrn, at a +7 test point is equal to ________ dBa0.A. 26 B. 65 C. 51 D. 46

46. A reading of -50 dBm on the disturbing pair, and -80 on the disturbed pair equals _____ dB of crosstalk coupling.A. 20 B. 30 C. 60 D. 25

47. Power is __________.A. actual amount of power reference to 1mW B. logarithmic ratio of two powers C. definite amount of energy per time period D. current flow per time period

48. 15 dBa F1A weighted, equals ___________.A. -90 dBm B. -82 dBm C. -85 dBm D. -70 dBm

49. You are measuring noise in a voice channel with a Lenkurt 601A, F1A weighting network and a flat meter. Your meter reads -47dBm. What is this reading in dBa?A. 77 dBa B. 35 dBa C. 38 dBa D. 32 dBa

50. You are measuring noise at a +3 dB level point, using the Lenkurt 601A, F1A weighting network, and a flat meter. The meter reading is -57dBm. This is ________dBa0.A. 20 B. 15 C. 25 D. 1751. You are measuring noise at a -6 dB level point, using the Lenkurt 601A, F1A weighting network, and a flat meter. The meter reading is -59 dBm. This is _________ dBa0.A. 24 B. 12 C. 23 D. 32

52. A measurement of -75 dBm, C-message weighted, would be _________ dBrnc.A. 8 B. 7 C. 9 D. 15

53. Your Western Electric 3A test set meter reading is -23 dBm at at test point level of -8 dB. This is ______ dBrnc0.A. 75 B. 29 C. 30 D. 31

54. At what power level does a 1 KHz tone cause zero interference (144 weighted)?A. 90 dB B. 90 dBm C. -90 dBm D. -90 dBm

55. Reference noise is ___________.A. a 1000 Hz, -90 dBm tone B. a noise that creates the same interfering effect as a 1000Hz, -90dBm tone C. a noise that creates zero dBrn in a voice channel D. B and C above

56. A practical dBrn measurement will almost always in a _______ number.A. positive B. negative C. imaginary D. fractional

57. What is the reference level for noise measurement, F1A weighted?A. -90 dBm B. -82 dBm C. -67 dBm D. -85 dBm

58. What is the reference tone level for dBrn?A. -90 dBm B. -82 dBm C. -67 dBm D. -85 dBm

59. What is the reference tone level for dBa?A. -90 dBm B. -82 dBm C. -67 dBm D. -85 dBm

60. Atmospheric noise becomes less severe at frequenciesA. above 30 MHz B. below 30 MHz C. above 3000 kHz D. below 3000kHz

61. 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

62. 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. Flourescent lights are another source of man-made noise

63. 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

64. Indicate the false statementA. The noise generated in a resistance or the resistive component of any impedance is random. B. Random noise power is proportional to the bandwidth over which is measured C. A random voltage across the resistor does not exist D. All formula referring to random noise are applicable only to the value of such noise.

65. The value of the resistor creating thermal noise is doubled. The noise power generated is therefore.A. halved B. quadrupled C. doubled D. unchanged

66. Indicate the false statement.A. HF mixer are generally noisier than HF amplifiers. B. Impulse noise voltage is dependent on bandwidth C. Thermal noise is independent of the frequency at which is measured. D. Industrial noise is usually of the impulse type.

67. An amplifier operating over the frequency range of 455 to 460 kHz has a 200 k input resistor. What is the RMS noise voltage at the input to this amplifier if the ambient temperature is 17C ?A. 40 V B. 4.0 V C. 400 V D. 4.0 mV

68. The first stage of a two-stage amplifier has a voltage gain of 10, a 600 input resistor, a 1600 equivalent noise resistance and 27k output resistor. For the second stage, these values are 25, 81k, 19k, and 1M, respectively. Calculate the equivalent input-noise resistance of this two stage amplifier.A. 2,518 k B. 2,518 C. 251.8 D. 12,518

69. The noise output of a resistor is amplified by a noiseless amplifier having a gain of 60 and a bandwidth of 20 kHz. A meter connected at the output of the amplifier reads 1mV RMS. If the bandwidth of the amplifier is reduced to 5kHz, its gain remaining constant, what does the meter read now?A. 0.5 mV B. 0.5 V C. 5.0 mV D. 5.0 V

70. The front-end of a television receiver, having a bandwidth of 7Mhz, and operating at a temperature of 27C , consists of an amplifier having a gain of 15 followed by a mixer whose gain is 20. The amplifier has a 300 input resistor and a shot noise equivalent resistance of 500; for the mixer, these values are 2.2k and 13.5k respectively, and the load resistance of the mixer is 470 k. Calculate the equivalent noise resistance for this television receiver.A. 8760 B. 875 C. 8.76 D. 0.876

71. One of the following is not a useful quantity for comparing the noise performance receivers.A. Input noise voltage B. Equivalent noise resistance C. Noise temperature D. Noise figure.

72. Indicate the false statement. Noise figure is defined asA. the ratio of the S/N power supplied at the input terminal of a receiver or amplifier to the S/N power supplied to the output or load resistor B. noise factor expressed in decibels C. an unwanted form of energy tending to interfere with the proper and easy reception and reproduction of wanted signals D. S/N of an ideal system divided by S/N at the output of the receiver or amplifier under test, both working at the same temperature over the same bandwidth and fed from the same source

73. Calculated the noise figure of the amplifier whose Req equals 2518 (RT=600) if its driven by a generator whose output impedance is 50.A. 39.4 B. 3.94 C. 394 D. 0.394

74. Calculate the noise figure of the receiver whose RF amplifier has an input resistance of 1000 and an equivalent shot-noise resistance of 2000, a gain of 25 and load resistance of 125 k. Given that the bandwidth is 1.0MHz and the temperature is 20C, and that the receiver is connected to an antenna with an impedance of 75.A. 30.3 B. 3.03 C. 303 D. .303

75. A receiver connected to an antenna whose resistance is 50 has an equivalent noise resistance of 30. 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

76. Most internal noise comes fromA. Shot noise B. Transit-time noise C. Thermal agitation D. Skin effect

77. Which of the following is not a source of external noise?A. Thermal agitation B. Auto ignition C. The sun D. Fluorescent lights

78. Noise can be reduced byA. widening the bandwidth B. narrowing the bandwidth C. increasing temperature D. increasing transistor current levels

79. Noise at the input to the receiver can be as high as severalA. microvolts B. milivolts C. volts D. kilo volts

80. Which circuit contributes most of the noise in a receiver?A. IF amplifier B. Demodulator C. AF amplifier D. Mixer

81. Which noise figure represents the lowest noise in receiver?A. 1.6 dB B. 2.1 dB C. 2.7 dB D. 3.4 dB

82. The transistor with the lowest noise figure in the microwave region is aA. MOSFET B. Dual-gate MOSFET C. JFET D. MESFET

83. What is the noise voltage across a 300 input resistance to a TV set with a 6MHz bandwidth and temperature of 30C?A. 2.3 V B. 3.8 V C. 5.5 V D. 5.4 V

84. Which of the following types of noise becomes of great importance at frequencies?A. Shot noise B. Random noise C. Impulse noise D. Transit-time noise

85. The solar cycle repeats the period of great electrical disturbance approximately everyA. 11 years B. 10 years C. 9 years D. 8 years

86. The square of the thermal noise voltage generated by a resistor is proportional toA. its resistance B. its temperature C. the bandwidth over which it is measured D. All of the above

87. Noise occurring in the presence of signal resulting from a mismatch between the exact value of an analog signal and the closet available quantizing step in a digital coder.A. Quantizing noise B. Thermal noise C. Impulse noise D. Crosstalk

88. Noise consisting of irregular pulses of short duration and relatively high amplitude,A. Quantizing noise B. Tone interference C. Impulse noise D. Cross talk

89. Noise that occurs via capacitive or inductive coupling in a cable.A. Crosstalk B. Quantizing noise C. Reference noise D. Tone interference

90. Sources of impulse noise induced in communication channels.A. Erroneous digital coding bit caused by an error on a transmission facility B. Transients due to relay operation C. Crosstalk from dc signaling systems D. All of these

91. Crosstalk due to incomplete suppression of sidebands or to intermodulation of two or more frequency-multiplexed channels which is unintelligible is classified asA. Impulse noise B. Thermal noise C. Quantizing noise D. Miscellaneous noise

92. ___________ is device that measures the internal open circuit voltage of an equivalent noise generator having an impedance of 600 and delivering noise power to a 600 load.A. Psophometer B. Barometer C. Reflectometer D. Voltmeter

93. External noise originating outside the solar systemA. Cosmic noise B. Solar noise C. Thermal noise D. Lunar noise

94. A noise whose source is within the solar system.A. Solar noise B. Thermal noise C. Cosmic noise D. Johnson Noise

95. The total noise power present in a 1-Hz bandwidth .A. Noise density B. Noise figure C. Noise limit D. Noise intensity

96. 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

97. What is the primary cause of atmospheric noise?A. Thunderstorm B. Lightning C. Thunderstorm and lightning D. Weather condition

98. 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

99. The major cause of atmospheric or static noise areA. Thunderstorms B. Airplanes C. Meteor showers D. All of these

100. Which of the following low noise transistors is commonly used at microwave frequencies?A. MOSFET B. GASFET C. MESFET D. JFET101. An amplifier operating over a 2 MHz bandwidth has a 80 ohms input resistance. It is operating at 27 degree Celsius, has a voltage gain of 200 and input signal of 6 microvolts rms. Calculate the output rms noise.a. 325.6 millivoltsb. 0.326 millivolts c. 32.55 microvoltsd. d. 0.3255 microvolts

102. Man-made noise is caused bya. Lightning dischargeb. Solar eruptionsc. Distant starsd. Arc discharges in electrical machines

103. Cosmic noise is produced bya. Lightning dischargeb. Solar eruptionc. Distant starsd. Industrial electrical discharges

104. One of the following type of noise becomes of great importance in high frequencies. It is the a. Shot noiseb. Random noisec. Impulse noised. Transit-time noise

105. Indicate the false statementa. HF mixers are generally noisier than HF amplifiersb. Impulse noise voltage is independent of bandwidthc. Thermal noise is independent of the frequency at which it is measuredd. Industrial noise is usually of the impulse type

106. The value of a resistor creating noise is doubled. The noise power generated is thereforea. Halvedb. Quadrupledc. Doubledd. Unchanged

107. One of the following is not useful for comparing the noise performance of receiversa. Input noise voltageb. Equivalent noise resistancec. Noise temperatured. Noise figure

108. Indicate the noise whose source is in a category different from thata. Solar noiseb. Cosmic noisec. Atmospheric noised. Galactic noise

109. Considered as the main source of an internal noisea. Flickerb. Thermal agitationc. Device imperfection d. Temperature change

110. Convert noise factor of 4.02 to equivalent noise temperature. Use 300 K for environmental temperaturea. 876 Kb. 900 Kc. 906 Kd. 875 K

111. Atmospheric noise is less severe at frequencies abovea. 10 GHzb. 30 MHzc. 1 GHzd. Audio level

112. The most common unit of noise measurement in white noise voltage testinga. NPRb. dBrnc. dBWd. dBm

113. What is the major cause of atmospheric or static noise?a. Meteor showersb. Sunspotsc. Airplanesd. Thunderstorms

114. Background noise is the same as the following EXCEPTa. Impulse noiseb. Thermal noisec. White noised. Gaussian noise

115. Noise is caused by the thermal agitation of electrons in resistancea. White noiseb. Thermal noisec. Johnsons noised. All of these

116. The unit of noise power of psophometera. dBab. pWpc. dBmd. dBm0

117. Extra-terrestrial noise is observable at frequencies from a. 0 to 20 KHzb. Above 2 GHzc. 8 MHz to 1.43 GHzd. 5 to 8 GHz

118. What signal-to-noise ratio is required for satisfactory telephone services?a. 50 dBb. 30 dBc. 40 dBd. 20 dB

119. A diode generator is required to produce 12 micro V of noise in a receiver with an input impedance of 75 ohms and a noise power bandwidth of 200 KHz. Determine the current through the diode in milliamperes.a. 0.4 Ab. 298 mAc. 0.35 Ad. 300 mA

120. The equivalent noise temperature of the amplifier is 25 K. What is the noise figure?a. 0.4 Ab. 298 mAc. 0.35 Ad. 300 mA

121. The resistor R1 and R2 are connected in series at 300 K and 400 K temperature respectively. If R1 is 200 ohms and R2 is 300 ohms, find the power produced at the load (RL = 500 ohms) over a bandwidth of 100 KHz.a. 0.05 nanowattsb. 0.2 nanowattsc. 0.5 femtowattsd. 2.0 femtowatts

122. The random unpredictable electric signals from natural causes, both internal and external to the system is known asa. Distortionb. Noisec. Distortiond. Interference

123. Given a factor of 10, what is the noise figure in dB?a. 20 dBb. 10 dBc. 50 dBd. 40 dB

124. The signal in a channel is measured to be 23 dBm while noise in the same channel is measured to be 23 dBm while noise in the same channel is measured to be 9 dBm. The signal to noise ratio therefore isa. 32 dBb. 5 dBc. -14 dBd. 14 dB

125. If voltage is equal to twice its original value, what is its corresponding change in dB?a. 3 dBb. 6 dBc. 9 dBd. 12 dB

126. NIF stand fora. Non-intrinsic noise figureb. Narrow interference figurec. Noise improvement factord. Noise interference figure

127. Two resistors rated 5 ohms and 10 ohms are connected in series and are at 27 degrees Celsius. Calculate their combined thermal noise voltage for a 10 KHz bandwidth.a. 0.05 millivoltsb. 0.5 millivoltsc. 0.05 microvoltsd. 0.005 microvolts

128. What is the reference frequency of CCITT psophometric noise measurement?a. 800 Hzb. 1500 Hzc. 3400 Hzd. 1000 Hz

129. A three-stage amplifier is to have an overall noise temperature no greater than 70 K. The overall gain of the amplifier is to be at least 45 dB. The amplifier is to be built by adding a low-noise first stage with existing characteristics as follows: stage 2 has 20 dB power gain and 3 dB noise figure. Stage 3 has 15 dB power gain and 6 dB noise figure. Calculate the maximum noise figure (in dB) that the first stage can have.a. 0.267 dBb. 0.56 dBc. 1.235 dBd. 0.985 dB

130. A transistor has measured S/N power of 60 at its input and 19 at its output. Determine the noise figure of the transistor.a. 5 dBb. 10 dBc. 2.5 dBd. 7.5 dB

131. Which does not affect noise in a channel?a. None of theseb. Bandwidthc. Temperatured. Quantizing level

132. Reference noise temperaturea. 70 deg Fb. 30 deg Cc. 290 Kelvind. 25 deg C

133. Industrial noise frequency is betweena. 200 to 3000 MHzb. 15 to 160 MHzc. 0 to 10 kHzd. 20 GHz

134. Noise from random acoustic or electric noise that has equal per cycle over a specified total frequency band a. Thermal noiseb. White noisec. Gaussian noised. All of these

135. A transistor amplifier has a measured S/N power of 100 at its input and 20 at its output. Determine the noise figure of the transistor.a. 14 dBb. 7 dBc. -6 dBd. -3 dB

136. What does the noise weighing curve show?a. Noise signals measured with a 144 handsetsb. Power levels of noise found in carrier systemsc. The interfering effect of other frequencies in a voice channel compared with a reference frequency of one kilohertzd. Interfering effects of signals compared with a 3-KHz tone

137. The signal power of the input to an amplifier 100 microW and the noise power is 1 microW. At the output, the signal power is 1 W and the noise power is 40 mW. What is the amplifier noise figure?a. -6 dBb. 9 dBc. 6 dBd. -3 dB

138. In measuring noise in a voice channel at a -4 dB test point level, the meter reads -70 dBm (F1A weighted), convert the reading into pWp.a. 53b. 93c. 63d. 83

139. An amplifier with 20 dB gain is connected to another with 10 dB gain by means of a transmission line with a loss of 4 dB. If a signal with a power level of -14 dBm were applied to the system, calculate the power output.a. 14 dBmb. -12 dBc. -20 dBd. 12 dBm

140. Two resistors, R1 and R2 have temperatures of 300 K and 400 K, respectively. What is the noise power if the two resistors are connected in series at 10 MHz bandwidth?a. 96.6 fWb. 55.2 fWc. 41.4 fWd. 88.36 fW

141. Determine the shot noise for a diode with a forward bias of 1.40 mA over an 80 kHz bandwidht. (q = 1.6x10 raised to minus 9 C)a. 6 nAb. 3 mAc. 12 nAd. 15 nA

142. The total noise power present in a 1 Hz bandwidth a. Noise densityb. Noise figurec. Noise limitd. Noise intensity

143. An amplifier with an overall gain of 20 dB is impressed with a signal whose power level is 1 watt. Calculate the output power in dBm.a. 50 dBmb. 150 dBc. 80 dBmd. 100 dBm

144. What is the effect on the signal to noise ratio of a system (in dB) if the bandwidth is doubled considering all other parameters to remain unchanged except the normal thermal noise only. The S/N will bea. Increased by a factor of 2b. Decreased by its valuec. Increased by a factor of 4d. Decreased to its value

145. Express the ratio in decibels of noise power ratio 50 is to 10 watts.a. 7 dBb. 21 dBc. 14 dBd. 3.5 dB

146. What do you call the noise coming from the sun and stars?a. Black-body noiseb. Space noisec. Galactic noised. All of these

147. A satellite has a noise figure of 1.6 dB. Find its equivalent noise temperature.a. 139 Kb. 192 Kc. 291 Kd. 129 K

148. What is the primary cause of atmospheric noise?a. Thunderstormb. Lightningc. Thunderstorm and lightningd. Weather condition

149. In a microwave communications system, determine the noise power in dBm for an equivalent noise bandwidth of 10 MHz.a. -104 dBmb. -114 dBmc. -94 dBmd. -174 dBm

150. The solar cycle repeats the period if great electrical disturbance approximately every a. 11 yearsb. 10 yearsc. 9 yearsd. 8 years151. A current change that is equal to twice its original value will correspond to a change ofa. 3 dB b. 9 dB c. 10 dB d. 6 dB

152. What does a power difference of 3 dB mean?a. A loss of one third of the power b. A loss of one-half of the power c. A loss of 3 watts of power d. No significant change

153. A gain of 60 dB is the same as a gain ofa. 10 volts/volt b. 100 volts/volt c. 1000 volts/volt d. 10,000 volts/volt

154. ______ is mathematically equal to the logarithm to the base ten of the power ratio P1 over P2.a. bel b. dB c. bel/10 d. dB/2

155. Noise that is produced by the active components within the receiver.a. Thermal b. External c. Internal d. White

156. Noise due to random variation in the arrival of charge carriers at the output electrode of an active devicea. Shot b. Impulse c. Thermal d. Dynamic

157. A network has a loss of 20 dB. What power ratio corresponds to this lossa. 0.01 b. 0.1 c. 10 d. 100

158. A receiver connected to an antenna whose resistance is 60 ohms has an equivalent noise resistance of 40 ohms. Calculate the receivers noise figure in decibels and its equivalent noise temperature.a. 1.67 & 194K b. 2.23 & 194K c. 1.67 & 174K d. 2.23 & 194K

159. _____ Noise is the most prevalent noise found in urban areas and is normally caused by the arc discharge from automobile or aircraft ignition systems, induction motors, switching gears, high voltage lines and the like.a. Industrial b. Johnson c. Flicker d. Mixer

160. The noise figure of a totally noiseless device is a. Unity b. Infinity c. Zero d. 100

161. Indicate the noise whose source is in a category different from that of the other three.a. Solar b. Cosmic c. Atmospheric d. Galactic

162. The ratio(in dB) of the power of a signal at point to the power of the same signal at the reference point.a. Transmission Level Point b. Noise Figure c. S/N Ratio d. Neper

163. A network has a power gain of 3 dB. If the input power is 100 watts, the output power isa. 50 watts b. 55 watts c. 60 watts d. 62 watts

164. Which of the following types of noise becomes of great importance at high frequencies?a. Shot b. Random c. Impulse d. Transmit time

165. The input current of a network is 190 A and the output is 1.3 A. The loss in decibels isa. 20.2b. 21.6c. 28.6d. 43.3

166. If a network connected in series have a gain of -0.5 dB, -0.3dB, -2dB and 6.8dB, the overall gain isa. 2 dBb. 2 dBc. 4 dBd. 4 dB

167. What is the gain, in dB, if the output to input ratio is 1000.a. 20b. 30c. 40d. 10

168. The following characteristics of noise excepta. Unwanted energyb. Predictable in characterc. Present in the channeld. Due to any cause

169. The equivalent noise temperature of the amplifier is 25 K what is the noise figure?a. 10.86b. 1.086c. 0.1086d. 1.86

170. A receiver connected to an antenna whose resistance is 50 ohms has an equivalent noise resistance of 30 ohms. What is the receivers noise temperature?a. 464Kb. 754Kc. 400Kd. 174K

171. A theoretical antenna has a gain of 1dB. Its gain in nepers isa. 8.686b. 0.1151c. 6.868d. 0.5111

172. What is the equivalent output of a circuit in dBm, if it has an output of 10 watts?a. 10 dBmb. 30 dBmc. 20 dBmd. 40 dBm

173. An amplifier with an input resistance of 1000 ohms is operating over a 4 MHz bandwidth. Calculate the rms voltage if the amplifier is operating at 27 C.a. 8.14 nVb. 8.14 uVc. 6.6 nVd. 6.6 uV

174. The value of a resistor creating thermal noise is doubled. The noise power generated is thereforea. Halvedb. Quadrupledc. Doubled d. Unchanged

175. One of the following is not a useful quantity for comparing the noise performance of receivers.a. Input noise voltageb. Equivalent noise resistancec. Noise temperatured. Noise figure

176. Any unwanted form of energy that tends to interfere with the wanted signal is calleda. Noiseb. Spectrumc. Radiationd. Absorption

177. The correct symbol for decibel isa. DBb. dBc. Dbd. db

178. _____ is the noise created outside the receiver.a. Internalb. Externalc. Shotd. Industrial

179. _____ is the noise created by man.a. Solarb. Industrialc. Extraterrestriald. Galactic

180. A voltage change that is equal to twice its original value correspond to a change ofa. 3 dBb. 6 dBc. 9 dBd. 10 dB

181. Indicate the voltage level in dB with reference to one volt. This unit is used in video or TV measurementa. dBWb. dBkc. dBmd. dBV

182. which of the following is not an actual amount of power?a. dBb. dBmc. dBwd. dBk

183. In noise analysis, the reference temperature isa. 75 Kb. 250 Kc. 290 Kd. 300 K

184. Noise from distant panels, stars, galaxies and other celestial objects are calleda. Cosmicb. Extraterrestrialc. Galacticd. Black body

185. Indicate which one of the following types of noise does not occur in transistorsa. Shot noiseb. Flicker noisec. Partition noised. Resistance noise

186. Which of the following is not a source of space noisea. Sunb. Starc. Lightningd. Black body

187. Noise that is due to the random and rapid motion of the charge carriers inside a resistive component.a. Johnsonb. Thermal Agitationc. Whited. All of the above

188. Indicate the false statement. The square of the thermal noise voltage generated by a resistor is proportional toa. Its resistanceb. Its temperaturec. Boltzmanns Constantd. The bandwidth over which it is measured

189. In a communication system, noise is likely to affect the signala. At the transmitterb. In the channelc. In the information sourced. At the destination

190. The noise power generated by a resistor is proportional toa. Temperatureb. Bandwidthc. a and bd. NOTA

191. Thermal noise is also known asa. Gaussian Noiseb. White Noisec. Johnson noised. All of the above

192. This type of noise has a power spectrum which decreases with increasing frequency. It is most important at low frequencies from 0 to about 100 Hz).a. Shot noiseb. Flicker noisec. Diode noised. BJT noise

193. Industrial noise extends up to what frequency?a. 500 MHzb. 500 GHzc. 500 THzd. 500 KHz

194. Impulse Noise isa. A function of currentb. A shot duration pulsec. Dependent of frequencyd. Dependent of temperature

195. When the power ratio of the output to input of a circuit is 200. What is the gain in dB?a. 23b. 46c. 23 d. 46

196. What is the reference level for random noise measurement, FIA weighted?a. 82 dBmb. 90 dBmc. 85 dBmd. 77 dBm

197. A 10 dB pad has an output level of -3 dBm. The level at the input is:a. 13 dBmb. -7 dBmc. 1 dBmd. 7 dBm

198. The sum of three signals of 45dBm each is ______ dBm.a. 45b. 135c. 20d. 50

199. It is characterized by high amplitude peaks of short duration in the total noise spectruma. Intermodulation voiceb. Impulse noisec. Dropoutd. Phase hits

200. Originally was determined by measuring the interfering effect of noise in a Type 144 handset. A tone of 1 kHz, having a power level of 90 dBm was selected as the reference level.a. Noise figureb. S/N ratioc. Signal Figure d. Figure of Merit201. A power level of 50 W could be expressed as: a. 1.39 dBm b. -4.3 dBm c. 1 dBm d. -13 dBm

202. If a power of 0.25 mW is launched into a fiber system with an overall loss of 15 dB the output power would be:a. 250 /W b. 31.6 W c. 7.9 W d. 15 dBm

203. A system having an input power of 2 mW an output power of 0.8mW has a loss of:a. 2.98 dBm b. 3.98 dB c. 3.98 W d. 1.98 mW

204. An output of -10 dB means that the power has beena. Halved in value b. Increased by a factor of 10 c. Reduced by a factor of 10 d. Doubled

205. Any unwanted form of energy interfering the reception of wanted signal is calleda. Noise b. Sideband c. Harmonics d. Modulation

206. Is the reduction of signal amplitude as it passed over the transmission medium.a. Noise b. Distortion c. Attenuation d. Interference

207. Signal waveform perturbation or deviation caused by imperfect response of the system to the desired signala. Noise b. Aliasing c. Distortion d. Interference

208. Signal attenuation can be corrected bya. Filtering b. Modulation c. Equalization d. Amplification

209. Distortion in a waveform can be corrected bya. Filtering b. Modulation c. Equalization d. Amplification

210. Signal contamination by extraneous or external sources, such as, other transmitters, power lines, and machinery.a. Noise b. Distortion c. Harmonics d. Interference

211. Man-made or industrial noise is also known asa. Noise b. Distortion c. Interference d. Thermal Noise

212. The noise performance of a receiver or circuit. It is expressed as ratio of the S/N power at the output.a. Noise figure b. S/N ratio c. Signal figure d. Figure of merit

213. Noise that is caused by natural disturbances such as lightning discharge.a. Static noise b. Space noise c. Atmospheric noise d. A or C

214. Atmospheric or static noise becomes less severe at frequenciesa. Below 30 KHz b. Between 30 KHz and 300 KHz c. Between 300 KHz and 30 MHz d. Above 30 MHz

215. Considered as space noise or extraterrestrial noisea. Solar noise b. Cosmic noise c. Black-body noise d. All of the above

216. Which statement is truea. Industrial noise is usually of impulse type b. Distant stars produce atmospheric noise c. Active switches are sources of man-made noise d. Static noise is due to lightning discharges and other natural electric disturbances occurring in the atmosphere.

217. Noise performance of microwave system is usually expressed in terms ofa. Noise voltage, Vn = 4KTBR b. Noise power, Pn = KTB c. Noise temperature, Te = (F 1)290 d. Noise figure, F = (S/N)I / (S/N)o

218. Which circuit contributes most to the noise at the receiver?a. RF amplifier b. Mixer c. Detector d. Local Oscillator

219. Which noise figure represents the lowest noise?a. 1.5 dB b. 2.0 dB c. 3.7 dB d. 4.1 dB

220. Denote the interference of noise in dB above an adjusted reference noise. The adjusted reference noise level was a 1 kHz tone, set at -85 dBma. dBa b. dBm c. dBa0 d. pWp

221. The extent of noise referred to a test tone level of zero dBm.a. dBa b. dBm c. dBa0 d. pWp

222. An amplifier operating over a 4 MHz bandwidth has a 100 input resistance and is operating at 300K. Determine the noise power generated.a. 1.656 x 10-14 Wattsb. 1656 nWc. 1.656 pWd. 1.656 uW

223. Generally used when noise readings are measured using the C-message weighting network. The reference level was 1 kHz tone, set at -90 dBma. dBab. dBmc. dBaOd. dBmC

224. The measurement of noise was made with a C-message filter, and the reading is taken at a test point where the level is zero dBm.a. dBaOb. dBmCoc. dBad. dBmC

225. Which of the following is not an important cause of distortion in DC signalinga. line resistanceb. line inductancec. line capacitanced. all of the above

226. There are a number of different sources of radio noise, the most important beinga. Galactic noiseb. Man-made noisec. Atmospheric noised. All of the above

227. The amount of noise power is measured using a psophometric weighting network. This unit of measurement is generally used in Europe where the standard reference tone is 800 hertz, 1 picowatt.a. dBab. dBmc. dBaOd. pWp

228. Noise produced mostly by lightning discharges in thunderstorms.a. White noiseb. Industrial noisec. Atmospheric noised. Extraterrestrial noise

229. Propagation of man made noise is chiefly bya. Transmission over power lines and by ground waveb. Space wavec. Sky waved. None of these

230. A more precise evaluation of the quality of a receiver as far as noise is concerneda. S/Nb. VSWRc. Noise factord. Noise margin

231. NIF stands fora. Non-intrinsic figureb. Noise interference figurec. Noise improvement factord. Narrow intermediate frequency

232. External noise fields are measured in terms of a. Dc valuesb. Rms valuesc. Peak valuesd. Average values

233. Form of interference caused by rain, hail, snow or dust stormsa. Shot noiseb. Galactic noisec. Impulse noised. Precipitation static

234. Extra-terrestrial noise is observable at frequencies froma. 0 to 20 KHzb. 8 MHz to 1.43 GHzc. 5 to 8 GHzd. 15 to 160 MHz

235. Industrial noise is observable from a. 15 to 160 MHzb. 200 to 3000 MHzc. 0 to 10 kHzd. 8 Mhz to 1.43 GHz

236. Noise that becomes significant at VHF range and abovea. Atmosphericb. Transit-timec. Galacticd. White

237. Noise figure for an amplifier with noise is alwaysa. 0 dBb. Infinitec. Less than 1d. Greater than 1

238. The noise generated by the tube, transistor or integrated circuit in an amplifier.a. White noiseb. Amplification noisec. Active noised. Dynamic Noise

239. Electrical noise inherent to a particular device, circuit or system that remains when no other signal is present.a. Shot noiseb. Thermal noisec. Background noised. Static noise

240. A wideband form of impulse noise generated by the electric arc in the spark plugs of an internal combustion engine. This noise is a common problem in mobile radio system.a. Thermal noiseb. Shot noisec. Amplification noised. Ignition noise

241. The amount of power in dB referred to one Kilowatta. dBWb. dBkc. dBmd. Dbv

242. Noise in any form of electromagnetic interference that can be traced to non-natural causes.a. Man-made noiseb. Distortionc. External noised. Internal noise

243. The frequency range wherein noise is said to be intense.a. Noise equivalent bandwidthb. Spectral responsec. Cut-off frequencyd. Noise cut-off frequency

244. Refers to the temperature that corresponds to the spectral energy distribution of a noise.a. Absolute temperatureb. Temperature bandc. Noise-equivalent temperatured. Critical temperature

245. A passive circuit, usually consisting of capacitance and/or inductance, that I inserted in series with the a-c power cord of an electronic device which will allow the 60-Hz current to pass and suppressed high frequency noise components.a. Noise filterb. Noise limiterc. Noise floord. Noise quieting

246. What do you call the level of background noise, relative to some reference signal.a. Noise figureb. Minimum noisec. Reference noised. Noise floor

247. A circuit often used in radio receivers that prevents externally generated noise from exceeding amplitude. They are also called noise clippersa. Noise floorb. Noise filterc. Noise limiterd. Noise clamper

248. It is referred to as a short burst of electromagnetic energy.a. Pulseb. Noise pulsec. Spiked. Noise floor

249. The reduction of internal noise level in a frequency-modulated (FM) receiver as a result of an incoming signal.a. Noise quietingb. Noise limitingc. Noise suppressiond. Noise degradation

250. Noise generated within electronic equipment by either passive or active components.a. Shot noiseb. Thermal noisec. Circuit noised. External noise