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- Noise -- What is a non-continuous noise of irregular pulses or spikes of short duration with high amplitudes?

a. Wanderb. Jitterc. Hitsd. Singingans: b

-What theorem sets a limit on the maximum capacity of a channel with a given no

ise level?a. Nyquist theoremb. Hartley lawc. Shannon-Hartley theoremd. Shannon theoremans: c

-Quantizing noise occurs ina. PCMb. PLMc. PDMd. PAMans: a

- Noise always affect the signal in a communications systems at the ____________ __.

a. transmitterb. channelc. information sourced. destinationans: b

- ________ is the random and unpredictable electric signals from natural causes,

both internal and external to the system.a. Interferenceb. Attenuation

c. Distortiond. Noiseans: d

-Noise from random acoustic or electric noise that has equal energy per cycle o

ver a specified total frequency band.a. Gaussian noiseb. White noisec. Thermal noised. All of the aboveans: d

-Which causes a quantization noise in PCM system?

a. Serial transmission errorsb. The approximation of the quantized signalc. The synchronization between encoder and decoderd. Binary coding techniquesans: b

-A particular circuit that rids FM of noise.a. Detectorb. Discriminatorc. Phase shifter

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d. Limiterans: d

-What is the reference noise temperature?a. 290 Kb. 30 degrees Cc. 70 degrees Fd. 25 degrees Cans: a

-Unwanted radio signal on assigned frequency.a. Splatterb. RFIc. Noised. EMIans: c

-What is the reliable measurement for comparing amplifier noise characteristics

?a. Thermal agitation noiseb. Noise factorc. Noise margind. Signal-to-noiseans: b

- ________ is measured on a circuit when it is correctly terminated but does not have any traffic.

a. White noiseb. Galactic noisec. Impulse noised. Atmospheric noiseans: a

-Which standard recommends crosstalk limits?a. CCITT G. 152b. CCITT G. 150c. CCITT G. 151

d. CCITT G. 161ans: c-

Which standard is utilized in intermodulation noise rates on PCM audio channels?

a. CCITT Rec. G. 151b. CCITT Rec. G. 172c. CCITT Rec. G. 190d. CCITT Rec. G. 190ans: b

-What is the reference frequency of CCITT phosphometric noise measurement?a. 800 Hz

b. 1000 Hzc. 1500 Hzd. 3400 Hzans: a

-Reference temperature used in noise analysis.a. 75 Kb. 250 Kc. 290 Kd. 300 K

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ans: c-

Which noise is produced by lighting discharges in thunderstorms?a. White noiseb. Extraterrestrial noisec. Industrial noised. Atmospheric noiseans: d

-Man-made noise is usually from ___________.a. transmission over power lines and by ground waveb. sky-wavec. space-waved. troposphereans: a

-nif stands fora. Non-intrinsic figureb. Noise improvement factorc. Narrow intermediate frequencyd. Noise interference figureans: b

-Industrial noise frequency is between ________________.

a. 0 to 10 kHzb. 160 MHz to 200 MHzc. 15 to 160 MHzd. 200 to 3000 MHzans: c

-External noise fields are measured in terms of ____________.a. rms valuesb. dc valuesc. average valuesd. peak valuesans: d

-

Form of interference caused by rain or dust storms.a. Precipitation staticb. Shot-noisec. Galactic noised. Impulse noiseans: a

-At 17 degrees C, the noise voltage generated by 5 k ohms resistor, operating o

ver a bandwidth of 20 kHz isa. 1.3 nVb. 1.3 uVc. 1.3 pVd. 1.3 mV

ans: b- ________ is an electric noise produced by thermal agitation of electrons in co

nductor and semiconductora. External noiseb. Internal noisec. Thermal noised. Flickerans: c

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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 dBb. 14.77 dBc. 30 dBd. 40 dBans: a

-The noise figure of the first circuit in tandem connection is 10.5 dB while it

s power gain is 15, what is the over all noise figure if the second circuit hasa noise figure of 11 dB?

a. 11.59 dBb. 11.23 dBc. 10.79 dBd. 10.5 dBans: c

-Is the interference coming from other communications channels.a. Jitterb. Crosstalkc. RFId. EMIans: b

-

What is the reference noise level?a. 10 pWb. 0 dBmc. 1 mWd. -90 dBmans: d

-What is the unit of noise power of psophometer?a. pWpb. dBac. dBmd. dBrnans: a

- A large emission of hydrogen from the sun that affects communications.a. Solar flareb. Cosmic disturbancec. Ballistic disturbanced. Solar noiseans: a

-Atmospheric noise is known as ___________ noise.a. staticb. cosmicc. solard. lunar

ans: a-Standard design reference for environmental noise temperature.a. 300 degrees Kb. 290 degrees Kc. 32 degrees Fd. 212 degrees Fans: b

-Absolute temperature in Kelvin.

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a. degrees C + 273b. degrees C + 75c. degrees C + 19d. degrees C + 290ans: a

-If bandwidth is doubled, the signal power is ___________.a. not changedb. quadrupledc. tripledd. doubledans: a

-Name one or more sources of noise bearing on electronic communications.a. Steam boilerb. Galaxiesc. Internal combustion engined. Both B and Cans: d

-The transmitter technique adopted to reduce the effect of noise is calleda. noise maskingb. antinoisec. noise killing

d. preemphasisans: d-

Deemphasis in the receiver in effect attenuates modulating signal components and noise in what frequency range?

a. dcb. lowc. intermediated. highans: d

-Atmospheric noise or static is not a great problema. at frequencies below 20 MHz

b. at frequencies below 5 MHzc. at frequencies above 30 MHzd. at frequencies above 1 MHzans: c

-What is the proper procedure for suppressing electrical noise in a mobile stat

ion?a. Apply shielding and filtering where necessaryb. Insulate all plain sheet metal surfaces from each otherc. Apply anti-static spray liberally to all nonmetallicd. Install filter capacitors in series with all dc wiringans: a

-

Where is the noise generated that primarily determines the signal-to-noise ration in a VHF (150 MHz) marine-band receiver?a. Man-made noiseb. in the atmospherec. in the receiver front endd. in the ionosphereans: c

-The difference between signal strength at a given point and a reference level

is __________.

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a. powerb. dBmc. leveld. ratioans: c

-Interfering effect of noise, C message weighted, is ________.a. dBab. dBmc. dBrncd. dBans: c

-F1A weighting refers to _________.a. -90 dBmb. dBrnc0c. dBrncd. F1A handsetans: d

-Reading a 58 dBrnC on your Western electric 3A test set at a + 7 test point is

equal to ____________ dBrnc0.a. 58b. 51

c. 65d. 27ans: b

-Reading a 58 dBrn, at a + 7 test point is equal to ___________ dBa0.a. 26b. 65c. 51d. 46ans: d

-A reading of -50 dBm on the disturbing pair, and -80 on the disturbed pair equ

als ________________ dB of crosstalk coupling.

a. 20b. 30c. 60d. 25ans: b

-Power is _________.a. actual amount of power reference to 1 mWb. logarithmic ratio of two powersc. definite amount of energy per time periodd. current flow per time periodans: c

-

15 dBa F1A weighted, equals __________.a. -90 dBmb. -82 dBmc. -85 dBmd. -70 dBmans: d

-You are measuring noise in a voice channel with a Lenkurt 601A, F1A weighting

network and a flat meter. Your meter reads -47 dBm. What is this reading in dBa?

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a. 77 dBab. 35 dBac. 38 dBad. 32 dBaans: c

-You are measuring noise at a +3 dB level point, using the Lenkurt 601A, F1A we

ighting network, and a flat meter. The meter reading is -57 dBm. This is _______ __ dBa0

a. 20b. 15c. 25d. 17ans: c

-You are measuring noise at a -6 dB level point, using the Lenkurt 601A, F1A we

ighting network, and a flat meter. The meter reading is -59 dBm. This is _______ ___ dBa0.

a. 24b. 12c. 23d. 32ans: d

-

A measurement of -75 dBm, C-message weighted, would be ____________ dBrnc.a. 8b. 7c. 9d. 15ans: d

-Your Western Electric 3A test set meter reading is -23 dBm at a test point lev

el of -8 dB. This is _____________ dBrnc0.a. 75b. 29c. 30d. 31

ans: a-At what power level does a 1 kHz tone cause zero interference (144 weighted)?a. 90 dBb. 90 dBmc. -90 dBd. -90 dBmans: d

-Reference noise is ___________.a. a 1000 Hz, -90 dBm toneb. a noise that creates the same interfering effect as a 1000 Hz, -90 dBm tone

c. a noise that creates zero dBrn in a voice channeld. B and C aboveans: d

-A practical dBrn measurement will almost always in a ____________ number.a. positiveb. negativec. imaginaryd. fractionalans: a

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-What is the reference level for noise measurement, F1A weighted?a. -90 dBmb. -82 dBmc. -67 dBmd. -85 dBmans: d

-What is the reference tone level for dBrn?a. -90 dBmb. -82 dBmc. -67 dBmd. -85 dBmans: a

-What is the reference tone level for dBa?a. -90 dBmb. -82 dBmc. -67 dBmd. -85 dBmans: d

-Atmospheric noise becomes less severe at frequenciesa. above 30 MHz

b. below 30 MHzc. above 3000 kHzd. below 3000 kHzans: a

-Indicate the noise whose sources are in category different from that of the ot

her three?a. Solar noiseb. Cosmic noisec. Atmospheric noised. Galactic noiseans: c

-

Indicate the false statement.a. Industrial noise is usually of the impulsive typeb. Static is caused by lightning discharges in thunderstorms and other natural

electric disturbances occurring in the atmospherec. Distant stars are another source of man-made noised. Fluorescent lights are another source of man-made noiseans: c

-Which of the following is not a source of industrial noise?a. Automobile ignitionb. Sunc. Electric motorsd. Leakage from high voltage line

ans: b-Indicate the false statement.a. The noise generated in a resistance or the resistive component of any imped

ance is randomb. Random noise power is proportional to the bandwidth over which it is measur

edc. A random voltage across the resistor does not existd. All formula referring to a random noise are applicable only to the value of

such noise

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ans: c-

The value of the resistor creating thermal noise is doubled. The noise power generated is therefore

a. halvedb. quadrupledc. doubledd. unchangedans: d

-Indicate the false statement.a. HF mixer are generally noisier than HF amplifiersb. Impulse noise voltage is dependent on bandwidthc. Thermal noise is independent of the frequency at which is measuredd. Industrial noise is usually of the impulse typeans: b

-An amplifier operating over the frequency range of 455 to 460 kHz has a 200 k

ohms input resistor. What is the RMS noise voltage at the input to this amplifier if the ambient temperature is 17 degrees C?

a. 40 uVb. 4.0 uVc. 400 uVd. 4.0 mV

ans: b-The 1st stage of a 2-stage amplifier has a voltage gain of 10, a 600 ohms inpu

t resistor, a 1600 ohms equivalent noise resistance & a 27 k ohms output resistor. For the 2nd stage, these values are 25, 81 k ohms, 10 k ohms, & a 1 M ohm, respectively. Calculate the equivalent input-noise resistance of this two stage amplifier.

a. 2,518 K ohmsb. 2,518 ohmsc. 251.8 ohmsd. 12.518 K ohmsans: b

-

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

a. 0.5 mVb. 0.5 uVc. 5.0 mVd. 5.0 uans: a

-The front-end of a television receiver, having a bandwidth of 7 MHz, and opera

ting at a temperature of 27 degrees C, consists of an amplifier having a gain of 15, followed by a mixer whose gain is 20. The amplifier has a 300 ohms input re

sistor and a shot noise equivalent resistance of 500 ohms; for the mixer, thesevalues are 2.2 kohms and 13.5 kohms, respectively, and the load resistance of the mixer is 470 kohms. Calculate the equivalent noise resistance for this television receiver.

a. 8760 ohmsb. 875 ohmsc. 8.76 ohmsd. 0.876 ohmans: b

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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 figureans: a

-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 resistorb. noise factor expressed in decibelsc. an unwanted form of energy tending to interfere with the proper and easy re

ception and reproduction of wanted signalsd. S/N of an ideal system divided by S/N at the output of the receiver or ampl

ifier under test, both working at the same temperature over the same bandwidth and fed from the same source

ans: c-

Calculate the noise figure of the amplifier whose Req equals 2518 ohms (R subT = 600 ohms) if it's driven by a generator whose output impedance is 50 ohms.

a. 39.4b. 3.94c. 394

d. 0.394ans: a-

Calculate the noise figure of the receiver whose RF amplifier has an input resistance of 1000 ohms & an equivalent shot-noise resistance of 2000 ohms, a gainof 25 and a load resistance of 125 k ohms. Given that the bandwidth is 1.0 MHz & the temperature is 20 degrees C, and that the receiver is connected to an antenna with an impedance of 75 ohms.

a. 30.3b. 3.03c. 303d. 0.303ans: a

- A receiver connected to an antenna whose resistance is 50 ohms has an equivalent noise resistance of 30 ohms. Calculate its equivalent noise temperature if the noise figure is equal to 1.6.

a. 17.4 Kb. 174 Kc. 1.74 Kd. 17 Kans: b

-Most internal noise comes froma. shot noiseb. transit-time noise

c. thermal agitationd. skin effectans: c

-Which of the following is not a source of external noise?a. Thermal agitationb. Auto ignitionc. The sund. Fluorescent lightsans: a

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-Noise can be reduced bya. widening the bandwidthb. narrowing the bandwidthc. increasing temperatured. increasing transistor current levelsans: b

-Noise at the input to a receiver can be as high as severala. microvoltsb. millivoltsc. voltsd. kilovoltsans: a

-Which circuit contributes most of the noise in a receiver?a. IF amplifierb. Demodulatorc. AF amplifierd. Mixerans: d

-Which noise figure represents the lowest noise?a. 1.6 dB

b. 2.1 dBc. 2.7 dBd. 3.4 dBans: a

-The transistor with the lowest noise figure in the microwave region is aa. MOSFETb. Dual-gate MOSFETc. JFETd. MESFETans: d

-What is the noise voltage across a 300 ohms input resistance to a TV set with

a 6 MHz bandwidth and the temperature of 30 degrees C?a. 2.3 uVb. 3.8 uVc. 5.5 uVd. 6.4 uVans: c

-Which of the following types of noise becomes of great importance at high freq

uencies?a. Shot noiseb. Random noisec. Impulse noised. Transit-time noise

ans: d-The solar cycle repeats the period of great electrical disturbance approximate

ly everya. 11 yearsb. 10 yearsc. 9 yearsd. 8 yearsans: a

-

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The square of the thermal noise voltage generated by a resistor is proportional to

a. its resistanceb. its temperaturec. the bandwidth over which it is measuredd. all of the aboveans: d

-Noise occurring in the presence of signal resulting from a mismatch between th

e exact value of an analog signal and the closest available quantizing step in a digital coder.

a. Quantizing noiseb. Thermal noisec. Impulse noised. Crosstalkans: a

-Noise consisting of irregular pulses of short duration and relatively high amp

litude.a. Quantizing noiseb. Tone interferencec. Impulse noised. Crosstalkans: c

- Noise that occurs via capacitive or inductive coupling in a cablea. Crosstalkb. Quantizing noisec. Reference noised. Tone interferenceans: a

-Sources of impulse noise induced in communication channels.a. Erroneous digital coding bit caused by an error on a transmission facilityb. Transients due to relay operationc. Crosstalk from dc signaling systemsd. All of these

ans: d-Crosstalks due to incomplete suppression of sidebands or to intermodulation of

two or more frequency-multiplexed channels which are unintelligible is classified as

a. impulse noiseb. thermal noisec. quantizing noised. miscellaneous noiseans: d

- __________ is a device that measures the internal open circuit voltage of an e

quivalent noise generator having an impedance of 600 ohms and delivering noise p

ower to a 600 ohms load.a. Psophometerb. Barometerc. Reflectometerd. Voltmeterans: a

-External noise originating outside the solar system.a. Cosmic noiseb. Solar noise

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