“COMMUNICATION REVIEWER”
1.
Also known as black-body noise A. cosmic noise C. solar noise B. extraterrestrial noise D. man made noise
2.
The square of the the thermal thermal noise noise voltage generated by a resistor resistor is not not proportional to A. Its resistance B. Its temperature C. Boltzmann’s constant
23.
An Angstrom used to describe a lightwave is equal to 10 10 raised to minus ______ micro meter. A. 3 C. 6 B. 10 D. 4
24.
What is the letter-number letter-number designation designation for carrier and one SB? A. J3E C. A3E B. H3E D. F3E
25.
In PLL frequency demodulator, demodulator, the information information or the modulating signal is the _____ signal. A. phase shift C. VCO B. error D. input
26.
What is the second detector detector is used for AM? A. ratio C. diode B. PLL D. lattice
27.
What is the letter-number letter-number designation designation for carrier and one SB? A. J3E C. A3E B. H3E D. F3E
28.
One of the the following statement is false, regarding regarding making the the IF value value very high. A. the image rejection will be very good B. there is no need to make the local oscillator extremely stable C. tracking will be greatly improved D. the selectivity will be very poor
29.
When the amplitude of the information in an AM AM modulator is equal to zero, what is the value of the modulation index? A. 1 C. 100 B. 0 D. infinity
D. The bandwidth over which it is measured 3.
4.
5.
Space noise contains less energy below A. 9 MHz C. 20 MHz B. 15 MHz D. 8 MHz A power power change change that is equal equal to twice its its original value will will correspond correspond to a change of A. 3 dB C. 10 dB B. 9 dB D. 6 dB Which of the the following is a desirable desirable value value of signal-to-noise signal-to-noise ratio in dB? dB? A. 0 C. 1 B. 100 D. 50
6.
Which of the following noise figure is most desirable? A. 0 dB C. 1 dB B. 100 dB D. infinity
7.
Also known as lock range A. capture range C. natural frequency B. free-running frequency D. tracking range
8.
Considered as the main source of an internal noise. A. Flicker C. Device imperfection B. Thermal agitation D. Temperature change
30.
The component used to produce AM at very high frequencies is a A. varactor C. cavity resonator B. thermistor D. PIN diode
The kind of noise that is caused by mismatched lines: A. echo noise C. partition noise B. impulse noise D. intermodulation noise
31.
The information information sources modulate the same carrier after it has been separated into two carrier signals are at 90 degrees out of phase with each other. A. QPSK C. PSK B. QUAM D. FSK
32.
The AM AM detector is sometimes called _____. A. first detector C. second detector B. third detector D. fourth detector
33.
He developed developed the first successful successful FM radio system system A. B.E. Alpine C. E.H. Armstrong B. N.S. Kapany D. A.C.S. Van Heel
34.
Maximum frequency frequency deviation deviation of a PM signal occurs occurs at A. zero-crossing points B. peak positive amplitudes C. peak negative amplitude D. peak positive and negative amplitude
9.
10.
A ten times power power change in a transmission system system is equivalent to: A. 10 dB C. 20 dB B. 100 dB D. 1 dB
11.
_____are types of noise generated by equipments equipments that that produces produces sparks. A. equipment noise C. space noise B. atmospheric noise D. internal noise
12.
Japan is part of what ITU region? A. 3 C. 2 B. 1 D. 4
13.
Which of the following following is is not used for communication communication A. X-rays C. Infrared B. Millimeter waves D. Microwaves
14.
_____are integer multiples of of the original input input signal. signal. A. interference C. fundamental B. harmonic D. distortion
35.
The cut-off frequency of pre-emphasis pre-emphasis and de-emphasis circuits circuits is A. 1 kHz C. 5 kHz B. 2.122 kHz D. 75 kHz
Electromagnetic waves produced primarily primarily by heat are are called A. Infrared C. Shortwaves B. Microwaves D. X-ray
36.
Musical instruments makes sounds sounds usually in what range? A. LF C. VF B. VLF D. HF
Which oscillators are preferred for carrier generators because because of their their good frequency stability? A. LC C. LR B. RC D. Crystal
37.
What is the the frequency frequency range of SHF? SHF? A. 3 – 30 GHz C. 30 – 300 MHz B. 30 – 300 GHz D. 300 – 3000 MHz
The frequency of an SCA channel subcarrier is _____. A. 38 kHz C. 67 kHz B. 15 kHz D. 53 kHz
38.
In psophometric noise weighting, one picowatt is equivalent to 800 Hz tone with a power of A. –90 dBm C. –65 dBm B. –85 dBm D. none of the above
A third symbol emission which represent represent data transmission transmission including telemetry and telecommand. A. B C. C B. D D. N
39.
The standard test tone has a frequency of _____ Hz. A. 1000 C. 100 B. 10 D. none of these
A radio signal travels ________ yards per microseconds. A. 273 C. 328 B. 618 D. 123.6
40.
The radio wavelength known as _____ falls within the medium frequency frequency range. A. centimetric C. hectometric B. decametric D. myriametric
The frequency band normally used to penetrate ocean ocean depths and therefore used for communicating with submarine is ________. A. EHF C. HF B. MF D. VLF
41.
The frequency band used as subcarriers, or signals signals which carry carry the baseband modulating information but in turn modulate another higherfrequency carrier is A. LF C. VLF B. MF D. VHF
42.
An amplifier with an overall gain of 20 dB is impressed with a signal whose power level is 1 watt. Calculate the power output in dBm. A. 50 C. 6 B. 60 D. 10
15.
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19.
20.
21.
In a double-tuned circuit, circuit, minimum bandwidth is obtained with _____ coupling A. under C. optimum B. over D. critical
22.
The transmission of information from multiple sources occurring on the same facility but not at the same time is known as _________. A. WDM C. TDM B. FDM D. CDM
43.
44.
What is the effect of 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 be ___________. A. increased by 6 dB B. increased by 3 dB C. decreased by 3 dB D. decreased by one-half
67.
An IF transformer of a radio receiver operates at 455 kHz. The primary circuit has Q of 50 and the secondary has a Q of 40. Find the bandwidth using the optimum coupling factor.
68.
A phase-locked loop has a VCO with a free running frequency of 14 MHz. As the frequency of the reference input is gradually raised from zero, the loop locks at 12 MHz and comes out of lock again at 18 MHz. Calculate the capture range.
69.
A receiver is tuned to a station at 590 kHz calculate the image rejection in decibels, assuming that the input filter consists of one tuned circuit with a Q of 40.
70.
A transistor has a power dissipation rating of 30 W. Assuming that the transistors is the only element that dissipates power in the circuit, calculate the power an amplifier, using this transistor, could deliver to the load if it operates as class-A with an efficiency of 30%
71.
A receiver uses low-side injection for the local oscillator, with an IF or 1750 kHz. The local oscillator is operating at 16.7 MHz. Find its image frequency.
72.
An AM transmitter operates into a 50 ohm resistive load. The RMS voltage measured at the output is 240 V without modulation and 260 V with modulation, calculate the modulation index.
73.
AN AM signal has the following characteristics: fc = 200 MHz; fm = 3 kHz; Ec = 50 V; Em = 20 V. Calculate the peak voltage of the upper side frequency.
74.
When measuring the selectivity of a receiver, you discover that a signal level of 400 microV on an adjacent channel is required to give the same output as a 1 microV signal on the channel to which the receiver is tuned. Calculate the adjacent channel selectivity in dB.
75.
An attenuator has a loss of 26 dB. If a power of 3 W is applied to the attenuator, find the output power.
76.
Determine the power saving in percent when the carrier is suppressed in an AM signal modulated to 80%
77.
The frequency band used by cellular telephones and mobile communication services is ____________.
78.
Assuming 100% modulation, what would be the transmitted power in the upper sideband of an AM signal if the carrier power is 1000 watts?
What is the main disadvantage of a single-tube transmitter? A. high resistivity C. low gain B. high attenuation D. frequency instability
79.
What determines the selectivity of a receiver? A. the bandwidth of the tuned circuits B. the frequency stability C. the power handling capability D. the gain of the amplifier
An AM signal has the following characteristics: the carrier frequency is 150 MHz, the modulating signal frequency is 3 kHz, the carrier voltage is 60 volts, where the modulating signal (Em) is 30 volts. Find the peak voltage of the lower side frequency.
80.
The power amplifier of an AM transmitter has an output power of 50 W and an efficiency of 60% and is collector-modulated. How much audio power is required to be supplied to this stage for 100% modulation. A filter-type SSB generator uses an ideal bandpass filter with a center frequency of 5.0 MHz and a bandwidth of 2.7 kHz. What frequency should be used for the carrier oscillator if the generator is to produce a USB signal with a baseband frequency response having a lower lim it of 280 Hz.
Audio signals are not propagated directly to space because: A. to do so will entail additional costs. B. the signal will be highly attenuated C. they will require antennas that are too long D. the signal that will be propagated will be too weak
45.
The highest frequencies are found in ________. A. radio waves C. radar waves B. ultraviolet waves D. x-rays
46.
First symbol in the designation of radio signals emission which refers to use of an unmodulated carrier. A. J B. N C. H D. A
47.
What is known as Johnson’s noise?
A. cosmic noise B. white noise 48.
49.
50.
51.
55.
C. solar noise D. static noise
What is the advantage of series modulation? A. capable of modulating very high frequencies B. low noise and interference C. capable of generating high power D. high gain selectivity The amplitude of a sine wave which is modulated by a musical program will ____________. A. contain harmonic frequencies B. be complex C. contain fundamental frequencies D. be complex and contain fundamental and harmonic f requencies In the spectrum of a frequency-modulated wave, the ____. A. amplitude of any sidebands depend on the modulation index B. carrier frequency disappears when the modulation index is large C. total number of sidebands depends on the modulation index D. carrier frequency disappears when the modulation percentage low
81. 56.
A phase-locked loop has a VCO with a free-running frequency of 14 MHz. As the frequency of the reference input is gradually raised from zero, the loop locks at 12 MHz and comes out again at 18 MHz. Find the lock range.
57.
A varactor has a maximum capacitance of 80 pF and is tuned circuit with 100 uH inductor. Find the tuning voltage necessary for the circuit to resonate at triple the frequency produced by the varactor.
58.
For an AM envelope with a maximum peak voltage of 52V and a minimum peak voltage of 24V, what is the percent modulation?
59.
An FM modulator has a modulator sensitivity of 50 kHz/V. Calculate the deviation and modulation index for a 3 kHz modulating signal of 2V peak.
60.
A collector-modulated class C amplifier has a carrier output power of 100 W, and with efficiency of 75%, calculate the transistor power dissipation, assuming that all the power dissipation that occurs comes from the transistor.
82.
For a 10-MHz crystal with a temperature coefficient of 10 Hz/MHz/C, what is the frequency shift if the temperature decreases 5 Celsius.
83.
For an AM transmitter with an unmodulated carrier power of 100 W that is modulated that is modulated simultaneously by three modulating signals with coefficients of modulation of 0.2, 0.4 and 0.5. What is effective modulation index.
84.
Given a noise factor of 10, what is the noise figure in dB?
85.
The signal power of an input to an amplifier is 100 uW and the noise power is 1 uW. At the output, the signal power is 1 W and the noise power is 40 mW. What is the amplifier noise figure?
61.
What is the percent total harmonic distortion for a fundamental frequency with amplitude of 9 Vrms, second harmonic amplitude of 0.3 Vrms, and the third harmonic amplitude of 0.1 Vrms?
86.
What is the standard design reference for environmental noise temperature in degrees centigrade?
62.
A receiver produces a noise power of 200mW with no signal. The output level increases by 5W when a signal is applied. Calculate (S+N)/N in decibels.
87.
63.
An amplifier with a noise figure of 6 dB has an input signal-to-noise ratio of 25 dB. Calculate the output signal-to-noise ratio in dB.
A 3-stage amplifier is to have an overall noise temperature no greater than 70 degrees 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 to an existing amplifier with existing characteristics as follows: Stage 2 has 20 dB power gain; 3 dB noise figure. Stage 3 has a 15 dB power gain and 6 dB noise figure. Calculate the maximum noise figure (in dB) that the first stage can have.
64.
A three stage amplifier has an input stage with noise ratio of 5 and a power gain of 50. Stages 2 and 3 have a noise ratio of 10 and power gain of 1000. Calculate the noise figure for the overall system.
88.
The resistor R1 and R2 are connected in series at 300 degrees K and 400 degrees K temperature respectively. If R1 is 200 ohms and R2 is 300 ohms, find the power at the load (R1 = 500 ohms) over the bandwidth of 100 kHz.
89.
Determine the shot noise for a diode with a forward bias of 1.40 mA over a 80 kHz bandwidth. (q = 1.6 x 10 raised to minus 19 C)
90.
For three cascaded amplifier stages, each with noise figures of 3 dB and power gains of 10 dB, determine the total noise figure in dB.
65.
Determine the noise figure for an equivalent noise temperature of 115K.
66.
When measuring the selectivity of a receiver, you discover that a signal level of 450 microV on an adjacent channel is required to give the same output as a 1 microV signal on the channel to which the receiver is tuned. Calculate the adjacent channel selectivity in dB.
91.
An amplifier has a noise figure of 2 dB. What is its equivalent noise temperature?
92.
A double-tuned IF transformer has k = 1.5kC. The primary Q is 30 and the secondary Q is 20. what is the bandwidth of the transformer at a frequency of 10.7 MHz?
93.
With an input power of 5 Watts, and a network loss of 30 dB, calculate the output power.
94.
What is the 12 octave for a 1-KHz repetitive wave?
95.
The standard design reference for environmental noise temperature in degree Fahrenheit?
96.
Phase modulation emission type G3E
97.
Industrial noise frequency is between ________.
98.
A transistor amplifier has a measured S/N power of 80 at its input and 25 at its output. Determine the noise figure of the transistor.
99.
Determine the modulation index of a standard FM broadcast having a hypothetical maximum carrier frequency deviation of ±12 kHz and a maximum modulating frequency of 4 kHz frequency of 4 kHz.
th
100. A SSB signal is generated around a 200-kHz carrier. Before filtering, the upper and lower sidebands are separated by 200 Hz. Calculate the filter Q required to obtain 40-dB suppression.
