Regional Maritime University

1 . Sample and Hold Circuit helps the_________ process

Conversion
Companding
Expansion
Error detection

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2 . Antennas can usually handle transmitting and receiving of electromagnetic waves. This property is called

superposition
Reciprocity
Duplication
Convolution

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3 . What is the name given to undesirable interference that is added to a signal being transmitted?

interference
noise
propagation delay
overtones

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4 . A signal with a wavelength of 1.5 m has a frequency of

200 KHz
450MHz
200 MHz
7.5mHz

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5 . A radio wave used in point to point communication consists of

both electric and magnetic fields.
an electric field only
a magnetic field only
non-magnetic field only

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6 . In the electromagnetic wave spectrum, the frequency of radio waves ranges from ??? to ???Hz

300K, 300G
300M, 300G
100K, 300M
100K, 350G

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7 . A process where the received signal is transformed into its original form is

amplification
damping
demodulation
oscillation

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8 . A device that can perform both modulation and demodulation is called

Modem
Oscillator
Analyzer
Computer

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9 . The process of impressing intelligence on the carrier is called

mixing
detection
modulation
impression

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10 . Which characteristic of a radio receiver refers to its ability to reject an unwanted signal

Sensitivity
Selectivity
Fidelity
Quality

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11 . There is distortion in intelligence when the modulation index,. ????? i. 0>m>1 ii. M=1 iii. m<1 iv. m>1

I, II and III
II and IV
IV only
II only

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12 . The carrier frequency remains constant during AM

TRUE
FALSE

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13 . Antennas radiate most effectively when their length is indirectly related to the wavelength of the transmitted signal.

TRUE
FALSE

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14 . ??? is the type of AM used to transmit a picture of the planet Jupiter on national TV

DSB-SC
SSB
VSB
All the above

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15 . In FM, the Carson?s Rule states that the bandwidth is equal to twice the sum of the modulating frequency and ______.

Carrier signal
Modulating signal
Frequency deviation

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16 . An FM receives signal ______

vary in amplitude with modulation
vary in frequency with modulation
vary in frequency and amplitude with wideband modulation
is not immune to noise

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17 . A type of modulation used in transmission of binary data in digital cell phones and low-speed computer modems is

Frequency shift-keying
Phase shift-keying
Phase modulation
Shift-shift keying

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18 . Name the technique used to extract multiple intelligence signals that have been transmitted simultaneously over a single communication channel.

multiplexing
modulation
enveloping
de-multiplexing

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19 . ????.. is the amount of change in carrier frequency produced by the modulating signal.

Frequency mediation
Frequency
Standard deviation
Frequency deviation

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20 . A process where the received signal is transformed into its original form is

Demodulation
damping
amplification
oscillation

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21 . An FM signal with frequency deviation of 90 KHz and modulating signal bandwidth of 5 KHz is applied to this device. The bandwidth of the output signal is

370 KHz
190 KHz
380 KHz
95 KHz

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22 . The FM produced by a phase modulator is called ????.

direct FM
indirect FM
None of the above

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23 . To make PM compatible with FM, the deviation produced by frequency variations in the modulating signal must be compensated for. This can be done by passing the intelligence signal through a low-pass RC network called??

frequency-correcting network
predistorter
1/f filter
All the above

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24 . A commonly used frequency range is 902 MHz to 928 MHz. The bandwidth is?

26
915
457.5
28

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25 . What mathematical operation does an amplitude modulator perform?

Addition
Division
Subtraction
Multiplication

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26 . ?????_determines the number of sideband components in FM.

carrier frequency
modulation frequency
modulation index
deviation ratio

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27 . Consider an angle modulation signal (??)=6??????[2???103+2sin(8000????)+4cos(8000????)]??. The average power of ??(??)is

10 W
18 W
20 W
28 W

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28 . What part of the carrier is varied by the intelligence during modulation in an AM system?

phase
frequency
amplitude
both a and c

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29 . The modulated peak value of a signal is 125 V and the unmodulated carrier value is 85 V. What is the modulation index?

0.47
0.68
0.32
1.47

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30 . Which one is not an advantage of SSB over AM?

Power saving
Requires half the bandwidth
Wider area of reception
Better fidelity

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31 . Which characteristic of a radio receiver refers to amplification?

Sensitivity
Selectivity
Fidelity
Quality

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32 . What aspect of the carrier is changed by modulation?

Frequency
Phase
Amplitude
Depends on the type of modulation

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33 . Frequency modulation and phase modulation are collectively referred to as

Amplitude modulation
Angle modulation
High fidelity modulation
All of the above

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34 . Electromagnetic Waves are refracted when they ___________.

pass into a medium of different dielectric constants
are polarized at right angles to the direction of propagation
encounter a perfectly conducting surface
pass through a small slot in a conducting plane

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35 . Attenuation refers to a loss introduced by a circuit or component.

TRUE
FALSE

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36 . A signal is expressed as V=200sint. At a particular time of the day, the frequency and peak voltage are???? and ???? respectively.

200, ?
100, 0.5?
200, 0.5?
100, 0.25?

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37 . A notch filter can be used to get rid of an annoying 120-Hz hum?

TRUE
FALSE

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38 . Which type of diode would make the best (most sensitive) AM demodulator?

Varactor diode
Schottky diode
Zener diode
Signal diode

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39 . The FM produced by a phase modulator is called indirect FM.

TRUE
FALSE

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40 . In FM, interfering signals on the same frequency are rejected, this is known as the capture effect.

TRUE
FALSE

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