Exam
Name___________________________________
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
1)
The IF amplifiers within an FM radio receiver are tuned to
1)
A)
455 kHz.
B)
4.55 MHz.
C)
100.7 MHz.
D)
10.7 MHz.
Answer:
D
A)
B)
C)
D)
2)
The phase detector in a PLL is followed by a low–pass filter. The low–pass filter passes the
________ and rejects all other frequencies.
2)
A)
input signal
B)
sum of the input and feedback signals
C)
feedback signal
D)
difference of the input and feedback signals
Answer:
D
A)
B)
C)
D)
3)
The outline of the peaks of the modulated carrier has the shape of the information signal, and is
called the
3)
A)
RF index.
B)
lower–side frequency.
C)
envelope.
D)
duty cycle.
Answer:
C
A)
B)
C)
D)
4)
The purpose of a balanced modulator is to eliminate
4)
A)
the carrier.
B)
the upper side–band.
C)
both side–bands.
D)
the lower side–band.
Answer:
A
A)
B)
C)
D)
1
5)
Most VCOs used in PLLs operate on the principle of
5)
A)
variable power.
B)
variable inductance.
C)
phase detection.
D)
variable reactance.
Answer:
D
A)
B)
C)
D)
6)
Combining an audio signal with an RF carrier in a nonlinear device is called
6)
A)
modulation.
B)
filtering.
C)
demodulation.
D)
neutralization.
Answer:
A
A)
B)
C)
D)
7)
The bandwidth of the low–pass filter in a PLL determines the
7)
A)
free–running frequency.
B)
capture range.
C)
lock range.
D)
phase difference.
Answer:
B
A)
B)
C)
D)
8)
If you receive an AM signal modulated by a pure sinusoidal signal in the audio frequency range,
you will hear
8)
A)
a single tone.
B)
static.
C)
nothing.
D)
distortion.
Answer:
A
A)
B)
C)
D)
9)
A basic IF Amplifier always has
9)
A)
a tuned (resonant) circuit on both the input and output.
B)
a tuned (resonant) circuit on the input.
C)
a tuned (resonant) circuit on the output.
D)
None of the above.
Answer:
A
A)
B)
C)
D)
2
10)
Mixing two signals by a nonlinear process is called
10)
A)
spectrum modulation.
B)
sum and product frequencies.
C)
heterodyning.
D)
bandwidth discrimination.
Answer:
C
A)
B)
C)
D)
11)
A mixer is basically a frequency
11)
A)
demodulator.
B)
doubler.
C)
converter.
D)
modulator.
Answer:
C
A)
B)
C)
D)
12)
The main difference between an FM receiver and an AM receiver is the method used to recover the
audio signal from the
12)
A)
modulated IF.
B)
detector.
C)
mixer.
D)
carrier.
Answer:
A
A)
B)
C)
D)
13)
The process of modifying a high frequency carrier by the information to be transmitted is called
13)
A)
multiplexing.
B)
modulation.
C)
discrimination.
D)
detection.
Answer:
B
A)
B)
C)
D)
14)
A PLL can be used as a(n)
14)
A)
series voltage regulator.
B)
audio amplifier.
C)
FM demodulator.
D)
Both B and C above.
Answer:
C
A)
B)
C)
D)
15)
The product of two sinusoidal signals is called
15)
A)
balanced modulation.
B)
lower side frequency.
C)
suppressed–carrier modulation.
D)
Both A and C above.
Answer:
D
A)
B)
C)
D)
3
16)
The quadrant classification of a linear multiplier indicates the number of ________ that the
multiplier can handle.
16)
A)
output polarity combinations
B)
scale factors
C)
transfer characteristics
D)
input polarity combinations
Answer:
D
A)
B)
C)
D)
17)
The signal loss that occurs when photons interact with the molecules of the core in a fiber–optic
cable is called
17)
A)
scattering.
B)
scattering.
C)
refraction.
D)
absorption.
Answer:
D
A)
B)
C)
D)
18)
Higher modulating frequencies are amplified more than the lower frequencies at the transmitting
end of an FM system by a process called
18)
A)
filtering.
B)
de–emphasis.
C)
pre–emphasis.
D)
full duplex.
Answer:
C
A)
B)
C)
D)
19)
For a PLL, the capture range is
19)
A)
always greater than the lock range.
B)
always two times the lock range.
C)
usually less than the lock range.
D)
always the same as the lock range.
Answer:
C
A)
B)
C)
D)
20)
In a PLL, to obtain lock, the signal frequency must come within the
20)
A)
lock range.
B)
capture range.
C)
deviation range.
D)
closed range.
Answer:
B
A)
B)
C)
D)
4
21)
A phase detector has
21)
A)
two input signals and one output signal.
B)
one input signal and two output signals.
C)
no input signals.
D)
three output signals.
Answer:
A
A)
B)
C)
D)
TRUE/FALSE. Write ‘T’ if the statement is true and ‘F’ if the statement is false.
22)
Fiber–optic cables have wider bandwidth, but are more susceptible to interference.
22)
Answer:
True
False
23)
Scattering is the loss of optical signal into the cladding of the fiber–optic cable.
23)
Answer:
True
False
24)
Balanced modulation is used in certain types of communications such as AM broadcast systems,
but is not used in single side–band systems.
24)
Answer:
True
False
5