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EST Electronics > EST > Flashcards

EST Flashcards

1
Q

Coaxial cable is not widely used for long
microwave transmission lines because of its
A. Highloss.
B. Highcost.
C. Large size.
D. Excessive radiation.

A

A

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2
Q

Stripline and microstrip transmission lines are
usually made with
A. Coax.
B. Parallel wires.
C. Twisted pair.
D. PCBs.

A

D

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3
Q

The most common cross section of a
waveguide is a
A. Square.
B. Circle.
C. Triangle.
D. Rectangle.

A

D

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4
Q

A rectangular waveguide has a width of 1 in.
and a height of 0.6 in. Its cutoff frequency is
A. 2.54GHz.
B. 3.0GHz.
C. 5.9GHz.
D. 11.8 GHz.

A

C

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5
Q

A waveguide has a cutoff frequency of 17
GHz. Which of the signals will not be passed by
the waveguide?
A. 15GHz
B. 18GHz
C. 22GHz
D. 25GHz

A

A

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6
Q

Signal propagation in a waveguide is by
A. Electrons.
B. Electric and magnetic fields.
C. Holes.
D. Airpressure.

A

B

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7
Q

A magnetic field is introduced into a
waveguide by a
A. Probe.
B. Dipole.
C. Stripline.
D. Capacitor.

A

A

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8
Q

A half-wavelength, closed section of a
waveguide that acts as a parallel resonant
circuit is known as a(n)
A. Half-wave section.
B. Cavity resonator.
C. LCRcircuit.
D. Directional coupler.

A

B

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9
Q

Decreasing the volume of a cavity causes its
resonant frequency to
A. Increase.
B. Decrease.
C. Remainthe same.
D. Dropto zero

A

A

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10
Q

A popular microwave mixer diode is the
A. Gunn.
B. Varactor.
C. Hotcarrier.
D. IMPATT.

A

A

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11
Q

Varactor and step-recovery diodes are
widely used in what type of circuit?
A. Amplifier
B. Oscillator
C. Frequency multiplier
D. Mixer

A

C

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12
Q

Which diode is a popular microwave
oscillator?
A. IMPATT
B. Gunn
C. Varactor
D. Schottky

A

B

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13
Q

Which type of diode does not ordinarily
operate with reverse bias?
A. Varactor
B. IMPATT
C. Snap-off
D. Tunnel

A

D

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14
Q

Low-power Gunn diodes are replacing
A. Reflex klystrons.
B. TWTs.
C. Magnetrons.
D. Varactor diodes.

A

A

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15
Q

High-power TWTs are replacing what in
microwave amplifiers?
A. MESFETs
B. Magnetrons
C. Klystrons
D. IMPATTdiodes

A

C

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16
Q

Using a small reflector to beam waves to
the larger parabolic reflector is known as
A. Focal feed.
B. Hornfeed.
C. Cassegrain feed.
D. Coaxfeed.

A

C

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17
Q

A common omnidirectional microwave
antenna is the
A. Horn.
B. Parabolic reflector.
C. Helical.
D. Bicone.

A

D

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18
Q

A transmitter having a 900-W carrier
transmits 1188 W when modulated with a single
sinewave. If the carrier is simultaneously
modulated with another sinewave at 60%
modulation, calculate the total transmitted
power.
A. 1084W
B. 1170 W
C. 1350W
D. 1224W

A

C

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19
Q

Low-level modulation is

A. The most economic approach for
low-power transmitters.
B. Characterized by the use of “linear”
power amplifiers to amplify the AM
signal.
C. Characterized by having the carrier
and the intelligence signals mix at low
power levels
D. All of the above

A

D

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20
Q

The main advantage of a high-level
modulation system compared to a low-level
system is that it
A. Allows more efficient amplification.
B. Allows use of low-powered intelligence
signal.
C. Provides
higher
modulation
percentage.
D. Is more economical

A

A

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21
Q

Double conversion is used to overcome the
problem of
A. Image frequency
B. Tracking
C. Diagonal clipping
D. Poor sensitivity

A

A

22
Q

Which of the following would occur in a
receiver not having AGC?
A. The speaker output level would
drastically change while tuning from a
weak signal to a strong signal.
B. Local stations would easily produce
distorted signals in the speaker.
C. There would be a constant need to
readjust the volume control as the
weather and ionosphere change.
D. All the above

A

D

23
Q

The simplest AM detector is the
A. Synchronous detector
B. Product detector
C. Heterodyne detector
D. Diode detector

A

D

24
Q

What is the difference between a balanced
modulator and a regular modulator?
A. a. There is no carrier produced in
the output of a balanced modulator.
B. b. In a balanced modulator, there is
180º phase shift between the upper
and lower sidebands.
C. c. In a balanced modulator, only one
sideband is produced.
D. d. In a balanced modulator, harmonics
of the sidebands are suppressed.

A

A

25
Q

The inherent ability of FM to minimize the
effect of undesired signals operating at the
same or nearly the same frequency as the
desired station is known as the
A. Capture effect
B. Signal-to-noise ratio
C. Noise figure
D. Bessel function

A

A

26
Q

An alphanumeric code for representing the
decimal values from 0 to 9 that is based on the
relationship that only one bit in a binary word
changes for each binary step is known as
A. ASCII
B. EBCDIC
C. Baudot code
D. Graycode

A

D

27
Q

When the message and the BCC are
transmitted as separate parts within the same
transmitted code, it is called a(n)
A. Systematic code
B. CRC
C. (n,k) cyclic code
D. Interleaved code

A

A

28
Q

The value left in the CRC dividing circuit
after all data have been shifted in is the
A. Quantile interval
B. Codec
C. BCC
D. Syndrome

A

D

29
Q

Which of the following is not an example of
code error detection and correction in a data
communication channel?
A. Parity
B. Frequency-shift keying
C. Block-check character

A

B

30
Q

Error-correcting techniques that allow for
correction at the receiver are called
A. Cyclic redundancy checks (CRC)
B. Block-check characters (BCC)
C. Forward error correcting (FEC)
D. Parity

A

C

31
Q

A special digital modulation technique that
achieves high data rates in limited-bandwidth
channels is called
A. Delta modulation
B. Pulse-coded modulation (PCM)
C. Quadrature amplitude modulation
(QAM)
D. Pulse amplitude modulation (PAM)

A

C

32
Q

A procedure that decides which device has
permission to transmit at a given time is called
A. Line control
B. Protocol
C. Flow control
D. Sequence control

A

A

33
Q

Diversity reception does not include:
A. Space diversity
B. Timediversity
C. Frequency diversity
D. Angle diversity

A

B

34
Q

Standard AM broadcast stations usually use
what type of transmitting antennas?
A. Driven collinear array
B. Marconi array
C. Yagi-Uda
D. Log-periodic

A

B

35
Q

Determine the dynamic range of a PCM
system that uses an 8-bit sign magnitude code.
A. 36dB
B. 38dB
C. 40dB
D. 42dB

A

D

36
Q

Find the maximum dynamic range for a
linear PCM system using 16-bit quantizing.
A. 98.08 dB
B. 97.12 dB
C. 96.3 dB
D. 99.8 dB

A

A

37
Q

For an 8-PSK modulator, with an input data
rate of 10 Mbps and a carrier frequency of 70
MHz, determine the baud rate
A. 5Mbaud
B. 10Mbaud
C. 8Mbaud
D. 3.33 Mbaud

A

D

38
Q

How much bandwidth would be required to
transmit a DS-1 signal with a data rate of 1.544
Mbps using a four-level code with a
signal-to-noise ratio of 15 dB (Use Shannon
Theorem)
A. 302.3 kHz
B. 301.2 kHz
C. 307.1 kHz
D. 300.1 kHz

A

C

39
Q

Determine the phase shift introduced by a
150-ft coaxial cable on a 25-MHz signal.
A.–68.4˚
B.–64.8˚
C. 68.4˚
D. 64.8 ˚

A

A

40
Q

Determine the length in feet of one-quarter
wavelength coaxial cable with velocity factor of
0.8 at a frequency of 49 MHz.
A. 1.22 ft
B. 4.02 ft
C. 4.9 ft
D. 2.7 ft

A

B

41
Q

A parallel wire transmission line has an
impedance of 300 ohms and a velocity factor of
0.8. Determine the diameter of the conductors if
they are 5/16 in apart.
A. 0.01 in
B. 0.03 in
C. 0.05 in
D. 0.07 in

A

B

42
Q

A one-quarter wave Q-matching section
made of microstrip is designed to match a
source of 50 Ω to a load of 136 Ω at 5.8 GHz.
The PCB dielectric constant is 2.4. Calculate
the required impedance of the microstrip
A. 82.46 Ω
B. 87.43 Ω
C. 85.78 Ω
D. 83.62 Ω

A

A

43
Q

The reflection coefficient of a transmission
line is 0.75. What is the SWR?
A. 5
B. 6
C. 7
D. 8

A

C

44
Q

A transmission line has an SWR of 1.65.
The power applied to the line is 50 W. What is
the amount of reflected power?
A. 3W
B. 4W
C. 5W
D. 6W

A

A

45
Q

Determine the delay of a 50-ft cable that
has a capacitance of 30 pF/ft and an inductance
of 75 nH/ft.
A. 50ns
B. 60ns
C. 15ns
D. 75ns

A

D

46
Q

A 52-Ω coaxial cable has a 36-Ω antenna
load. What is the SWR?
A. 1.54
B. 1.34
C. 1.44
D. 1.24

A

C

47
Q

A transmission line has an SWR of 1.75.
The power applied to the line is 20 W. How
much power is reflected? What is the loss of the
cable in dB?
A. 11.3 dB
B. 10.9 dB
C. 8.7 dB
D. 9.1 dB

A

A

48
Q

A shorted transmission line 5 in long acts as
a parallel resonant circuit at which frequency?
A. 545MHz
B. 584MHz
C. 550.34 MHz
D. 590.55 MHz

A

D

49
Q

Calculate the numerical aperture when an
optical fiber and its cladding have refractive
indexes of 1.535 and 1.490, respectively.
A. 0.35
B. 0.36
C. 0.37
D. 0.38

A

C

50
Q

Determine the radio horizon for a transmit
antenna that is 100 ft high and a receiving
antenna that is 50 ft high.
A. 22.14 mi
B. 24.14 mi
C. 26.14 mi
D. 28.14 m

A

B

EST Electronics (2 decks)

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