EST

Question 1

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

Answer 1

A

Question 2

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

Answer 2

D

Question 3

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

Answer 3

D

Question 4

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.

Answer 4

C

Question 5

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

Answer 5

A

Question 6

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

Answer 6

B

Question 7

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

Answer 7

A

Question 8

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.

Answer 8

B

Question 9

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

Answer 9

A

Question 10

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

Answer 10

A

Question 11

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

Answer 11

C

Question 12

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

Answer 12

B

Question 13

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

Answer 13

D

Question 14

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

Answer 14

A

Question 15

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

Answer 15

C

Question 16

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.

Answer 16

C

Question 17

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

Answer 17

D

Question 18

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

Answer 18

C

Question 19

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

Answer 19

D

Question 20

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

Answer 20

A

Question 21

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

Answer 21

A

Question 22

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

Answer 22

D

Question 23

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

Answer 23

D

Question 24

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.

Answer 24

A

Question 25

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

Answer 25

A

Question 26

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

Answer 26

D

Question 27

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

Answer 27

A

Question 28

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

Answer 28

D

Question 29

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

Answer 29

B

Question 30

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

Answer 30

C

Question 31

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)

Answer 31

C

Question 32

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

Answer 32

A

Question 33

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

Answer 33

B

Question 34

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

Answer 34

B

Question 35

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

Answer 35

D

Question 36

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

Answer 36

A

Question 37

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

Answer 37

D

Question 38

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

Answer 38

C

Question 39

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 ˚

Answer 39

A

Question 40

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

Answer 40

B

Question 41

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

Answer 41

B

Question 42

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

Answer 42

A

Question 43

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

Answer 43

C

Question 44

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

Answer 44

A

Question 45

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

Answer 45

D

Question 46

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

Answer 46

C

Question 47

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

Answer 47

A

Question 48

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

Answer 48

D

Question 49

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

Answer 49

C

Question 50

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

Answer 50

B