Microwave Communications - MCQs (1300)

1. __________ is the progressive decrease

of signal strength with increasing
distance.

A. Radiation

B. Attenuation

C. Modulation

D. Propagation

2. Calculate the effective earths radius if

the surface refractivity is 301.

5. Rainfall is an important factor for

fading of radio waves at frequencies
above

A. 10 GHz

B. 100 GHz

C. 1 GHz

D. 100 MHz

6. Theoretically electromagnetic radiation

field strength varies in inverse proportion
to the square of the distance, but when
atmospheric attenuation effects and the
absorption of the terrain are taken into
account the attenuation can be as high
as the inverse _______ power of the
distance.

A. 8493 km

B. 8493 mmi

A. Third

C. 6370 km

B. Fourth

D. 6370 mi

C. Fifth

D. Sixth

3. If k-factor is greater than 1, the array

beam is bent

A. Away from the earth

B. towards the ionosphere,

C. towards the earth

D. towards the outer space

4. the antenna separations (in meters)

required for optimum operation of a
space diversity system can be calculated
from:

A. S = 2R/L

B. S = 3R/L

C. S = R/RL

D. S = R/L

where R = effective earth radius (m) and

L = path length (m)

7. What do you call an attenuation that

occurs over many different wavelengths
of the carrier?

A. Rayleigh fading

B. Rician fading

C. Wavelength fading

D. Slow fading

8. Which of the reception problems below

that is not due to multipath?

A. Delayed spreading

B. Rayleigh fading

C. Random Doppler shift

D. Slow fading

9. Which causes multipath or frequencyselective fading?

A. Small reflector

C. At the collector end of the helix

B. Nearer reflector

C. Further reflector

D. At the control grid of the

electron gun

D. Large reflector

10. In microwave transmission using

digital radio, what causes most
intersymbol interference?

14. Coupling into and out of a travelingwave tube can be accompanied by a

A. Waveguide match

B. Cavity match

A. Delayed spreading

C. Direct coax-helix match

B. Rayleigh fading

D. All of the above

C. Random Doppler shift

D. Slow fading

11. A shipboard equipment which

measures the distance between the
ships bottom and the ocean floor.

15. a high-power microwave pulse of the

order of megawatts can be generated by
a

A. traveling-wave tube

B. magnetron

A. Fathometer

C. reflex klystron

B. Echosounder

D. Gunn diode

C. LORAN

D. SONAR

12. The cavity resonator

16. A traveling-wave tube (TWT)

amplifies by virtue of

A. The absorption of energy by the

signal from an electron stream

A. Is equivalent to an LC resonant
circuit

B. The effect of an external

magnetic field

B. In a reflect klystron has its

output taken from the reflector
plate

C. The energy contained the cavity

resonators

C. Produces a frequency which is

independent of the cavity size.

D. The energy liberated form the

collector

D. Has a low Q factor for narrow

operation.

13. At what position is the input signal

inserted into a traveling-wave tube?

A. At the cathode end of the helix

B. At the collector

17. What is the purpose of the

electromagnetic field which surrounds a
traveling-wave tube?

A. To accelerate the electron

B. To velocity modulate the

electron beam

C. To keep the electrons from

spreading out

D. To slow down the signal on the

helix

C. Density modulation at the input

cavity creates velocity modulation
at the output cavity

D. Phase modulation at the input

cavity creates velocity modulation
at the output cavity.

18. Which of the following is used as an

oscillator device in the SHF band?

A. Thyratron tube

B. Tunnel diode

C. Klystron tube

D. Both B and C

22. The frequency of the oscillation

generated by a magnetron, is mainly
determined by

A. The flux density of the external

magnet

B. The ratio of the dc cathode

voltage to the magnetic flux
density

C. The number of the cavity

resonators

D. The dimension of each cavity

resonator

19. Microwave frequencies are normally

regarded as those in the range of

A. 1 to 500 MHz

B. 1000 to 10,000 GHz

C. 1 to 100 GHz

D. 10 to 1000 GHz

20. The highest frequency which a

conventional vacuum-tube oscillator can
generate is not limited by the

23. If the instantaneous RF potentials on

the two sides of a magnetron cavity are
of opposite polarity, the operation is in
the

A. mode

A. Electron transit time

B. /2 mode

B. Distributed lead inductance

C. 2 mode

C. Inter-electrode capacitance

D. /4 mode

D. Degree of emission from the

cathode

21. As the electron beam moves through

a klystrons intercavity drift space

A. Frequency modulation at the

input cavity creates velocity
modulation at the output cavity

B. Velocity modulation at the input

cavity creates density modulation
at the output cavity

24. The Gunn diode oscillator

A. Is capable of generating
continuous microwave power of the
order of kilowatt

B. Generates frequencies which are

below 100 MHz

C. Operates over a positive

resistance characteristic

D. Depends on the formation of

charge domain

25. What ferrite device can be used

instead of duplexer of isolate microwave
transmitter and receiver when both are
connected to the same antenna?

29. Klystron oscillators are most often

used in the frequency range of

A. 300 to 3000 MHz

A. Isolator

B. 3000 to 30000 MHz

B. Magnetron

C. 30 to 30000 MHz

C. Simplex

D. 10 to 10000 MHz

D. Circulator

26. To achieve good bearing resolution

when using a pulsed-radar set, an
important requirement is

A. A narrow, antenna-beam width

in the vertical plane
B. A narrow, antenna-beam width
in the horizontal plane

C. A low repetition rate

D. A high duty cycle

27. When used in conjunction with a

radar set, the purpose of an echo box is
to provide an artificial target.

A. Which may be used to tune the

radar synchronizer

B. Which may be used to tune the

radar receiver

C. To the tone of the pulse

repetition

D. Tune the magnetron to the

correct frequency

28. In a radar-set receiver, the usual

mixer stage is

A. And FET

B. A tunnel diode

C. A silicon crystal

D. A Rochelle salts crystal

30. Oscillators of a klystron tube are

maintained

A. By bunches of electrons passing

the cavity grids

B. By plate-to-cathode feedback

C. By feedback between the

accelerating grid and the repeller

D. By circulating bunches of
electrons within the cavities.

31. What allow microwave to pass in only

one direction?

A. RF emitter

B. Capacitor

C. Varactor-triac

D. Ferrite emitter

32. In an SHF pulsed radar set, a reflex

klystron can be used as a

A. Single mixer stage

B. Local oscillator

C. Transmitter oscillator

D. Duplexer stage

33. A Class-S Emergency PositionIndicating Radio Beacon (E.P.I.R.B)

A. Must be capable of floating or

being secured to a survival

B. Must have its battery replaced

after emergency use

C. May be tested during the first

five minutes of any hour

D. All of these

34. A PPI cathode-ray tube as used on a

radar set

D. Bunching would occur earlier in

time

38. The coarse frequency adjustment of a

reflex klystron is accomplished by

A. The AFC system

A. Is used to check the percentage

of modulation

B. Adjusting the flexible wall of the

resonant cavity

B. Indicates both the range and

azimuth of a target

C. An adjustment in the
synchronizer

C. Indicates only the range of a

target

D. Varying the repeller voltage

D. Is used for receiver alignment

35. The resonant frequency of a cavity

resonator depends upon

A. The mode of operation

B. Its electrical dimensions

C. Its physical dimensions

D. The capacitor which tunes it

36. The maximum usable range of the

usual radar set (on any particular range
setting) is determined by

A. The width of the transmitted

pulses

B. The interval between

transmitted pulses

C. The bandwidth of the receiver IF

stages

D. The duty cycle

37. A reflex klystron is oscillating at the

frequency of its resonant cavity. If the
reflector voltage is made slightly less
negative, the

A. Oscillation will cease

B. Output power would increase

C. The frequency will decrease

39. In a pulsed radar set, the STC circuit

is used to

A. Improve the target bearing

resolution

B. Increases receiver sensitivity for

echoes from targets

C. Vary the pulse frequency in

order to control the maximum
target

D. Reduce interference from the

effects of sea return

40. In a pulsed radar set, the function of

the duplexer is to

A. Aid in calibrating the display unit

B. Prevent frequency drift in the

klystron

C. Allow the transmitter and the

receiver to operate from a common
antenna

D. All of these

41. A magnetron is operated at a duty

cycle of 0.001. It has a peak power
output of 100 kilowatts. Its average
power is

A. 10,000 watts

B. 100 watts

C. 1,000 watts

D. 1,000,000 watts

42. The aquadag coating on the inside of

PPI tube is used

A. To focus the beam of primary

electrons

B. To shield the electron beam from

unidirectional magnetic

C. As a second anode and to

prevent the build-up of secondary
field

D. All of these

43. If the duration of the radar

transmitted pulse, on a particular range
of operation, is increased, the required
bandwidth of the receivers IF amplifiers

A. Must remain as before

B. Must be increased

C. May be decreased

D. Must be doubled

44. The main frequency determining

element of a klystron is

B. A reduction in horizontal
resolution

C. No noticeable effect

D. A decrease in gain

46. Which of the following permits a

microwave signal to travel in one
direction with virtually no loss, but
severely attenuates any signal
attempting to travel in the reverse
direction?

A. Isolator

B. Wave trap

C. Tunnel diode

D. Circulator

47. It is possible to increase the

maximum range of a radar equipment by

A. Lowering the pulse frequency

B. Raising the peak power of the

transmitter

C. Narrowing the beam width and

increasing the pulse duration

D. All of these

48. When it is desired that short-range

targets be clearly seen on a pulsed-radar
set, it is important that the receiver and
display system have

A. The repeller voltage

B. The accelerating voltage

C. Its resonant cavity

A. A long time constant

D. Its mode of operation

B. Low-pass filters

C. The shortest possible time

D. The restricted high-frequency

response

45. A thin layer of dirt and grime coverts

the reflecting surface of the parabolic
dish of a radar set. The particular effect
on the performance of the radar will be

A. A decrease in range

49. Which of the following is used as a

high power microwave oscillator?

A. Thyratron

B. Magnetron

C. Klystron

D. Reflex-klystron

50. Which of the following operating

frequencies is used for the modern loran
navigational system?

C. Produce a trigger pulse for the

transmitter

D. As a single local oscillator

converter stage

54. The intensity of the echoes (target

definition) on a PPI display is determined
by the

A. Loran C: 100 kHz

A. Radio frequency

B. Loran D: 10.2 kHz

C. Loran A: 1950 kHz

B. Pulse frequency and antenna

rotation rate

D. Loran B: 900 kH

C. Duty cycle

D. Average power

51. Which ferrite device can be used

instead of a duplexer to isolate a
microwave transmitter and receiver when
both are connected to the same
antenna?

55. A duplexer circuit allows a transmitter

and a receiver to operate from the same
antenna with virtually no interaction. This
circuit may be replaced by a (an)

A. Isolator

A. loss waveguide

B. Magnetron

B. circulator

C. Simplex

C. isolator

D. Circulator

D. gyrator

52. The pulse frequency is equal to

A. Duty cycle/pulse width

B. The reciprocal of the pulse

repetition rate

C. Pulse width x peak

power/average power

D. All of these

53. In a radar set, a blocking oscillator

can be used to

A. Act as the local oscillator

converter stage
B. Provide the sweep voltage for
the PPI tube

56. Which of the following frequencies

are used by a class-C Emergency
Position-Indicating Radio Beacon
(E.P.I.R.B)?

A. 156.65 MHz

B. 121.5 MHz

C. 156.76 MHz and 156.8 MHz

D. All of these

57. The repetition rate of a pulsed radar

system indicates the

A. Frequency of the range-marker

oscillator

B. Reciprocal of the duty cycle

C. Number of target echoes

received on one second

D. Frequencies of the duty cycle

58. The radar set, sensitivity-time control

circuit

A. Controls the width of the

magnetron pulse

B. Is used to increase sea return

C. Can reduce sea-return response

D. Discriminates between targets

that are very close together.

59. Which of the following is the ferrite

device that buffers a microwave source
from the effects of a varying load, and
thereby prevents the formation of
standing waves?

A. Circulator

B. Duplexer

C. Isolator

D. Diplexer

60. Pulsed radar sets are primarily used

to find the

A. Targets range and bearing

B. Size and speed of a target

C. Speed and course of a target

D. Targets range of speed

61. Which of the following factors is

mainly concerned in the design of an
antenna system for pulsed radar set?

A. Duty cycle

B. Radio frequency

C. Pulse frequency

D. Pulse length

62. In a radar set receivers, an ac AFC

system may be used to

A. Automatically maintain the

correct magnetron frequency

B. Keep the IF stages on frequency

C. Maintain the desired klystron

frequency

D. Provide automatic control of

receiver gain

63. The input signal is introduced into the

traveling-wave tube at the

A. Cathode

B. Anode

C. Cathode end of the helix

D. Collector end of the helix

64. The display on the PPI scope of a

radar set will have greater intensity
under the following conditions

A. Higher antenna rotation speeds

B. Lower pulse repetition rate

C. Lower antenna rotation speeds

D. Both lower antenna rotation

speeds and higher pulse repetition

65. The operating frequency of loran C

lies within the

A. LF band

B. VLF band

C. MF band

D. HF band

66. The PPI tubes have an aquadag

coating on the inside of the tube. The
purpose of this coating is

71. Which of the following is a microwave

frequency?

A. To act as the second anode

B. To shield the tube magnetically

C. To decelerate the electron beam

A. 1.7 MHz

D. To deflect the electron beam

B. 750 MHz

C. 0.98 GHz

D. 22 GHz

67. A traveling-wave tube Is used at

frequencies in the order of

72. Which of the following is not a

common microwave application?

A. 30 MHz

B. 300 MHz

C. 8000 MHz

A. Radar

D. 100 MHz

B. Mobile radio

C. Telephone

D. Satellite communications

68. The main benefit of using

microwaves is

A. Lower-cost equipment

B. Simpler equipment

C. Greater transmission distances

D. More spectrum space for signals

69. Radio communication are regulated

in the Philippines by the

A. DOTC

B. KBP

C. NTC

D. Department of Defense

70. Which of the following is not a

disadvantage of microwaves?

A. Higher-cost equipment

B. Line-of-sight transmission

C. Conventional components are

not usable

D. Circuits are more difficult to

analyze

73. Coaxial cable is not widely used for

long microwave transmission lines
because of its

A. High loss

B. High cost

C. Large size

D. Excessive radiation

74. Stripline and microstrip transmission

lines are usually made with

A. Coax

B. Parallel wires

C. Twisted pair

D. PCBs

75. The most common cross section of a

waveguide is a

A. Square

B. Circle

C. Triangle

D. Rectangle

76. A rectangular waveguide has a width

of 1 inch and a height of 0.6 in. Its cutoff
frequency is

81. A magnetic field is introduced into

waveguide by a

A. 2.54 GHz

A. Probe

B. 3.0 GHz

B. Dipole

C. 5.9 GHz

C. Stripline

D. 11.8 GHz

D. Capacitor

77. A waveguide has a cutoff frequency

of 17 GHz. Which of the following signals
will not be passed by the waveguide?

82. A half-wavelength, close section of a

waveguide that acts as a parallel
resonant circuit is known as a(n)

A. 15 GHz

B. 18 GHz

A. Half-wave section

C. 22 GHz

B. Cavity resonator

D. 255 GHz

C. LCR circuit

D. Directional coupler

78. Signal propagation in a waveguide is

by

83. Decreasing the volume of a cavity

causes its resonant frequency to

A. Electrons

B. Holes

A. Increase

C. Electric and magnetic fields

B. Decrease

D. Air pressure

C. Remain the same

D. Drop to zero

79. When the electric field in a

waveguide is perpendicular to the
direction of wave propagation, the mode
is said to be

84. __________ is a popular microwave

mixer diode.

A. Vertical polarization

A. Gunn

B. Horizontal polarization

B. Varactor

C. Transverse electric

C. Hot carrier

D. Transverse magnetic

D. IMPATT

80. The dominant mode in most

rectangular waveguide is

A. TE
B. TE
C. TM
D. TM

85. Varactor and step-recovery diodes

are widely used in what type of circuit?

A. Amplifier

B. Oscillator

C. Frequency multiplier

D. Mixer

1.0

1.2

0.1

1.1

86. Which diode is a popular microwave

oscillator?

A. IMPATT

B. Gunn

C. Varactor

D. Schottky

87. Which type of diodes does not

ordinarily operate with reverse bias?

A. Varactor

B. IMPATT

C. Snap-off

D. Tunnel

88. Low-power Gunn diodes are replacing

91. A reflex klystron is used as a(n)

A. Amplifier

B. Oscillator

C. Mixer

D. Frequency multiplier

92. For proper operation, a magnetron

must be accompanied by a

A. Cavity resonator

B. Strong electric field

C. Permanent magnet

D. High dc voltage

93. The operating frequency of klystrons

and magnetrons is set by the

A. Reflex klystrons

A. Cavity resonators

B. TWTs

B. DC supply voltage

C. Magnetrons

C. Input signal frequency

D. Varactor diodes

D. Number of cavities

89. Which of the following is not a

microwave tube?

A. Traveling-wave tube

B. Cathode-ray tube

C. Klystron

D. Magnetron

90. In a klystron amplifier, velocity

modulation of the electron beam is
produced by the

94. A magnetron is used only as a/an

A. Amplifier

B. Oscillator

C. Mixer

D. Frequency multiplier

95. A common application for magnetron

is in

A. Radar

A. Collector

B. Satellites

B. Catcher cavity

C. Two-way radio

C. Cathode

D. TV sets

D. Buncher cavity

96. In a TWT, the electron beam is

density-modulated by a

D. Outage time

101. The free space attenuation between

two microwave antennas 40 km apart
operating at 8 GHz is

A. Permanent magnet

B. Modulation transformer

A. 146.7 dB

C. Helix

B. 142.55 dB

D. Cavity resonator

C. 82.5 dB

D. 86.7 dB

97. The main advantage of a TWT over a

klystron for microwave amplification is

102. An active microwave radio repeater

that can provide drops and inserts.

A. Lower cost

B. Smaller size

A. Broadband repeater

C. Higher power

B. Baseband repeater

D. Wider bandwidth

C. IF repeater

D. RF repeater

98. High-power TWTs are replacing what

in microwave amplifiers?

A. MESFETs

B. Magnetrons

C. Klystrons

D. IMPATT diodes

99. The most widely used microwave

antenna

A. Half-wave dipole

B. Parabolic

C. Hyperbolic

D. Horn

100. ______________ is a measure of

reliability expressed as the average
number of hours between successive
failures.

A. MTBF

B. MTTR

C. Downtime

103. If the correction factor k equals 4/3

of the earths curvature, the microwave
beam would have a curvature that is
___________ than that of the earth.

A. More

B. Less

C. Equal

D. Not related

104. The optimum clearance from an

obstacle in an microwave system is
accepted as __________ of the first fresnel
zone radius.

A. 0.6

B. 0.5

C. 0.9

D. 1.5

105. The microwave beam curves the

same than that of the earth when the
value of the correction factor k equals

A. 0

B. 4/3

C. 2/3

D. Infinity

106. The time from the transmission of a

radar pulse to its reception is 0.12 ms.
The distance to the target is how many
nautical miles?

relative motion between the radar set

and a target?

A. Amplitude

B. Phase

C. Frequency

D. Duty cycle

111. The most widely used radar

transmitter component is a

A. 4.85 nmi

B. 9.7 nmi

A. Klystron

C. 11.2 nmi

B. Magnetron

D. 18.4 nmi

C. TWT

D. Power transistor

107. The ability of a radar to determine

the bearing to a target depends upon the

A. Antenna directivity

B. Speed of light

C. Speed of the target

D. Frequency of the signal

108. The pulse duration of a radar signal

is 699ns. The PRF is 185 pulses per
second. The duty cycle is

A. 0.216 %

B. 0.130 %

C. 0.013 %

D. 0.407 %

109. The Doppler effect allows which

characteristics of a target to be
measured?

A. Distance

B. Azimuth

C. Altitude

D. Speed

110. The Doppler effect is a change in

what signal characteristics produced by

112. Low-power radar transmitters

and receivers use which component?

A. GaAs FET

B. Magnetron

C. Gunn diode

D. Klystron

113. What component in a duplexer

protects the receiver from the higher
transmitter output?

A. Waveguide

B. Bandpass filter

C. Notch filter

D. Spark gap

114. Most radar antennas use a

A. Dipole

B. Broadside array

C. Horn and parabolic reflector

D. Collinear array

115. The most common radar display is

the

120. A microwave band of 10.9 to 36.

GHz is considered as

A. A scan

B. Color CRT

C. LCD

A. C-band

D. PPI

B. X-band

C. Q-band

D. K-band

116. A radar antenna using multiple

diploes or slot antennas in a matrix with
variable phase shifters is called a/an

A. A scan

B. Phased array

C. Broadside

D. Circulator polarized array

117. Which of the following is a typical

radar operating frequency?

121. A microwave communications

system space loss calculation formula.

A. 94.2 + 20 log f + 20 log d

B. 92.4 + 20 log f + 20 log d

C. 94.2 + 10 log f + 20 log d

D. 92.3 + 10 log f + 20 log d

122. A waveguide is also a

A. 60 MHz

B. 450 MHz

A. Low pass filter

C. 900 MHz

B. High pass filter

D. 10 GHz

C. Band pass filter

D. Band stop filter

118. A microwave system requires the

use of repeaters when

A. The intervening terrain is

favorable

B. The distances involve are grater

C. The required reliability is meet

D. The radio fading is unacceptable

119. Are transmission lines which convey

electromagnetic waves in highest
frequencies

123. A method of diversity reception

where the signal is transmitted on two
difference frequencies over the same
path

A. Space diversity

B. Frequency diversity

C. Polarization diversity

D. Wavelength diversity

124. A wire used to reduce the skin effect

A. Twister pair of telephone wires

A. AWG # 14

B. Waveguides

B. AWG # 15

C. Power lines

C. Copper wire

D. Coaxial cables

D. Litz wire

125. Space diversity transmission means

transmitting and receiving on two or
more.

A. Reduce tower height

B. Minimize interference to and

from other neighboring stations

A. Different frequencies

C. Shorten waveguide length

B. Antennas operating on two

different frequencies

D. Easy to install

C. Antennas operating on the same

frequencies

D. Identical frequencies

126. The best system configuration to

overcome multipath fading of microwave
system over the water

A. Space diversity

B. Frequency diversity

C. Polarization diversity

D. Wavelength diversity

127. When the value of k increases, the

effective result is _______ of the
equivalent curvature

130. What is the cut-off frequency of a

waveguide?

A. The highest frequency the

waveguide operates

B. The lowest frequency the

waveguide operates

C. The same as the operating

frequency

D. The only frequency the

waveguide operates.

131. When the clearance above the

obstruction is equal to the radii of even
fresnel zones at the point of reflection.
The RSL is

A. Increased

B. Decreased

A. Flattening

C. Constant

B. Bulging

D. Above threshold

C. Sharp curvature

D. All of these

128. A traveling wave tube consists of

132. What is the wavelength of a wave in

a waveguide?

A. Greater than in free space

B. Depends only on the waveguide

dimensions and the free-space
wavelength

A. Electron gun, helix and repeller

B. Electron gun, helix and collector

C. Electron gun, repeller and

collector

C. Inversely proportional to the

phase velocity

D. Buncher cavity and catcher

cavity

D. Inversely proportional to the

group velocity

129. Advantage of periscope antenna in

microwave

133. The CCIR hypothetical reference

circuit covering a distance of 25000 km
consists of a total of how many hops?

A. 5

B. 10

C. 24

D. 54

134. Water causes

more attenuation particularly on what
frequency?

138. _________ is a microwave link

between the down-town terminal and
another out of town terminal.

A. STL

B. Uplink

C. Downlink

D. Terrestrial

139. Attenuator is used in the traveling

wave tube to

A. 20 GHz

B. 63 GHz

C. 183 GHz

A. Prevent oscillation

D. 202 GHz

B. Increase gain

C. Prevent saturation

D. All of these

135. At what frequency does oxygen

cause excessive attenuation?

A. 60 GHz

B. 50 GHz

C. 40 GHz

D. 30 GHz

136. Which of the following is an

atmospheric attenuation?

140. Is a method of diversity reception

applied to reflective path to reduce
fading.

A. Frequency diversity

B. Space diversity

C. Polarization diversity

D. Wavelength diversity

141. What is the effective earths radius

used in communications design?

A. Attenuation due to water vapor

and oxygen

B. Attenuation due to mist and fog

A. 4000 miles

C. Attenuation due to other gases

B. K x 4000 miles

D. Attenuation due to rain.

C. 5000 miles

D. K x 5280 miles

137. A microwave system operating at

the 6 GHz band is carrying 600 voice
channels. What is the noise loading
power in dBmO?

142. IF bandwidth of a radar system is

inversely proportional to

A. 12.78

A. Pulse width

B. 26.78

B. Pulse interval

C. 27.78

C. Peak transmit power

D. 10.25

D. All of these

143. EADI stands for

A. Electronic Air Data Indicator

B. Electronic Altitude and Distance

Indicator

C. Electronic Altitude and Director

Indicator

D. Electronic Air and Distance

Indicator

144. Which aircraft navigational system

determines the time to station (TTS) or
time to go (TTG)?

A. ADF

B. DME

C. Timer

D. ATC

145. What frequency does a radio

altimeter operate?

A. 33500 kHz

B. 43000 kHz

C. 33500 MHz

D. 43500 MHz

146. What inflight system allows

passengers to make telephone calls,
send faxes, and computer data shop and
play computer games, etc.?

A. Inflight Satellite System

B. Terrestrial Flight Telephone

System

C. World Airline Entertainment

System

D. Satellite Phone

147. ADF stands for

A. Audio Direction Findings

B. Automatic Direction Finder

C. Alternate Direction Finder

D. Automatic Distance Finder

148. RF carrier of the middle marker is

modulated at ____ Hz.

A. 1300

B. 1400

C. 1500

D. 1600

149. Which of the following is considered

as the major advantage of using a helix
traveling wave tube?

A. Cheaper

B. Less noise

C. High power

D. Wide bandwidth

150. RADAR stands for

A. Radio Distance and Ranging

B. Radio Detection and Ranging

C. Radio Direction and Ranging

D. Radio Distance and Range

151. Attenuator is used in the travelling

wave tube to

a. Help bunching

b. Prevent oscillations

c. Prevent saturation

d. Increase gain

152. The multicavity klystron

a. Is not a good low-level amplifier

because of noise

b. Has a high repeller voltage to

ensure a rapid transmit time

c. Is not suitable for pulsed

operation

d. Needs a long transit time

through the buncher cavity to
ensure current modulation

153. What is the effective radiated power

of a repeater with 450 W transmitting
power output, 4 dB feedline loss, 6dB
duplexer loss, and 7 dB circulator and
feedline loss and antenna gain of 25 dB?

c. Post-tuning drift

d. Tuning sensitivity

157. A rectangular waveguide has a

width of 1.2 in and a height of 0.7 in. the
waveguide will pass all signals above __
GHz.

a. 4 GHz

b. 8.44 GHz

c. 10 GHz

d. 4.92 GHz

158. Waveguides are

a. 2893.31 W

a. A hollow tube that carries HF

b. 2523.83 W

b. Solid conductors of RF

c. 2839.31 W

d. 2425.38 W

c. Coaxial cables
d. Copper wire

154. Magnetron oscillator are used for

159. A TWT is sometimes preferred to the

multi-cavity klystron amplifier because
the former

a. Generating SHF signals

b. Multiplexing

a. Is more efficient

c. Generating rich harmonics

b. Has a greater bandwidth

d. FM demodulation

c. Has a higher number of modes

d. Produces a higher output power

155. A microwave tube which has the

advantage of having a high efficiency

160. Variation in oscillator frequency with

changes in load SWR

a. Cross-field amplifier

b. Helix traveling wave tube

a. Frequency pulling

c. Klystron

b. Frequency pushing

d. Gridded tube

c. Post-tuning drift

d. Tuning sensitivity

156. What term is used to describe

the variation in a microwave oscillator
frequency caused by power supply
voltage or current changes?

a. Frequency pulling

b. Frequency pushing

161. It is the frequency change of an

electronically tuned oscillator at a
specified time after it has reached its
desired frequency

a. Frequency pulling

c. 5600 km

b. Frequency pushing

d. 4850 km

c. Post-tuning drift

d. Tuning sensitivity

162. What is the power level of the

smallest signal that can be detected
above the noise by a Schottky diode?

166. What is the power level of the

largest signal that will still be in the
square-law range of a Schottky diode?

a. -20 dBm

b. 0 dBm

a. -20 dBm

c. -60 dBm

b. 0 dBm

d. -100 dBm

c. -60 dBm

d. -100 dBm

163. A line-of-sight radio link operating at

a frequency of 6GHz has a separation of
$0 km between antennas. An obstacle in
the path is located 10 km from the
transmitting antenna. By how much must
the beam clear the obstacle?

a. 11.6 m

b. 13.4 m

c. 19.34 m

d. 22.33 m

167. A component that combines

microwave signals from separate
transmission lines into one common
transmission line and allows no coupling
between the separate lines

a. Isolator

b. Circulator

c. Directional coupler

d. Combiner

168. Telemetry is a microwave

communications system which operates
at

164. AM isolator

a. Acts a buffer between

microwave oscillators coupled to a
waveguide

b. Acts as a buffer to protect a

microwave oscillator
form variations in the load changes

c. Shields UHF circuits from RF

transmitter

d. Both a and b

165. What is the effective earths radius

when Ns = 300?

a. 8500 km

b. 9320 km

a. 600 MHz

b. 3.9 GHz

c. 4 GHz

d. 2 GHz

169. What is the maximum power that

can be obtained from a microwave
semiconductor?

a. 1 W

b. 500 mW

c. 10 W

d. 4 W

170. The cavity magnetron uses

strapping to

and a distance of 40 km, determine the

free-space path loss in dB.

a. Prevent mode-jumping

a. 80 dB

b. Prevent cathode back-heating

b. 84.2 dB

c. Ensure bunching

c. 140 dB

d. Improve the phase-focusing

effect

d. 144.2 dB

171. As a result of reflections from a

plane conducting wall, electromagnetic
waves acquire an apparent velocity
greater that the velocity of light in space.
This is called the

a. Velocity of propagation

b. Normal velocity

c. Group velocity

d. Phase velocity

172. Which of the following is a method

of modulating digital signals onto a
microwave carrier?

a. FSK

b. Biphase

c. Quadraphase

d. All of the above

173. Suppose that the transmitter and

receiver towers have equal height. How
high would they have to be to
communicate over a distance of 34 km?

a. 23.5 m

b. 28.47 m

c. 17 m

d. 8.47 m

174. In microwave communications

system, for a carrier frequency of 6 GHz

175. A microwave relay repeater that

receives the modulated microwave
carrier and obtains the baseband signal
from it, and them modulates the
baseband signal onto another carries and
retransmit the new carrier with the
baseband modulated onto it

a. Heterodyne repeater

b. Baseband repeater

c. RF repeater

d. Regenerative repeater

176. Which is the frequency range of the

most common industrial microwave relay
band?

a. 6.575-6.875 GHz

b. 3.7-4.2 GHz

c. 5.925-6.425 GHz

d. 10.7-11.7 GHz\

177. When a particular mode is excited in

a waveguide, there appears an extra
electric component, in the direction of
propagation. The resulting mode is

a. Transverse-electric

b. Transverse-magnetic

c. Longitudinal

d. Transverse-electromagnetic

178. Waveguide construction

a. Should not use silver plating

b. Should not use copper

c. Should not have short vertical

runs

d. Should not have long horizontal

runs

179. In a microwave system, the antenna

sees a sky temperature of 120 K, and the
antenna feedline has a loss of 3
dB. Calculate the noise temperature of
the antenna/feedline system, referenced
to the receiver input.

a. 205 K

b. 233.33 K

c. 182 K

d. 210 K

180. A choke flange may be used to

couple two waveguides

a. The smaller cross section

needed at any frequency

b. Lower attenuation

c. Freedom from spurious modes

d. Rotation of polarization

183. A circulator

a. Cools dc motors during heavy

loads

b. Allows two or more antennas to

feed one transmitter

c. Allows one antenna to feed two

separate microwave transmitters
and receivers at the same time

d. Insulates UHF frequencies on

transmission lines

184. What is the free-space loss in dB

between two microwave parabolic
antennas 38 km apart operating at 7
GHz?

a. To help in the alignment of the

waveguides

b. Because it is simpler than any

other join

a. 85.10 dB

c. To compensate for discontinuities

at the join

b. 80.90 dB

c. 140.90 dB

d. To increase the bandwidth of the

system

d. 145.10 dB

181. A PIN diode is

185. A ruby maser amplifier must be

cooled

a. A metal semiconductor pointcontact diode

a. Because the maser amplification

generates a lot of heat

b. A microwave mixer diode

b. To increase bandwidth

c. Often used a microwave detector

d. Suitable for use as a microwave

switch

c. Because it cannot operate at

room temperature

d. To improve the noise

performance

182. For some applications, circular

waveguides may be used preferred to
rectangular ones because

186. The glass tube of a TWT may be

coated with aquadag to

a. Help focusing

b. Provide attenuation

c. Improve bunching

d. Increase gain

187. An antenna covering that the

transmitted or receives microwave power
can pass through, used to protect the
antenna and the antenna feed from
weather

a. Shroud

b. Sub-reflector

c. Radome

d. Offset antenna

188. Waveguide are

a. Used exclusively in high

frequency power supplies

b. Ceramic couplers attached to

the antenna terminals

c. High-pass filters used at low

radio frequencies

d. Hollow metal conductors used to

carry high-frequency current

189. A microwave device which is

unlikely to be used a pulsed device. It is
based on the principle of operation of a
traveling wave tube.

a. Multicavity klyston

b. Cross-field amplifier (CFA)

c. Backward wave oscillator (BWO)

d. Coaxial magnetron

190. A magnetic field is used in the

cavity magnetron to

a. Prevent anode current in the

absence of oscillations

b. Ensure that the oscillations are

pulsed

c. Help in focusing the electron

beam thus preventing spreading

d. Ensure that the electors will orbit

around the cathode

191. In a micro wave communications

system, if the minimum carrier-to-noise
(C/N) requirements for a receiver with a
10MHz bandwidth is 22 dB, the minimum
receive carrier power is

a. -82 dB

b. 76 dBm

c. 84 dB

d. -82 dBm

192. A rectangular waveguide used for

microwave transmission has a width of
1.4 inches and a height of 0.8 inches. All
signals above __ GHz will be passed by
the waveguide.

a. 4.3 GHz

b. 2 GHz

c. 4.2 GHz

d. 5 GHz

193. A pyramidal horn has an aperture

(opening) of 58 mm in the E plane and 78
mm in the H plane. It operates at 14 GHz.
Calculate the gain in dBi.

a. 19.29

b. 24.14

c. 15.8

d. 19.31

194. A magnetron whose oscillating

frequency is electronically adjustable
over a wide range is called a

a. Coaxial magnetron

b. Dither-tuned magnetron

c. Frequency agile magnetron

d. VTM

195. Conductance takes place in a

waveguide

a. By inter-electron delay

b. Through electrostatic field

reluctance

c. In the same manner as a

transmission line

d. Through electromagnetic and

electrostatic fields in the walls of
the waveguide

196. Indicate the false statement.

Klystron amplifiers may use intermediate
cavities to

a. Prevent the oscillations that

occurs in two-cavity klystrons

b. Increase the bandwidth of the

device

c. Improve power gain

d. Increase the efficiency of the

klystron

197. The primary purpose of the helix in

a traveling wave tube is to

a. Prevent the electron beam from

spreading in the long tube

b. Reduce the axial velocity of the

RF field

c. Ensure broadband operation

d. Reduce the noise figure

198. A microwave device which allows RF

energy to pass through in one direction
with very little loss, but absorbs RF
power in the opposite direction

a. Circulator

b. Wave trap

c. Multiplexer

d. Isolator

199. A parametric amplifier must be

cooled

a. Because parametric
amplification generates a lot of
heat

b. To increase bandwidth

c. Because it cannot operate at

room temperature

d. To improve the noise

performance

200. For low attenuation, the best

transmission medium is

a. Flexible waveguide

b. Ridged waveguide

c. Rectangular waveguide

d. Coaxial line

201. IF repeaters are also called

a) heterodyne receiver

b) mixer/receiver

c) radio receiver

d) FM receiver

202. It is the difference between the

nominal output power of a transmitter
and the minimum input power required
by a receiver

a) RSL

c) prevent saturation

b) IRL

d) increase the gain

c) system gain

d) FSL

203. A phenomenon whereby the

frequency of a reflected of a reflected
signal is shifted if there is relative motion
between the source and reflecting object.

a) Doppler effect

b) Hall effect

c) Marconi effect

d) Maxwell effect

204. A ferrite is

207. A magnetron is used only as

a) amplifier

b) oscillator

c) mixer

d) frequency multiplier

208. A backward-wave oscillator is based

on the

a) rising-sun magnetron

b) crossed-field amplifier

c) coaxial magnetron

d) traveling-wave tube

a) a nonconductor with magnetic

properties

b) an intermetallic compound with

particularly good conductivity

c) an insulator which heavily

attenuates magnetic fields

a) coax

d) a microwave semiconductor
invented by Faraday

b) parallel lines

c) twisted pair

d) PCBs

205. The primary purpose of the helix in

a traveling-wave tube is to

a) prevent the electron beam from

spreading in the long tube

b) reduce the axial velocity of the

RF field

c) ensure the broadband operation

d) reduce the noise figure

206. The attenuator is used in the

travelling-wave tube to

a) help bunching

b) prevent oscillations

209. Stripline and microstrip transmission

lines are usually made with

210. Which of the following is not a

microwave tube?

a) Traveling-wave tube

b) Cathode-ray tube

c) Klystron

d) Magnetron

211. Indicate which is not true.

Compared with other types of radar,
phased array radar has the following
advantages

a) very fast scanning

b) ability to track and scan

simultaneously

c) circuit simplicity

d) ability to track many targets

simultaneously

212. Given the frequency and dimensions

of 5 GHz and 7 cm by 9 cm respectively,
the beam of the pyramidal horn is about
______.

a) 27 degrees

b) 53 degrees

c) 60 degrees

d) 80 degrees

213. The diameter of a parabolic reflector

should be at least how many
wavelengths at the operating frequency?

216. Indicate which one of the following

applications or advantages of radar
beacons is false:

a) target identification

b) navigation

c) very significant extension of the

maximum range

d) more accurate tracking enemy

targets

217. Refers to more than one

transmission path or method of
transmission available between
transmitter and a receiver.

a) diversity

b) polarization

c) efficiency

d) accuracy

218. A solution to the blind speed

problem is to

a) 1

b) 2

c) 5

a) change the Doppler frequency

d) 10

b) vary the RF

c) use monopulse

d) use MTI

214. A type of microwave repeater where

the received RF carrier is down-converted
to an IF frequency, amplified filtered and
further demodulated to baseband.

219. A direct path that exist between the

transmit and receive antennas

a) RF repeater

b) IF repeater

a) LOS

c) baseband repeater

b) direct waves

d) radio repeater

c) space waves

d) terrestrial waves

215. In order to reduce cross-sectional

dimensions, the waveguide to use is

a) circular

b) ridged

c) rectangular

d) flexible

220. The function of the quartz delay line

in an MTI radar is to

a) help in subtracting
a complete scan from the previous
scan

b) match the phase of the coho and

the stalo

c) match the phase of the coho and

the output oscillator

d) delay a sweep so that the next

sweep can be subtracted from it

221. Type of diversity where it modulates

two different RF carrier frequencies with
the same IF intelligence, then
transmitting both RF signals to a given
destination.

225. A pyramidal horn used at 5 GHz has

an aperture that is 7 cm by 9 cm. The
gain is about

a) 10.5 dB

b) 11.1 dB

c) 22.6 dB

d) 35.8 dB

226. Type of diversity where the output

of the transmitter is fed to two or
more antennas that are physically
separated by an appreciable wavelengths

a) polarization diversity

b) quad diversity

c) space diversity

a) quad diversity

d) frequency diversity

b) wavelength diversity

c) space diversity

d) hybrid diversity

222. The coho in MTI radar operates at

the

a) intermediate frequency

b) transmitted frequency

c) received-frequency

a) moving-target plotting on the PPI

d) pulse operation frequency

b) the MTI system

c) FM radar

d) CW radar

223. Which type of diode does not

ordinarily operate with reverse bias?

227. The Doppler effect is used in

(indicate the false statement)

228. A type of diversity where a single RF

carrier is propagated with two different
electromagnetic polarization.

a) Varactor

b) IMPATT

c) Snapp-off

a) space diversity

d) Tunnel

b) wavelength diversity

c) polarization diversity

d) hybrid diversity

224. What happens when a horn antenna

is made longer?

229. The A scope displays

a) gain increases

b) beam width decreases

a) the target position and range

c) bandwidth increases

d) bandwidth decreases

b) the target range, but not

position

c) the target position, but not

range

d) neither range nor position, but

only velocity

230. The glass tube of a TWT may be

coated with aquadag to

a) help focusing

b) provide attenuation

c) improve bunching

d) increase gain

231. Type of diversity which consists of a

standard frequency diversity path where
the two transmitter/receiver pair at one
end of the path are separated from each
other and connected to
different antennas that are vertically
separated as in space diversity

a) quad diversity

b) wavelength diversity

c) space diversity

d) hybrid diversity

232. The biggest disadvantage of CW

Doppler radar is that

b) quad diversity

c) space diversity

d) wavelength diversity

234. If the target cross section is

changing, the best system for accurate
tracking in

a) lobe switching

b) sequential lobing

c) conical switching

d) monopulse

235. The multicavity klystron

a) is not good low-level amplifier

because of noise

b) has a high repeller voltage to

ensure a rapid transmit time

c) is not suitable for pulse

operation

d) needs a long transmit time

through the buncher cavity to
ensure current modulation

236. An arrangement that avoids a

service interruption during periods of
deep fades or equipment failures.

a) service switching arrangement

a) it does not give the target

velocity

b) protection switching
arrangement

b) it does not give the target range

c) a transponder is required at the

target

c) interruption switching
arrangement

d) equipment switching
arrangement

d) it does not give the target

position

233. The combination of the frequency,

space, polarization and receiver diversity
into one system

a) hybrid diversity

237. A type of attenuator where

attenuation is accomplished by insertion
of a thin card of resistive material
through a slot in the top of a waveguide

a) flap attenuator

b) vane attenuator

c) slot attenuator

d) directional coupler

b) the receiver might be

overloaded

c) it will not be received

d) the target will appear closer

than it really is

238. After a target has been acquired,

the best scanning system for tracking is

242. Points in the microwave system

baseband signals either originate or
terminate

a) nodding

b) spiral

c) conical

a) terminator

d) helical

b) terminal stations

c) terminating equipment

d) terminal equipment

239. A duplexer is used

a) to couple two
different antennas to a transmitter
without mutual interference

b) to allow the one antenna to be

used for reception or transmission
without mutual interference

c) to prevent interference between

two antennas when they are
connected to a receiver

d) to increase the speed of pulses

in pulsed radar

240. Type of protection switching

arrangement where each working radio
channel has a dedicated backup or spare
channel

a) hot swap

b) hot backup

c) hot standby

d) hot diversity

241. If a return echo arrives after the

allocated pulse interval,

a) it will interfere with the

operation of the transmitter

243. A half wavelength, closed section of

a waveguide that acts as a parallel
resonant circuit is known as _____.

a) half-wave section

b) cavity resonator

c) LCR circuit

d) directional couple

244. Decreasing the volume of a cavity

causes its resonant frequency to

a) increase

b) decrease

c) remains the same

d) drop to zero

245. The IF bandwidth of a radar receiver

is inversely proportional to the

a) pulse width

b) pulse repetition frequency

c) pulse interval

d) the target will appear closer

than it really is

246. Which of the following devices are

not being used in microwave power
amplifier?

250. The power that leaks out of the back

and sides of the transmit antenna
interfering with the signal entering with
the signal entering the input of a nearby
receive antenna.

a) klystron tubes

b) traveling wave tubes

a) ringaround

c) IMPATT

b) ringabout

d) magnetron

c) roundabout

d) turnaround

247. Which is not true? A high PRF will

a) make the returned echoes easier

to distinguish from noise

b) make the target tracking easier

with conical scanning

c) increase the maximum range

d) have no effect on the range

resolution

248. It is a unidirectional device often

made up of ferrite material used in
conjunction with a channel-combining
network to prevent the output from
interfering with the output of another
transmitter

251. Which of the following is not true:

The radar cross section of a target

a) depends on the frequency used

b) may be reduced by special

coating of the target

c) depends on the aspect of a

target, if this non-spherical

d) is equal to the actual crosssectional area for small targets

252. It is a general term applied to the

reduction in signal strength at the input
to a receiver

a) fading

a) circulator

b) attenuation

b) magic tee

c) absorption

c) isolator

d) ghosting

d) rat race

249. Which is not true about the

following: Flat-topped rectangular pulses
must be transmitted in radar to

253. Indicate which of the following

cannot be followed by the word
waveguide

a) elliptical

a) allow a good minimum range

b) flexible

b) make the returned echoes easier

to distinguish from the noise

c) coaxial

d) ridged

c) prevent frequency changes in

the magnetron
d) allow accurate range
measurements

254. If the ratio of the antenna diameter

to the wavelength in a radar system is

high, this will result in (indicate the false

statement)

a) large maximum range

b) good target discrimination

c) difficult target acquisition

d) increased capture area

255. High-power TWTs are replacing what

in microwave amplifiers?

b) 2

c) 4

d) 8

259. If the peak transmitted power in a

radar system is increased by a factor of
15, the maximum range will be increased
by a factor of

a) 2

b) 4

a) MESFETs

c) 8

b) Magnetrons

d) 16

c) Klystrons

d) IMPATT diodes

256. The most widely used microwave

antenna is a

260. Varactor and steprecovery diodes are widely used in what

type of circuit?

a) amplifier

b) oscillator

a) half-wave dipole

c) frequency multiplier

b) quarter-wave probe

d) mixer

c) single loop

d) horn

257. Applies to propagation variables in

the physical radio path which affect
changes in path loss between the
transmitter at one station and its
normal receiver at the other station.

261. It is defined as line loss incurred by

an electromagnetic wave as it
propagates in a straight line through a
vacuum with no absorption or reflection
of energy from nearby objects.

a) IRL

b) FSL

a) ghosting

c) RSL

b) absorption

d) Eb/No

c) attenuation

d) fading

258. If the antenna diameter in a radar

system is increased by a factor of 4, the
maximum range will be increased by a
factor of

a) square root of 2

262. For proper operation, a magnetron

must be accompanied by a

a) cavity resonator

b) strong electric field

c) permanent magnet

d) high dc voltage

263. A police radar speed trap functions

at a frequency of 1.024 GHz in direct line
with your car. The reflected energy from
your car is shifted 275 Hz in
frequency. Calculate the speed in miles
per hour?

a) 60 mph

b) 70 mph

c) 80 mph

d) 90 mph

264. It is the ratio of the wideband carrier

to the wideband noise power

deteriorates as a signal passes through a

circuit or series of circuits

a) noise factor

b) signal to noise ratio

c) carrier to noise ratio

d) dynamic range

268. What is the peak power of a radar

pulse if the pulse width is 1s, the pulse
repetition rate is 900, and the average
power is 18 W?

a) 10 kW

a) carrier to noise ratio

b) 15 kW

b) signal to noise ratio

c) 20 kW

c) energy per bit per noise density

ratio

d) 30 kW

d) noise figure

265. What is the duty cycle of a radar

pulse if the pulse width is 1s, the pulse
repetition rate is 900, and the average
power is 18 W?

a) 0.09 %

b) 0.99 %

c) 0.90 %

d) 1.00 %

266. A microwave tube amplifier uses an

axial magnetic field and a radial electric
field. This is the

a) reflex klystron

b) coaxial magnetron

c) traveling-wave magnetron

d) CFA

267. Figure of merit used to indicate how

much the signal-to-noise ratio

269. The point where the antenna

is mounted with respect to the parabolic
reflector is called the

a) focal point

b) center

c) locus

d) tangent

270. The operating frequency of klystron

and magnetrons is set by the

a) cavity resonators

b) DC supply voltage

c) input signal frequency

d) Number of cavities

271. Using a small reflector to beam

waves to the larger parabolic reflector is
known as

a) focal feed

b) horn feed

c) cassegrain feed

d) coax feed

272. If the noise figures and gains of

each of the amplifiers in cascade is 3 dB
and 10 dB respectively. What is the total
noise figure?

276. What is the distance in nautical

miles to a target if it takes 123 s for a
radar pulse to travel from the radar
antenna to the target, back to the
antenna, and be displayed on the PPI
scope?

a) 2.12 dB

a) 10 nmi

b) 3.24 dB

b) 5 nmi

c) 1.24 dB

c) 20 nmi

d) 4.23 dB

d) 15 nmi

273. One of the following is unlikely to be

used as a pulsed device

a) multicavity klystron

b) BWO

c) CFA

d) TWT

274. Calculate the maximum ambiguous

range for a radar system with PRT equal
to 400s.

a) 13.8 mi

b) 43.5 mi

c) 16.4 mi

d) 32.8 mi

275. When electromagnetic waves are

propagated in a waveguide

a) they travel along the broader

walls of the guide

b) they are reflected from the walls

but do not travel along them

c) they travel through the dielectric

without the walls

d) they travel along all four walls of

the waveguide

277. Waveguides are used mainly for

microwave signals because

a) they depend on straight-line

propagation which applies to
microwaves only

b) losses would be too heavy at

lower frequencies

c) there are no generators powerful

enough to excite them at lower
frequencies

d) they would be too bulky at lower

frequencies

278. Calculate the coupling of a

directional coupler that has 70 mW into
the main guide and 0.35 mW out the
secondary guide.

a) 13 dB

b) 23 dB

c) 33 dB

d) 10 dB

279. The wavelength of a wave in a

waveguide

a) is greater than in free space

b) depends only on the waveguide

dimensions and the free space
wavelength

c) is inversely proportional to the

phase velocity

d) is directly proportional to the

group velocity

280. A rectangular waveguide is 1 cm by

2 cm. Calculate the cutoff frequency

a) 3.5 GHz

b) 15 GHz

c) 7.5 GHz

d) 4 GHz

281. The main difference between the

operation of transmission liners and
waveguides is that

a) the latter is not distributed, like

transmission lines
b) the former can use stubs and
quarter-wave transformers, unlike
the latter
c) transmission lines use the
principal mode of propagation, and
therefore do not suffer from lowfrequency cut-off
d) terms such as impedance
matching and standing-wave ratio
cannot be applied to waveguides

282. The useful power of the transmitter

that is contained in the radiated pulses is
termed as ______.

a) rms power

b) rated power

c) peak power

d) average power

283. In radars, echoes that are produced

when the reflected beam is strong
enough to make a second trip

a) double range echoes

b) double frequencies echoes

c) second return echoes

d) second time around echoes

284. Indicate the false statement.

Compared with equivalent transmission
lines, 3 GHz waveguides

a) are less lossy

b) can carry higher powers

c) are less bulky

d) have lower attenuation

285. The range beyond which targets

appear as second return echoes is called

a) maximum range

b) maximum unambiguous range

c) maximum usable range

d) any of these

286. When a particular mode is excited in

a waveguide, there appears an extra
electric component, in the direction of
propagation. The resulting mode is

a) transverse electric

b) transverse magnetic

c) longitudinal

d) transverse-electromagnetic

287. In radars, echoes that arrive after

the transmission of the next pulse are
called _____.

a) second return echoes

b) second time around echoes

c) multiple time around echoes

d) any of these

288. When electromagnetic waves are

reflected at an angle from a wall, their
wavelength along the wall is

a) the same as the free space

b) the same as the wavelength

perpendicular to the wall

c) shortened because of the

Doppler effect

d) greater than in the actual

direction of propagation

289. A radar mile is equivalent to

a) 2000 mi

b) 2000 m

c) 2000 yd

d) 2000 km

290. As a result of reflections from a

plane conducting wall, electromagnetic
waves acquire an apparent velocity of
light in space

a) the group velocity of the signal

becomes zero

b) the phase velocity of the signal

becomes infinite

c) the characteristic impedance of

the guide becomes infinite

d) the wavelength within the

waveguide becomes infinite

293. In radars, the duration of the pulse

is

a) duty cycle

b) pulse width

c) pulse amplitude

d) pulse cycle

294. A signal propagated in a waveguide

has a full wave electric intensity change
between two further walls, and no
component of the electric field in the
direction of propagation. The mode is

a) TE11

a) velocity of propagation

b) TE10

b) normal velocity

c) TM22

c) group velocity

d) TE20

d) phase velocity

291. In radars, the time between pulses

is called ______.

295. In radars, the number of the pulses

transmitted per second is called

a) pulse repetition frequency

a) rest time

b) pulse repetition time

b) duration time

c) pulse repetition phase

c) delay time

d) pulse number of repetition

d) propagation time

292. Indicate the false statement. When

the free-space wavelength of a signal
equals the cutoff wavelength of the guide

296. Which of the following is incorrect?

The dominant mode of propagation is
preferred with rectangular waveguides
because

a) it leads to the smallest

waveguide dimensions

b) the resulting impedance can be

matched directly to coaxial lines

them to each other, which could not be

use?

a) rat-race

c) it is easier to excite than other

modes

b) E-plane T

c) hybrid ring

d) propagation of it without any

spurious generation can be
ensured

d) magic T

297. It is a mean of employing radio

waves to detect and locate objects such
as aircraft, ships and land masses.

a) detectors

b) radars

c) repeaters

d) beacons

298. A choke flange may be used to

couple two waveguides

a) to help the alignment of the

waveguides

b) because it is simpler than any

other join

c) to compensate for
discontinuities at the join

d) to increase the bandwidth of the

system

299. The resonant frequency of a cavity

may be varied by changing any of these
parameters except:

a) cavity volume

b) cavity inductance

c) cavity capacitance

d) cavity resistance

300. In order to couple two generators to

a waveguide system without coupling

Answers
1. Attenuation
2. 8493 km
3. towards the earth
4. S = 3R/L

21. Velocity modulation at the input

cavity creates density modulation at
the output cavity
22. The dimension of each cavity
resonator
23. mode

5. 10 GHz

24. Depends on the formation of

charge domain

6. Sixth

25. Circulator

7. Slow fading

26. A narrow, antenna-beam width in

the horizontal plane

8. Slow fading
9. Large reflector
10. Delayed spreading
11. SONAR
12. Is equivalent to an LC resonant
circuit
13. 2000 Hz
14. All of the above
15. magnetron
16. The absorption of energy by the
signal from an electron stream
17. To keep the electrons from
spreading out
18. Both B and C
19. 1 to 100 GHz
20. Degree of emission from
the cathode

27. Which may be used to tune the

radar receiver
28. A silicon crystal
29. 3000 to 30000 MHz
30. By bunches of electrons passing
the cavity grids
31. Ferrite emitter
32. Local oscillator
33. All of these
34. Indicates both the range
and azimuth of a target
35. Its physical dimensions
36. The interval between transmitted
pulses
37. The frequency will decrease
38. Adjusting the flexible wall of the
resonant cavity

39. Reduce interference from the

effects of sea return

60. Targets range and bearing

61. Radio frequency

40. Allow the transmitter and the

receiver to operate from a common
antenna

62. Maintain the desired klystron

frequency

41. 100 watts

63. Cathode end of the helix

42. As a second anode and to prevent

the build-up of secondary field

64. Both lower antenna rotation

speeds and higher pulse repetition

43. May be decreased

65. LF band

44. Its resonant cavity

66. To act as the second anode

45. No noticeable effect

67. 8000 MHz

46. Isolator

68. More spectrum space for signals

47. All of these

69. NTC

48. The shortest possible time

70. Higher-cost equipment

49. Magnetron

71. 22 GHz

50. Loran C: 100 kHz

72. Mobile radio

51. Circulator

73. High loss

52. Duty cycle/pulse width

74. PCBs

53. Produce a trigger pulse for the

transmitter

75. Rectangle

54. Pulse frequency and antenna

rotation rate
55. circulator
56. 156.76 MHz and 156.8 MHz
57. Frequencies of the duty cycle
58. Can reduce sea-return response
59. Isolator

76. 5.9 GHz

77. 15 GHz
78. Electric and magnetic fields
79. Transverse electric
80. TE

1.0

81. Probe

82. Cavity resonator

105. Infinity

83. Decrease

106. 9.7 nmi

84. Hot carrier

107. Antenna directivity

85. Frequency multiplier

108. 0.013 %

86. Gunn

109. Speed

87. Tunnel

110. Frequency

88. Reflex klystrons

111. Magnetron

89. Cathode-ray tube

112. Gunn diode

90. Catcher cavity

113. Spark gap

91. Oscillator

114. Horn and parabolic reflector

92. Permanent magnet

115. PPI

93. Cavity resonators

116. Phased array

94. Oscillator

117. 10 GHz

95. Radar

118. The distances involve are grater

96. Helix

119. Waveguides

97. Wider bandwidth

120. K-band

98. Klystrons

121. 92.4 + 20 log f + 20 log d

99. Horn

122. High pass filter

100. MTBF

123. Frequency diversity

101. 142.55 dB

124. Litz wire

102. Baseband repeater

125. Antennas operating on the same

frequencies

103. More
126. Frequency diversity
104. 0.6

127. Flattening

148. 1300

128. Electron gun, helix and collector

149. 6 AND gates and one 4-bit

binary adder

129. Shorten waveguide length

150. Radio Detection and Ranging
130. The lowest frequency the
waveguide operates
131. Decreased

151. Prevent oscillations

152. Is not a good low-level amplifier
because of noise

132. Greater than in free space

153. 2839.31 W
133. 54
154. Generating SHF signals
134. 183 GHz
155. Cross-field amplifier
135. 60 GHz
156. Frequency pushing
136. Attenuation due to water vapor
and oxygen

157. 4.92 GHz

137. 12.78

158. A hollow tube that carries HF

138. Terrestrial

159. Has a greater bandwidth

139. Prevent oscillation

160. Frequency pulling

140. Space diversity

161. Post-tuning drift

141. K x 4000 miles

162. -60 dBm

142. Pulse width

163. 11.6 m

143. Electronic Altitude and Director

Indicator

164. Both a and b

165. 8500 km

144. DME
166. -20 dBm
145. 43500 MHz
167. Combiner
146. Terrestrial Flight Telephone
System

168. 2 GHz

147. Automatic Direction Finder

169. 10 W

170. Prevent mode-jumping

190. Ensure that the electors will orbit

around the cathode

171. Phase velocity

191. -82 dBm
172. All of the above
192. 4.3 GHz
173. 17 m
193. 19.29
174. 140 dB
194. VTM
175. Baseband repeater
176. 6.575 - 6.875 GHz
177. Transverse-magnetic
178. Should not have long horizontal
runs
179. 205 K
180. To compensate for discontinuities
at the join
181. Suitable for use as a microwave
switch
182. Lower attenuation
183. Allows one antenna to feed two
separate microwave transmitters and
receivers at the same time

195. Through electromagnetic and

electrostatic fields in the walls of the
waveguide
196. Prevent the oscillations that
occurs in two-cavity klystrons
197. Reduce the axial velocity of the
RF field
198. Isolator
199. To improve the noise
performance
200. Rectangular waveguide
201. heterodyne receiver
202. system gain
203. Doppler effect

184. 140.90 dB
185. Because it cannot operate at
room temperature

204. a nonconductor with magnetic

properties

186. Provide attenuation

205. reduce the axial velocity of the

RF field

187. Radome

206. prevent oscillations

188. Hollow metal conductors used to

carry high-frequency current

207. oscillator
208. traveling-wave tube

189. Backward wave oscillator (BWO)

209. PCBs

230. provide attenuation

210. Cathode-ray tube

231. hybrid diversity

211. circuit simplicity

232. it does not give the target range

212. 53 degrees

233. quad diversity

213. 10

234. monopulse

214. baseband repeater

235. is not good low-level amplifier

because of noise

215. ridged
216. more accurate tracking enemy
targets

236. protection switching

arrangement
237. flap attenuator

217. diversity
238. conical
218. vary the RF
219. LOS

239. to allow the one antenna to be

used for reception or transmission
without mutual interference

220. help in subtracting

a complete scan from the previous
scan

240. hot standby

221. frequency diversity

241. the target will appear closer than

it really is

222. intermediate frequency

242. terminal stations

223. Tunnel

243. cavity resonator

224. gain increases

244. increase

225. 10.5 dB

245. pulse width

226. space diversity

246. magnetron

227. moving-target plotting on the PPI

247. increase the maximum range

228. polarization diversity

248. isolator

229. the target range, but not position

249. make the returned echoes easier

to distinguish from the noise

250. ringaround

272. 3.24 dB

251. is equal to the actual crosssectional area for small targets

273. BWO
274. 32.8 mi

252. fading
253. coaxial

275. they are reflected from

the walls but do not travel along them

254. increased capture area

276. 10 nmi

255. Klystrons

277. they would be too bulky at

lower frequencies

256. horn
278. 23 dB
257. fading
279. is greater than in free space
258. 4
280. 7.5 GHz
259. 2
260. frequency multiplier
261. FSL
262. permanent magnet
263. 90 mph
264. carrier to noise ratio
265. 0.09 %
266. CFA
267. noise factor

281. transmission lines use the

principal mode of propagation, and
therefore do not suffer from lowfrequency cut-off
282. peak power
283. double range echoes
284. are less bulky
285. any of these
286. transverse magnetic
287. any of these

268. 20 kW

288. greater than in the actual

direction of propagation

269. focal point

289. 2000 yd

270. cavity resonators

290. phase velocity

271. cassegrain feed

291. rest time

292. the wavelength within the

waveguide becomes infinite

297. radars

293. pulse width

298. to compensate for discontinuities

at the join

294. TE20

299. cavity resistance

295. pulse repetition frequency

300. E-plane T

296. the resulting impedance can be

matched directly to coaxial lines