Microwave

_____ is the progressive decrease of signal strength with increasing distance.
a. radiation
b. attenuation
c. modulation
d. propagation

b. attenuation

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

c. towards the earth

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

a. 10 Ghz

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

d. slow fading

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

d. slow fading

which causes multipath or frequency-selective fading?
a. small reflector
b. nearer reflector
c. further reflector
d. large reflector

d. large reflector

a shipboard equipment which measures the distance between the ship's bottom and the floor.
a. fathometer
b. echosounder
c. LORAN
d. SONAR

d. SONAR

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
c. at the collector end of the helix
d. at the control grid of the electron gun

a. at the cathode end of the helix

traveling-wave tube (TWT) amplifies by virtue of
a. the absorption of energy by the signal from an electron stream
b. the effect of an external magnetic field
c. the energy contained the cavity resonators
d. the energy liberated from the collector

a. the absorption of energy by the signal from an electron stream

which of the following is used as an oscillator device in the SHF band?
a. thyratron tube
b. tunnel diode
c. klystron tube
d. tunnel diode and klystron tube

d. tunnel diode and klystron tube

the highest frequency which an conventional vacuum-tube oscillator can generate is not limited by the
a. electron transit time
b. distributed lead inductance
c. inter-electrode capacitance
d. degree of emission from the cathode

d. degree of emission from the cathode

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

d. the dimension of each cavity resonator

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

d. depends on the formation of charge domain

what ferrite device can be used instead of duplexer of isolate microwave transmitter and receiver when both are connected to the same antenna?
a. isolator
b. magnetron
c. simplex
d. circulator

d. circulator

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

b. a narrow, antenna-beam width in the horizontal plane

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

a. by bunches of electrons passing the cavity grids

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

b. local oscillator

a PPI cathode-ray tube as used on a radar set
a. is used to check the percentage of modulation
b. indicates both the range and azimuth of a target
c. indicates only the range of a target
d. is used for receiver alignment

b. indicates both the range and azimuth of a target

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

c. its physical dimensions

the coarse frequency adjustment of a reflex klystron is accomplished by
a. the AFC system
b. adjusting the flexible wall of the resonant cavity
c. an adjustment in the synchronizer
d. varying the repeller voltage

b. adjusting the flexible wall of the resonant cavity

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

d. reduce interference from the effects of sea return

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

c. as a second anode and to prevent the build-up of secondary field

if the duration of the radar transmitted pulse on a particular range of operation, is increased the required bandwidth of the receiver's IF amplifiers
a. must remain as before
b. must be increased
c. may be decreased
d. must be doubled

c. may be decreased

the main frequency determining element of a klystron is
a. the repeller voltage
b. the accelerating voltage
c. its resonant cavity
d. its mode of operation

c. its resonant cavity

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
b. a reduction in horizontal resolution
c. no noticeable effect
d. a decrease in gain

c. no noticeable effect

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. a long time constant
b. low-pass filters
c. the shortest possible time
d. the restricted high-frequency response

c. the shortest possible time

which of the following is used as a high power microwave oscillator
a. thyratron
b. magnetron
c. klystron
d. reflex-klystron

b. magnetron

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?
a. isolator
b. magnetron
c. simplex
d. circulator

d. circulator

which of the following is the ferrite device that buffers a microwave source from the effects of a varying load, the thereby prevents the formation of standing waves?
a. circulator
b. duplexer
c. isolator
d. duplexer

c. isolator

pulsed radar sets are primarily used to find the
a. target's range and bearing
b. size and speed of a target
c. speed and course of a target
d. targets range of speed

a. target's range and bearing

a traveling wave tube is used at frequencies in order of
a. 30 Mhz
b. 300 Mhz
c. 8,000 Mhz
d. 100 Mhz

c. 8,000 Mhz

radio communication are regulated in the philippines by the
a. DOTC
b. KBP
c. NTC
d. Department of Defense

c. NTC

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

a. high loss

the most common cross section of a waveguide is a
a. square
b. circle
c. triangle
d. rectangle

d. rectangle

the most dominant mode in most rectangular waveguide is
a. TE 1.0
b. TE 1.2
c. TM 0.1
d. TM 1.1

a. TE 1.0

a magnetic field is introduced into waveguide by a
a. probe
b. dipole
c. stripline
d. capacitor

a. probe

decreasing the volume of a cavity causes its resonant frequency to
a. increase
b. decrease
c. remains the same
d. drop to zero

b. decrease

which diode is a popular microwave oscillator?
a. IMPATT
b. Gunn
c. Varactor
d. Schottky

b. Gunn

which type of diodes does not ordinarily operate with reverse bias?
a. varactor
b. IMPATT
c. snap-off
d. tunnel

d. tunnel

low-power gunn diodes are replacing
a. reflex klystrons
b. TWTs
c. magnetrons
d. varactor diodes

a. reflex klystrons

which of the following is not a microwave tube?
a. traveling wave tube
b. cathode ray tube
c. klystron
d. magnetron

b. cathode ray tube

in a klystron amplifier velocity modulation of the electron beam is produced by the
a. collector
b. catcher cavity
c. cathode
d. buncher cavity

b. catcher cavity

a reflex klystron is used as a(n)
a. amplifier
b. oscillator
c. mixer
d. frequency multiplier

b. oscillator

for proper operation a magnetron must be accompanied by a
a. cavity resonator
b. strong electric field
c. permanent magnet
d. high dc voltage

c. permanent magnet

a magnetron is used only as a/an
a. amplifier
b. oscillator
c. mixer
d. frequency multiplier

b. oscillator

high power TWTs are replacing what in microwave amplifiers?
a. MESFETs
b. magnetrons
c. klystrons
d. IMPATT diodes

c. klystrons

___ is a measure of reliability express as the average number of hours between successive failures.
a. MTBF
b. MTTR
c. downtime
d. outage time

a. MTBF

an active microwave radio repeater that can provide drops and inserts
a. broadband repeater
b. baseband repeater
c. IF repeater
d. RF repeater

b. baseband repeater

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

d. infinity

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 target

a. antenna directivity

what component in a duplexer protects the receiver from the higher transmitter output?
a. waveguide
b. bandpass filter
c. notch filter
d. spark gap

d. spark gap

the most common radar display is the
a. a scan
b. color CRT
c. LCD
d. PPI

d. PPI

which of the following is a typical radar operating frequency?
a. 60 Mhz
b. 450 Mhz
c. 900 Mhz
d. 10 Ghz

d. 10 Ghz

a microwave system requires the use of repeaters when
a. the intervening terrain is favorable
b. the distances involve are greater
c. the required reliability is meet
d. the radio fading is unacceptable

b. the distances involve are greater

are transmission lines which conver electromagnetic waves in highest frequencies
a. twisted pair or telephone lines
b. waveguides
c. power lines
d. coaxial cables

b. waveguides

a waveguide is also a
a. low pass filter
b. high pass filter
c. band pass filter
d. band stop filter

b. high pass filter

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

b. frequency diversity

a wire used to reduce skin effect
a. AWG#14
b. AWG#15
c. copper wire
d. litz wire

d. litz wire

space diversity transmission means transmitting and receiving on two or more
a. different frequencies
b. antennas operating on two different frequencies
c. antennas operating on the same frequencies
d. identical frequencies

c. antennas operating on the same frequencies

when the value of k increases the effective result is ___ of the equivalent curvature
a. flattening
b. bulging
c. sharp curvature

a. flattening

a traveling wave tube consists of
a. electron gun, helix and repeller
b. electron gun, helix and collector
c. electron gun, repeller and collector
d. buncher cavity and catcher cavity

b. electron gun, helix and collector

water causes more attenuation particularly on what frequency?
a. 20 Ghz
b. 63 Ghz
c. 183 Ghz
d. 202 Ghz

c. 183 Ghz

attenuator is used in the traveling wave tube to
a. prevent oscillation
b. increase gain
c. prevent saturation

a. prevent oscillation

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

d. wide bandwidth

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

c. 10 W

the cavity magnetron uses strapping to
a. prevent mode jumping
b. prevent cathode back heating
c. ensure bunching
d. improve the phase focusing effect

a. prevent mode jumping

for some applications, circular waveguides may be used preferred to rectangular ones because
a. the smaller cross section needed at any frequency
b. lower attenuation
c. freedom from surious modes
d. rotation of polarization

b. lower attenuation

a range of microwave frequencies more easily passed by the atmosphere than others is called a
a. window
b. critical frequency
c. gyro frequency range
d. resonance in the atmosphere

a. window

when microwave signals follow the curvature of the earth this is known as
a. the faraday effect
b. ducting
c. tropospheric scatter
d. ionospheric reflection

b. ducting

the radius in the circular zone is in the first fresnel zone when the reflected path is ___ longer than the direct path.
a. λ/2
b. λ
c. λ/4
d. λ/8

a. λ/2

the principal mode for a circular waveguide
a. TE10
b. TM20
c. TE11
d. TEM

c. TE11

the international equivalent of the TE mode
a. H
b. E
c. Z
d. TEM

a. H

the characteristic wave impedance of a waveguide in the TE mode is ___ that of the TM mode.
a. equal to
b. higher than
c. lower than
d. NOTA

b. higher than

a common omnidirectional microwave antenna is the
a. horn
b. parabolic reflector
c. helical
d. bicone

d. bicone

the output of a helical antenna is
a. vertically polarized
b. horizontally polarized
c. circularly polarized
d. linearly polarized

c. circularly polarized

in microwave transmission using digital radio, what causes most intersymbol interference?
a. delayed spreading
b. rayleigh fading
c. random doppler shift
d. slow fading

a. delayed spreading

the cavity resonator
a. is equivalent to an LC resonant circuit
b. in a reflect klystron has its output taken from the reflector plate
c. produces a frequency which is independent of the cavity size
d. has a low q factor for narrow operation

a. is equivalent to an LC resonant circuit

a high-power microwave pulse of the order of megawatts can be generated by a
a. traveling-wave tube
b. magnetron
c. reflex klystron
d. gunn diode

b. magnetron

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. to keep the electrons from spreading out

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

c. 1 to 100 Ghz

as the electron beam moves through a klystron's interactivity 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
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

b. velocity modulation at the input cavity creates density modulation at the output cavity

if the instantaneous RF potentials on the two sides of a magnetron cavity are of opposite polarity the operation is in the
a. Π mode
b. Π/2 mode
c. 2Π mode
d. Π/4 mode

a. Π mode

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

b. which may be used to tune the radar receiver

in a radar-set receiver, the usual mixer stage is
a. AND FET
B. a tunner diode
c. a silicon crystal
d. a rochelle salts and crystal

c. a silicon crystal

klystron oscillators are most often used in the frequency range of
a. 300 to 3,000 Mhz
b. 3,000 to 30,000 Mhz
c. 30 to 30,000 Mhz
d. 10 to 10000 Mhz

b. 3,000 to 30,000 Mhz

what allow microwave to pass in only one direction
a. RF emitter
b. capacitor
c. varactor triac
d. ferrite emitter

d. ferrite emitter

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

b. the interval between transmitted pulses

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
d. bunching would occur earlier in time

c. the frequency will decrease

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

b. 100 watts

which of the following permits a microwave signal to travel in one
direction with virtually no loss, but severly attenuates any signal attempting to travel in the reverse direction?
a. isolator
b. wave trap
c. tunnel diode
d. circulator

a. isolator

the intensity of the echoes on a PPI display is determined by the
a. radio frequency
b. pulse frequency and antenna rotation rate
c. duty cycle
d. average power

b. pulse frequency and antenna rotation rate

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. loss waveguide
b. circulator
c. isolator
d. gyrator

b. circulator

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

d. frequencies of the duty cycle

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

c. can reduce sea-return response

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

b. radio frequency

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

c. maintain the desired klystron frequency

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

c. cathode end of the helix

the display onthe 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

d. both lower antenna rotation speeds and higher pulse repetition

the operation frequency of loran C lies within the
a. LF band
b. VLF band
c. MF band
d. HF band

a. LF band

the PPI tubes have an aquadag coating on the inside of the tube. The purpose of this coating is
a. to act as the second anode
b. to shield the tube magnetically
c. to decelerate the electron beam
d. to deflect the electron beam

a. to act as the second anode