RC Exam - EST 21 to EST 30

Complete Answers for EST RC Exams (21 to 30)

Increasing the intensity causes an increase in loudness but not in a direct proportion. For instance, doubling the loudness of a sound requires about a \____ increase in the intensity of the sound.
Triple
Tenfold
Double
Quintuple

Tenfold

As a frequency is lowered, absorption of the radio wave \_____.
Remains the same
Decreases
Cannot be determined
Increases

Increases

The \____ layer reflects VLF waves; is important for long range VLF communications; refracts LF and MF waves for short range communications; absorbs HF waves; has little effect on VHF and above; and disappears at night.
E
F
A
D

D

The velocity of propagation of a wave along a waveguide is \_____ than its velocity through free space (speed of light).
The same
Less
More
Cannot be determined

Less

In sound propagation, sound travels \_____ in harder materials (such as steel), compared to liquids and gases.
Fastest
Slower
Slowest
Intermediately

Fastest

The radius of bends in the waveguide must measure greater than \____ wavelengths at the operating frequency of the equipment to avoid excessive attenuation.
15
3
2
4

2

The amount of \______ that is produced by a radio transmitter can be controlled by cutting transmitting antennas to the correct frequency, limiting bandwidth, and using electronic filtering networks and metallic Shielding.
Shock noise
Flux noise
Magnetic flux
Electromagnetic interference

Electromagnetic interference

The density of a medium, temperature, and atmospheric pressure affect the velocity of sound. If temperature, density, or pressure increases, the velocity of sound \_____ and vice versa.
Cannot be Determined
Stays the same
Increases
Decreases

Increases

It is the ability of a strained body to recover its shape after deformation, as from a vibration or compression.
Strength
Plasticity
Ductility
Elasticity

Elasticity

As a radio wave enters a region of \_____ ionization, the increase in velocity of the upper part of the wave causes it to be bent back toward the Earth.
None of the choices
Similar
Decreasing
Increasing

Increasing

The speed of light \______ as the density of the substance through which the light passes increases.
Stays the same
Decreases
Increases
Cannot be determined

Decreases

Radio waves transmitted at frequencies \_____ than the critical frequency of a given layer will pass through the layer and be lost in space.
Lower
Equal to
Higher
None of the choices

Higher

A waveguide may also be terminated in a resistive load that is matched to the characteristic impedance of the waveguide. The resistive load is most often called a \______.
None of the choices
Dummy load
Live load
Real load

Dummy load

Antennas high above the ground should be \______ polarized to get the greatest possible signal strength to the Earth's surface.
Vertically
Elliptically
Circular
Horizontally

Horizontally

The term \_____ is used to describe the frequency of a sound.
Cleft
Pitch
Tempo
Vibrato

Pitch

The \____ the frequency of a radio wave, the more rapidly the wave is refracted by a given degree of ionization.
Equal to
None of the choices
Greater
Lower

Lower

In the\______ mode, the entire magnetic field has no portion parallel to the length axis.
Longitudinal magnetic (LM)
Transverse magnetic (TM)
Transverse electric (TE)
Longitudinal electric (LE)

Transverse magnetic (TM)

The \_______ has relatively little effect on radio waves because it is a relatively calm region with little or no temperature changes.
Hydrosphere
Biosphere
Geosphere
Stratosphere

Stratosphere

In bending waveguides, the E bend must have a radius greater than \______ to prevent reflections.
One wavelength
Half of a wavelength
None of the choices
Two wavelengths

Two wavelengths

Usually the \______band is used for sky wave propagation.
Infrared frequency (IF)
Extremely high frequency (EHF)
High frequency (HF)
Medium frequency (MF)

High frequency (HF)

It is defined as the vehicle through which the wave travels from one point to the next.
Medium
Vessel
Transport
Vehicle

Medium

As the signal take-off angle is increased, the height of the scatter volume is increased. When this occurs, the amount of received energy \_______.
Increases
Remains the same
Decreases
None of the choices

Decreases

The magnitude of the received signal depends on the number of turbulences causing scatter in the desired direction and the gain of the receiving antenna. The scatter area used for tropospheric scatter is known as the \_______.
Zone of scatter
Scatter zone
Scatter volume
Scatter area

Scatter volume

In waveguides, it is a type of coupler widely used in radar and communications systems.
Bidirectional coupler
Directional coupler
Directional binder
Bidirectional binder

Bidirectional coupler

Longitudinal waves are sometimes called \________.
Power Waves
Compression Waves
Neutral Waves
Expansion Waves

Compression Waves

When it operates to reinforce energy coming from the driver toward itself, the parasitic element is referred to as a \______.
Reflector
Focus
Directrix
Director

Director

For a parallel-resonant circuit, at resonance the impedance appears as a very high resistance. A loss-free circuit has infinite impedance (an open circuit). Other than at resonance, the impedance \______ rapidly.
None of the choices
Decreases
Increases
Heats up

Decreases

In antenna arrays, \_____ are those in which the greatest amount of radiation occurs.
Side lobes
Minor lobes
Reverse lobes
Major lobes

Major lobes

A \______ is a plot of the radiated energy from an antenna.
Radiation resistance
Gain
Radiation pattern
Beamwidth

Radiation pattern

In antenna radiation, a \____ is the area of a radiation pattern that is covered by radiation.
Delta
Lobe
Club
Bulb

Lobe

A \_____ element is connected directly to the transmission line. It obtains its power directly from the transmitter or, as a receiving antenna, it delivers the received energy directly to the receiver.
Driven
Parasitic
Passive
Resistive

Driven

\______ polarization is used for ground-wave transmission, allowing the radio wave to travel a considerable distance along the ground surface with minimum attenuation.
Horizontal
Circular
Elliptical
Vertical

Vertical

A \________ array is one that contains two or more parasitic elements with the driven element.
Multielement parasitic
Single driven
Single parasitic
Multielement drive

Multielement parasitic

The flow of ac current near the surface of a conductor at RF frequencies.
Skim wave
Skin effect
Surface flow
Surface wave

Skin effect

In antenna arrays, a \_____ array radiates in only one general direction.
Omnidirectional
None of the choices
Unidirectional
Bidirectional

Unidirectional

A longitudinal wave that has been expanded or rarefied (made less dense) as it moves away from the source.
Rarefied wave
Power wave
None of the choices
Energy wave

Rarefied wave

The direction of maximum radiation of a collinear array is \_____ to the axis of the elements.
Obtuse
Acute
Perpendicular
Parallel

Perpendicular

The directivity pattern resulting from the action of parasitic elements depends on 3 factors. These are:
(1) the tuning, determined by the length of the parasitic element, (2) the spacing between the parasitic and driven elements, (3) the diameter of the driven element
(1) the tuning, determined by the length of the parasitic element, (2) the spacing between the parasitic and driven elements, (3) the diameter of the parasitic element
(1) the tuning, determined by the length of the driven element, (2) the spacing between the parasitic and driven elements, (3) the diameter of the driven element
(1) the tuning, determined by the length of the driven element, (2) the spacing between the parasitic and driven elements, (3) the diameter of the parasitic element

(1) the tuning, determined by the length of the parasitic element, (2) the spacing between the parasitic and driven elements, (3) the diameter of the parasitic element

The \________ is one of the many types that has been developed primarily for omnidirectional vhf communications.
Parabolic antenna
Turnstile antenna
Truncated antenna
Deltoid antenna

Turnstile antenna

A \_____ line has no standing waves of current and voltage and is either infinitely long or terminated in its characteristic impedance.
Non-resonant
Resonant
Short-circuited
Open-circuited

Non-resonant

\______ is the heating of an insulating material by placing it in a high-frequency electric field. The heat results from internal losses during the rapid reversal of polarization of molecules in the dielectric material.
Frequency burn
Radio burn
Polarization
Dielectric heating

Dielectric heating

\______ operate with one end grounded and are mounted perpendicular to the Earth or to a surface acting as a ground. They are used for frequencies below 2 MHz and may be used at higher frequencies in certain applications.
Marconi antennas
Hertz antennas
Dipole antennas
Yagi-Uda antennas

Marconi antennas

A transmission line is considered to be electrically \____ when its physical length is short compared to a quarter-wavelength of the energy it is to carry.
Capacitive
Short
Resistive
Open

Short

For a \_______ transmission line, the reflected voltage has the opposite polarity but the same amplitude as the incident wave.
Resistive
Short-circuited
Open-circuited
Capacitive

Short-circuited

The \______operates independently of ground; therefore, it may be installed far above the surface of the Earth or other absorbing bodies.
Quarter-wave antenna
Full-wave antenna
None of the choices
Half-wave antenna

Half-wave antenna

It consists of four conductors joined to form a diamond shape. The antenna is placed end to end and terminated by a noninductive resistor to produce a uni-directional pattern.
Rhomboid antenna
Rhombic antenna
Parallel antenna
Driven antenna

Rhombic antenna

\______ is the ratio of the energy radiated in the principal direction compared to the energy radiated in the opposite direction for a given antenna.
Back-to-front ratio
Efficiency
Front-to-back ratio
Directivity ratio

Front-to-back ratio

For Yagi antennas, a greater number of parasitic elements causes the array to have a narrower frequency response as well as a narrower \_______.
Directivity
Resistance
Gain
Beamwidth

Beamwidth

\_________ is possible because antenna characteristics are essentially the same for sending and receiving electromagnetic energy.
Antenna reciprocity
Radiation matching
Radiation consistency
Antenna interoperability

Antenna reciprocity

The chief advantage of the rigid coaxial line is its ability to:
Be more flexible
Minimize radiation losses
Be used as a structural member
Increase mechanical strength

Minimize radiation losses

The ungrounded end of the quarter-wave antenna has a \____ impedance, which causes \____ voltage and \____ current.
High, low, high
High, high, low
Low, high, low
Low, low, high

High, high, low

In wave propagation, it is the maximum frequency at which a radio wave can be transmitted vertically and still be refracted back to earth.
Maximum usable frequency
Critical frequency
None of the choices
Maximum return frequency

Critical frequency

The presence of standing waves describes the condition of \_____ in an antenna. The waves travel back and forth in the antenna reinforcing each other and the electromagnetic waves are transmitted into space at maximum radiation.
Resonance
None of the choices
Non-resonance
Consonance

Resonance

For a parasitic array, when the parasitic element is placed so that it radiates away from the driven element, the element is a \_____.
Driver
Director
Focus
Reflector

Director

A \______ consists of 2 lengths of wire rod, each 1/4 wavelength long at a certain frequency. It is the basic unit from which many complex antennas are constructed.
Isotropic
Dipole
Isenthalpic
Isobaric

Dipole

To change the electrical length of an antenna, you can insert either an inductor or a capacitor in \_____ with the antenna.
Parallel
Series-parallel
None of the choices
Series

Series

A simple horizontal antenna is \______. This characteristic is useful when you desire to minimize interference from certain directions.
Bidirectional
Omnidirectional
None of the choices
Unidirectional
Next

Bidirectional

A \_____ is an ordinary half-wave antenna that has one or more additional conductors connected across its ends.
Folded dipole antenna
Dipole antenna
Isotropic antenna
None of the choices

Folded dipole antenna

The \______ quarter-wave antenna acts as if another quarter-wave were actually down in the earth.
Voltage-feed
Grounded
Ungrounded
Current-feed

Grounded

A \_______ is an antenna that is a wavelength or longer at the operating frequency.

Long-wire antenna

\_______ consist of a single wire that is two or more wavelengths long.
Direct antenna
Beverage antenna
Isotropic antenna
Whip antenna

Beverage antenna

In antenna arrays, a \_____ array radiates in opposite directions along the line of maximum radiation.
None of the choices
Omnidirectional
Unidirectional
Bidirectional

Bidirectional

Small changes in antenna locations do not cause large variations in the field intensity of \_______ waves.
Vertically polarized
Circularly polarized
Horizontally polarized
Elliptically polarized

Horizontally polarized

For a dipole, the current is \_____ at the center and \_____ at the ends.
Minimum, maximum
Maximum, minimum
Minimum, minimum
Maximum, maximum

Maximum, minimum

A half-wave antenna with a reflector consisting of two flat metal surfaces meeting at an angle behind the radiator.
Central-reflector antenna
Corner-reflector antenna
Deflector antenna
Diffraction antenna

Corner-reflector antenna

The \______ of a folded dipole varies much more slowly as the frequency is varied from resonance.
Resistance
Conductance
Radiance
Reactance

Reactance

For a parasitic array, when the parasitic element is placed so that it radiates toward the driven element, the parasitic element is a \_____.
Focus
Driver
Reflector
Director

Reflector

The ground screen and the counterpoise are used to reduce losses caused by the ground in the immediate vicinity of the antenna. The \____ is buried below the surface of the earth. The \____ is installed above the ground.
Anchor. counterpoise
Ground screen, counterpoise
Ground screen, counterpoise
Counterpoise. ground screen

Ground screen, counterpoise

The radiation pattern in the horizontal plane of a dipole is a \______ circle than that of the doublet.
Smaller
Similar
None of the choices
Larger

Larger

The 3 factors that determine the type, size, and shape of the antenna are:
(1) the velocity of operation of the transmitter, (2) the amount of power to be radiated, and (3) the general direction of the receiving set
(1) the frequency of operation of the transmitter, (2) the amount of power to be radiated, and (3) the general direction of the receiving set
(1) the frequency of operation of the transmitter, (2) the type of signal to be radiated, and (3) the general direction of the receiving set
(1) the modulation of operation of the transmitter, (2) the amount of power to be radiated, and (3) the general direction of the receiving set

(1) the frequency of operation of the transmitter, (2) the amount of power to be radiated, and (3) the general direction of the receiving set

For a dipole, the voltage is \_____ at the center and \_____ at the ends.
Minimum, minimum
Maximum, minimum
Minimum, maximum
Maximum, maximum

Minimum, maximum

In antenna arrays, multielement arrays frequently are classified according to their \______.
Directivity
Physical size
Range
Gain

Directivity

If all of the elements in an array are driven, the array is referred to as a driven array. What is another name for a driven array?
Powered array
None of the choices
Fed array
Connector array

Connector array

\______ transmission is used at high frequencies. Either horizontal or vertical polarization can be used with this transmission because they arrive at the receiving antenna elliptically polarized.
Solid wave
Ground wave
Sky-wave
Space wave

Sky-wave

When the antenna is mounted at right angles to the transmission line and \______ polarization is used, the line is kept out of the direct field of the antenna.
Circular
Elliptical
Horizontal
Vertical

Horizontal

\_______ combine magnetic properties with a high resistance to current flow. They are constructed from compounds of ferrous metal oxides to achieve the desired characteristics.
Copper devices
Ferrite devices
Iron devices
None of the choices

Ferrite devices

The primary material used in the construction of ferrites is normally a compound of \____ with impurities of other oxides added.
Iron oxide
Lead
Copper ore
None of the choices

Iron oxide

When simple antennas are used, the transmission line, which is usually vertical, is less affected by a \_____ mounted antenna.
Horizontally
Vertically
Elliptically
Circularly

Horizontally

A semipermanent joint, called a \_____, provides good electromagnetic continuity between sections of waveguide with very little power loss.
Congestion joint
Efficient joint
Choke joint
Squeeze joint

Choke joint

For transmission over bodies of water, as the frequency increases, the minimum antenna height \______.
Decreases
Increases
Remains the same
None of the choices

Decreases

It is the rate at which the disturbance travels through the medium, or the velocity with which the crest of the wave moves along.
Wave momentum
Crest movement
Wave speed
Velocity of propagation

Velocity of propagation

The ratio between the amount of energy propagated in these directions compared to the energy that would be propagated if the antenna were not directional is known as its \_____.
Loss
Radiation resistance
Beamwidth
Gain

Gain

When antennas are located near dense forests or among buildings, \____ polarized waves suffer lower losses especially above 100 MHz.
Elliptically
Vertically
Circularly
Horizontally

Horizontally

The height of a wave crest above the reference line is called the \______. of the wave. It gives a relative indication of the amount of energy the wave transmits.
Frequency
Period
Amplitude
Wavelength

Amplitude

What are the three basic elements for transmission and reception of sound that must be present before a sound can be produced?
(1) the disturbance (2) a sound stage and (3) the detector.
(1) the source (2) a medium for carrying the sound and (3) the preceptor.
(1) the source (2) a medium for carrying the sound and (3) the detector.
(1) the disturbance (2) a medium for carrying the sound and (3) the detector.

(1) the source (2) a medium for carrying the sound and (3) the detector.

Simple vertical antennas can be used to provide \________ communication. This is an advantage when communications must take place from a moving vehicle.
Omnidirectional
Bidirectional
Unidirectional
Cannot be determined

Omnidirectional

Resonant cavities have a very \____ Q and can be built to handle relatively large amounts of power.
High
Low
None of the choices
Non-resonant

High

There are two variables that determine the primary frequency of any resonant cavity. The first variable is PHYSICAL SIZE. In general, the smaller the cavity, the \_____ its resonant frequency.
Lower
More similar
Higher
None of the choices

Higher

T junctions are divided into two basic types, the \____ and the \____.
E-type, H-type
X-type, C-type
M-type, N-type
G-type, X-type

E-type, H-type

\_______ can account for the ability of the AM radio waves (due to their low frequency) to travel over a mountain, while FM and TV signals (due to their higher frequencies) are blocked.
Refraction
Diffraction
Diffusion
Reflection

Diffraction

Any waveguide that is exposed to the weather should be painted and all joints sealed. \_____ prevents natural corrosion, and sealing the joints prevents moisture from entering the waveguide.
Proper painting
Proper tightening
Proper grounding
None of the choices

Proper painting

When a wave passes through one medium and encounters a medium having different characteristics, what are the three things that can occur to the wave?
(1) Some of the energy can be reflected back into the initial medium; (2) some of the energy can be transmitted into the second medium where it may continue at a different velocity; or (3) some of the energy can be absorbed by the medium.
(1) Some of the energy can be reflected back into the initial medium; (2 the energy will stay at the boundary layer and not proceed into the next medium (3) some of the energy can be absorbed by the medium.
(1) Some of the energy can be reflected back into the initial medium; (2) some of the energy can be transmitted into the second medium where it may continue at a different velocity; or (3) The energy escapes through the boundary layer
(1) Some of the energy will escape the two media (2) some of the energy can be transmitted into the second medium where it may continue at a different velocity; or (3) some of the energy can be absorbed by the medium.

(1) Some of the energy can be reflected back into the initial medium; (2) some of the energy can be transmitted into the second medium where it may continue at a different velocity; or (3) some of the energy can be absorbed by the medium.

A maximum movement of electrons is in the center of the antenna at all times; therefore, the center of the antenna is at a low impedance. This condition is called a \______ of current.
Power wave
Incident wave
Reflected wave
Standing wave

Standing wave

There are two variables that determine the primary frequency of any resonant cavity. The second controlling factor is the \_____ of the cavity.
Thickness
Shape
Humidity
Material

Shape

The \______is used primarily in high-powered radar and communications systems to perform two functions. two functions. During the transmit period, the hybrid ring couples microwave energy from the transmitter to the antenna and allows no energy to reach the receiver. During the receive cycle, the hybrid ring couples energy from the antenna to the receiver and allows no energy to reach the transmitter.
T-X junction
R-X junction
Hybrid ring
None of the choices

Hybrid ring

\_____ antennas are less likely to pick up man-made interference.
Elliptical
Horizontal
Circular
Vertical

Horizontal

A type of hybrid junction that overcomes the power limitation of the magic-T is the hybrid ring is called a \_____.
Rat race
Rat ring
None of the choices
Hybrid race

Rat race

Radiation is somewhat less affected by reflections from aircraft flying over the transmission path when \_____ polarization is used.
Elliptical
Vertical
Circular
Horizontal

Vertical

\_____ prevents standing waves at the end of a waveguide system.
Waveguide disruptor
Waveguide termination
Waveguide end
Waveguide cutter

Waveguide termination

There are two variables that determine the primary frequency of any resonant cavity. The second controlling factor is the \_____ of the cavity.
Material
Thickness
Humidity
Shape

Shape