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WorksheetsRAE CLASS A 2
Total questions: 107
Worksheet time: 3hrs 41mins
What term describes a wide-bandwidth communications system in which the RF carrier varies according to some predetermined sequence?
Amplitude compandor single sideband
AMTOR
Time-domain frequency modulation
Spread-spectrum communication
What spread-spectrum communications technique alters the centre frequency of a conventional carrier many times per second in accordance with a pseudo-random list of channels?
Frequency hopping
Direct sequence
Time-domain frequency modulation
Frequency compandor spread-spectrum
What spread-spectrum communications technique uses a very fast binary bit stream to shift the phase of an RF carrier?
Frequency hopping
Direct sequence
Binary phase-shift keying
Phase compandor spread-spectrum
What controls the spreading sequence of an amateur spread-spectrum transmission?
A frequency-agile linear amplifier
A crystal-controlled filter linked to a high-speed crystal switching mechanism
A binary linear feedback shift register
A binary code which varies if propagation changes
Why are spread-spectrum communications so resistant to interference?
Interfering signals are removed by a frequency-agile crystal filter
Spread-spectrum transmitters use much higher power than conventional carrier-frequency transmitters
Spread-spectrum transmitters can "hunt" for the best carrier frequency to use within a given RF spectrum
Only signals using the correct spreading sequence are received
Why do spread-spectrum communications interfere so little with conventional channelized communications in the same band?
A spread-spectrum transmitter avoids channels within the band which are in use by conventional transmitters
Spread-spectrum signals appear only as low-level noise in conventional receivers
Spread-spectrum signals change too rapidly to be detected by conventional receivers
Special crystal filters are needed in conventional receivers to detect spread-spectrum signals
What is the term for the amplitude of the maximum positive excursion of a signal as viewed on an oscilloscope?
Peak-to-peak voltage
Inverse peak negative voltage
RMS voltage
Peak positive voltage
What is the easiest voltage amplitude dimension to measure by viewing a pure sine wave signal on an oscilloscope?
Peak-to-peak voltage
RMS voltage
Average voltage
DC voltage
What is the relationship between the peak-to-peak voltage and the peak voltage amplitude in a symmetrical waveform?
1:1
2:1
3:1
4:1
What input-amplitude parameter is valuable in evaluating the signal-handling capability of a Class A amplifier?
Peak voltage
RMS voltage
An average reading power output meter
Resting voltage
What is the PEP output of a transmitter that has a maximum peak of 30 volts to a 50-ohm load as observed on an oscilloscope?
4.5 watts
9 watts
16 watts
18 watts
If an RMS-reading AC voltmeter reads 65 volts on a sinusoidal waveform, what is the peak-to-peak voltage?
46 volts
92 volts
130 volts
184 volts
What is the advantage of using a peak reading voltmeter to monitor the output of a single-sideband transmitter?
It would be easy to calculate the PEP output of the transmitter
It would be easy to calculate the RMS output power of the transmitter
It would be easy to calculate the SWR on the transmission line
It would be easy to observe the output amplitude variations
What are electromagnetic waves?
Alternating currents in the core of an electromagnet
A wave consisting of two electric fields at right angles to each other
A wave consisting of an electric field and a magnetic field at right angles to each other
A wave consisting of two magnetic fields at right angles to each other
Why don't electromagnetic waves penetrate a good conductor for more than a fraction of a wavelength?
Electromagnetic waves are reflected by the surface of a good conductor
Oxide on the conductor surface acts as a magnetic shield
The electromagnetic waves are dissipated as eddy currents in the conductor surface
The resistance of the conductor surface dissipates the electromagnetic waves
Which of the following best describes electromagnetic waves travelling in free space?
Electric and magnetic fields become aligned as they travel
The energy propagates through a medium with a high refractive index
The waves are reflected by the ionosphere and return to their source
Changing electric and magnetic fields propagate the energy across a vacuum
What is meant by circularly polarised electromagnetic waves?
Waves with an electric field bent into a circular shape
Waves with a rotating electric field
Waves that circle the Earth
Waves produced by a loop antenna
What is the polarisation of an electromagnetic wave if its magnetic field is parallel to the surface of the Earth?
Circular
Horizontal
Elliptical
Vertical
What is the polarisation of an electromagnetic wave if its magnetic field is perpendicular to the surface of the Earth?
Horizontal
Circular
Elliptical
Vertical
What is the primary source of noise that can be heard in an HF-band receiver with an antenna connected?
Detector noise
Man-made noise
Receiver front-end noise
Atmospheric noise
What is the primary source of noise that can be heard in a VHF/UHF- band receiver with an antenna connected?
Receiver front-end noise
Man-made noise
Atmospheric noise
Detector noise
Which of the following describes an isotropic radiator?
A grounded radiator used to measure earth conductivity
A horizontal radiator used to compare Yagi antennas
A theoretical radiator used to compare other antennas
A spacecraft radiator used to direct signals toward the earth
When is it useful to refer to an isotropic radiator?
When comparing the gains of directional antennas
When testing a transmission line for standing-wave ratio
When directing a transmission toward the tropical latitudes
When using a dummy load to tune a transmitter
How much gain does a 1/2-wavelength dipole have over an isotropic radiator?
About 1.5 dB
About 2.1 dB
About 3.0 dB
About 6.0 dB
Which of the following antennas has no gain in any direction?
Quarter-wave vertical
Yagi
Half-wave dipole
Isotropic radiator
Which of the following describes the radiation pattern of an isotropic radiator?
A tear drop in the vertical plane
A circle in the horizontal plane
A sphere with the antenna in the centre
Crossed polarised with a spiral shape
Why would one need to know the radiation resistance of an antenna?
To match impedances for maximum power transfer
To measure the near-field radiation density from a transmitting antenna
To calculate the front-to-side ratio of the antenna
To calculate the front-to-back ratio of the antenna
What factors determine the radiation resistance of an antenna?
Transmission-line length and antenna height
Antenna location with respect to nearby objects and the conductors' length/diameter ratio
It is a physical constant and is the same for all antennas
Sunspot activity and time of day
What is the term for the ratio of the radiation resistance of an antenna to the total resistance of the system?
Effective radiated power
Radiation conversion loss
Antenna efficiency
Beamwidth
What is included in the total resistance of an antenna system?
Radiation resistance plus space impedance
Radiation resistance plus transmission resistance
Transmission-line resistance plus radiation resistance
Radiation resistance plus ohmic resistance
What is a folded dipole antenna?
A one-quarter dipole wavelength long
A type of ground-plane antenna
A dipole whose ends are connected by a one-half wavelength piece of wire
A hypothetical antenna used in theoretical discussions to replace the radiation resistance
What is meant by antenna gain?
The numerical ratio relating the radiated signal strength of an antenna to that of another antenna
The numerical ratio of the signal in the forward direction to the signal in the back direction
The numerical ratio of the amount of power radiated by an antenna compared to the transmitter output power
The final amplifier gain minus the transmission-line losses (including any phasing lines present)
What is meant by antenna bandwidth?
Antenna length divided by the number of elements
The frequency range over which an antenna can be expected to perform well
The angle between the half-power radiation points
The angle between the half-power radiation points
How can the approximate beam width of a beam antenna be determined?
Note the two points where the signal strength of the antenna is down 3 dB from the maximum signal point and compute the angular difference
Measure the ratio of the signal strengths of the radiated power lobes from the front and rear of the antenna
Draw two imaginary lines through the ends of the elements and measure the angle between the lines
Measure the ratio of the signal strengths of the radiated power lobes from the front and side of the antenna
How is antenna efficiency calculated?
(radiation resistance / transmission resistance) x 100%
(radiation resistance / total resistance) x 100%
(total resistance / radiation resistance) x 100%
(effective radiated power / transmitter output) x 100%
How can the efficiency of an HF grounded vertical antenna be made comparable to that of a half-wave dipole antenna?
By installing a good ground radial system
By isolating the coax shield from ground
By shortening the vertical
By lengthening the vertical
What factors determine the receiving antenna gain required at an amateur satellite station in earth operation?
Height, transmitter power and antennas of satellite
Length of transmission line and impedance match between receiver and transmission line
Preamplifier location on transmission line and presence or absence of RF amplifier stages
Height of earth antenna and satellite orbit
What factors determine the EIRP required by an amateur satellite station in earth operation?
Satellite antennas and height, satellite receiver sensitivity
Path loss, earth antenna gain, signal-to-noise ratio
Satellite transmitter power and orientation of ground receiving antenna
Elevation of satellite above the horizon, signal-to-noise ratio, satellite transmitter power
What is the beamwidth of a symmetrical pattern antenna with a gain of 20 dB as compared to an isotropic radiator?
10.1 degrees
20.3 degrees
45.0 degrees
60.9 degrees
How does the gain of a parabolic dish antenna change when the operating frequency is doubled?
Gain does not change
Gain is multiplied by 0.707
Gain increases 6 dB
Gain increases 3 dB
How is circular polarisation produced using linearly polarised antennas?
Stack two Yagis, fed 90 degrees out of phase, to form an array of the respective elements in parallel planes
Stack two Yagis, fed in phase, to form an array of the respective elements in parallel planes
Arrange two Yagis perpendicular to each other, with the driven elements in the same plane, fed 90 degrees out of phase
Arrange two Yagis perpendicular to each other, with the driven elements in the same plane, fed in phase
How does the beamwidth of an antenna vary as the gain is increased?
It increases geometrically
It increases arithmetically
It is essentially unaffected
It decreases
Why does a satellite communications antenna system for earth operation need to have rotators for both azimuth and elevation control?
In order to track the satellite as it orbits the earth
Because the antennas are large and heavy
In order to point the antenna above the horizon to avoid terrestrial interference
To rotate antenna polarisation along the azimuth and elevate the system towards the satellite
For a shortened vertical antenna, where should a loading coil be placed to minimise losses and produce the most effective performance?
Near the centre of the vertical radiator
As low as possible on the vertical radiator
As close to the transmitter as possible
At a voltage node
Why should an HF mobile antenna loading coil have a high ratio of reactance to resistance?
To swamp out harmonics
To maximise losses
To minimise losses
To minimise the Q
What is a disadvantage of using a trap antenna?
It will radiate harmonics
It can only be used for single-band operation
It is too sharply directional at lower frequencies
It must be neutralised
How must the driven element in a 3-element Yagi be tuned to use a "hairpin" matching system?
The driven element reactance is capacitive
The driven element reactance is inductive
The driven element resonance is higher than the operating frequency
The driven element radiation resistance is higher than the characteristic impedance of the transmission line
What is the equivalent lumped-constant network for a "hairpin" matching system on a 3-element Yagi?
Pi network
Pi-L network
L network
Parallel-resonant tank
What happens to the bandwidth of an antenna as it is shortened through the use of loading coils?
It is increased
It is decreased
No change occurs
It becomes flat
What is an advantage of using top loading in a shortened HF vertical antenna?
Lower Q
Greater structural strength
Higher losses
Improved radiation efficiency
What system matches a high-impedance transmission line to a lower impedance antenna by connecting the line to the driven element in two places, spaced a fraction of a wavelength each side of element centre?
The gamma matching system
The delta matching system
The omega matching system
The stub matching system
What system matches an unbalanced feed line to an antenna by feeding the driven element both at the centre of the element and at a fraction of a wavelength to one side of centre?
The gamma matching system
The delta matching system
The omega matching system
The stub matching system
What impedance matching system uses a short perpendicular section of transmission line connected to the feed line near the antenna?
The gamma matching system
The delta matching system
The omega matching system
The stub matching system
What should be the approximate capacitance of the resonating capacitor in a gamma matching circuit on a 1/2-wavelength dipole antenna for the 20-meter wavelength band?
70 pF
140 pF
200 pF
0.2 pF
What kind of impedance does a 1/4-wavelength transmission line present to a generator when the line is shorted at the far end?
A very high impedance
A very low impedance
The same as the characteristic impedance of the transmission line
The same as the generator output impedance
What kind of impedance does a 1/2-wavelength transmission line present to a generator when the line is open at the far end?
A very high impedance
A very low impedance
The same as the characteristic impedance of the line
The same as the output impedance of the generator
What is the velocity factor of a transmission line?
The ratio of the characteristic impedance of the line to the terminating impedance
The index of shielding for coaxial cable
The velocity of the wave on the transmission line multiplied by the velocity of light in a vacuum
The velocity of the wave on the transmission line divided by the velocity of light in a vacuum
What determines the velocity factor in a transmission line?
The termination impedance
The line length
Dielectrics in the line
The centre conductor resistivity
Why is the physical length of a coaxial cable transmission line shorter than its electrical length?
Skin effect is less pronounced in the coaxial cable
The characteristic impedance is higher in the parallel feed line
The surge impedance is higher in the parallel feed line
Electrical signals move more slowly in a coaxial cable than in air
What is the typical velocity factor for a coaxial cable with polyethene dielectric?
2.70
0.66
0.30
0.10
What would be the physical length of a typical coaxial transmission line that is electrically one-quarter wavelength long at 14.1 MHz? (Assume a velocity factor of 0.66.)
20 meters
2.33 meters
3.51 meters
0.25 meters
What is the physical length of a parallel conductor feed line that is electrically one-half wavelength long at 14.10 MHz? (Assume a velocity factor of 0.95.)
15 meters
20.2 meters
10.1 meters
70.8 meters
What parameter best describes the interactions at the load end of a mismatched transmission line?
Characteristic impedance
Reflection coefficient
Velocity factor
Dielectric Constant
Which of the following measurements describes a mismatched transmission line?
An SWR less than 1:1
A reflection coefficient greater than 1
A dielectric constant greater than 1
An SWR greater than 1:1
What characteristic will 450-ohm ladder line have at 50 MHz, as compared to 0.195-inch-diameter coaxial cable (such as RG-58)?
Lower loss in dB/100 feet
Higher SWR
Smaller reflection coefficient
Lower velocity factor
What would be the physical length of a typical coaxial transmission line that is electrically one-quarter wavelength long at 7.2 MHz? (Assume a velocity factor of 0.66.)
10 meters
6.9 meters
24 meters
50 meters
What kind of impedance does a 1/8-wavelength transmission line present to a generator when the line is shorted at the far end?
A capacitive reactance
The same as the characteristic impedance of the line
An inductive reactance
The same as the input impedance of the final generator stage
What kind of impedance does a 1/8-wavelength transmission line present to a generator when the line is open at the far end?
A capacitive reactance
The same as the characteristic impedance of the line
An inductive reactance
The same as the input impedance of the final generator stage
What kind of impedance does a 1/4-wavelength transmission line present to a generator when the line is open at the far end?
A very high impedance
A very low impedance
The same as the characteristic impedance of the line
The same as the input impedance of the final generator stage
What kind of impedance does a 1/4-wavelength transmission line present to a generator when the line is shorted at the far end?
A very high impedance
A very low impedance
The same as the characteristic impedance of the line
The same as the input impedance of the final generator stage
What kind of impedance does a 1/2-wavelength transmission line present to a generator when the line is shorted at the far end?
A very high impedance
A very low impedance
The same as the characteristic impedance of the line
The same as the input impedance of the final generator stage
What kind of impedance does a 1/2-wavelength transmission line present to a generator when the line is open at the far end?
A very high impedance
A very low impedance
The same as the characteristic impedance of the line
The same as the input impedance of the final generator stage
What is the radiation pattern of two 1/4-wavelength vertical antennas spaced 1/2-wavelength apart and fed 180 degrees out of phase?
Unidirectional cardioid
Omnidirectional
Figure-8 broadside to the antennas
Figure-8 end-fire in line with the antennas
What is the radiation pattern of two 1/4-wavelength vertical antennas spaced 1/2-wavelength apart and fed in phase?
Unidirectional cardioid
Omnidirectional
Figure-8 broadside to the antennas
Figure-8 end-fire in line with the antennas
What is the radiation pattern of two 1/4-wavelength vertical antennas spaced 1/4-wavelength apart and fed 180 degrees out of phase?
Unidirectional cardioid
Omnidirectional
Figure-8 broadside to the antennas
Figure-8 end-fire in line with the antennas
What is the radiation pattern for two 1/4-wavelength vertical antennas spaced 1/8-wavelength apart and fed 180 degrees out of phase?
Unidirectional cardioid
Omnidirectional
Figure-8 broadside to the antennas
Figure-8 end-fire in line with the antennas
What is the radiation pattern of two 1/4-wavelength vertical antennas spaced 1/4-wavelength apart and fed 90 degrees out of phase?
Unidirectional cardioid
Figure-8 end-fire
Figure-8 broadside
Omnidirectional
What is the radiation pattern for two 1/4-wavelength vertical antennas spaced 1/4-wavelength apart and fed in phase?
Substantially unidirectional
Elliptical
Cardioid unidirectional
Figure-8 end-fire in line with the antennas
Which of the following is the best description of a resonant rhombic antenna?
Unidirectional; four-sided, each side a half-wavelength long; terminated in a resistance equal to its characteristic impedance
Bidirectional; four-sided, each side approximately one wavelength long; open at the end opposite the transmission line connection
Four-sided; an LC network at each vertex except for the transmission connection; tuned to resonate at the operating frequency
Four-sided, each side of a different physical length; traps at each vertex for changing resonance according to band usage
What are the advantages of a nonresonant rhombic antenna?
Wide frequency range, high gain and high front-to-back ratio
High front-to-back ratio, compact size and high gain
Unidirectional radiation pattern, high gain and compact size
Bidirectional radiation pattern, high gain and wide frequency range
What are the disadvantages of a nonresonant rhombic antenna?
A large area for proper installation and a narrow bandwidth
A large area for proper installation and a low front-to-back ratio
A large area and four sturdy support for proper installation
A large amount of aluminium tubing and a low front-to-back ratio
What is the effect of a terminating resistor on a rhombic antenna?
It reflects the standing waves on the antenna elements back to the transmitter
It changes the radiation pattern from essentially bidirectional to essentially unidirectional
It changes the radiation pattern from horizontal to vertical polarisation
It decreases the ground loss
How is the far-field elevation pattern of a vertically polarised antenna affected by being mounted over seawater versus rocky ground?
The low-angle radiation decreases
The high-angle radiation increases
Both the high- and low-angle radiation decrease
The low-angle radiation increases
If only a modest on-ground radial system can be used with an eighth-wavelength-high, inductively loaded vertical antenna, what would be the best compromise to minimise near-field losses?
4 radial wires, 1 wavelength long
8 radial wires, a half-wavelength long
A wire-mesh screen at the antenna base, an eighth-wavelength square
4 radial wires, 2 wavelengths long
What is one characteristic of a Beverage antenna?
For best performance, it must not exceed 1/4 wavelength in length at the desired frequency
For best performance, it must be mounted more than 1 wavelength above ground at the desired frequency
For best performance, it should be configured as four-sided loop
For best performance, it should be as long as possible
What determines the free-space polarisation of an antenna?
The orientation of its magnetic field (H-Field)
The orientation of its free space characteristic impedance
The orientation of its electric field (E-Field)
Its elevation pattern
What information is needed to evaluate the gain of an antenna accurately?
Radiation resistance
E-Field and H-Field patterns
Loss resistance
All of these choices
Which is NOT an important reason to evaluate antenna again across the whole frequency band for which it was designed?
The gain may fall off rapidly over the whole frequency band
The feed point impedance may change radically with frequency
The rearward pattern lobes may vary excessively with frequency
The dielectric constant may vary significantly
What usually occurs if a Yagi antenna is designed solely for maximum forward gain?
The front-to-back ratio increases
The feed point impedance becomes very low
The frequency response is widened over the whole frequency band
The SWR is reduced
If the boom of a Yagi antenna is lengthened and the elements are properly returned, what usually occurs?
The gain increases
The SWR decreases
The front-to-back ratio increases
The gain bandwidth decreases rapidly
What type of computer program is commonly used for modelling antennas?
Graphical analysis
Method of Moments
Mutual impedance analysis
Calculus differentiation with respect to physical properties
What is the principle of a "Method of Moments" analysis?
A wire is modelled as a series of segments, each having a distinct value of current
A wire is modelled as a single sine-wave current generator
A wire is modelled as a series of points, each having a distinct location in space
A wire is modelled as a series of segments, each having a distinct value of voltage across it
Which of the following causes opposition to the flow of alternating current in an inductor?
Conductance
Reluctance
Admittance
Reactance
What precaution should operator observe if the installation of an indoor transmitting antenna?
Locate the antenna close to the operating position to minimise feedline radiation
Position the antenna along the edge of a wall to reduce parasitic radiation
Make sure that MPE limits not exceeded in occupied areas
Make sure the antenna properly shielded
Which of these choices should be observed when climbing a tower using a safety belt or harness?
Never lean back and rely on the belt alone to support your weight
Confirm that the belt is rated for the weight of the climber and that it is within its allowable service life
Ensure that all heavy tools are securely fastened to the belt D-ring
All of these choices are correct
What should be done by any person preparing to climb a tower that supports electrically powered devices?
Notify the electric company that a person will be working on the tower
Make sure all circuits that supply power to the tower are locked out and tagged
Unground the base of the tower
All of these choices are correct
Why should soldered joints not be used with the wires that connect the base of a tower to a system of ground rods?
The resistance of solder is too high
Solder flux will prevent a low conductivity connection
Solder has too high a dielectric constant to provide adequate lightning protection
A soldered joint will likely be destroyed by the heat of a lightning strike
Which of the following is a danger from lead-tin solder?
Lead can contaminate food if hands are not washed carefully after handling the solder
High voltages can cause lead-tin solder to disintegrate suddenly
Tin in the solder can "cold flow" causing shorts in the circuit
RF energy can convert the lead into a poisonous gas
Which of the following is good practice for lightning protection grounds?
They must be bonded to all buried water and gas lines
Bends in ground wires must be made as close as possible to a right angle
Lightning grounds must be connected to all ungrounded wiring
They must be bonded together with all other grounds
Which of the following is true of an emergency generator installation?
The generator should be located in a well-ventilated area
The generator must be insulated from ground
The generator must be insulated from ground
All of these choices are correct
What is one way that RF energy can affect human body tissue?
It heats body tissue
It causes radiation poisoning
It causes the blood count to reach a dangerously low level
It cools body tissue
What does "time averaging" mean about RF radiation exposure?
The average amount of power developed by the transmitter over a specific 24 hour period
The average time it takes RF radiation to have any long-term effect on the body
The total time of the exposure
The total RF exposure averaged over a certain time
What effect does transmitter duty cycle have when evaluating RF exposure?
A lower transmitter duty cycle permits greater short-term exposure levels
A higher transmitter duty cycle permits greater short-term exposure levels
Low duty cycle transmitters are exempt from RF exposure evaluation requirements
High duty cycle transmitters are exempt from RF exposure requirements
What type of instrument can be used to measure an RF field accurately?
A receiver with an S meter
A calibrated field strength meter with a calibrated antenna
SWR meter with a peak-reading function
An oscilloscope with a high-stability crystal marker generator
What precaution should operator take whenever adjustments or repairing to an antenna?
Ensure that you and the antenna structure are grounded
Turn off the transmitter and disconnect the feed line
Wear a radiation badge
All of these choices are correct
Which of the following is a primary reason for not placing a gasoline-fueled generator inside an occupied area?
Danger of carbon monoxide poisoning
Danger of engine over torque
Lack of oxygen for adequate combustion
Lack of nitrogen for adequate combustion
Why must the metal enclosure of every item of station equipment be grounded?
It prevents a blown fuse in the event of an internal short circuit
It prevents signal overload
It ensures that the neutral wire is grounded
It ensures that hazardous voltages cannot appear on the chassis
