E9 Questions
85 questions in this subelement. Click any question ID for more details.
Answer: D
What is the effective radiated power (ERP) of a repeater station with 150 watts transmitter power output, 2 dB feed line loss, 2.2 dB duplexer loss, and 7 dBd antenna gain?
A469 watts
B78.7 watts
C420 watts
D286 watts
Answer: C
What term describing total radiated power takes into account all gains and losses?
APower factor
BHalf-power bandwidth
CEffective radiated power
DApparent power
Answer: B
Which of the following factors affect the feed point impedance of an antenna?
ATransmission line length
BAntenna height
CThe settings of an antenna tuner at the transmitter
DThe input power level
Answer: D
What does the term “ground gain” mean?
AThe change in signal strength caused by grounding the antenna
BThe gain of the antenna with respect to a dipole at ground level
CTo force net gain to 0 dB by grounding part of the antenna
DAn increase in signal strength from ground reflections in the environment of the antenna
Answer: A
What is the effective radiated power (ERP) of a repeater station with 200 watts transmitter power output, 4 dB feed line loss, 3.2 dB duplexer loss, 0.8 dB circulator loss, and 10 dBd antenna gain?
A317 watts
B2,000 watts
C126 watts
D300 watts
Answer: B
What is the effective isotropic radiated power (EIRP) of a repeater station with 200 watts transmitter power output, 2 dB feed line loss, 2.8 dB duplexer loss, 1.2 dB circulator loss, and 7 dBi antenna gain?
A159 watts
B252 watts
C632 watts
D63.2 watts
Answer: A
Which frequency band has the smallest first Fresnel zone?
A5.8 GHz
B3.4 GHz
C2.4 GHz
D900 MHz
Answer: B
What is antenna efficiency?
ARadiation resistance divided by transmission resistance
BRadiation resistance divided by total resistance
CTotal resistance divided by radiation resistance
DEffective radiated power divided by transmitter output
Answer: A
Which of the following improves the efficiency of a ground-mounted quarter-wave vertical antenna?
AInstalling a ground radial system
BIsolating the coax shield from ground
CShortening the radiating element
DAll these choices are correct
Answer: C
Which of the following determines ground losses for a ground-mounted vertical antenna operating on HF?
AThe standing wave ratio
BDistance from the transmitter
CSoil conductivity
DTake-off angle
Answer: A
How much gain does an antenna have compared to a half-wavelength dipole if it has 6 dB gain over an isotropic radiator?
A3.85 dB
B6.0 dB
C8.15 dB
D2.79 dB
Answer: D
What is the front-to-back ratio of the antenna radiation pattern shown in Figure E9-1?
A36 dB
B14 dB
C24 dB
D18 dB
Answer: D
What is the front-to-side ratio of the antenna radiation pattern shown in Figure E9-1?
A12 dB
B24 dB
C18 dB
D14 dB
Answer: B
What is the front-to-back ratio of the radiation pattern shown in Figure E9-2?
A15 dB
B28 dB
C3 dB
D38 dB
Answer: A
What type of antenna pattern is shown in Figure E9-2?
AElevation
BAzimuth
CNear field
DPolarization
Answer: C
What is the elevation angle of peak response in the antenna radiation pattern shown in Figure E9-2?
A45 degrees
B75 degrees
C7.5 degrees
D25 degrees
Answer: C
What is the difference in radiated power between a lossless antenna with gain and an isotropic radiator driven by the same power?
AThe power radiated from the directional antenna is increased by the gain of the antenna
BThe power radiated from the directional antenna is stronger by its front-to-back ratio
CThey are the same
DThe power radiated from the isotropic radiator is 2.15 dB greater than that from the directional antenna
Answer: D
What is the far field of an antenna?
AThe region of the ionosphere where radiated power is not refracted
BThe region where radiated power dissipates over a specified time period
CThe region where radiated field strengths are constant
DThe region where the shape of the radiation pattern no longer varies with distance
Answer: B
What type of analysis is commonly used for modeling antennas?
AGraphical analysis
BMethod of Moments
CMutual impedance analysis
DCalculus differentiation with respect to physical properties
Answer: A
What is the principle of a Method of Moments analysis?
AA wire is modeled as a series of segments, each having a uniform value of current
BA wire is modeled as a single sine-wave current generator
CA wire is modeled as a single sine-wave voltage source
DA wire is modeled as a series of segments, each having a distinct value of voltage across it
Answer: C
What is a disadvantage of decreasing the number of wire segments in an antenna model below 10 segments per half-wavelength?
AGround conductivity will not be accurately modeled
BThe resulting design will favor radiation of harmonic energy
CThe computed feed point impedance may be incorrect
DThe antenna will become mechanically unstable
Answer: A
What type of radiation pattern is created by two 1/4-wavelength vertical antennas spaced 1/4- wavelength apart and fed 90 degrees out of phase?
ACardioid
BA figure-eight end-fire along the axis of the array
CA figure-eight broadside to the axis of the array
DOmni-directional
Answer: C
What type of radiation pattern is created by two 1/4-wavelength vertical antennas spaced 1/2- wavelength apart and fed in phase?
AOmni-directional
BCardioid
CA figure-eight broadside to the axis of the array
DA figure-eight end-fire along the axis of the array
Answer: B
What happens to the radiation pattern of an unterminated long wire antenna as the wire length is increased?
AFewer lobes form with the major lobes increasing closer to broadside to the wire
BAdditional lobes form with major lobes increasingly aligned with the axis of the antenna
CThe elevation angle increases, and the front-to-rear ratio decreases
DThe elevation angle increases, while the front-to-rear ratio is unaffected
Answer: A
What is the purpose of feeding an off-center-fed dipole (OCFD) between the center and one end instead of at the midpoint?
ATo create a similar feed point impedance on multiple bands
BTo suppress off-center lobes at higher frequencies
CTo resonate the antenna across a wider range of frequencies
DTo reduce common-mode current coupling on the feed line shield
Answer: B
What is the effect of adding a terminating resistor to a rhombic or long-wire antenna?
AIt reflects the standing waves on the antenna elements back to the transmitter
BIt changes the radiation pattern from bidirectional to unidirectional
CIt changes the radiation pattern from horizontal to vertical polarization
DIt decreases the ground loss
Answer: A
What is the approximate feed point impedance at the center of a two-wire half-wave folded dipole antenna?
A300 ohms
B72 ohms
C50 ohms
D450 ohms
Answer: C
What is a folded dipole antenna?
AA dipole one-quarter wavelength long
BA center-fed dipole with the ends folded down 90 degrees at the midpoint of each side
CA half-wave dipole with an additional parallel wire connecting its two ends
DA dipole configured to provide forward gain
Answer: A
Which of the following describes a G5RV antenna?
AA wire antenna center-fed through a specific length of open-wire line connected to a balun and coaxial feed line
BA multi-band trap antenna
CA phased array antenna consisting of multiple loops
DA wide band dipole using shorted coaxial cable for the radiating elements and fed with a 4:1 balun
Answer: B
Which of the following describes a Zepp antenna?
AA horizontal array capable of quickly changing the direction of maximum radiation by changing phasing lines
BAn end-fed half-wavelength dipole
CAn omni-directional antenna commonly used for satellite communications
DA vertical array capable of quickly changing the direction of maximum radiation by changing phasing lines
Answer: D
How is the far-field elevation pattern of a vertically polarized antenna affected by being mounted over seawater versus soil?
ARadiation at low angles decreases
BAdditional lobes appear at higher elevation angles
CSeparate elevation lobes will combine into a single lobe
DRadiation at low angles increases
Answer: C
Which of the following describes an extended double Zepp antenna?
AAn end-fed full-wave dipole antenna
BA center-fed 1.5-wavelength dipole antenna
CA center-fed 1.25-wavelength dipole antenna
DAn end-fed 2-wavelength dipole antenna
Answer: B
How does the radiation pattern of a horizontally polarized antenna vary with increasing height above ground?
AThe takeoff angle of the lowest elevation lobe increases
BThe takeoff angle of the lowest elevation lobe decreases
CThe horizontal beamwidth increases
DThe horizontal beamwidth decreases
Answer: B
How does the radiation pattern of a horizontally-polarized antenna mounted above a long slope compare with the same antenna mounted above flat ground?
AThe main lobe takeoff angle increases in the downhill direction
BThe main lobe takeoff angle decreases in the downhill direction
CThe horizontal beamwidth decreases in the downhill direction
DThe horizontal beamwidth increases in the uphill direction
Answer: C
How can two linearly polarized Yagi antennas be used to produce circular polarization?
AStack two Yagis to form an array with the respective elements in parallel planes fed 90 degrees out of phase
BStack two Yagis to form an array with the respective elements in parallel planes fed in phase
CArrange two Yagis on the same axis and perpendicular to each other with the driven elements at the same point on the boom and fed 90 degrees out of phase
DArrange two Yagis collinear to each other with the driven elements fed 180 degrees out of phase
Answer: A
What is the most efficient location for a loading coil on an electrically short whip?
ANear the center of the vertical radiator
BAs low as possible on the vertical radiator
CAt a voltage maximum
DAt a voltage null
Answer: C
Why should antenna loading coils have a high ratio of reactance to resistance?
ATo swamp out harmonics
BTo lower the radiation angle
CTo maximize efficiency
DTo minimize the Q
Answer: D
Approximately how long is a Yagi’s driven element?
A234 divided by frequency in MHz
B1005 divided by frequency in MHz
C1/4 wavelength
D1/2 wavelength
Answer: B
What happens to SWR bandwidth when one or more loading coils are used to resonate an electrically short antenna?
AIt is increased
BIt is decreased
CIt is unchanged if the loading coil is located at the feed point
DIt is unchanged if the loading coil is located at a voltage maximum point
Answer: D
What is an advantage of top loading an electrically short HF vertical antenna?
ALower Q
BGreater structural strength
CHigher losses
DImproved radiation efficiency
Answer: B
What happens as the Q of an antenna increases?
ASWR bandwidth increases
BSWR bandwidth decreases
CGain is reduced
DMore common-mode current is present on the feed line
Answer: D
What is the function of a loading coil in an electrically short antenna?
ATo increase the SWR bandwidth by increasing net reactance
BTo lower the losses
CTo lower the Q
DTo resonate the antenna by cancelling the capacitive reactance
Answer: B
How does radiation resistance of a base-fed whip antenna change below its resonant frequency?
ARadiation resistance increases
BRadiation resistance decreases
CRadiation resistance becomes imaginary
DRadiation resistance does not depend on frequency
Answer: D
Why do most two-element Yagis with normal spacing have a reflector instead of a director?
ALower SWR
BHigher receiving directivity factor
CGreater front-to-side
DHigher gain
Answer: C
What is the purpose of making a Yagi’s parasitic elements either longer or shorter than resonance?
AWind torque cancellation
BMechanical balance
CControl of phase shift
DMinimize losses
Answer: A
What antenna matching system matches coaxial cable to an antenna by connecting the shield to the center of the antenna and the conductor a fraction of a wavelength to one side?
AGamma match
BDelta match
CT-match
DStub match
Answer: D
What matching system uses a short length of transmission line connected in parallel with the feed line at or near the feed point?
AGamma match
BDelta match
CT-match
DStub match
Answer: B
What is the purpose of the series capacitor in a gamma match?
ATo provide DC isolation between the feed line and the antenna
BTo cancel unwanted inductive reactance
CTo provide a rejection notch that prevents the radiation of harmonics
DTo transform the antenna impedance to a higher value
Answer: A
What Yagi driven element feed point impedance is required to use a beta or hairpin matching system?
ACapacitive (driven element electrically shorter than 1/2 wavelength)
BInductive (driven element electrically longer than 1/2 wavelength)
CPurely resistive
DPurely reactive
Answer: C
Which of these transmission line impedances would be suitable for constructing a quarter-wave Q- section for matching a 100-ohm feed point impedance to a 50-ohm transmission line?
A50 ohms
B62 ohms
C75 ohms
D90 ohms
Answer: B
What parameter describes the interaction of a load and transmission line?
ACharacteristic impedance
BReflection coefficient
CVelocity factor
DDielectric constant
Answer: C
What is a use for a Wilkinson divider?
ATo divide the operating frequency of a transmitter signal so it can be used on a lower frequency band
BTo feed high-impedance antennas from a low-impedance source
CTo divide power equally between two 50-ohm loads while maintaining 50-ohm input impedance
DTo divide the frequency of the input to a counter to increase its frequency range
Answer: C
Which of the following is used to shunt feed a grounded tower at its base?
ADouble-bazooka match
BBeta or hairpin match
CGamma match
DAll these choices are correct
Answer: A
What is the purpose of using multiple driven elements connected through phasing lines?
ATo control the antenna’s radiation pattern
BTo prevent harmonic radiation from the transmitter
CTo allow single-band antennas to operate on other bands
DTo create a low-angle radiation pattern
Answer: C
Which of the following has the biggest effect on the velocity factor of a transmission line?
AThe characteristic impedance
BThe transmission line length
CThe insulating dielectric material
DThe center conductor resistivity
Answer: D
Why is the electrical length of a coaxial cable longer than its physical length?
ASkin effect is less pronounced in the coaxial cable
BSkin effect is more pronounced in the coaxial cable
CElectromagnetic waves move faster in coaxial cable than in air
DElectromagnetic waves move more slowly in a coaxial cable than in air
Answer: B
What impedance does a 1/2-wavelength transmission line present to an RF generator when the line is shorted at the far end?
AVery high impedance
BVery low impedance
CThe same as the characteristic impedance of the line
DThe same as the output impedance of the RF generator
Answer: D
What is microstrip?
ASpecial shielding material designed for microwave frequencies
BMiniature coax used for low power applications
CShort lengths of coax mounted on printed circuit boards to minimize time delay between microwave circuits
DPrecision printed circuit conductors above a ground plane that provide constant impedance interconnects at microwave frequencies
Answer: C
What is the approximate physical length of an air-insulated, parallel conductor transmission line that is electrically 1/2 wavelength long at 14.10 MHz?
A7.0 meters
B8.5 meters
C10.6 meters
D13.3 meters
Answer: A
How does parallel conductor transmission line compare to coaxial cable with a plastic dielectric?
ALower loss
BHigher SWR
CSmaller reflection coefficient
DLower velocity factor
Answer: D
Which of the following is a significant difference between foam dielectric coaxial cable and solid dielectric coaxial cable, assuming all other parameters are the same?
AFoam dielectric coaxial cable has lower safe maximum operating voltage
BFoam dielectric coaxial cable has lower loss per unit of length
CFoam dielectric coaxial cable has higher velocity factor
DAll these choices are correct
Answer: A
What impedance does a 1/4-wavelength transmission line present to an RF generator when the line is shorted at the far end?
AVery high impedance
BVery low impedance
CThe same as the characteristic impedance of the transmission line
DThe same as the generator output impedance
Answer: C
What impedance does a 1/8-wavelength transmission line present to an RF generator when the line is shorted at the far end?
AA capacitive reactance
BThe same as the characteristic impedance of the line
CAn inductive reactance
DZero
Answer: C
What impedance does a 1/8-wavelength transmission line present to an RF generator when the line is open at the far end?
AThe same as the characteristic impedance of the line
BAn inductive reactance
CA capacitive reactance
DInfinite
Answer: D
What impedance does a 1/4-wavelength transmission line present to an RF generator when the line is open at the far end?
AThe same as the characteristic impedance of the line
BThe same as the input impedance to the generator
CVery high impedance
DVery low impedance
Answer: B
What type of coordinate system is used in a Smith chart?
AVoltage circles and current arcs
BResistance circles and reactance arcs
CVoltage chords and current chords
DResistance lines and reactance chords
Answer: C
Which of the following is often determined using a Smith chart?
ABeam headings and radiation patterns
BSatellite azimuth and elevation bearings
CImpedance and SWR values in transmission lines
DPoint-to-point propagation reliability as a function of frequency
Answer: C
What are the two families of circles and arcs that make up a Smith chart?
AInductance and capacitance
BReactance and voltage
CResistance and reactance
DVoltage and impedance
Answer: A
Which of the following is a common use for a Smith chart?
ADetermine the length and position of an impedance matching stub
BDetermine the impedance of a transmission line, given the physical dimensions
CDetermine the gain of an antenna given the physical and electrical parameters
DDetermine the loss/100 feet of a transmission line, given the velocity factor and conductor materials
Answer: B
On the Smith chart shown in Figure E9-3, what is the name for the large outer circle on which the reactance arcs terminate?
APrime axis
BReactance axis
CImpedance axis
DPolar axis
Answer: D
On the Smith chart shown in Figure E9-3, what is the only straight line shown?
AThe reactance axis
BThe current axis
CThe voltage axis
DThe resistance axis
Answer: C
How is a Smith chart normalized?
AReassign the reactance axis with resistance values
BReassign the resistance axis with reactance values
CReassign the prime center’s impedance value
DReassign the prime center to the reactance axis
Answer: A
What third family of circles is often added to a Smith chart during the process of designing impedance matching networks?
AConstant-SWR circles
BTransmission line length circles
CCoaxial-length circles
DRadiation-pattern circles
Answer: D
What do the arcs on a Smith chart represent?
AFrequency
BSWR
CPoints with constant resistance
DPoints with constant reactance
Answer: B
In what units are the wavelength scales on a Smith chart calibrated?
AIn fractions of transmission line electrical frequency
BIn fractions of transmission line electrical wavelength
CIn fractions of antenna electrical wavelength
DIn fractions of antenna electrical frequency
Answer: A
Which is generally true for 160- and 80-meter receiving antennas?
AAtmospheric noise is so high that directivity is much more important than losses
BThey must be erected at least 1/2 wavelength above the ground to attain good directivity
CLow loss coax transmission line is essential for good performance
DAll these choices are correct
Answer: D
What is receiving directivity factor (RDF)?
AForward gain compared to the gain in the reverse direction
BRelative directivity compared to isotropic
CRelative directivity compared to a dipole
DPeak antenna gain compared to average gain over the hemisphere around and above the antenna
Answer: B
What is the purpose of placing an electrostatic shield around a small-loop direction-finding antenna?
AIt adds capacitive loading, increasing the bandwidth of the antenna
BIt eliminates unbalanced capacitive coupling to the antenna’s surroundings, improving the depth of its nulls
CIt eliminates tracking errors caused by strong out-of-band signals
DIt increases signal strength by providing a better match to the feed line
Answer: A
What challenge is presented by a small wire-loop antenna for direction finding?
AIt has a bidirectional null pattern
BIt does not have a clearly defined null
CIt is practical for use only on VHF and higher bands
DAll these choices are correct
Answer: D
What indicates the correct value of terminating resistance for a Beverage antenna?
AMaximum feed point DC resistance at the center of the desired frequency range
BMinimum low-angle front-to-back ratio at the design frequency
CMaximum DC current in the terminating resistor
DMinimum variation in SWR over the desired frequency range
Answer: B
What is the function of a Beverage antenna’s termination resistor?
AIncrease the front-to-side ratio
BAbsorb signals from the reverse direction
CDecrease SWR bandwidth
DEliminate harmonic reception
Answer: A
What is the function of a sense antenna?
AIt modifies the pattern of a DF antenna to provide a null in only one direction
BIt increases the sensitivity of a DF antenna array
CIt allows DF antennas to receive signals at different vertical angles
DIt provides diversity reception that cancels multipath signals
Answer: A
What type of radiation pattern is created by a single-turn, terminated loop such as a pennant antenna?
ACardioid
BBidirectional
COmnidirectional
DHyperbolic
Answer: C
How can the output voltage of a multiple-turn receiving loop antenna be increased?
ABy reducing the permeability of the loop shield
BBy utilizing high impedance wire for the coupling loop
CBy increasing the number of turns and/or the area enclosed by the loop
DAll these choices are correct
Answer: B
What feature of a cardioid pattern antenna makes it useful for direction-finding antennas?
AA very sharp peak
BA single null
CBroadband response
DHigh radiation angle