What is an isotropic radiator?
CA hypothetical, lossless antenna having equal radiation intensity in all directions used as a reference for antenna gain
extra pool
Subelement E9 question review
All 93 official questions with the exact winning phrase marked.
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?
D286 watts
What term describing total radiated power takes into account all gains and losses?
CEffective radiated power
Which of the following factors affect the feed point impedance of an antenna?
BAntenna height
What does the term “ground gain” mean?
DAn increase in signal strength from ground reflections in the environment of the antenna
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
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?
B252 watts
Which frequency band has the smallest first Fresnel zone?
A5.8 GHz
What is antenna efficiency?
BRadiation resistance divided by total resistance
Which of the following improves the efficiency of a ground-mounted quarter-wave vertical antenna?
AInstalling a ground radial system
Which of the following determines ground losses for a ground-mounted vertical antenna operating on HF?
CSoil conductivity
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
What is the 3 dB beamwidth of the antenna radiation pattern shown in Figure E9-1?
B50 degrees
What is the front-to-back ratio of the antenna radiation pattern shown in Figure E9-1?
D18 dB
What is the front-to-side ratio of the antenna radiation pattern shown in Figure E9-1?
D14 dB
What is the front-to-back ratio of the radiation pattern shown in Figure E9-2?
B28 dB
What type of antenna pattern is shown in Figure E9-2?
AElevation
What is the elevation angle of peak response in the antenna radiation pattern shown in Figure E9-2?
C7.5 degrees
What is the difference in radiated power between a lossless antenna with gain and an isotropic radiator driven by the same power?
CThey are the same
What is the far field of an antenna?
DThe region where the shape of the radiation pattern no longer varies with distance
What type of analysis is commonly used for modeling antennas?
BMethod of Moments
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
What is a disadvantage of decreasing the number of wire segments in an antenna model below 10 segments per half-wavelength?
CThe computed feed point impedance may be incorrect
What type of radiation pattern is created by two 1/4-wavelength vertical antennas spaced 1/2-wavelength apart and fed 180 degrees out of phase?
DA figure-eight oriented along the axis of the array
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
What type of radiation pattern is created by two 1/4-wavelength vertical antennas spaced 1/2-wavelength apart and fed in phase?
CA figure-eight broadside to the axis of the array
What happens to the radiation pattern of an unterminated long wire antenna as the wire length is increased?
BAdditional lobes form with major lobes increasingly aligned with the axis of the antenna
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
What is the effect of adding a terminating resistor to a rhombic or long-wire antenna?
BIt changes the radiation pattern from bidirectional to unidirectional
What is the approximate feed point impedance at the center of a two-wire half-wave folded dipole antenna?
A300 ohms
What is a folded dipole antenna?
CA half-wave dipole with an additional parallel wire connecting its two ends
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
Which of the following describes a Zepp antenna?
BAn end-fed half-wavelength dipole
How is the far-field elevation pattern of a vertically polarized antenna affected by being mounted over seawater versus soil?
DRadiation at low angles increases
Which of the following describes an extended double Zepp antenna?
CA center-fed 1.25-wavelength dipole antenna
How does the radiation pattern of a horizontally polarized antenna vary with increasing height above ground?
BThe takeoff angle of the lowest elevation lobe decreases
How does the radiation pattern of a horizontally-polarized antenna mounted above a long slope compare with the same antenna mounted above flat ground?
BThe main lobe takeoff angle decreases in the downhill direction
How much does the gain of an ideal parabolic reflector antenna increase when the operating frequency is doubled?
D6 dB
How can two linearly polarized Yagi antennas be used to produce circular polarization?
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
What is the most efficient location for a loading coil on an electrically short whip?
ANear the center of the vertical radiator
Why should antenna loading coils have a high ratio of reactance to resistance?
CTo maximize efficiency
Approximately how long is a Yagi’s driven element?
D1/2 wavelength
What happens to SWR bandwidth when one or more loading coils are used to resonate an electrically short antenna?
BIt is decreased
What is an advantage of top loading an electrically short HF vertical antenna?
DImproved radiation efficiency
What happens as the Q of an antenna increases?
BSWR bandwidth decreases
What is the function of a loading coil in an electrically short antenna?
DTo resonate the antenna by cancelling the capacitive reactance
How does radiation resistance of a base-fed whip antenna change below its resonant frequency?
BRadiation resistance decreases
Why do most two-element Yagis with normal spacing have a reflector instead of a director?
DHigher gain
What is the purpose of making a Yagi’s parasitic elements either longer or shorter than resonance?
CControl of phase shift
Which matching system for Yagi antennas requires the driven element to be insulated from the boom?
BBeta or hairpin
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
What matching system uses a short length of transmission line connected in parallel with the feed line at or near the feed point?
DStub match
What is the purpose of the series capacitor in a gamma match?
BTo cancel unwanted inductive reactance
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)
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?
C75 ohms
What parameter describes the interaction of a load and transmission line?
BReflection coefficient
What is a use for a Wilkinson divider?
CTo divide power equally between two 50-ohm loads while maintaining 50-ohm input impedance
Which of the following is used to shunt feed a grounded tower at its base?
CGamma match
What is the purpose of using multiple driven elements connected through phasing lines?
ATo control the antenna’s radiation pattern
What is the velocity factor of a transmission line?
DThe velocity of a wave in the transmission line divided by the velocity of light in a vacuum
Which of the following has the biggest effect on the velocity factor of a transmission line?
CThe insulating dielectric material
Why is the electrical length of a coaxial cable longer than its physical length?
DElectromagnetic waves move more slowly in a coaxial cable than in air
What impedance does a 1/2-wavelength transmission line present to an RF generator when the line is shorted at the far end?
BVery low impedance
What is microstrip?
DPrecision printed circuit conductors above a ground plane that provide constant impedance interconnects at microwave frequencies
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?
C10.6 meters
How does parallel conductor transmission line compare to coaxial cable with a plastic dielectric?
ALower loss
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?
DAll these choices are correct
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
What impedance does a 1/8-wavelength transmission line present to an RF generator when the line is shorted at the far end?
CAn inductive reactance
What impedance does a 1/8-wavelength transmission line present to an RF generator when the line is open at the far end?
CA capacitive reactance
What impedance does a 1/4-wavelength transmission line present to an RF generator when the line is open at the far end?
DVery low impedance
Which of the following can be calculated using a Smith chart?
AImpedance along transmission lines
What type of coordinate system is used in a Smith chart?
BResistance circles and reactance arcs
Which of the following is often determined using a Smith chart?
CImpedance and SWR values in transmission lines
What are the two families of circles and arcs that make up a Smith chart?
CResistance and reactance
Which of the following is a common use for a Smith chart?
ADetermine the length and position of an impedance matching stub
On the Smith chart shown in Figure E9-3, what is the name for the large outer circle on which the reactance arcs terminate?
BReactance axis
On the Smith chart shown in Figure E9-3, what is the only straight line shown?
DThe resistance axis
How is a Smith chart normalized?
CReassign the prime center’s impedance value
What third family of circles is often added to a Smith chart during the process of designing impedance matching networks?
AConstant-SWR circles
What do the arcs on a Smith chart represent?
DPoints with constant reactance
In what units are the wavelength scales on a Smith chart calibrated?
BIn fractions of transmission line electrical wavelength
When constructing a Beverage antenna, which of the following factors should be included in the design to achieve good performance at the desired frequency?
DIt should be at least one wavelength long
Which is generally true for 160- and 80-meter receiving antennas?
AAtmospheric noise is so high that directivity is much more important than losses
What is receiving directivity factor (RDF)?
DPeak antenna gain compared to average gain over the hemisphere around and above the antenna
What is the purpose of placing an electrostatic shield around a small-loop direction-finding antenna?
BIt eliminates unbalanced capacitive coupling to the antenna’s surroundings, improving the depth of its nulls
What challenge is presented by a small wire-loop antenna for direction finding?
AIt has a bidirectional null pattern
What indicates the correct value of terminating resistance for a Beverage antenna?
DMinimum variation in SWR over the desired frequency range
What is the function of a Beverage antenna’s termination resistor?
BAbsorb signals from the reverse direction
What is the function of a sense antenna?
AIt modifies the pattern of a DF antenna to provide a null in only one direction
What type of radiation pattern is created by a single-turn, terminated loop such as a pennant antenna?
ACardioid
How can the output voltage of a multiple-turn receiving loop antenna be increased?
CBy increasing the number of turns and/or the area enclosed by the loop
What feature of a cardioid pattern antenna makes it useful for direction-finding antennas?
BA single null