Subelements 6, 8, and 9 comprise only 25% of the test.

Feedlines and Antennas

E9A01 (C)Which of the following describes an isotropic radiator?

C. A theoretical radiator used to compare other antennas

E9A02 (A)When is it useful to refer to an isotropic radiator?

A. When comparing the gains of directional antennas

E9A03 (B)How much gain does a 1/2-wavelength dipole have over an isotropic radiator?

B. About 2.1 dB

E9A04 (D)Which of the following antennas has no gain in any direction?

D. Isotropic radiator

E9A05 (C)Which of the following describes the radiation pattern of an isotropic radiator?

C. A sphere with the antenna in the center

E9A06 (A)Why would one need to know the feed point impedance of an antenna?

A. To match impedances for maximum power transfer

E9A07 (B)What factors determine the radiation resistance of an antenna?

B. Antenna location with respect to nearby objects and the conductors' length/diameter ratio

E9A08 (C)What is the term for the ratio of the radiation resistance of an antenna to the total resistance of the system?

C. Antenna efficiency

E9A09 (D)What is included in the total resistance of an antenna system?

D. Radiation resistance plus ohmic resistance

E9A10 (C)What is a folded dipole antenna?

C. A dipole whose ends are connected by a one-half wavelength piece of wire

E9A11 (A)What is meant by antenna gain?

A. The numerical ratio relating the radiated signal strength of an antenna to that of another antenna

E9A12 (B)What is meant by antenna bandwidth?

B. The frequency range over which an antenna can be expected to perform well

E9A13 (A)How can the approximate beamwidth of a beam antenna be determined?

A. 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

E9A14 (B)How is antenna efficiency calculated?

B. (radiation resistance / total resistance) x 100%

E9A15 (A)How can the efficiency of an HF grounded vertical antenna be made comparable to that of a half-wave dipole antenna?

A. By installing a good ground radial system

E9A16 (D)What theoretical reference antenna provides a comparison for antenna measurements?

D. Isotropic radiator

E9A17 (A)How much gain does an antenna have over a 1/2-wavelength dipole when it has 6 dB gain over an isotropic radiator?

A. About 3.9 dB

E9A18 (B)How much gain does an antenna have over a 1/2-wavelength dipole when it has 12 dB gain over an isotropic radiator?

B. About 9.9 dB

E9A19 (D)Which of the following describes the directivity of an isotropic radiator?

D. No directivity at all

E9A20 (C)What is meant by the radiation resistance of an antenna?

C. The equivalent resistance that would dissipate the same amount of power as that radiated from an antenna

E9B01 (C)What determines the free-space polarization of an antenna?

C. The orientation of its electric field (E Field)

E9B02 (B)In the free-space H-Field radiation pattern shown in Figure E9-1, what is the 3-dB beamwidth?

B. 50 degrees

E9B03 (B)In the free-space H-Field pattern shown in Figure E9-1, what is the front-to-back ratio?

B. 18 dB

E9B04 (B)In the free-space H-field pattern shown in Figure E9-1, what is the front-to-side ratio?

B. 14 dB

E9B05 (D)What information is needed to accurately evaluate the gain of an antenna?

D. All of these choices

E9B06 (D)Which is NOT an important reason to evaluate a gain antenna across the whole frequency band for which it was designed?

D. The dielectric constant may vary significantly

E9B07 (B)What usually occurs if a Yagi antenna is designed solely for maximum forward gain?

B. The feed-point impedance becomes very low

E9B08 (A)If the boom of a Yagi antenna is lengthened and the elements are properly retuned, what usually occurs?

A. The gain increases

E9B09 (B)What type of computer program is commonly used for modeling antennas?

B. Method of Moments

E9B10 (A)What is the principle of a Method of Moments analysis?

A. A wire is modeled as a series of segments, each having a distinct value of current

E9C01 (D)What is the radiation pattern of two 1/4-wavelength vertical antennas spaced 1/2-wavelength apart and fed 180 degrees out of phase?

D. Figure-8 end-fire in line with the antennas

E9C02 (A)What is the radiation pattern of two 1/4-wavelength vertical antennas spaced 1/4-wavelength apart and fed 90 degrees out of phase?

A. Unidirectional cardioid

E9C03 (C)What is the radiation pattern of two 1/4-wavelength vertical antennas spaced 1/2-wavelength apart and fed in phase?

C. Figure-8 broadside to the antennas

E9C04 (D)What is the radiation pattern of two 1/4-wavelength vertical antennas spaced 1/4-wavelength apart and fed 180 degrees out of phase?

D. Figure-8 end-fire in line with the antennas

E9C05 (D)What is the radiation pattern for two 1/4-wavelength vertical antennas spaced 1/8-wavelength apart and fed 180 degrees out of phase?

D. Figure-8 end-fire in line with the antennas

E9C06 (B)What is the radiation pattern for two 1/4-wavelength vertical antennas spaced 1/4-wavelength apart and fed in phase?

B. Elliptical

E9C07 (B)Which of the following is the best description of a resonant rhombic antenna?

B. Bidirectional; four-sided, each side approximately one wavelength long; open at the end opposite the transmission line connection

E9C08 (A)What are the advantages of a terminated rhombic antenna?

A. Wide frequency range, high gain and high front-to-back ratio

E9C09 (C)What are the disadvantages of a terminated rhombic antenna for the HF bands?

C. A large area and four sturdy supports for proper installation

E9C10 (B)What is the effect of a terminating resistor on a rhombic antenna?

B. It changes the radiation pattern from essentially bidirectional to essentially unidirectional

E9C11 (A)What type of antenna pattern over real ground is shown in Figure E9-2?

A. Elevation pattern

E9C12 (C)In the H field antenna radiation pattern shown in Figure E9-2, what is the elevation angle of the peak response?

C. 7.5 degrees

E9C13 (B)In the H field antenna radiation pattern shown in Figure E9-2, what is the front-to-back ratio?

B. 28 dB

E9C14 (A)In the H field antenna radiation pattern shown in Figure E9-2, how many elevation lobes appear in the forward direction?

A. 4

E9C15 (D)How is the far-field elevation pattern of a vertically polarized antenna affected by being mounted over seawater versus rocky ground?

D. The low-angle radiation increases

E9C16 (C)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 minimize near-field losses?

C. A wire-mesh screen at the antenna base, an eighth-wavelength square

E9C17 (D)What is one characteristic of a Beverage antenna?

D. For best performance it should be longer than one wavelength

E9C18 (B)How would the electric field be oriented for a Yagi with three elements mounted parallel to the ground?

B. Horizontally

E9C19 (A)What strongly affects the shape of the far-field, low-angle elevation pattern of a vertically polarized antenna?

A. The conductivity and dielectric constant of the soil

E9C20 (B)Why are elevated-radial counterpoises popular with vertically polarized antennas?

B. They reduce the near-field ground losses, compared to on-ground radial systems using more radials

E9C21 (C)What is a terminated rhombic antenna?

C. A unidirectional antenna terminated in a resistance equal to its characteristic impedance

E9D01 (A)What factors determine the receiving antenna gain required at an amateur satellite station in earth operation?

A. Height, transmitter power and antennas of satellite

E9D02 (A)What factors determine the EIRP required by an amateur satellite station in earth operation?

A. Satellite antennas and height, satellite receiver sensitivity

E9D03 (B)What is the approximate beamwidth of a symmetrical pattern antenna with a gain of 20 dB as compared to an isotropic radiator?

B. 20 degrees

E9D04 (C)How does the gain of a parabolic dish antenna change when the operating frequency is doubled?

C. Gain increases 6 dB

E9D05 (C)How is circular polarization produced using linearly polarized antennas?

C. Arrange two Yagis perpendicular to each other, with the driven elements in the same plane, fed 90 degrees out of phase

E9D06 (D)How does the beamwidth of an antenna vary as the gain is increased?

D. It decreases

E9D07 (A)Why does a satellite communications antenna system for earth operation need to have rotators for both azimuth and elevation control?

A. In order to track the satellite as it orbits the earth

E9D08 (A)For a shortened vertical antenna, where should a loading coil be placed to minimize losses and produce the most effective performance?

A. Near the center of the vertical radiator

E9D09 (C)Why should an HF mobile antenna loading coil have a high ratio of reactance to resistance?

C. To minimize losses

E9D10 (A)What is a disadvantage of using a trap antenna?

A. It will radiate harmonics

E9D11 (A)How must the driven element in a 3-element Yagi be tuned to use a hairpin matching system?

A. The driven element reactance is capacitive

E9D12 (C)What is the equivalent lumped-constant network for a hairpin matching system on a 3-element Yagi?

C. L network

E9D13 (B)What happens to the bandwidth of an antenna as it is shortened through the use of loading coils?

B. It is decreased

E9D14 (D)What is an advantage of using top loading in a shortened HF vertical antenna?

D. Improved radiation efficiency

E9D15 (A)What is the approximate input terminal impedance at the center of a folded dipole antenna?

A. 300 ohms

E9D16 (D)Why is a loading coil often used with an HF mobile antenna?

D. To tune out the capacitive reactance

E9D17 (D)What is an advantage of using a trap antenna?

D. It may be used for multi-band operation

E9D18 (B)What happens at the base feed-point of a fixed length HF mobile antenna as the frequency of operation is lowered?

B. The resistance decreases and the capacitive reactance increases

E9D19 (B)What is the beamwidth of a symmetrical pattern antenna with a gain of 30 dB as compared to an isotropic radiator?

B. 6.4 degrees

E9D20 (C)What is the beamwidth of a symmetrical pattern antenna with a gain of 15 dB as compared to an isotropic radiator?

C. 36 degrees

E9D21 (D)What is the beamwidth of a symmetrical pattern antenna with a gain of 12 dB as compared to an isotropic radiator?

D. 51 degrees

E9E01 (B)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 center?

B. The delta matching system

E9E02 (A)What system matches an unbalanced feed line to an antenna by feeding the driven element both at the center of the element and at a fraction of a wavelength to one side of center?

A. The gamma matching system

E9E03 (D)What impedance matching system uses a short perpendicular section of transmission line connected to the feed line near the antenna?

D. The stub matching system

E9E04 (B)What should be the approximate capacitance of the resonating capacitor in a gamma matching circuit on a Yagi beam antenna for the 20-meter band?

B. 140 pF

E9E05 (D)What should be the approximate capacitance of the resonating capacitor in a gamma matching circuit on a Yagi beam antenna for the 10-meter band?

D. 70 pF

E9E06 (D)What is the velocity factor of a transmission line?

D. The velocity of the wave on the transmission line divided by the velocity of light in a vacuum

E9E07 (C)What determines the velocity factor in a transmission line?

C. Dielectrics in the line

E9E08 (D)Why is the physical length of a coaxial cable transmission line shorter than its electrical length?

D. RF energy moves slower along the coaxial cable

E9E09 (B)What is the typical velocity factor for a coaxial cable with polyethylene dielectric?

B. 0.66

E9E10 (C)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.)

C. 3.5 meters

E9E11 (C)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.)

C. 10 meters

E9E12 (B)What parameter best describes the interactions at the load end of a mismatched transmission line?

B. Reflection coefficient

E9E13 (D)Which of the following measurements describes a mismatched transmission line?

D. An SWR greater than 1:1

E9E14 (A)What characteristic will 450-ohm ladder line have at 50 MHz, as compared to 0.195-inch-diameter coaxial cable (such as RG-58)?

A. Lower loss in dB/100 feet

E9E15 (A)What is the term for the ratio of the actual velocity at which a signal travels through a transmission line to the speed of light in a vacuum?

A. Velocity factor

E9E16 (B)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.)

B. 6.9 meters

E9E17 (C)What kind of impedance does a 1/8-wavelength transmission line present to a generator when the line is shorted at the far end?

C. An inductive reactance

E9E18 (C)What kind of impedance does a 1/8-wavelength transmission line present to a generator when the line is open at the far end?

C. A capacitive reactance

E9E19 (B)What kind of impedance does a 1/4-wavelength transmission line present to a generator when the line is open at the far end?

B. A very low impedance

E9E20 (A)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. A very high impedance

E9E21 (B)What kind of impedance does a 1/2-wavelength transmission line present to a generator when the line is shorted at the far end?

B. A very low impedance

E9E22 (A)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. A very high impedance