Extra · E9
ANTENNAS AND TRANSMISSION LINES
Antenna and feed line theory at its deepest: gain, directivity, matching networks, and the transmission-line math that explains why a real antenna system behaves the way it measures.
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93 questions across 8 groups
Group E9A
- E9A01What is an isotropic radiator?
- E9A02What 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?
- E9A03What term describing total radiated power takes into account all gains and losses?
- E9A04Which of the following factors affect the feed point impedance of an antenna?
- E9A05What does the term “ground gain” mean?
- E9A06What 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?
- E9A07What 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?
- E9A08Which frequency band has the smallest first Fresnel zone?
- E9A09What is antenna efficiency?
- E9A10Which of the following improves the efficiency of a ground-mounted quarter-wave vertical antenna?
- E9A11Which of the following determines ground losses for a ground-mounted vertical antenna operating on HF?
- E9A12How much gain does an antenna have compared to a half-wavelength dipole if it has 6 dB gain over an isotropic radiator?
Group E9B
- E9B01What is the 3 dB beamwidth of the antenna radiation pattern shown in Figure E9-1?
- E9B02What is the front-to-back ratio of the antenna radiation pattern shown in Figure E9-1?
- E9B03What is the front-to-side ratio of the antenna radiation pattern shown in Figure E9-1?
- E9B04What is the front-to-back ratio of the radiation pattern shown in Figure E9-2?
- E9B05What type of antenna pattern is shown in Figure E9-2?
- E9B06What is the elevation angle of peak response in the antenna radiation pattern shown in Figure E9-2?
- E9B07What is the difference in radiated power between a lossless antenna with gain and an isotropic radiator driven by the same power?
- E9B08What is the far field of an antenna?
- E9B09What type of analysis is commonly used for modeling antennas?
- E9B10What is the principle of a Method of Moments analysis?
- E9B11What is a disadvantage of decreasing the number of wire segments in an antenna model below 10 segments per half-wavelength?
Group E9C
- E9C01What 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?
- E9C02What 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?
- E9C03What type of radiation pattern is created by two 1/4-wavelength vertical antennas spaced 1/2- wavelength apart and fed in phase?
- E9C04What happens to the radiation pattern of an unterminated long wire antenna as the wire length is increased?
- E9C05What is the purpose of feeding an off-center-fed dipole (OCFD) between the center and one end instead of at the midpoint?
- E9C06What is the effect of adding a terminating resistor to a rhombic or long-wire antenna?
- E9C07What is the approximate feed point impedance at the center of a two-wire half-wave folded dipole antenna?
- E9C08What is a folded dipole antenna?
- E9C09Which of the following describes a G5RV antenna?
- E9C10Which of the following describes a Zepp antenna?
- E9C11How is the far-field elevation pattern of a vertically polarized antenna affected by being mounted over seawater versus soil?
- E9C12Which of the following describes an extended double Zepp antenna?
- E9C13How does the radiation pattern of a horizontally polarized antenna vary with increasing height above ground?
- E9C14How does the radiation pattern of a horizontally-polarized antenna mounted above a long slope compare with the same antenna mounted above flat ground?
Group E9D
- E9D01How much does the gain of an ideal parabolic reflector antenna increase when the operating frequency is doubled?
- E9D02How can two linearly polarized Yagi antennas be used to produce circular polarization?
- E9D03What is the most efficient location for a loading coil on an electrically short whip?
- E9D04Why should antenna loading coils have a high ratio of reactance to resistance?
- E9D05Approximately how long is a Yagi’s driven element?
- E9D06What happens to SWR bandwidth when one or more loading coils are used to resonate an electrically short antenna?
- E9D07What is an advantage of top loading an electrically short HF vertical antenna?
- E9D08What happens as the Q of an antenna increases?
- E9D09What is the function of a loading coil in an electrically short antenna?
- E9D10How does radiation resistance of a base-fed whip antenna change below its resonant frequency?
- E9D11Why do most two-element Yagis with normal spacing have a reflector instead of a director?
- E9D12What is the purpose of making a Yagi’s parasitic elements either longer or shorter than resonance?
Group E9E
- E9E01Which matching system for Yagi antennas requires the driven element to be insulated from the boom?
- E9E02What 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?
- E9E03What matching system uses a short length of transmission line connected in parallel with the feed line at or near the feed point?
- E9E04What is the purpose of the series capacitor in a gamma match?
- E9E05What Yagi driven element feed point impedance is required to use a beta or hairpin matching system?
- E9E06Which 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?
- E9E07What parameter describes the interaction of a load and transmission line?
- E9E08What is a use for a Wilkinson divider?
- E9E09Which of the following is used to shunt feed a grounded tower at its base?
- E9E11What is the purpose of using multiple driven elements connected through phasing lines?
Group E9F
- E9F01What is the velocity factor of a transmission line?
- E9F02Which of the following has the biggest effect on the velocity factor of a transmission line?
- E9F03Why is the electrical length of a coaxial cable longer than its physical length?
- E9F04What impedance does a 1/2-wavelength transmission line present to an RF generator when the line is shorted at the far end?
- E9F05What is microstrip?
- E9F06What is the approximate physical length of an air-insulated, parallel conductor transmission line that is electrically 1/2 wavelength long at 14.10 MHz?
- E9F07How does parallel conductor transmission line compare to coaxial cable with a plastic dielectric?
- E9F08Which of the following is a significant difference between foam dielectric coaxial cable and solid dielectric coaxial cable, assuming all other parameters are the same?
- E9F09What impedance does a 1/4-wavelength transmission line present to an RF generator when the line is shorted at the far end?
- E9F10What impedance does a 1/8-wavelength transmission line present to an RF generator when the line is shorted at the far end?
- E9F11What impedance does a 1/8-wavelength transmission line present to an RF generator when the line is open at the far end?
- E9F12What impedance does a 1/4-wavelength transmission line present to an RF generator when the line is open at the far end?
Group E9G
- E9G01Which of the following can be calculated using a Smith chart?
- E9G02What type of coordinate system is used in a Smith chart?
- E9G03Which of the following is often determined using a Smith chart?
- E9G04What are the two families of circles and arcs that make up a Smith chart?
- E9G05Which of the following is a common use for a Smith chart?
- E9G06On the Smith chart shown in Figure E9-3, what is the name for the large outer circle on which the reactance arcs terminate?
- E9G07On the Smith chart shown in Figure E9-3, what is the only straight line shown?
- E9G08How is a Smith chart normalized?
- E9G09What third family of circles is often added to a Smith chart during the process of designing impedance matching networks?
- E9G10What do the arcs on a Smith chart represent?
- E9G11In what units are the wavelength scales on a Smith chart calibrated?
Group E9H
- E9H01When constructing a Beverage antenna, which of the following factors should be included in the design to achieve good performance at the desired frequency?
- E9H02Which is generally true for 160- and 80-meter receiving antennas?
- E9H03What is receiving directivity factor (RDF)?
- E9H04What is the purpose of placing an electrostatic shield around a small-loop direction-finding antenna?
- E9H05What challenge is presented by a small wire-loop antenna for direction finding?
- E9H06What indicates the correct value of terminating resistance for a Beverage antenna?
- E9H07What is the function of a Beverage antenna’s termination resistor?
- E9H08What is the function of a sense antenna?
- E9H09What type of radiation pattern is created by a single-turn, terminated loop such as a pennant antenna?
- E9H10How can the output voltage of a multiple-turn receiving loop antenna be increased?
- E9H11What feature of a cardioid pattern antenna makes it useful for direction-finding antennas?