General · G9
ANTENNAS AND FEED LINES
HF antenna theory: dipoles, verticals, feed line loss, and matching a real antenna system to the bands your new privileges just opened up.
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46 questions across 4 groups
Group G9A
- G9A01Which of the following factors determine the characteristic impedance of a parallel conductor feed line?
- G9A02What is the relationship between high standing wave ratio (SWR) and transmission line loss?
- G9A03What is the nominal characteristic impedance of “window line” transmission line?
- G9A04What causes reflected power at an antenna’s feed point?
- G9A05How does the attenuation of coaxial cable change with increasing frequency?
- G9A06In what units is RF feed line loss usually expressed?
- G9A07What must be done to prevent standing waves on a feed line connected to an antenna?
- G9A08If the SWR on an antenna feed line is 5:1, and a matching network at the transmitter end of the feed line is adjusted to present a 1:1 SWR to the transmitter, what is the resulting SWR on the feed line?
- G9A09What standing wave ratio results from connecting a 50-ohm feed line to a 200-ohm resistive load?
- G9A10What standing wave ratio results from connecting a 50-ohm feed line to a 10-ohm resistive load?
- G9A11What is the effect of transmission line loss on SWR measured at the input to the line?
Group G9B
- G9B01What is a characteristic of a random-wire HF antenna connected directly to the transmitter?
- G9B02Which of the following is a common way to adjust the feed point impedance of an elevated quarter-wave ground-plane vertical antenna to be approximately 50 ohms?
- G9B03Which of the following best describes the radiation pattern of a quarter-wave ground-plane vertical antenna?
- G9B04What is the radiation pattern of a dipole antenna in free space in a plane containing the conductor?
- G9B05How does antenna height affect the azimuthal radiation pattern of a horizontal dipole HF antenna at elevation angles higher than about 45 degrees?
- G9B06Where should the radial wires of a ground-mounted vertical antenna system be placed?
- G9B07How does the feed point impedance of a horizontal 1/2 wave dipole antenna change as the antenna height is reduced to 1/10 wavelength above ground?
- G9B08How does the feed point impedance of a 1/2 wave dipole change as the feed point is moved from the center toward the ends?
- G9B09Which of the following is an advantage of using a horizontally polarized as compared to a vertically polarized HF antenna?
- G9B10What is the approximate length for a 1/2 wave dipole antenna cut for 14.250 MHz?
- G9B11What is the approximate length for a 1/2 wave dipole antenna cut for 3.550 MHz?
- G9B12What is the approximate length for a 1/4 wave monopole antenna cut for 28.5 MHz?
Group G9C
- G9C01Which of the following would increase the bandwidth of a Yagi antenna?
- G9C02What is the approximate length of the driven element of a Yagi antenna?
- G9C03How do the lengths of a three-element Yagi reflector and director compare to that of the driven element?
- G9C04How does antenna gain in dBi compare to gain stated in dBd for the same antenna?
- G9C05What is the primary effect of increasing boom length and adding directors to a Yagi antenna?
- G9C07What does “front-to-back ratio” mean in reference to a Yagi antenna?
- G9C08What is meant by the “main lobe” of a directive antenna?
- G9C09In free space, how does the gain of two three-element, horizontally polarized Yagi antennas spaced vertically 1/2 wavelength apart typically compare to the gain of a single three-element Yagi?
- G9C10Which of the following can be adjusted to optimize forward gain, front-to-back ratio, or SWR bandwidth of a Yagi antenna?
- G9C11What is a beta or hairpin match?
- G9C12Which of the following is a characteristic of using a gamma match with a Yagi antenna?
Group G9D
- G9D01Which of the following antenna types will be most effective as a near vertical incidence skywave (NVIS) antenna for short-skip communications on 40 meters during the day?
- G9D02What is the feed point impedance of an end-fed half-wave antenna?
- G9D03In which direction is the maximum radiation from a VHF/UHF “halo” antenna?
- G9D04What is the primary function of antenna traps?
- G9D05What is an advantage of vertically stacking horizontally polarized Yagi antennas?
- G9D06Which of the following is an advantage of a log-periodic antenna?
- G9D07Which of the following describes a log-periodic antenna?
- G9D08How does a “screwdriver” mobile antenna adjust its feed point impedance?
- G9D09What is the primary use of a Beverage antenna?
- G9D10In which direction or directions does an electrically small loop (less than 1/10 wavelength in circumference) have nulls in its radiation pattern?
- G9D11Which of the following is a disadvantage of multiband antennas?
- G9D12What is the common name of a dipole with a single central support?