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Subelement 6

Feedlines and Antenna Systems

Section 6-05

standing waves, standing wave ratio, SWR meter

What does an SWR reading of 1:1 mean?

  • Correct Answer
    The best impedance match has been attained
  • An antenna for another frequency band is probably connected
  • No power is going to the antenna
  • The SWR meter is broken
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What does an SWR reading of less than 1.5:1 mean?

  • Correct Answer
    A fairly good impedance match
  • An impedance match which is too low
  • An impedance mismatch; something may be wrong with the antenna system
  • An antenna gain of 1.5
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What kind of SWR reading may mean poor electrical contact between parts of an antenna system?

  • A negative reading
  • No reading at all
  • Correct Answer
    A jumpy reading
  • A very low reading
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What does a very high SWR reading mean?

  • The transmitter is putting out more power than normal, showing that it is about to go bad
  • Correct Answer
    The antenna is the wrong length, or there may be an open or shorted connection somewhere in the feed line
  • There is a large amount of solar radiation, which means very poor radio conditions
  • The signals coming from the antenna are unusually strong, which means very good radio conditions
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What does standing-wave ratio mean?

  • Correct Answer
    The ratio of maximum to minimum voltages on a feed line
  • The ratio of maximum to minimum inductances on a feed line
  • The ratio of maximum to minimum resistances on a feed line
  • The ratio of maximum to minimum impedances on a feed line
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If your antenna feed line gets hot when you are transmitting, what might this mean?

  • You should transmit using less power
  • The conductors in the feed line are not insulated very well
  • The feed line is too long
  • Correct Answer
    The SWR may be too high, or the feed line loss may be high
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If the characteristic impedance of the feedline does not match the antenna input impedance then:

  • heat is produced at the junction
  • the SWR reading falls to 1:1
  • the antenna will not radiate any signal
  • Correct Answer
    standing waves are produced in the feedline
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The result of the presence of standing waves on a transmission line is:

  • perfect impedance match between transmitter and feedline
  • maximum transfer of energy to the antenna from the transmitter
  • lack of radiation from the transmission line
  • Correct Answer
    reduced transfer of RF energy to the antenna
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An SWR meter measures the degree of match between transmission line and antenna by:

  • Correct Answer
    comparing forward and reflected voltage
  • measuring radiated RF energy
  • measuring the conductor temperature
  • inserting a diode in the feed line
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A resonant antenna having a feed point impedance of 200 ohms is connected to a feed line and transmitter which have an impedance of 50 ohms. What will the standing wave ratio of this system be?

  • 6:1
  • 3:1
  • Correct Answer
    4:1
  • 5:1
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The type of feed line best suited to operating at a high standing wave ratio is:

  • 75 ohm twin-lead
  • Correct Answer
    600 ohm open-wire
  • coaxial line
  • 300 ohm twin-lead
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