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G9A09

ANTENNAS AND FEED LINES · - Feed lines: characteristic impedance and attenuation; standing wave ratio (SWR) calculation, measurement, and effects; antenna feed point matching

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What standing wave ratio results from connecting a 50-ohm feed line to a 200-ohm resistive load?

  1. A4:1
  2. B1:4
  3. C2:1
  4. D1:2
Why SWR from a purely resistive mismatch is just the ratio of the two impedances, larger divided by smaller: 200 / 50 = 4, written as 4:1. Because the load is resistive there is no reactance to complicate the calculation. SWR is always expressed with the larger value first, so it is never less than 1:1.
Watch out The inverted form 1:4 is not how SWR is written; SWR is by definition at least 1:1, so the bigger number always comes first. 2:1 would come from a 100-ohm load on 50-ohm line.
Divide big by small, never smaller than 1:1. 200/50 = 4:1.
HamSandwich explanation, first draft. The question and answers are the NCVEC text.
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The rest of G9A

  1. G9A01 Which of the following factors determine the characteristic impedance of a parallel conductor feed line?
  2. G9A02 What is the relationship between high standing wave ratio (SWR) and transmission line loss?
  3. G9A03 What is the nominal characteristic impedance of "window line" transmission line?
  4. G9A04 What causes reflected power at an antenna's feed point?
  5. G9A05 How does the attenuation of coaxial cable change with increasing frequency?
  6. G9A06 In what units is RF feed line loss usually expressed?
  7. G9A07 What must be done to prevent standing waves on a feed line connected to an antenna?
  8. G9A08 If the SWR on an antenna feed line is 5:1, and a matching network at the transmitter end of the feed line is …
  9. G9A09 What standing wave ratio results from connecting a 50-ohm feed line to a 200-ohm resistive load?
  10. G9A10 What standing wave ratio results from connecting a 50-ohm feed line to a 10-ohm resistive load?
  11. G9A11 What is the effect of transmission line loss on SWR measured at the input to the line?
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