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E9H06

ANTENNAS AND TRANSMISSION LINES · Receiving antennas: radio direction finding (RDF) techniques; Beverage antennas; single- and multiple-turn loops

E9H06E9H →

What indicates the correct value of terminating resistance for a Beverage antenna?

  1. AMaximum feed point DC resistance at the center of the desired frequency range
  2. BMinimum low-angle front-to-back ratio at the design frequency
  3. CMaximum DC current in the terminating resistor
  4. DMinimum variation in SWR over the desired frequency range
Why A Beverage is a traveling-wave antenna: energy runs down the long wire and is absorbed by the resistor at the far end, so no standing wave forms. When the terminating resistance matches the wire's characteristic impedance (typically 400-600 ohms over ground), the feed point impedance stops being resonant and stays nearly constant with frequency. So the practical test is to sweep the band and adjust the terminating resistor for the flattest, least variable SWR.
Watch out The front-to-back choice has it backwards: proper termination gives maximum front-to-back ratio, since the resistor absorbs the rearward wave instead of reflecting it. The DC current choice is a distractor because the antenna carries RF, not DC.
Terminated = traveling wave = no resonance, so impedance stays flat. Tune the resistor for flattest SWR across the band.
HamSandwich explanation, first draft. The question and answers are the NCVEC text.
← E9H05 All of E9H E9H07 →

The rest of E9H

  1. E9H01 When constructing a Beverage antenna, which of the following factors should be included in the design to achi…
  2. E9H02 Which is generally true for 160- and 80-meter receiving antennas?
  3. E9H03 What is receiving directivity factor (RDF)?
  4. E9H04 What is the purpose of placing an electrostatic shield around a small-loop direction-finding antenna?
  5. E9H05 What challenge is presented by a small wire-loop antenna for direction finding?
  6. E9H06 What indicates the correct value of terminating resistance for a Beverage antenna?
  7. E9H07 What is the function of a Beverage antenna's termination resistor?
  8. E9H08 What is the function of a sense antenna?
  9. E9H09 What type of radiation pattern is created by a single-turn, terminated loop such as a pennant antenna?
  10. E9H10 How can the output voltage of a multiple-turn receiving loop antenna be increased?
  11. E9H11 What feature of a cardioid pattern antenna makes it useful for direction-finding antennas?
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