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Pregunta 522

What is the purpose of feeding an off-center-fed dipole (OCFD) between the center and one end instead of at the midpoint?

  1. To create a similar feed point impedance on multiple bandsRespuesta correcta
  2. To suppress off-center lobes at higher frequencies
  3. To resonate the antenna across a wider range of frequencies
  4. To reduce common-mode current coupling on the feed line shield

Explicación

A center-fed dipole sits at a current maximum on its fundamental but at a high-impedance voltage maximum on the even harmonics, so its feed point impedance swings wildly from band to band. Moving the feed away from the midpoint finds a location where the impedance is comparable on several harmonically related bands, so one fixed transformer can serve them all.

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