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  • $\begingroup$ The currents on a short dipole are in phase: the potential phase mismatch is at the feed. When transmitting, the energy reflected from the far reaches of the antenna returns to the feed. Ideally you'd like the feed to reflect it back into the antenna in phase with the energy coming from the transmitter. If the antenna isn't self-resonant, you need a reactive network at the feed to achieve this. $\endgroup$
    – John Doty
    Commented Jul 6 at 11:58
  • $\begingroup$ @JohnDoty I don't get your point - do you mean it as additional information regarding a dipole shorter than $\lambda/2$? I agree such dipole has a current that is everywhere almost with the same phase; but my point was it has very small magnitude, due to short length and capacitance, and effective radiating dipole moment is small due to short length. Increasing length of the dipole will result in increase of both. Is your point that one can increase the current amplitude or emitted power also by changing impedance of the circuit feeding the dipole, without altering the dipole length? $\endgroup$
    – Ján Lalinský
    Commented Jul 6 at 21:16
  • $\begingroup$ Yes: the impedance controls the phase of the wave reflected back into the dipole. $\endgroup$
    – John Doty
    Commented Jul 6 at 21:19
  • $\begingroup$ I understand impedance matching is a good thing to do regardless of the dipole length, to minimize losses in the feeding circuit. But I don't understand "wave reflected back into the dipole", the way I understand the current wave, it exists only on the dipole line, the feeding circuit has negligible dimensions, so there is no reflection at the feeding point, unless there is a node there (which happens only in the resonant case). Can you recommend a book/source on this? $\endgroup$
    – Ján Lalinský
    Commented Jul 6 at 22:00
  • 1
    $\begingroup$ @JánLalinský Electromagnetic Waves and Antennas by Sophocles J Orfandis has it all with Chapter 17 about linear and loop antennas and section 17.3 detailing standing-wave antennas. $\endgroup$
    – Farcher
    Commented Jul 8 at 10:02