I understand the shape of the dipole antenna, but how is it fed so that the current only flows through one direction during the half cycle? Even in a normal pole antenna, is there a ground at the edge of the antenna so that there is a potential difference?


A1: It doesn't flow through one direction during the half cycle, it's AC.

"Normal pole antenna" - what kind is this antenna? Perhaps you meant quarter wavelength antenna?

A2: The current flows through air due to the capacitance, from one half to the another half of the antenna - for a dipole.

For a quarter length, the ground acts as the second part of the antenna, therefore the coax is grounded at the antenna. A dipole antenna has to use BALUN transformer if fed from coax.

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  • \$\begingroup\$ I don't understand,is this correct:upload.wikimedia.org/wikipedia/commons/1/10/…, if it is without a potential difference, why does current flow to the poles at all? \$\endgroup\$ – user163416 May 1 '19 at 14:03
  • \$\begingroup\$ en.wikipedia.org/wiki/Dipole_antenna \$\endgroup\$ – Marko Buršič May 1 '19 at 14:05
  • 1
    \$\begingroup\$ @user163416 It's like a capacitor. The potential difference is between each half of antenna. \$\endgroup\$ – Marko Buršič May 1 '19 at 14:43
  • \$\begingroup\$ oh, this was the answer I was searching for. Thanks. But if this is the case, shouldn't the charges be more cramped at the small gap rather than going near the edge/pole edges? And wouldn't that mean no creation of the em waves? And does that also mean the simple capacitor circuit leads to this radiation? \$\endgroup\$ – user163416 May 1 '19 at 15:37
  • \$\begingroup\$ A balun is not essential with a coax transmission line. \$\endgroup\$ – Chu May 2 '19 at 0:14

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