Are all antennas traveling wave antennas?
A standing wave occurs when two signals that have the same frequency are traveling in opposite directions through a medium simultaneously.

Most antennas, such as the simple dipole, have impedance discontinuities at their ends that cause energy to be reflected back down the conductor, creating the conditions required for standing waves.

On the other hand, traveling wave antennas such as the Beverage or rhombic are deliberately terminated at their end(s) by a resistance that matches the characteristic impedance of the conductor. This eliminates the energy reflection and the backward-traveling wave, leaving only the forward-traveling wave &mdash; and no standing wave.