According all the answers to a question about What is the advantage of making an antenna resonant different lengths of the antenna rod could be tuned to resonance with the antenna generator.
You can introduce shift with additional components to get the antenna to look resistive again, and get the best signal power from it. But the gain will not be as in the ideal case. Source
In my understaning the tuning of antennas with different lengths to the same frequency leads to different voltages, with which the electrons in the rod get drived. Different voltages lead to different accelerations of these electrons and this leads to the emission of photons with different energy content.
I’m curious about the reflection behaviour of the radiation as a function of the used voltage. The reflection could be from the ionosphere as well as from buildings or other obstacles.