You are making things more complicated than they have to be. Yes, there is an orgy of signals present on an antenna. You only care about one of them. It is easy to find; use filters built mostly inside the radio receiver. Most of the work happens in the radio hardware. Radios have a specification called selectivity, which measures the performance of a radio receiver to respond only to the radio signal it is tuned to and reject other signals nearby in frequency. Radios use several stages to filter a frequency of interest. The filter bandwidth and rejection ratio are so high the detector circuit cannot detect any other signal.

To a lesser extent, the antenna can act as a filter by adjusting the resonant length and augmenting the radio’s selectivity. Think of it like your spouse, and you are watching a game on TV. Your spouse blathers on, but you don’t hear a word of it; you filter it out and only hear the TV.

You are making things more complicated than they have to be. You are looking in the wrong place for an answer. Yes, there is an orgy of signals present on any antenna. You only care about one of them. It is easy to find; use filters built inside the radio receiver. The antenna has little to do with it. Most of the work happens inside the radio by signal processing. 

Radios have a specification called selectivity, which measures the performance of a radio receiver to respond only to the radio signal it is tuned to and reject other signals nearby in frequency. Radios use several stages to filter a frequency of interest. The filter bandwidth and rejection ratio are so high the detector circuit cannot detect any other signal.

To a lesser extent, the antenna can act as a shallow filter by adjusting the resonant length and augmenting the radio’s selectivity. Resonance is important if transmitting, not so much receiving. Think of it like your spouse, and you are watching a game on TV. Your spouse blathers on, but you don’t hear a word of it; you filter it out and only hear the TV.