Maybe this is a naive question, but how does an antenna, fractal or
otherwise, know what kind of transmitter is driving it? Why are
software radios more suited to this design?

vy 73

Andy, M1EBV


True frequency and waveform agility is the goal in SDR . Wideband, or
controlled multiband, is needed. Ham requirements are well met at present with
a variety of antenna designs that are nearly periodic in a fairly narrow
frequency coverage, a fairly easy problem to solve.
73,
Chip N1iR