Hmm .. just had an idea. Instead of constant wave source I used random source. Or better 'sources'. Every pixel on the 50 column is 'sourced' with random numbers. Ie all wavelength from 1px and lower will be present in the noise. Result:
Very poor shadow, not extruding over 2 diameters. Even if there are higher frequencies present, then there was in the first case. The coherence indeed did it, I guess. There are also a lot lower frequencies present now. Unfortunately I can't easily create random source with predefined spectrum.
Ok .. I lower my statement into: at 130m Kilo might, but might not, create a shadow on BB.
