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Carl wrote “Important detail Neil Radio8Z, but what about the field strength of your signal out beyond the wet foliage?”
The far field strength is also reduced but this is due to the change in antenna system resistance (which increased) noted with the presence of the foliage. This might also be due to the absorption by the plants of moisture from the soil which would lower the soil conductivity, but since I have not measured soil conductivity this is speculation.
You are correct that the effect is the same as if it were the plants absorbing the signal but I am not willing to assign this as a cause and attribute decreased field strength to absorption by the foliage. Absorption by the foliage would not appear as increased antenna system resistance.
It has been long observed that waves are not absorbed by matter which is smaller than one wavelength. This is why the electron microscope was developed. It is known that the resolution of a microscope is limited by the wavelength of light and using electrons which have a much smaller wavelength than light gives higher resolution. By the same reasoning, radio waves will not be blocked by objects smaller than one wavelength.